The proximate composition, vitamin C, α-tocopherol, dietary fibers, minerals, fatty acid and amino acid profiles of three tropical edible seaweeds, Eucheuma cottonii (Rhodophyta), Caulerpa lentillifera (Chlorophyta) and Sargassum polycystum (Phaeophyta) were studied. The seaweeds were high in ash (37.15-46.19%) and dietary fibers (25.05-39.67%) and low in lipid content (0.29-1.11%) on dry weight (DW) basis. These seaweeds contained 12.01-15.53% macro-minerals (Na, K, Ca and Mg) and 7.53-71.53 mg.100 g −1 trace minerals (Fe, Zn, Cu, Se and I). The crude protein content of E. cottonii (9.76% DW) and C. lentillifera (10.41% DW) were higher than that of S. polycystum (5.4% DW), and protein chemical scores are between 20 and 67%. The PUFA content of E. cottonii was 51.55%, C. lentillifera 16.76% and S. polycystum 20.34%. Eicosapentaenoic acid (EPA), accounted for 24.98% of all fatty acids in E. cottonii. These seaweeds have significant vitamin C (∼35 mg.100 g −1 ) and α-tocopherol (5.85-11.29 mg.100 g −1 ) contents.

The antioxidant activity of eight edible species of Malaysian North Borneo seaweeds obtained from Sabah waters (Kudat, Tanjung Aru and Semporna) consisting of three red seaweeds (Eucheuma cottonii, E. spinosum and Halymenia durvillaei), two green seaweeds (Caulerpa lentillifera and C. racemosa) and three brown seaweeds (Dictyota dichotoma, Sargassum polycystum and Padina sp.) were determined. Methanol and diethyl ether were used as extraction solvent. The antioxidant activities were determined by two methods, TEAC (trolox equivalent antioxidant capacity) and FRAP (ferric reducing antioxidant power) assays. The total phenolic content of the extract was determined according to the Folin-Ciocalteu method and results were expressed as phloroglucinol equivalents. The methanolic extracts of green seaweeds, C. lentillifera and C. racemosa, and the brown seaweed, S. polycystum showed better radical-scavenging and reducing power ability, and higher phenolic content than the other seaweeds. The TEAC and FRAP assays showed positive and significantly high correlation (R 2 =0.89). There was a strong correlation (R 2 =0.96) between the reducing power and the total phenolic content of the seaweeds methanolic dry extracts. These seaweeds could be potential rich sources of natural antioxidants.

A study on the proximate composition, minerals, vitamins, carotenoids, amino acids, fatty acids profiles and some physicochemical properties of freeze dried Gracilaria changii was conducted. It was discovered that this seaweed was high in dietary fibre (64.74±0.82%), low in fat (0.30±0.02%) and Na/K ratio (0.12±0.02). The total amino acid content was 91.90±7.70% mainly essential amino acids (55.87±2.15mgg) which were comparable to FAO/WHO requirements. The fatty acid profiles were dominated by the polyunsaturated fatty acids particularly docosahexaenoic (48.36±6.76%) which led to low ω6/ω3, atherogenic, and thrombogenic index. The physicochemical properties of this seaweed namely the water holding and the swelling capacity were comparable to some commercial fibre rich products. This study suggested that G. changii could be potentially used as ingredients to improve nutritive value and texture of functional foods for human consumption.

This study was designed to investigate the comparative in vivo cardiovascular protective effects of red, green, and brown tropical seaweeds, namely, Kappaphycus alvarezii (or Eucheuma cottonii), Caulerpa lentillifera, and Sargassum polycystum, in rats fed on high-cholesterol/high-fat (HCF) diets. Male Sprague-Dawley rats (weighing 260-300 g) on the HCF diet had significantly increased body weight, plasma total cholesterol (TC), plasma low-density lipoprotein cholesterol (LDL-C), plasma triglycerides (TG), lipid peroxidation, and erythrocyte glutathione peroxidase (GSH-Px) and superoxide dismutase levels after 16 weeks. Supplementing 5% seaweeds to HCF diet significantly reduced plasma TC (-11.4% to -18.5%), LDL-C (-22% to -49.3%), and TG (-33.7% to -36.1%) levels and significantly increased HDL-C levels (16.3-55%). Among the seaweeds, S. polycystum showed the best anti-obesity and blood GSH-Px properties, K. alvarezii showed the best antihyperlipemic and in vivo antioxidation effects, and C. lentillifera was most effective at reducing plasma TC. All seaweeds significantly reduced body weight gain, erythrocyte GSH-Px, and plasma lipid peroxidation of HCF diet rats towards the values of normal rats.

