Introduction
Seaweeds have long been recognized for their exceptional nutritional composition and their increasing relevance in human diets and nutraceutical applications (Elango et al., Reference Elango, Sankaranarayanan and Ganapathy2026). Rich in a wide range of bioactive molecules, they are increasingly viewed as sustainable and transformative food resources with the potential to strengthen global food security and address the challenges posed by a growing population (Webb et al., Reference Webb, Somers and Thilsted2023). Meeting the nutritional demands of an estimated global population of 10 billion people by 2050 will require diversification beyond land-based food production systems. In this context, seaweeds have been identified as one of the 50 future foods that can enable this transition (Malafronte et al., Reference Malafronte, Yilmaz-Turan, Krona, Martinez-Sanz, Vilaplana and Lopez-Sanchez2021). Traditionally consumed in coastal regions worldwide, seaweeds are now gaining broader international acceptance as consumers seek nutrient-dense and environmentally sustainable food sources. Their long-standing use in East and Southeast Asia, particularly in Japan, is supported by cohort studies linking habitual consumption to reduced risks of ischemic heart disease and stroke, factors associated with increased longevity (Ferdouse et al., Reference Ferdouse, Holdt, Smith, Murúa and Yang2018; Murai et al., Reference Murai, Yamagishi, Kishida and Iso2020). In contrast, Western utilization has historically centered on algae-derived hydrocolloids as gelling, thickening, and stabilizing agents in the food industry (Ścieszka and Klewicka, Reference Ścieszka and Klewicka2018). Modern culinary movements, including phycogastronomy, have further expanded the adoption of seaweeds across diverse cultural and gastronomic contexts (Salido et al., Reference Salido, Soto and Seoane2023).
Seaweed cultivation offers a sustainable production system that eliminates the need for arable land, freshwater, and synthetic fertilizers while achieving high biomass productivity and supporting environmental sustainability and economic development (Sultana et al., Reference Sultana, Wahab, Nahiduzzaman, Mohiuddin, Iqbal, Shakil, Mamun, Khan, Wong and Asaduzzaman2023). The global seaweed sector represents a rapidly expanding bioeconomy valued at approximately $5.5–6 billion annually, with an estimated 7.5–8 million tons harvested from wild and cultivated sources. Most production is destined for human consumption, with more than 600 species identified as edible and generating nearly $5 billion per year, while the remainder supports hydrocolloid extraction, fertilizers, and animal feed industries (Jang et al., Reference Jang, Cho, Jeong and Kim2012). As consumer preferences shift toward functional and nutrient-rich foods, seaweeds and their derivatives are increasingly incorporated into modern diets and are now regarded as foods of the future. This growing attention largely reflects their unique nutritional profile. Seaweeds are rich sources of essential minerals such as calcium, potassium, magnesium, and iron and have been successfully incorporated into a variety of food products such as bread, milk, meat, and fish (Raja et al., Reference Raja, Kadirvel and Subramaniyan2022). They are also among the richest natural sources of iodine, substantially contributing to dietary intake, with elevated iodine concentrations observed in the breast milk of Japanese and Korean mothers who regularly consume seaweed (Gupta and Abu-Ghannam, Reference Gupta and Abu-Ghannam2011). Their proteins often surpass conventional plant sources such as beans in biological quality (Ścieszka and Klewicka, Reference Ścieszka and Klewicka2018) and offer better-balanced amino acid profiles than many terrestrial plants that fail to meet Recommended Dietary Allowances for essential amino acids (EAAs; Raja et al., Reference Raja, Kadirvel and Subramaniyan2022). In addition, seaweeds contain vitamins A, B1, B12, C, D, and E, and minerals such as calcium, phosphorus, sodium, potassium, and iodine. Seaweed-derived polysaccharides also function as dietary fibres that have prebiotic properties, with reported benefits including modulation of the gut microbiota profile, increased stool bulk, and reduced colon cancer risk (Gupta and Abu-Ghannam, Reference Gupta and Abu-Ghannam2011). Beyond nutritional value, marine seaweeds are also rich sources of natural antioxidants and antimicrobial agents. Their incorporation into food systems can improve functional properties, such as enhancing water and fat retention, increasing oxidative stability in meat and cereal-based products, and enriching amino acid and fatty acid (FA) profiles in pasta with minimal effects on texture (Malafronte et al., Reference Malafronte, Yilmaz-Turan, Krona, Martinez-Sanz, Vilaplana and Lopez-Sanchez2021). Seaweeds are also widely utilized in pharmaceuticals, biofuels, fertilizers, and animal feeds (El-Beltagi et al., Reference El-Beltagi, Mohamed, Mohamed, Ramadan, Barqawi and Mansour2022), while contributing socio-economic benefits to coastal communities through livelihood support and ecosystem protection (Tagliapietra and MTPS, Reference Tagliapietra and MTPS2023).
Among seaweeds, the Sargassaceae family is distinguished by its distinctive biochemical and nutritional attributes. Species of this group, particularly Sargassum and Turbinaria, are widely distributed and often form dense underwater forests in tropical and subtropical regions, providing essential habitats for diverse marine communities (Stiger-Pouvreau et al., Reference Stiger-Pouvreau, Jégou, Cérantola, Guérard, Le Lann, Wiencke and Bischof2014; George et al., Reference George, Chakraborty, James, Pai, Jalal and Paulose2026). These seaweeds are recognized as rich sources of structurally diverse polysaccharides (such as fucoidan and alginates), phenolic compounds (phlorotannins), and EAAs, which are linked to antioxidant, anti-inflammatory, anticancer, and immunomodulatory activities (Park et al., Reference Park, Han, Shin, Park, Shin, Park, Roy, Lee, Kumagai, Kishimura and Chun2023; Jang et al., Reference Jang, Lee, Lee, Park, Lee and Lee2024; George et al., Reference George, Chakraborty, James and Pai2025a, Reference George, Chakraborty, James and Pai2025b). Owing to these properties, Sargassaceae species have been identified as promising resources for functional food development, nutraceutical applications, and therapeutic interventions. However, chemical profiles can vary substantially among species, and many taxa remain insufficiently characterized, warranting the need for further investigation into their biochemical diversity and bioactive potential (Stiger-Pouvreau et al., Reference Stiger-Pouvreau, Jégou, Cérantola, Guérard, Le Lann, Wiencke and Bischof2014). Aligned with the FAO Blue Transformation agenda, which prioritizes sustainable utilization of aquatic resources (Food and Agriculture Organization of the United Nations (FAO), 2022), the present study investigates the nutritional composition of three brown seaweeds in the family Sargassaceae: Sargassum plagiophyllum, Turbinaria ornata, and Turbinaria decurrens. The analysis encompasses proximate composition, amino acid profile, FA composition, and mineral content to provide a comprehensive understanding of their nutritional quality. Such profiling is essential for evaluating their potential as sustainable sources of key nutrients and bioactive compounds, and for supporting their application in the formulation of functional foods and nutraceutical products.
Materials and methods
Sample procurement and processing
Brown seaweeds belonging to the family Sargassaceae, namely Sargassum plagiophyllum, T. ornata, and T. decurrens (5 kg each), were collected in March 2025 from Mandapam, Gulf of Mannar, Tamil Nadu, India (8°48′ N, 78°9′ E–9°17′ N, 79°7′ E) (Figure 1a–d). The collected specimens were taxonomically authenticated by the ICAR–Central Marine Fisheries Research Institute (ICAR-CMFRI), Tuticorin, India, and voucher specimens were deposited in the Marine Biodiversity Museum, ICAR-CMFRI, under accession numbers AB.3.1.1.5 (Sargassum plagiophyllum), AB.3.1.2.3 (T. ornata), and AB.3.1.2.2 (T. decurrens). The freshly harvested specimens were thoroughly rinsed with distilled water to remove mucus, sand, salt, dirt, and epiphytic contaminants. Following cleaning, the samples were shade-dried to preserve heat- and light-sensitive bioactive compounds. After complete drying, the samples were finely milled, stored in airtight glass vials wrapped with aluminium foil, and maintained at −20 °C until further analysis.
Study area and representative images of the selected brown seaweeds. (a) Map showing the location of the sampling site at Mandapam, Gulf of Mannar, Tamil Nadu, India (8°48′ N, 78°9′ E–9°17′ N, 79°7′ E). (b) Sargassum plagiophyllum. (c) Turbinaria ornata. (d) Turbinaria decurrens.
Biochemical profiling of marine seaweeds
Chemicals and reagents
All reagents and chemicals used in this study were of analytical grade. Glacial acetic acid, acetone, isopropanol, O-phthalaldehyde, sodium potassium tartrate, and copper (II) sulphate pentahydrate were obtained from Sigma-Aldrich (USA), HiMedia Laboratories (USA), and Sisco Research Laboratories (India).
Carbohydrate determination
Total carbohydrates were quantified using a phenol–sulphuric acid colorimetric assay modified from Masuko et al. (Reference Masuko, Minami, Iwasaki, Majima, Nishimura and Lee2005). Briefly, 50 mg of dried sample was reacted with 150 µL of concentrated sulphuric acid (96%) and 30 µL of a 5% phenol solution. The mixture was allowed to stand at room temperature for 5 min to facilitate colour development, after which absorbance was recorded at 488 nm using a Multiskan SkyHigh Microplate Spectrophotometer (Thermo Fisher Scientific, Waltham, MA, USA). A glucose standard curve was employed for calibration, and carbohydrate content was expressed as a percentage of dry weight (DW; % w/w)
The carbohydrate content was calculated using equation (1):
\begin{equation}\% Carbohydrate = \frac{{XV}}{W} \times 100\end{equation}where X is the carbohydrate concentration obtained from the calibration curve (g/mL); Vis the volume of the solution containing the carbohydrates (mL); and W is the sample weight (g).
