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, Fe²⁺ 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), Fe²⁺ 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.