The effect of different drying techniques on the phytochemical content and antioxidant activity of Kappaphycus alvarezii ('crocodile' morphotype) were investigated. Phytochemical (total phenolic, flavonoid, anthocyanin and carotenoid content) and antioxidant activity of the seaweed were determined. The seaweed was dried using seven types of drying techniques; oven drying (temperature of 40°C), oven drying (temperature of 80°C), sun drying, hang drying, sauna drying, shade drying and freeze drying. There were significant differences in the phytochemical content and antioxidant activity between the dried seaweed samples. The total phenolic content of the dried samples were in the range of 26.11 to 53.33 mg gallic acid equivalent (GAE) per 100 g, total flavonoid content from 9.83 to 25.67 mg catechin equivalent (CE) per 100 g, total anthocyanin content from 0.05 to 0.11 mg cyanidin-3-glucoside equivalent (C-3-GE) per gramme and total carotenoid content from 0.03 to 0.24 mg β-carotene equivalent (BCE) per gram, respectively. The oven-dried (40 and 80°C) and shade-dried samples contained the highest values of phytochemical content as compared to other dried samples tested. Antioxidant activity were determined using 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2-azino-bis-(3-ethyl-benzothiazoline-6-sulphonic acid) (ABTS) and ferric reducing/antioxidant power (FRAP) assays. The oven-dried (40 and 80°C) and shade-dried samples also displayed stronger scavenging activity and reducing ability as compared to other dried samples tested. The lower values of phytochemical content and weak antioxidant activity were detected in sun-dried and sauna-dried samples. This finding suggested that different drying techniques greatly influence the occurrence of phytochemical content and antioxidant activity in seaweeds.

This study determined the levels of polyphenols, flavonoids, carotenoids and antioxidant activity of the edible red seaweed, Gracilaria changii. Freeze-dried G. changii powder was extracted using five solvent systems: 80 % ethanol, 80 % methanol, 80 % acetone, ethyl acetate and water. The antioxidant activity of the extracts was measured using three assays, namely 2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric reducing power (FRAP) and β-carotene bleaching assays (BCB). The total phenolics (TPC) and total flavonoids content (TFC) and the total carotenoids content (TCC) were also determined. Ethanol extract had the highest yield followed by methanol > water > acetone > ethyl acetate extract. The radical scavenging effects of all the extracts showing dose-dependency properties with the ethyl acetate extract of G. changii exhibiting the highest radical scavenging effect (EC 50 of 0.51±0.09 mg mL

The consumption of either ethanolic or water extracts of S. polycystum dose dependently reduced dyslipidaemia in type 2 diabetic rats. S. polycystum is a potential insulin sensitiser, for a comestible complementary therapy in the management of type 2 diabetes which can help reduce atherogenic risk.

Central composite design of response surface methodology (RSM) was employed to optimize the extraction time (X 1 : 99.5-290.5 min) and temperature (X 2 : 30.1-54.9°C) of Schizophyllum commune aqueous extract with high antioxidant activities and total phenolic content (TPC). Results indicated that the data were adequately fitted into four second-order polynomial models. The extraction time and temperature were found to have significant linear, quadratic and interaction effects on antioxidant activities and TPC. The optimal extraction time and temperature were: 290.5 min and 35.7°C (DPPH • scavenging ability); 180.7 min and 41.7°C (ABTS •+ inhibition ability); 185.2 min and 42.4°C (ferric reducing antioxidant power, FRAP); 290.5 min and 40.3°C (TPC). These optimum conditions yielded 85.10%; 94.31%; 0.74 mM Fe 2+ equivalent/100 g; 635.76 mg gallic acid equivalent/100 g, respectively. The yields of antioxidant activities and TPC obtained experimentally were close to its predicted values. The establishment of such model provides a good experimental basis employing RSM for optimizing the extraction time and temperature on antioxidants from S. commune aqueous extract.