Protein determination
Protein content was determined using the Lowry assay (Lowry et al., Reference Lowry, Rosebrough, Farr and Randall1951), with freshly prepared analytical reagents. The Lowry reagent consisted of 0.5% CuSO₄ · 5H₂O, 1% sodium potassium tartrate, and 2% Na₂CO₃ in 0.1 N NaOH, mixed in a 1:1:48 ratio. The Folin–Ciocalteu reagent was diluted by adding 5 mL of a 2 N solution to 15 mL of distilled water. A calibration curve was prepared using bovine serum albumin. For measurements, 1 mL of seaweed extract (1000 ppm) was combined with 5 mL of Lowry reagent and 0.5 mL of diluted Folin reagent (1:1 v/v in water), followed by incubation in the dark at room temperature for 20 min. Absorbance was recorded at 660 nm using a Multiskan SkyHigh Microplate Spectrophotometer (Thermo Fisher Scientific, Waltham, MA, USA). Protein content was calculated and expressed as % w/w. Protein concentration was calculated using equation (2);
\begin{equation}\% Protein = \frac{{XV}}{W} \times 100\end{equation}where X is the protein concentration obtained from the calibration curve (g/mL); V is the volume of the solution containing the proteins (mL); and W is the sample weight (g).
Cholesterol determination
Total cholesterol in the seaweed samples was measured using a modified method of Wanasundara and Shahidi (Reference Wanasundara and Shahidi1999). O-phthalaldehyde reagent (50 mg dL−1) was prepared in glacial acetic acid and used as the chromogenic agent. A cholesterol stock solution (1000 ppm in ethanol) was serially diluted to prepare standards ranging from 0 to 1000 µg/mL. For colour development, 0.1 mL of each standard was mixed with 2 mL of O-phthalaldehyde reagent and 1 mL of concentrated sulphuric acid, incubated for 10 min, and the absorbance was recorded at 550 nm to construct a standard curve. For sample extraction, 0.1 g of dried biomass was combined with 3 mL ethanol and 0.3 mL of 33% KOH and heated at 60 °C for 15 min. After cooling, 10 mL hexane was added to extract lipids, followed by washing with 3 mL of double-distilled water. The hexane layer was evaporated, and the dried extract was resuspended in 1 mL of concentrated H₂SO₄. After homogenization and a 10-min reaction period, absorbance was measured at 550 nm. Cholesterol concentration was calculated from the standard curve and expressed as mg per 100 g DW.
Lipid content determination
Total lipid content was determined using a Soxtec fat analyser with petroleum ether as the extraction solvent following the AOAC Official Methods of Analysis (AOAC, 2019). Briefly, a known quantity of dried, powdered seaweed was accurately weighed into a cellulose thimble, and 60 mL of petroleum ether was added to the aluminium extraction cup. The thimble was attached to the Soxtec analyser, and lipid extraction was carried out through sequential boiling, rinsing, and solvent recovery for approximately 1 h. Following extraction, the aluminium cup containing the extracted lipids was dried in a hot-air oven at 100 °C for 1 h, cooled to room temperature in a desiccator, and weighed. Total lipid content was determined gravimetrically and expressed as g/100 g DW.
Crude fibre estimation
Crude fibre content was determined using the acid–alkali digestion method following AOAC (2019). Prior to fibre analysis, a separate portion of the dried seaweed powder was defatted using petroleum ether in a Soxtec fat analyser. Briefly, the dried sample was placed in a cellulose extraction thimble, and 60 mL of petroleum ether was added to the aluminium extraction cup. The sample was subjected to sequential boiling, rinsing, and solvent recovery for approximately 1 h. The defatted residue remaining in the extraction thimble was removed, dried to eliminate residual petroleum ether, and used for crude fibre determination. Approximately 0.5–0.8 g DW of the defatted sample was successively digested with 1.25% (w/v) sulphuric acid and 1.25% (w/v) sodium hydroxide under controlled heating. Following each digestion, the residue was thoroughly washed with distilled water until neutral, transferred to pre-weighed crucibles, dried to constant weight, and subsequently ashed in a muffle furnace at 600 °C for 3 h. After cooling in a desiccator, the crucibles were reweighed, and crude fibre content was calculated from the loss in weight after ashing and expressed as g/100 g DW.
Ash and moisture content
Ash content was quantified by placing 2–3 g of dried seaweed material in pre-weighed silica crucibles and combusting them in a muffle furnace at 600 °C for 3 h, following the procedure outlined by Premarathna et al. (Reference Premarathna, Tuvikene, Fernando, Adhikari, Perera, Ranahewa, Howlader, Wangchuk, Jayasooriya and Rajapakse2022). After cooling in a desiccator, the residue was weighed to quantify the total ash content. The ash percentage was calculated using equation (3);
\begin{equation}\% Ash = \left( {\frac{{Final \, residue \, weight}}{{Initial \, sample \, weight}}} \right) \times 100\end{equation}Moisture content of the seaweeds was determined by drying the samples in a hot-air oven at 105 °C until a stable weight was achieved, after which the reduction in mass was calculated and reported as a percentage of the original sample weight.
Amino acid composition
Amino acid composition was determined using the AccQ-Tag derivatization method with a Waters HPLC system. Approximately 0.1 g DW of seaweed sample was hydrolysed by refluxing with 6 N HCl at 110 °C for 24 h in nitrogen-flushed, sealed tubes to minimize oxidative degradation. The hydrolyzed mixture was concentrated by repeated rotary evaporation, and the dried residue was reconstituted in 0.05 N HCl and stored at 4 °C until further processing. The reconstituted sample was passed through a 0.2 µm nylon syringe filter (Whatman), then derivatized with AccQ-Tag Ultra reagents by combining borate buffer, derivatizing reagent, and sample in a 7:2:1 ratio (v/v/v). Chromatographic separation was performed on a Waters reversed-phase C18 column (Bridge BE+, 2.5 µm, 4.6 × 100 mm) maintained at 55 ± 1 °C. Derivatives were detected at 260 nm using a Waters 2489 dual absorbance detector. Each extract was analysed in triplicate, and chromatographic data were processed using Empower software (version 3). Amino acids were identified and quantified using external calibration standards. Results were expressed on a protein basis (g/100 g protein) and included total essential amino acids (ΣTEAA), total non-essential amino acids (ΣTNEAA), total amino acids (ΣTAA), total aromatic amino acids (ΣTArAA), total sulphur-containing amino acids (ΣTSCAA), along with associated ratios such as ΣTEAA/ΣTAA, Arg/Lys, and Leu/Ile.
FA composition and lipid quality indices
FAs were quantified following derivatization of extracted lipids to their methyl esters, based on the procedure reported by Metcalfe et al. (Reference Metcalfe, Schmitz and Pelka1966). Lipid extracts were subjected to transesterification by refluxing with methanolic potassium hydroxide at 80 °C for 30 min under a nitrogen atmosphere. Subsequently, boron trifluoride in methanol (5 mL) was added to promote methyl ester formation, and the mixture was further refluxed for 5 min. After cooling, fatty acid methyl esters (FAMEs) were extracted using petroleum ether (2:1, v/v), washed repeatedly with double-distilled water, dried over anhydrous sodium sulphate, and concentrated using a rotary evaporator at 40 °C. FAMEs were analysed using a Shimadzu Nexis GC-2030 Gas Chromatograph coupled with a Mass Spectrometer system (Shimadzu, Japan) equipped with an SH-Rxi-5Sil MS column (30 m × 0.25 mm, 0.25 µm film). Samples were injected in splitless mode. The oven programme initiated at 60 °C, increased to 150 °C at 15 °C/min with a 5-min hold, then ramped to 280 °C at 25 °C/min, followed by a final 15-min hold. Injector and ion source temperatures were set at 260 °C and 230 °C, respectively. Helium (>99.99% purity) served as the carrier gas at 1.22 mL/min and 74.4 kPa. FAME identification and quantification were achieved by comparison with the Supelco™ 37 Component FAME Mix. Results were expressed as percentages of total FAs, and summed values for saturated fatty acids (∑SFA), monounsaturated fatty acids (∑MUFAs), and polyunsaturated fatty acids (∑PUFAs) were calculated from chromatographic peak areas. Lipid quality indices such as the atherogenic index (AI) and thrombogenic index (TI) were determined according to Khalili Tilami and Kouřimská (Reference Khalili Tilami and Kouřimská2022). The hypocholesterolaemic/hypercholesterolaemic (h/H) ratio was calculated as described by Santos-Silva et al. (Reference Santos-Silva, Bessa and Santos-Silva2002), using equations 4–6.
