Patricia Matanjun

Antioxidant activities and phenolics content of eight species of seaweeds from North Borneo

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 (R2 = 0.89). There was a strong correlation (R2 = 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.

Evaluation of Antioxidant Activities in Relation to Total Phenolics and Flavonoids Content of Selected Malaysian Wild Edible Plants by Multivariate Analysis

The aim of this study was to determine the antioxidant activity, total phenolics, and total flavonoid content of six freeze dried wild edible plants, namely Helminthostachys zeylanica, Schismatoglottis ahmadii, Heckeria umbelatum, Lasia spinosa, Gonostegia hirta, and Aniseia martinicense from Sabah, Malaysia. All leaves had higher levels of total phenolics, flavonoids, and antioxidant activity than stems and flowers for all extracts, except the stem of Gonostegia hirta. Integrated antioxidant activity index showed the leaf of Heckeria umbellatum and Aniseia martinicense possessed the highest antioxidant activity for all extracts. Principal component analysis identified that the phenolic group present in the hot water and methanolic extracts was the main factor for higher values observed in oxygen radical absorbance capacity and ferric reducing antioxidant power assays. These wild edible plants are good natural sources of antioxidants to be incorporated as functional ingredients in the food industry.

Chemical composition and physicochemical properties of tropical red seaweed, Gracilaria changii

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-1) 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.

Comparative study of drying methods on chemical constituents of Malaysian red seaweed

ABSTRACT This study determined the proximate composition, phytochemical and antioxidant activity of the edible red seaweed, Kappaphycus alvarezii, under different drying conditions, namely, oven dried, sun dried, vacuum dried, and freeze dried. The proximate composition of K. alvarezii has shown no significant difference (p > 0.05) in macronutrient components except fat content. Phytochemical studies conducted on total phenolic content and total flavonoid content showed that vacuum-dried extracts demonstrated the highest total phenolic content at 12.97 mg PGE g−1 DE. In vitro antioxidant activities of seaweed extract by ferric-reducing antioxidant potential and 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity proved that oven-dried extracts showed the highest ferric-reducing antioxidant power value, 272.95 µM TE mg−1, and highest scavenging activity, EC50 9.55 mg mL−1. In general, sun-dried extracts showed lowest antioxidant among all treatments.

Characterization of phenolic compounds, carotenoids, vitamins and antioxidant activities of selected Malaysian wild edible plants

This study was carried out to characterize phenolic compounds, carotenoids, vitamins and the antioxidant activity of selected wild edible plants. Plant extracts were purified, and phenolic compounds comprising 11 phenolic acids (hydroxybenzoic acid and hydrocinnamic acid) and 33 flavonoids (including catechin, glycosides and aglycones) were analysed using High Performance Liquid Chromatography - Diode Array Detector (HPLC-DAD). Furthermore, the contents of ascorbic acid and tocopherol ((α and γ tocopherol) and carotenoids (lutein and β-carotene) were also determined. The major phenolics identified consisted of glycosides of flavones (apigenin and luteolin) and flavonols (kaempferol and quercetin). Among the phenolic acids identified after hydrolysis, coumaric acid was the predominant phenolic acid in all the extracts of wild plants. Ascorbic acid [53.8 mg/100 g fresh weight (FW)] and β-carotene (656.5 mg/100 g FW) showed the highest content in the leaf of Heckeria umbellatum. In conclusion, the leaves of H. umbellatum, Aniseia martinicensis and Gonostegia hirta have excellent potential in the future to emerge as functional ingredients.