Evaluation of phenolic contents and antioxidant activities of brown seaweeds belonging to Turbinaria spp. (Phaeophyta, Sargassaceae) collected from Gulf of Mannar.

OBJECTIVE: To evaluate the antioxidant activities and total phenolic contents of brown seaweeds belonging to Turbinaria spp. [Turbinaria conoides (T. conoides) and Turbinaria ornata (T. ornata) collected from Gulf of Mannar of southeastern coast of India in various in vitro systems.
METHODS: The antioxidant activity was evaluated using different in vitro systems, viz., 1, 1-diphenyl-2-picrylhydrazyl (DPPH), 2, 2'-azino-bis-3 ethylbenzothiozoline-6-sulfonic acid diammonium salt (ABTS), H2O2/HO radical scavenging, Fe(2+) ion chelating ability, and reducing potential. Folin-Ciocalteu method was used to determine the total phenolic content of the extracts, and the results were expressed as mg of gallic acid equivalents (GE)/g of the seaweed extracts. Thiobarbituric acid-reactive substances assay was employed to assess the ability of the seaweed extracts to inhibit lipid oxidation.
RESULTS: Ethyl acetate (EtOAc) fraction of T. conoides registered significantly higher phenolic content (105.97 mg GE/g) than that of T. ornata (69.63 mg GE/g). Significantly higher antioxidant potential as determined by DPPH (64.14%) radical scavenging activity was registered in EtOAc fraction of T. ornata. A higher ABTS(•+) radical scavenging (IC50 3.16 µg/mL), Fe(2+) chelating (IC50 0.46 mg/mL), H2O2 scavenging (IC50 4.25 mg/mL), lipid peroxidation inhibitory (TBARS, IC50 0.21 mg/mL), and reducing abilities (IC50 52.67 mg/mL) (P<0.05) were realized in EtOAc fraction of T. ornata than other fractions.
CONCLUSIONS: This study indicated the potential use of T. conoides and T. ornata as candidate species to be used as food supplements/functional foods to increase shelf-life of food items for human consumption, and nutraceuticals to deter deleterious free radical-induced life-threatening diseases.