Atherogenic index:
\begin{equation}\frac{{C12:0\: + 4 \times C14:0 + C16:0}}{{{{\Sigma }}MUFA + {{\Sigma }}n - 3PUFA + {{\Sigma }}n - 6PUFA}}\:\end{equation}Thrombogenic index:
\begin{equation}\frac{{C14:0 + C16:0 + C18:0}}{{0.5{{\Sigma }}MUFA + 0.5{{\Sigma }}n - 6PUFA + 3{{\Sigma }}n - 3PUFA + \frac{{{{\Sigma }}n - 3PUFA}}{{{{\Sigma }}n - 6PUFA}}}}\end{equation}The h/H ratio:
\begin{equation}\frac{\begin{array}{c}18:1n - 9 + 18:2n - 6 + 20:4n - 6 + 18:3n - 3 \\ + 20:5n - 3 + 22:5n - 3 + 22:6n - 3\:\end{array}}{{14:0 + 16:0}}\end{equation}Mineral composition
Mineral elements were quantified using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) on a Thermo Fisher iCAP™ Q instrument. Samples were pre-digested using concentrated nitric acid (HNO₃) to ensure complete dissolution. Sodium levels were assessed separately using flame photometry (Systronics 1027). ICP-MS was operated in helium kinetic energy discrimination mode for enhanced selectivity and sensitivity. Both macro- and micro-minerals were detected and quantified, with results expressed in mg kg−1 DW.
Statistical analyses
All experimental data were subjected to one-way analysis of variance to test for significant differences among species. Statistical analyses were performed using SPSS software (version 13.0, SPSS Inc., USA). Measurements were conducted in triplicate, and results are presented as mean ± standard deviation (SD). Statistical significance was defined at p < 0.05. To explore multivariate patterns in FA composition, principal component analysis (PCA) was conducted in R Studio (version 4.1.1) using the autoplot package and hierarcical clustering was performed using the pheatmap package.
Results and discussion
General
Seaweeds are valuable sources of bioactive compounds, including vitamins, proteins, EAAs, omega-3 FAs, minerals, carotenoids, polyphenols, and polysaccharides, many of which exhibit anti-oxidant, anticancer, antidiabetic, antimicrobial, and anti-inflammatory activities (Matos et al., Reference Matos, Cardoso, Serralheiro, Bandarra and Afonso2024). Their potential as functional food ingredients and nutraceuticals is increasingly recognized, particularly in the management of metabolic disorders, such as hyperglycaemia, hypercholesterolemia, and hyperlipidemia (Cherry et al., Reference Cherry, O’Hara, Magee, McSorley and Allsopp2019). Among seaweeds, the genus Sargassum (family Sargassaceae) is widely distributed in tropical and subtropical regions and has been traditionally consumed in various cultures (Cherry et al., Reference Cherry, O’Hara, Magee, McSorley and Allsopp2019). Sargassum species are rich in diverse bioactive compounds, including terpenoids, sterols, sulphated polysaccharides, polyphenols, sargaquinoic acids, sargachromenol, and pheophytin, many of which have demonstrated pharmacological activity (Rushdi et al., Reference Rushdi, Abdel-Rahman, Saber, Attia, Abdelraheem, Madkour, Hassan, Elmaidomy and Abdelmohsen2020). This study aims to offer a comprehensive overview of the nutritional profile inherent in selected brown seaweeds belonging to the family Sargassaceae, emphasizing their potential as valuable components in health-promoting formulations and in the management of metabolic diseases.
Biochemical composition
Protein content
S. plagiophyllum exhibited the highest protein content (14.75%), followed by T. decurrens (13.10%) and T. ornata (12.24%) (Table 1). These values are higher than those recently reported by Silva et al. (Reference Silva, Soares, Carpena, Fernandes, Chamorro, Delerue-Matos, Barroso and Prieto2026), who observed protein contents ranging from 5.78% in Ascophyllum nodosum to 9.72% in Fucus spiralis. Likewise, the protein contents recorded in the present study exceeded those reported by Premarathna et al. (Reference Premarathna, Tuvikene, Fernando, Adhikari, Perera, Ranahewa, Howlader, Wangchuk, Jayasooriya and Rajapakse2022) for Ulva lactuca (6.89%), Caulerpa racemosa (8.77%), and Stoechospermum polypodioides (8.02%). These findings indicate that the investigated brown seaweeds, particularly S. plagiophyllum, are comparatively rich sources of protein. Variations in protein content among seaweed species are commonly attributed to species-specific genetic characteristics, seasonal growth stage, environmental conditions, nutrient availability, particularly nitrogen concentration, and geographical location, all of which influence protein biosynthesis and accumulation.
Biochemical composition (g/100 g sample) of S. plagiophyllum, T. ornata, and T. decurrens
Table 1 Long description
Biochemical analysis values are reported for S. plagiophyllum, T. ornata, and T. decurrens in grams per 100 grams sample, with cholesterol reported in milligrams per 100 grams dry weight. Protein is 14.75a plus or minus 0.11 for S. plagiophyllum, 12.24c plus or minus 0.24 for T. ornata, and 13.10b plus or minus 0.19 for T. decurrens. Dry matter is 90.24a plus or minus 0.09, 89.62b plus or minus 0.18, and 89.60b plus or minus 0.12, while moisture is 9.76b plus or minus 0.22, 10.38a plus or minus 0.19, and 10.40a plus or minus 0.26. Crude ash is 16.15a plus or minus 0.22, 16.41a plus or minus 0.22, and 14.17b plus or minus 0.22. Lipid is 1.02c plus or minus 0.13, 1.95a plus or minus 0.11, and 1.60b plus or minus 0.42, and crude fibre is 6.12c plus or minus 0.14, 9.40a plus or minus 0.18, and 7.94b plus or minus 0.37. Cholesterol is 0.22a plus or minus 0.06, 0.18b plus or minus 0.07, and 0.14c plus or minus 0.02, with superscript letters shown next to the means.
Data were expressed as mean ± SD. Samples were analysed in triplicate (n = 3), and means followed by different superscripts (a–c) within the same row indicated significant difference (p < 0.05).
* Cholesterol content was expressed in mg/100 g DW. #The dry matter is expressed as percentage
When compared with terrestrial sources, the protein contents of S. plagiophyllum and T. decurrens are comparable to those of nuts such as Brazil nuts, hazelnuts, and pine nuts (11–15%), whereas pecans and macadamias generally contain less than 10% protein (Day et al., Reference Day, Cakebread and Loveday2021). These comparisons suggest that the studied brown seaweeds can provide protein levels comparable to, or greater than, several commonly consumed plant foods, supporting their potential as alternative protein contributors in human diets. The dietary significance of these findings is further supported by current global food trends. High consumption of red meat has been associated with adverse health and environmental impacts, driving increased interest in sustainable plant-derived protein sources (Qin et al., Reference Qin, Wang and Luo2022). Although plant proteins, such as soy and pea are increasingly utilized as alternatives to animal proteins, their nutritional functionality may be limited by imbalances in EAA composition (Ghelichi and Jacobsen, Reference Ghelichi and Jacobsen2025). Current dietary guidelines recommend a protein intake of 0.8 g kg−1 body weight day−1 for healthy adults, while higher intakes (1.0–1.2 g kg−1 day−1) have been recommended for older adults to support the maintenance of muscle mass and physical function (Bauer et al., Reference Bauer, Biolo, Cederholm, Cesari, Cruz-Jentoft, Morley, Phillips, Sieber, Stehle, Teta, Visvanathan, Volpi and Boirie2013). In this context, the comparatively high protein contents observed in the investigated brown seaweeds suggest that they could serve as valuable complementary dietary protein sources, contributing to adequate protein intake as part of diversified and sustainable diets. Overall, the favourable protein content, together with the increasing demand for environmentally sustainable food resources, highlights the potential of these brown seaweeds as nutritionally valuable ingredients for functional foods and other value-added food applications.
Carbohydrate content
The biochemical composition of the three brown seaweeds, S. plagiophyllum, T. decurrens, and T. ornata, revealed noticeable variation in total carbohydrate content. S. plagiophyllum exhibited the highest total carbohydrate content (67.05%), followed by those in T. decurrens (61.25%) and T. ornata (60.09%) (Table 1). These values are comparable to those reported for Saccharina japonica (66.0%) and slightly higher than Hizikia fusiforme (59.0%), although lower than Gelidium amansii (74.4%) (Jang et al., Reference Jang, Cho, Jeong and Kim2012). Such variations in carbohydrate content among seaweed species are commonly influenced by species-specific characteristics, seasonal growth stage, environmental conditions, geographical location, nutrient availability, and differences in the abundance of structural and storage polysaccharides. The relatively high carbohydrate contents observed in the investigated species are primarily attributable to the abundance of structural and storage polysaccharides, including alginate, fucoidan, and laminarin, which are characteristic constituents of brown seaweed cell walls. These polysaccharides not only contribute to the structural integrity and environmental adaptability of the algae but also enhance their nutritional value because they largely occur as non-starch dietary fibres with recognized physiological benefits, including improved glycaemic control, cholesterol regulation, and modulation of gut health (Gabbia and De Martin, Reference Gabbia and De Martin2020).
When compared with terrestrial crops, cereal grains, such as wheat, rice, maize, and barley generally contain 70–72% carbohydrates (Bouchard et al., Reference Bouchard, Malalgoda, Storsley, Malunga, Netticadan and Thandapilly2022). Although the carbohydrate contents of the investigated seaweeds are slightly lower than those of cereals, they differ considerably in carbohydrate quality because a substantial proportion consists of bioactive non-starch polysaccharides rather than digestible starch. Current dietary guidelines recommend a carbohydrate intake of approximately 130 g day−1 for individuals aged ≥1 year, with carbohydrates providing 45–65% of total daily energy intake (Slavin and Engstrom, Reference Slavin and Engstrom2024). In this context, the investigated brown seaweeds may serve as valuable complementary ingredients in balanced diets by providing moderate carbohydrate levels together with biologically active polysaccharides. Overall, the comparatively high carbohydrate contents, coupled with the presence of nutritionally important polysaccharides, such as alginate, laminarin, and fucoidan, highlight the potential of these brown seaweeds as functional food ingredients with both nutritional and health-promoting properties.
Moisture and dry matter content
The moisture content of the studied brown seaweeds ranged from 9.76% in S. plagiophyllum to 10.40% in T. decurrens, with corresponding dry matter values exceeding 89% across all samples (Table 1). The relatively low moisture content observed in S. plagiophyllum is advantageous, as it contributes to longer shelf life, better preservation, and higher nutrient concentration on a DW basis. The moisture levels recorded in this study are consistent with those reported for other brown seaweeds, such as Padina boergesenii and Sargassum linearifolium (Choudhary et al., Reference Choudhary, Khandwal, Gupta, Patel and Mishra2023), confirming that the analysed species exhibit moisture characteristics typical of processed and dried seaweeds. The high dry matter content observed across all samples further indicates their suitability for long-term storage, industrial processing, and incorporation into various food and nutraceutical formulations.
Ash and fibre content
Crude ash content, determined as the inorganic residue remaining after incineration at 600 °C, varied among the analysed brown seaweed species. T. ornata exhibited the highest ash content (16.41%), followed by S. plagiophyllum (16.15%) and T. decurrens (14.17%) (Table 1). These values indicate a substantial accumulation of mineral constituents and are consistent with the generally high ash contents reported for brown seaweeds (Puri et al., Reference Puri, Hu and Naterer2024). Premarathna et al. (Reference Premarathna, Tuvikene, Fernando, Adhikari, Perera, Ranahewa, Howlader, Wangchuk, Jayasooriya and Rajapakse2022) reported lower ash contents for Sargassum ilicifolium (13.15%) and Padina antillarum (5.26%), suggesting that the species investigated in the present study possess comparatively higher mineral reserves. Such variations are commonly attributed to species-specific characteristics, geographical location, seawater mineral composition, seasonal growth stage, and environmental conditions. The relatively higher ash contents observed in T. ornata and S. plagiophyllum suggest that these species may serve as valuable dietary sources of essential minerals. In comparison, the ash content of most terrestrial vegetables generally ranges between 5 and 10 g/100 g DW (Rupérez, Reference Rupérez2002), further highlighting the superior mineral richness of the investigated brown seaweeds and their potential application as ingredients in functional foods and marine-derived mineral supplements.
Crude fibre content also differed among the species, with T. ornata showing the highest value (9.40 g/100 g DW), followed by T. decurrens (7.94 g/100 g DW) and S. plagiophyllum (6.12 g/100 g DW). Although direct comparison is limited because the present study determined crude fibre rather than total dietary fibre, the observed values fall within the range reported for edible seaweeds, including Gelidium amansii (11.6%) and Hizikia fusiforme (4.2%) (Jang et al., Reference Jang, Cho, Jeong and Kim2012). These findings are also consistent with recent nutritional assessments highlighting brown seaweeds as valuable dietary fibre sources, although fibre content varies considerably depending on species, environmental conditions, and the analytical method employed (Silva et al., Reference Silva, Soares, Carpena, Fernandes, Chamorro, Delerue-Matos, Barroso and Prieto2026). Dietary fibre plays a crucial role in maintaining gastrointestinal health, promoting digestion, regulating serum cholesterol, and supporting metabolic health (Fu et al., Reference Fu, Zheng, Gao and Xu2022). Moreover, the structurally diverse polysaccharides present in brown seaweeds confer functional and bioactive properties that are not typically found in terrestrial plant fibres, further enhancing their nutritional value (Shannon and Abu-Ghannam, Reference Shannon and Abu-Ghannam2019). Regular consumption of fibre-rich seaweeds may also support appetite regulation and contribute to meeting the recommended dietary fibre intake of 25–30 g day−1 for adults (World Health Organization, 2023). Collectively, the appreciable crude fibre content observed in the studied seaweeds, together with the unique functional characteristics of marine dietary fibres, supports their potential incorporation into functional foods and health-promoting dietary formulations.
Lipid and cholesterol content
Brown seaweeds are widely regarded as low-lipid foods, a characteristic that contributes to their increasing recognition as heart-healthy dietary ingredients (Gnayem et al., Reference Gnayem, Unis, Gnaim, Israel, Gnaim and Golberg2025). Consistent with this general trend, all three species analysed in the present study exhibited low lipid content, with T. ornata recording the highest level (1.95 g/100 g DW), followed by T. decurrens (1.60 g/100 g DW) and S. plagiophyllum (1.02 g/100 g DW). These values are comparable to lipid concentrations reported for other edible brown seaweeds, including Saccharina japonica (1.6%) and Undaria pinnatifida (1.8%) (Jang et al., Reference Jang, Cho, Jeong and Kim2012). Recent reviews have similarly recognized that brown seaweeds generally possess low lipid contents, although considerable interspecific and seasonal variation may occur, with some species accumulating substantially higher lipid levels under specific environmental conditions (Alloyarova et al., Reference Alloyarova, Kolotova and Derkach2024). Although present in relatively low quantities, lipids remain nutritionally and technologically important, contributing to the texture, flavour, and aroma of food products while supplying essential FAs (Food and Agriculture Organization of the United Nations (FAO), 2010). Therefore, the low lipid content observed in the present study, together with the favourable FA composition described in the subsequent section, enhances the nutritional value of these seaweeds by providing essential lipids without substantially increasing energy or saturated fat intake, thereby supporting their potential use as healthy functional food ingredients.
Cholesterol levels were very low across all species, with S. plagiophyllum containing 0.22 mg/100 g DW, T. ornata 0.18 mg/100 g DW, and T. decurrens 0.14 mg/100 g DW. This co-occurrence of low lipid and minimal cholesterol content highlights the nutritional advantages of these seaweeds and suggests their potential use in low-fat, cholesterol-free food formulations aimed at promoting cardiovascular health. This nutritional relevance is further highlighted by evidence that dietary cholesterol intake often coincides with higher saturated fat consumption, which is well documented to increase low-density lipoprotein (LDL) cholesterol and elevate cardiovascular disease risk (Soliman, Reference Soliman2018). Consequently, seaweeds with lesser lipid and cholesterol contents may offer an inherent dietary advantage in mitigating cardiovascular risk.
FA composition
Principal component analysis
PCA was applied to the FA profile dataset to assess the patterns and identify the major FAs that contribute to differences among the three brown seaweed species (S. plagiophyllum, T. ornata, and T. decurrens). The PCA demonstrated strong dimensional reduction, with PC1 explaining 76.12% of the total variance and PC2 accounting for an additional 23.72%, resulting in a cumulative 99.84% variance captured by the first two components (Figure 2a), indicating minimal information loss. The PCA revealed clear and distinct clustering among the three species, indicating species-specific FA signatures. Hierarchical clustering and heatmap analysis corroborated the PCA results, showing clear species-specific clustering of samples and grouping of FAs into saturated (SFA), monounsaturated (MUFA), and polyunsaturated (PUFA) classes (Figure 2b). The sample clustering observed in the PCA of saturated and unsaturated fatty acids reflects underlying differences in individual FA composition among the three brown seaweeds (Figure 3a and 3b). SFAs, including C14:0, C17:0, and C22:0, showed strong positive loadings on PC1 and contributed substantially to the separation of S. plagiophyllum and T. ornata. In contrast, C12:0 was more strongly associated with PC2, contributing to the distinct positioning of T. decurrens (Figure 3a). Similarly, in the case of unsaturated FAs, arachidonic acid (ARA) was primarily associated with the separation of T. decurrens, whereas docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) were associated with S. plagiophyllum and T. ornata, respectively (Figure 3b).
Multivariate analysis of fatty acid profiles in brown seaweeds. (a) Principal component analysis (PCA) score plot based on all identified fatty acids, showing clear separation among S. plagiophyllum (SP), T. ornata (TO), and T. decurrens (TD) along PC1 (76.12%) and PC2 (23.72%). (b) Hierarchical clustering heatmap of fatty acid composition across the three seaweed species, with rows representing individual fatty acids and columns representing samples. Data are z-score normalized, and colours indicate relative abundance (green, higher; red, lower). Fatty acids are grouped into saturated (SFA), monounsaturated (MUFA), and polyunsaturated (PUFA) classes, and dendrograms reflect similarity patterns among both fatty acids and seaweed species.
Figure 2 Long description
The scatter plot shows principal component analysis of fatty acids in seaweeds, with PC1 at 76.12 percent and PC2 at 23.72 percent. Samples SP1, SP2, SP3, TO1, TO2, TO3, TD1, TD2 and TD3 are plotted, showing separation among seaweed types. The heat map displays fatty acid composition across seaweed species, with rows for fatty acids like C14:1n-7, C14:0, C20:5n-3, C20:4n-6, C18:1n-9, C22:6n-3, C17:0 and C22:0. Columns represent samples. Colors indicate relative abundance, with green for higher and red for lower values. The legend shows a gradient from plus one to minus one. Fatty acids are grouped into saturated, monounsaturated and polyunsaturated classes, with dendrograms showing similarity patterns among fatty acids and seaweed species.
Principal component analysis (PCA) biplots illustrating the distribution of saturated and unsaturated fatty acids in brown seaweeds. (a) PCA biplot of saturated fatty acids showing sample clustering and the contribution of individual fatty acids to separation along PC1 (88.64%) and PC2 (11.35%). (b) PCA biplot of unsaturated fatty acids, highlighting the influence of major MUFAs and PUFAs on sample discrimination along PC1 (66.31%) and PC2 (33.49%). Each point represents biological replicates of S. plagiophyllum (SP), T. ornata (TO), and T. decurrens (TD), while red arrows denote fatty acid loading vectors.
Figure 3 Long description
A scatter biplot titled, Saturated fatty acids. The x-axis is labeled, PC1 (88.64 percent), with tick labels at minus 0.2, 0.0 and 0.2. The y-axis is labeled, PC2 (11.35 percent), with tick labels at minus 0.25, 0.0 and 0.25. Nine points are labeled SP1, SP2, SP3, TO1, TO2, TO3, TD1, TD2 and TD3. SP1, SP2 and SP3 are plotted at positive PC1 and positive PC2. TO1, TO2 and TO3 are plotted at negative PC1, with TO1 at negative PC2 and TO2 and TO3 near PC2 equals 0. TD1 and TD3 are plotted at positive PC1 and negative PC2 and TD2 is plotted at positive PC1 and near PC2 equals 0. Four arrow vectors start near the origin and are labeled C14, C17, C22 and C12. C14, C17 and C22 point toward positive PC1 and positive PC2. C12 points toward positive PC1 and negative PC2. The image B showing a scatter biplot titled, Unsaturated fatty acids. The x-axis is labeled, PC1 (66.31 percent), with tick labels at minus 0.6, minus 0.3, 0.0, 0.3 and 0.6. The y-axis is labeled, PC2 (33.49 percent), with tick labels at minus 0.8, minus 0.4, 0.0, 0.4 and 0.8. Nine points are labeled SP1, SP2, SP3, TO1, TO2, TO3, TD1, TD2 and TD3. TD1, TD2 and TD3 are plotted at negative PC1 and positive PC2. SP1 and SP2 are plotted at negative PC1 and negative PC2 and SP3 is plotted at negative PC1 and near PC2 equals 0. TO1, TO2 and TO3 are plotted at positive PC1 and near PC2 equals 0. Seven arrow vectors start near the origin and are labeled ARA, C18:1n-9, DHA, C14:1n-7, C24:1, EPA and C20:4n-6. ARA and C18:1n-9 point toward negative PC1 and positive PC2. DHA points toward negative PC1 and negative PC2. C14:1n-7, C24:1, EPA and C20:4n-6 point toward positive PC1, with EPA and C20:4n-6 also pointing toward positive PC2.
SFAs and unsaturated FAs
Among the SFAs, lauric acid (C12:0) and behenic acid (C22:0) were predominant in all three species. S. plagiophyllum recorded the highest total SFA content (64.21%), followed by T. decurrens (61.70%) and T. ornata (51.66%). These levels are comparable to those reported for other brown seaweeds, such as Dictyota dichotoma (61.64%) and Padina tetrastromatica (60.53%) described by Dashtaki et al. (Reference Dashtaki, Esteki, Mehdinia and Simal-Gandara2025), indicating that SFAs constitute a major fraction of FAs in brown seaweeds. However, the relatively lower SFA proportion observed in T. ornata suggests a more balanced and nutritionally favourable lipid composition. MUFAs were represented mainly by myristoleic acid (C14:1n-7) and oleic acid (C18:1n-9). T. decurrens had the highest MUFA content (5.90%), followed by S. plagiophyllum (5.52%) and T. ornata (5.21%), consistent with values reported in other edible seaweeds such as Halimeda opuntia and Caulerpa racemosa (Premarathna et al., Reference Premarathna, Tuvikene, Fernando, Adhikari, Perera, Ranahewa, Howlader, Wangchuk, Jayasooriya and Rajapakse2022).
Individual SFAs exert distinct effects on plasma lipoprotein cholesterol levels. Lauric (C12:0), myristic (C14:0), and palmitic (C16:0) acids increase LDL cholesterol, whereas stearic acid (C18:0) has little to no impact (Food and Agriculture Organization of the United Nations (FAO), 2010). Consequently, replacing SFAs (C12:0–C16:0) with MUFAs can lower LDL cholesterol and improve the total-to-high-density lipoprotein cholesterol ratio (Food and Agriculture Organization of the United Nations (FAO), 2010). MUFA-rich diets have also been shown to reduce insulin requirements and lower plasma glucose and insulin levels in individuals with type 2 diabetes, compared with high-SFA or low-fat, high-carbohydrate diets (López-Miranda et al., Reference López-Miranda, Pérez-Martínez, Pérez-Jiménez and Chow2006). Despite this evidence, major health authorities, including the Institute of Medicine, the United States Department of Agriculture, the European Food Safety Authority, and the Academy of Nutrition and Dietetics (formerly the American Dietetic Association), do not provide specific recommendations for MUFA intake. By contrast, the Academy of Nutrition and Dietetics and the Canadian Dietetic Association recommend that MUFAs contribute less than 20% of total daily energy intake, while the American Heart Association sets an upper limit of 20% in its guidelines (Schwingshackl and Hoffmann, Reference Schwingshackl and Hoffmann2014). The PUFA fraction was dominated by eicosadienoic acid (20:2n-6), ARA (20:4n-6), EPA (20:5n-3), and DHA (22:6n-3). Total PUFA content was highest in T. ornata (43.12%), followed by T. decurrens (32.39%) and S. plagiophyllum (29.25%). These values are comparable to those reported for Cystoseira humilis (47.67%), Fucus guiryi (41.05%), and Sacchorhiza polyschides (26.12%) by Belattmania et al. (Reference Belattmania, Engelen, Pereira, Serrão, Custódio, Varela, Zrid, Reani and Sabour2018), confirming the high degree of unsaturation typical of brown seaweeds. The PUFA composition pattern, dominated by long-chain n-3 and n-6 FAs such as EPA and ARA, aligns with previous findings for various Phaeophyceae species (Belattmania et al., Reference Belattmania, Engelen, Pereira, Serrão, Custódio, Varela, Zrid, Reani and Sabour2018). The predominance of unsaturated FAs observed in the present study is also consistent with reports for other edible brown seaweeds, including Ascophyllum nodosum, Fucus spiralis, and Bifurcaria bifurcata, where MUFAs and PUFAs constituted a substantial proportion of the total lipid fraction (Silva et al., Reference Silva, Soares, Carpena, Fernandes, Chamorro, Delerue-Matos, Barroso and Prieto2026). Both F. guiryi and S. polyschides exhibited significant levels of EPA and DHA, supporting the notion that brown seaweeds from diverse geographic regions share similar lipid biosynthetic pathways (Belattmania et al., Reference Belattmania, Engelen, Pereira, Serrão, Custódio, Varela, Zrid, Reani and Sabour2018). The ω-6 (n-6) FAs are more abundant than ω-3 (n-3) in all species, with Σn-6 ranging from 27.37% (S. plagiophyllum) to 40.59% (T. ornata), while Σn-3 ranged from 1.70% to 2.53%.
From a nutritional perspective, long-chain PUFAs such as ARA, EPA, and DHA are physiologically important because mammals have only a limited capacity to synthesize these FAs, making dietary intake essential for maintaining optimal health. DHA is a major structural component of neuronal membrane phospholipids and plays a critical role in neural development, immune function, and cell signaling, while EPA and DHA are widely recognized for their cardioprotective, anti-inflammatory, and neuroprotective properties (Djuricic and Calder, Reference Djuricic and Calder2021). ARA serves as a precursor of prostaglandins and other eicosanoids involved in immune modulation, blood clotting, and stress responses. However, an imbalance in the dietary intake of n-6 and n-3 FAs, particularly excessive n-6 intake, has been associated with an increased risk of chronic diseases, including cardiovascular disorders, certain cancers, and diabetes, whereas n-3 FAs exhibit anti-inflammatory and anti-oxidant activities (Shanab et al., Reference Shanab, Hafez and Fouad2018). Therefore, maintaining an appropriate dietary n-6/n-3 ratio is considered important for promoting long-term health. The acceptable macronutrient distribution range for total PUFA, encompassing both n-6 and n-3 FAs, is estimated to be 6–11% of total energy intake, while the minimum intake required to prevent deficiency is approximately 2.5–3.5% of total energy (Food and Agriculture Organization of the United Nations (FAO), 2010). Furthermore, FAO recommends a daily intake of 0.25 g of combined EPA and DHA for healthy adults, increasing to 0.30 g day−1, including at least 0.20 g day−1 of DHA, for pregnant and lactating women to support foetal and infant development (Food and Agriculture Organization of the United Nations (FAO), 2010). Given the increasing demand for sustainable alternative sources of long-chain ω-3 FAs, identifying marine resources rich in these bioactive lipids is of considerable nutritional interest. In this context, the high PUFA content observed in T. ornata, together with the appreciable levels present in T. decurrens and S. plagiophyllum, highlights the potential of these brown seaweeds as promising sustainable sources of health-promoting FAs for functional food and nutraceutical applications. These findings are consistent with previous reports highlighting the nutritional significance of marine-derived EPA and DHA and further support the potential of brown seaweeds as complementary and sustainable sources of health-beneficial long-chain n-3 FAs (Mohdeb et al., Reference Mohdeb, Boutaoui, Merabet, Acila, Roula, Roula and Kara2025).
Nutritional indices
Nutritional quality indices indicated favourable lipid profiles for all three brown seaweed species. The AI and TI, which assess the potential impact of dietary lipids on cardiovascular health, varied among the three brown seaweed species. AI was highest in S. plagiophyllum (0.92) and lowest in T. decurrens (0.78), with T. ornata showing an intermediate value (0.87). In contrast, TI was highest in T. ornata (0.16), followed by S. plagiophyllum (0.10) and T. decurrens (0.06) (Figure 4a, Table 2). Lower AI and TI values are desirable, as they denote a reduced risk of atheroma and thrombosis (Ulbricht and Southgate, Reference Ulbricht and Southgate1991). The AI reflects the balance between atherogenic FAs (primarily lauric, myristic, and palmitic acids) and anti-atherogenic unsaturated FAs, whereas TI estimates the tendency of dietary lipids to promote thrombus formation by considering the balance between pro- and anti-thrombogenic FAs (Khalili Tilami and Kouřimská, Reference Khalili Tilami and Kouřimská2022).
Comparative analysis of amino acid- and lipid-based nutritional indices in the three brown seaweeds. (a) Lipid-associated nutritional indices comprising ΣPUFA/ΣSFA, AI, TI, and h/H ratio for the same species. (b) Ratios derived from essential and non-essential amino acids, including TEAA/TAA, TNEAA/TAA, TEAA/TNEAA, and TSCAA in S. plagiophyllum, T. ornata, and T. decurrens. Data are presented as mean ± SD. Samples were analysed in triplicate (n = 3). Different lowercase letters above bars indicate significant differences among species at p < 0.05.
Figure 4 Long description
A grouped bar graph titled, Lipid Quality Indices. The x axis lists, summation PUFA slash summation S F A, A I, T I, h slash H. The y axis label is, Nutritional indices value, with tick labels from 0.0 to 2.0. For summation P U F A slash summation S F A, the plotted values are 0.46 for S. plagiophyllum, 0.83 for T. ornata and 0.53 for T. decurrens. For A I, the plotted values are 0.92 for S. plagiophyllum, 0.87 for T. ornata and 0.78 for T. decurrens. For T I, the plotted values are 0.10 for S. plagiophyllum, 0.16 for T. ornata and 0.06 for T. decurrens. For h slash H, the plotted values are 1.38 for S. plagiophyllum, 1.79 for T. ornata and 1.51 for T. decurrens. The image B showing a grouped bar graph titled, Nutritional Health Indices. The x axis lists, T E A A slash T A A, N E A A slash T A A, T E A A slash N E A A, A A T E A A, T S C A A. The y axis label is, Nutritional indices value, with tick labels from 0.0 to 14.0. For T E A A slash T A A, the plotted values are 0.22 for S. plagiophyllum, 0.18 for T. ornata and 0.20 for T. decurrens. For N E A A slash T A A, the plotted values are 0.78 for S. plagiophyllum, 0.82 for T. ornata and 0.80 for T. decurrens. For T E A A slash N E A A, the plotted values are 0.28 for S. plagiophyllum, 0.22 for T. ornata and 0.25 for T. decurrens. For A A T E A A, the plotted values are 2.0 for S. plagiophyllum, 2.5 for T. ornata and 2.2 for T. decurrens. For T S C A A, the plotted values are 5.0 for S. plagiophyllum, 4.0 for T. ornata and 12.0 for T. decurrens.
Fatty acid composition (% total fatty acids) of seaweed species collected in March 2025
Table 2 Long description
Percent of total fatty acids is reported for three seaweed species, S. plagiophyllum, T. ornata, and T. decurrens, with values shown as mean plus or minus standard deviation and superscript letters. For saturated fatty acids, 12:0 is 22.84b, 22.02c, and 23.79a; 14:0 is 2.27b, 5.01a, and 1.52c; 17:0 is 17.16a, 13.85c, and 16.46b; and 22:0 is 21.94a, 10.78c, and 19.93b for S. plagiophyllum, T. ornata, and T. decurrens, respectively. The saturated fatty acids total is 64.21a for S. plagiophyllum, 51.66c for T. ornata, and 61.70b for T. decurrens. For monounsaturated fatty acids, 14:1 n minus 7 is 4.22c, 4.52a, and 4.42b, and 18:1 n minus 9 is 1.30b, 0.69c, and 1.48a; the monounsaturated fatty acids total is 5.52b, 5.21c, and 5.90a. For polyunsaturated fatty acids, 20:2 n minus 6 is 27.19c, 40.44a, and 30.30b; 20:4 n minus 6 is 0.18b, 0.15b, and 0.39a; 20:5 n minus 3 is 0.98b, 1.74a, and 0.95b; and 22:6 n minus 3 is 0.90a, 0.79b, and 0.75b; the polyunsaturated fatty acids total is 29.25c, 43.12a, and 32.39b. Totals for n minus 3 are 1.88b, 2.53a, and 1.70c, and totals for n minus 6 are 27.37c, 40.59a, and 30.69b; DHA plus EPA is 1.88b, 2.53a, and 1.70c. The polyunsaturated to saturated ratio is 0.46c, 0.83a, and 0.53b, and the indices listed are AI at 0.92a, 0.87b, and 0.78c, TI at 0.10b, 0.16a, and 0.06c, and h over H at 1.38c, 1.79a, and 1.51b.
Data are presented as mean ± SD of three independent replicates (n = 3). Means followed by different superscript letters (a–c) within the same row indicate significant differences (p < 0.05).
The AI values recorded in this study are comparable to those reported for Cystoseira indica (0.66) and Sargassum fusiforme (0.94), while the TI values are similar to those of Dictyota dichotoma (0.09) and Laminaria ochroleuca (1.06) (Chen and Liu, Reference Chen and Liu2020). Among the studied species, T. decurrens exhibited the lowest AI and TI values, indicating a more favourable FA composition with reduced atherogenic and thrombogenic potential. These findings are consistent with previous reports showing that brown seaweeds generally possess favourable nutritional indices owing to their high proportion of unsaturated FAs (Soares et al., Reference Soares, Sousa, Machado, Vieira, Carvalho, Ramalhosa, Morais, Correia, Oliva-Teles, Domingues and Delerue-Matos2021; Silva et al., Reference Silva, Soares, Carpena, Fernandes, Chamorro, Delerue-Matos, Barroso and Prieto2026), further supporting the potential of T. decurrens as a source of heart-healthy lipids. When compared with common dietary foods, the AI values of the studied seaweeds fall within the range reported for fish (0.21–1.41) and meat (0.165–1.32) and are considerably lower than those reported for dairy products (1.42–5.13), which are generally associated with a greater atherogenic potential (Chen and Liu, Reference Chen and Liu2020). Likewise, the TI values are comparable to those reported for crops (0.139–0.56), fish (0.14–0.87), and meat (0.288–1.694), while remaining substantially lower than the upper values reported for dairy products (0.39–5.04), further emphasizing the favourable nutritional quality of these brown seaweeds (Chen and Liu, Reference Chen and Liu2020).
The h/H ratio ranged from 1.38 in S. plagiophyllum to 1.79 in T. ornata, further indicating a favourable lipid balance, particularly in T. ornata, which displayed the highest value (Figure 4a, Table 2). A higher h/H ratio is associated with improved serum lipid profiles and enhanced cardiovascular protection. When compared with common foods, the h/H values of these seaweeds are similar to those found in meat (1.27–2.786), and for T. ornata, are close to the lower range seen in shellfish (1.73–4.75) and fish (1.54–4.83), which are known for their heart-healthy fat profiles (Chen and Liu, Reference Chen and Liu2020).
The h/H ratio represents the balance between hypocholesterolemic FAs (mainly cis-oleic acid and PUFAs) and hypercholesterolemic FAs, with higher values indicating a more favourable lipid profile for cardiovascular health (Chen and Liu, Reference Chen and Liu2020).
In addition, all three seaweeds have higher h/H values than dairy products (0.32–1.29), which are generally linked with less favourable effects on cholesterol (Chen and Liu, Reference Chen and Liu2020). The PUFA/SFA ratio is a key nutritional index used to evaluate the cardiovascular impact of dietary lipids, as higher values are generally associated with reduced serum LDL cholesterol and improved lipid metabolism (Chen and Liu, Reference Chen and Liu2020). In this study, the ratio varied among the species, with T. ornata showing the highest value (0.83), followed by T. decurrens (0.53) and S. plagiophyllum (0.46). A ratio of ≥0.45 is recommended to support a favourable balance between polyunsaturated and saturated fats (Vijay et al., Reference Vijay, Chakraborty and Pai2025), and all three seaweeds met or exceeded this threshold, particularly T. ornata. These values fall within the typical range reported for seaweeds (0.42–2.12) and are comparable to Padina tetrastromatica (0.85) (Kumar et al., Reference Kumar, Sahoo and Levine2015), whereas Sargassum pallidum shows a much lower ratio (0.20) (Chen et al., Reference Chen, Xu, Liu, Zhang, Liu and Guan2016).
Importantly, the PUFA/SFA ratios observed here were higher than those reported for several other dietary sources, including meat (0.11–0.42), fish (0.50–1.62), shellfish (0.20–2.10), and dairy products (0.02–0.175) (Vijay et al., Reference Vijay, Chakraborty and Pai2025), indicating a comparatively favourable lipid profile. The elevated PUFA/SFA ratio in T. ornata suggests superior lipid quality with potential cardiovascular benefits, while T. decurrens and S. plagiophyllum also demonstrate nutritionally advantageous FA compositions. These findings support the potential application of these brown seaweeds as functional food ingredients or nutraceutical components aimed at cardiovascular health.
Amino acid profile and nutritional significance
The EAA composition of the three brown seaweeds differed significantly (p < 0.05), with T. decurrens exhibiting the highest TEAA content (61.55 g/100 g protein), followed by T. ornata (60.50 g/100 g protein) and S. plagiophyllum (56.72 g/100 g protein) (Table 3, Figure 4b). Several nutritionally relevant amino acids were present at notable levels, including phenylalanine in S. plagiophyllum (12.10 g/100 g protein), arginine in T. ornata (13.57 g/100 g protein), and valine in T. decurrens (8.46 g/100 g protein). Lysine was also highest in T. decurrens (4.92 g/100 g protein) compared with the other species. EAAs are indispensable nutrients that function not only in protein synthesis but also as precursors for coenzymes, hormones, nucleic acids, and numerous other biomolecules involved in normal physiological processes (Paoletti et al., Reference Paoletti, Courtney-Martin and Elango2024). When considered against adult indispensable amino acid requirements (e.g., lysine: 30 mg kg−1 day−1; leucine: 39 mg kg−1 day−1; valine: 26 mg kg−1 day−1), the relatively high proportions of EAAs observed indicate that these seaweeds could contribute to meeting physiological amino acid demands (FAO/WHO/UNU, 2007), particularly within plant-based diets where EAA supply may be limiting. This favourable EAA composition suggests that the investigated brown seaweeds could improve the overall amino acid quality of plant-based diets when consumed alongside conventional plant protein sources, thereby contributing to a more balanced indispensable amino acid intake (Paoletti et al., Reference Paoletti, Courtney-Martin and Elango2024). Although the amino acids identified in these seaweeds are not unique to marine algae and are also found in terrestrial plants, their nutritional significance lies in their relatively balanced amino acid composition and appreciable levels of EAAs. In particular, the comparatively higher lysine content in T. decurrens, together with the abundance of phenylalanine, arginine, and valine across the studied species, highlights their potential to complement terrestrial plant proteins that are often limited in one or more EAAs. Collectively, these observations underscore the potential of these brown seaweeds as nutritionally valuable supplements.
Amino acid composition (g/100 g protein) of the selected brown seaweeds
Table 3 Long description
Values are amino acid composition in grams per 100 grams protein for three brown seaweeds, S. plagiophyllum, Turbinaria ornata, and Turbinaria decurrens, reported as mean plus or minus standard deviation with letter superscripts. Essential amino acids list Thr, Val, His, Lys, Met, Leu, Ileu, Phe, and Arg, plus the total essential amino acids, TEAA. For TEAA, S. plagiophyllum is 56.72a plus or minus 0.61, Turbinaria ornata is 60.50b plus or minus 0.61, and Turbinaria decurrens is 61.55a plus or minus 0.46. Selected essential amino acids include Lys at 0.56c plus or minus 0.04 for S. plagiophyllum, 2.50b plus or minus 0.03 for Turbinaria ornata, and 4.92a plus or minus 0.06 for Turbinaria decurrens, and Met at 3.88b plus or minus 0.03, 3.84b plus or minus 0.09, and 7.74a plus or minus 0.04, respectively. Non essential amino acids list Glu, Asp, Ser, Gly, Ala, Pro, Tyr, and Cys, plus the total non essential amino acids, TNEAA, which are 42.29a plus or minus 0.37 for S. plagiophyllum, 39.50b plus or minus 0.60 for Turbinaria ornata, and 38.45c plus or minus 0.21 for Turbinaria decurrens. Ratio rows report TEAA to TAA as 0.57b plus or minus 0.01, 0.61a plus or minus 0.01, and 0.62a plus or minus 0.01, and TEAA to TNEAA as 1.34c plus or minus 0.02, 1.53b plus or minus 0.03, and 1.60a plus or minus 0.02. Additional totals and ratios include TArAA at 19.87a plus or minus 0.12, 13.74b plus or minus 0.05, and 11.29c plus or minus 0.05, TSCAA at 5.54b plus or minus 0.23, 4.99c plus or minus 0.43, and 11.65a plus or minus 0.05, Arg to Lys at 15.32a plus or minus 1.09, 5.43b plus or minus 0.07, and 1.47c plus or minus 0.02, and Leu to Ile at 1.52b plus or minus 0.03, 1.59a plus or minus 0.03, and 1.33c plus or minus 0.01.
TEAA, total essential amino acids; TNEAA, total non-essential amino acids; TAA, total amino acids; TarAA, total aromatic amino acids (tryptophan was not determined); TSCAA, total sulphur containing amino acids (cysteine and methionine). Data were expressed as mean ± SD. Samples were analysed in triplicate (n = 3), and means followed by different superscripts (a–c) within the same row indicated significant differences (p < 0.05).
For non-essential amino acids, S. plagiophyllum recorded the highest TNEAA content (42.29 g/100 g protein), followed by T. ornata (39.50 g/100 g protein) and T. decurrens (38.45 g/100 g protein), with glycine being the most abundant at 10.76 g/100 g protein in T. ornata. In addition to their nutritional significance, the elevated levels of glutamic acid and aspartic acid are known to enhance the characteristic umami taste of seaweed and seafood (Stiger-Pouvreau et al., Reference Stiger-Pouvreau, Jégou, Cérantola, Guérard, Le Lann, Wiencke and Bischof2014). In this study, S. plagiophyllum contained the highest glutamic acid levels, while T. decurrens showed the greatest aspartic acid content. These species-specific variations indicate differing umami potentials, suggesting that all three seaweeds exhibit appreciable sensory attributes in addition to their nutritional value. Lysine is generally considered a limiting amino acid in most algal species, while cysteine is frequently low (Pereira et al., Reference Pereira, Cotas and Gonçalves2024).
The adult daily requirement for lysine is 30 mg kg−1 body weight day−1 (FAO/WHO/UNU, 2007), reflecting its importance in supporting synthesis and metabolic functions. However, in the present study, T. decurrens exhibited comparatively high concentrations of lysine (4.92 g/100 g For non-essential amino acids, S. plagiophyllum recorded the highest TNEAA content (42.29 g/100 g protein), followed by T. ornata (39.50 g/100 g protein) and T. decurrens (38.45 g/100 g protein), with glycine being the most abundant at 10.76 g/100 g protein in T. ornata. In addition to their nutritional significance, the elevated levels of glutamic acid and aspartic acid are known to enhance the characteristic umami taste of seaweed and seafood (Stiger-Pouvreau et al., Reference Stiger-Pouvreau, Jégou, Cérantola, Guérard, Le Lann, Wiencke and Bischof2014) and cysteine (3.91 g/100 g protein), indicating a more balanced amino acid composition relative to typical seaweed profiles and highlighting its potential to overcome the common lysine and sulphur amino acid limitations observed in algal proteins.
The TEAA/TNEAA ratio ranged from 1.34 in S. plagiophyllum to 1.60 in T. decurrens, confirming a nutritionally balanced amino acid distribution. TArAA were highest in S. plagiophyllum (19.87 g/100 g protein), primarily due to its elevated phenylalanine and tyrosine levels, while TSCAA were significantly higher in T. decurrens (11.65 g/100 g protein), highlighting its potential as a rich source of methionine and cysteine. Sulphur-containing amino acids play vital roles in maintaining cellular integrity by regulating redox balance and supporting detoxification of reactive species, with methionine being essential and cysteine derived from methionine metabolism (Townsend et al., Reference Townsend, Tew and Tapiero2004).
Current recommendations specify daily intakes of 10 mg kg−1 body weight for methionine and 4 mg kg−1 for cysteine and a combined requirement of 15 mg kg−1 day−1 for total sulphur amino acids (FAO/WHO/UNU, 2007). Consequently, T. decurrens could serve as an effective complement to methionine-deficient legume proteins in blended plant-based formulations. Based on the comparative profile, T. decurrens demonstrated a superior amino acid balance and higher concentrations of essential and sulphur-containing amino acids, indicating greater nutritional quality among the analysed seaweed species.
Mineral composition
The mineral composition of the three brown algal species showed significant variations (p < 0.05) among both macro- and micro-minerals (Table 4). Potassium (K) was the most abundant macro-element across all species, followed by calcium (Ca), magnesium (Mg), and sodium (Na). T. ornata exhibited the highest concentrations of Na (1333.21 mg kg−1), Ca (3265.42 mg kg−1), and K (11643.61 mg kg−1), whereas S. plagiophyllum showed comparatively lower levels of these elements. Conversely, S. plagiophyllum recorded the highest Mg content (7160.92 mg kg−1), exceeding those of T. ornata (4793.31 mg kg−1) and T. decurrens (4510.63 mg kg−1). The dominance of K among macronutrients aligns with previous reports on Phaeophyceae (Meng et al., Reference Meng, Mu, Sun and Garcia-Vaquero2022), reflecting its central role in growth and metabolic functions of plants and seaweeds (Barot et al., Reference Barot, Nirmal Kumar and Kumar2019). A similar predominance of potassium among the major minerals has recently been reported in brown seaweeds including Ascophyllum nodosum, Fucus spiralis, and Bifurcaria bifurcata (Silva et al., Reference Silva, Soares, Carpena, Fernandes, Chamorro, Delerue-Matos, Barroso and Prieto2026), suggesting that potassium accumulation is a characteristic feature of Phaeophyceae. From a nutritional standpoint, potassium is relevant not only for algal metabolism but also for human health. The WHO recommends an average potassium intake of 3.5 g day−1 from food to help lower blood pressure and reduce the risk of cardiovascular disease, stroke, and coronary heart disease in adults (World Health Organization (WHO), 2012). Similarly, the recommended average intake is approximately 1200 mg day−1 for calcium and 210–320 mg day−1 for magnesium to support healthy bone and dental function (Pai et al., Reference Pai, Chakraborty, Vijay and Chakraborty2025).
Mineral compositions (mg kg−1 dry tissue) of selected brown seaweeds
Table 4 Long description
Mineral concentrations in milligrams per kilogram dry tissue are listed for three brown seaweeds, S. plagiophyllum, T. ornata, and T. decurrens, with mean values and standard deviations. Macro minerals: Na is 849.16c plus or minus 0.06 for S. plagiophyllum, 1333.21a plus or minus 0.05 for T. ornata, and 879.34b plus or minus 0.19 for T. decurrens. Ca is 3038.09c plus or minus 0.21, 3265.42a plus or minus 0.21, and 3196.34b plus or minus 0.06, respectively. K is 9273.50c plus or minus 0.05, 11643.61a plus or minus 0.03, and 9799.50b plus or minus 0.07, respectively. Mg is 7160.92a plus or minus 0.07 for S. plagiophyllum, 4793.31b plus or minus 0.03 for T. ornata, and 4510.63c plus or minus 0.12 for T. decurrens. Micro minerals: Zn is 31.76c plus or minus 0.08, 169.83a plus or minus 0.08, and 123.82b plus or minus 0.04, respectively. Mn is 20.70c plus or minus 0.03 for S. plagiophyllum, 34.81b plus or minus 0.10 for T. ornata, and 105.19a plus or minus 0.06 for T. decurrens. Cu is 5.82c plus or minus 0.10, 19.22a plus or minus 0.09, and 12.04b plus or minus 0.04, respectively. Fe is 59.49c plus or minus 0.07, 241.31a plus or minus 0.08, and 230.33b plus or minus 0.05, respectively. Se is listed as BDL for all three seaweeds, and each mean includes a superscript letter shown next to the value.
Data were expressed as mean ± SD. Samples were analysed in triplicates (n = 3), and means followed by different superscripts (a–c) within the same row indicated significant differences (p < 0.05).
Among the trace elements, Fe exhibited the highest concentration, followed by Mn, Zn, and Cu. T. ornata had the highest Fe content (241.31 mg kg−1), closely followed by T. decurrens (230.33 mg kg−1), while S. plagiophyllum contained the lowest (59.49 mg kg−1). The predominance of iron among the trace elements agrees with the observations of Silva et al. (Reference Silva, Soares, Carpena, Fernandes, Chamorro, Delerue-Matos, Barroso and Prieto2026), who also reported iron as one of the major micronutrients in edible brown seaweeds. Such high iron levels further support the nutritional importance of these species as potential dietary sources of essential trace minerals. Iron is an essential micronutrient required for oxygen transport, erythropoiesis, and cellular energy metabolism (MacGregor et al., Reference MacGregor, Conway and Henderson2024). The WHO recommends a minimum daily iron intake of 1.8 mg to support normal physiological functions (Pai et al., Reference Pai, Chakraborty, Vijay and Chakraborty2025). Similarly, Mn content was markedly higher in T. decurrens (105.19 mg kg−1) than in T. ornata (34.81 mg kg−1) and S. plagiophyllum (20.70 mg kg−1). T. ornata also displayed the highest Zn (169.83 mg kg−1) and Cu (19.22 mg kg−1) concentrations, indicating efficient trace metal accumulation capacity. Zinc is essential for immune function, DNA synthesis, and wound healing (Wessels et al., Reference Wessels, Maywald and Rink2017), whereas copper functions as a co-factor for numerous enzymes involved in connective tissue formation and anti-oxidant defence (An et al., Reference An, Li, Huang, Chen, Shan and Zhang2022). The WHO recommends a daily intake of 3–5 mg of manganese, an essential trace element that functions as a co-factor for enzymes involved in metabolism, anti-oxidant defence, and bone formation (Pai et al., Reference Pai, Chakraborty, Vijay and Chakraborty2025).
Compared to terrestrial plant-based foods such as nuts, the mineral contents of the studied brown seaweeds are markedly higher. For instance, Na in the seaweeds (849–1333 mg kg−1) exceeds the range reported for common nuts such as almonds (1.0 mg/100 g) and cashews (12.0 mg/100 g). Similarly, the Ca and Mg levels in T. ornata (3265 and 4793 mg kg−1, respectively) are greater than those in walnuts (Ca: 61–98 mg/100 g; Mg: 158–201 mg/100 g) and hazelnuts (Ca: 84–114 mg/100 g; Mg: 140–163 mg/100 g). Micronutrient enrichment was also pronounced. The Fe content of T. ornata (241.31 mg kg−1, ≈24.1 mg/100 g) was several times higher than that reported for iron-rich nuts like pine nuts (5.53–6.64 mg/100 g) and almonds (3.71–6.21 mg/100 g). Similarly, the Zn levels in T. ornata (169.83 mg kg−1, ≈17.0 mg/100 g) surpass those found in most nuts (typically 1.5–6.7 mg/100 g) (Gonçalves et al., Reference Gonçalves, Pinto, Aires, Morais, Bacelar, Anjos, Ferreira-Cardoso, Oliveira, Vilela and Cosme2023). These comparisons indicate that brown seaweeds are richer sources of essential minerals than terrestrial nut species, emphasizing their potential as functional food ingredients or natural mineral supplements. Their high mineral density, coupled with low lipid content and additional bioactive compounds, further enhances their value in human nutrition and nutraceutical applications.
Conclusions
By assessing key nutritional attributes, this study identifies three edible Sargassaceae seaweeds as valuable marine resources with significant potential for improving human nutrition and health. The compositional analysis of S. plagiophyllum, T. ornata, and T. decurrens revealed favourable biochemical characteristics, characterized by high proportions of EAAs and distinct species-specific patterns of carbohydrate and mineral accumulation. Lipid profiling confirmed the characteristically low total lipid and cholesterol content of brown seaweeds, accompanied by FA compositions enriched in long-chain n-3 and n-6 PUFAs. Beneficial PUFA/SFA ratios, together with low AI and TI, particularly in T. decurrens and T. ornata, indicate a cardioprotective lipid profile that may support cardiovascular and metabolic health applications. The mineral composition demonstrated notable enrichment of macro- and micro-minerals, including potassium, calcium, magnesium, iron, zinc, manganese, and copper, often exceeding concentrations reported for commonly consumed terrestrial plant foods. The compositional characteristics align with FAO/WHO/UNU recommendations for high-quality plant-based proteins and essential micronutrients, supporting the feasibility of these seaweeds as sustainable, health-promoting food ingredients. The combined attributes – high-quality protein, beneficial lipid composition, dietary fibre, and mineral density – establish S. plagiophyllum, T. ornata, and T. decurrens as promising candidates for incorporation into functional foods, nutraceuticals, and plant-based formulations designed to improve cardiovascular and metabolic health, while contributing to nutritionally diverse and sustainable food systems. Integration of these seaweeds into human diets may enhance nutritional security and promote public health. Further research, including well-designed in vivo studies, is required to elucidate their pharmacological properties and therapeutic applications.
Acknowledgements
Research was supported by the Indian Council of Agricultural Research, Department of Agricultural Research and Education, Government of India. The authors also extend their sincere appreciation to the Director of ICAR-CMFRI and to the Department of Marine Biology, Cochin University of Science and Technology, for their support and facilitation of the research activities. Additional acknowledgement is extended to Mahatma Gandhi University, Kottayam, and DST-SAIF, Cochin, for providing essential data and analytical support.
Author contributions
A.M.G.: Writing-original draft, Visualization, Validation, Software, Methodology, Investigation, Formal analysis, Conceptualization. K.C.: Writing – original draft, Supervision, Resources, Formal analysis, Data curation, Conceptualization. A.P.V.: Statistical analysis, Visualization, Validation, Software, Methodology, Investigation, Formal analysis, Review and editing. A.H.G.: Formal analysis, Review and editing.
Declaration of interest
The authors affirm that there are no conflicts of interest, including financial, personal, or any other associations with individuals or organizations that might inappropriately affect or appear to affect the integrity of the current work.
Data availability statement
All data generated or examined in the course of this study are comprehensively presented within this published article.
Ethics and approach
This article does not involve any studies conducted on human participants or animals by any of the authors.
Funding statement
The authors sincerely acknowledge funding support from the ICAR Challenge Research Project titled “Development of high-value pharmacophores and nutraceutical products from marine macroalgae for human health management and combating lifestyle diseases” (Grant number ICAR-Challenge/216502). The senior author (A.M.G.) gratefully acknowledges the Innovation in Science Pursuit for Inspired Research (INSPIRE) programme of the Department of Science and Technology, New Delhi, India, for providing financial support (Fellowship ID: IF220045).
