Screening and Partial Characterization of Natural Antioxidants from Seaweeds Collected From, Rameshwaram Southeast Coast of India

Abstract

The aim of this work is to estimate in-vitro antioxidant activities such as total antioxidant capacity, free radicals (DPPH) scavenging activity, hydrogen peroxides (H2 O2 ) scavenging activity, total reducing power scavenging activity and total phenols, of various extracts of seaweeds such as aqueous, acetone, ethanol, methanol, and pigments content by spectrophotometric method, of 33 seaweeds species among which 11 Chlorophyta, 11 Phaeophyceae and 11 Rhodophyta, collected during 2016 from two stations viz. Olaikuda and Vadakkadu, at Rameshwaram, southeast coast of India. Among four different extracts aqueous extracts from all seaweeds had minimum activity than acetone, methanol and ethanol. The Rhodophyta and Phaeophyceae had high antioxidant activity in comparing to Chlorophyta. The highest total antioxidant activity was found in acetone extract from Turbinaria decurrens (98.97±0.00%), followed by its methanol extract (98.81±0.60%) and ethanol extract (98.58±0.53%). The highest reducing power and H2 O2 scavenging activity were found in acetone extract of Caulerpa racemosa (383.25±1.04%), and methanol extract from Caulerpa racemosa var. macrophysa (24.91±0.49%). The methanol extract from Caulerpa scalpelliformis contained the highest total phenol (85.23±0.12%). The Chloro-a and Chloro-b contents were the highest in Gracilaria foliifera (13.69±0.38% mg/gm dry wt.) and Caulerpa racemosa var. macrophysa (9.12 ±0.12% mg/gm dry wt.) likewise carotenoid was also the highest in Gracilaria foliifera (0.054±0.0003% mg/gm dry wt.) and Caulerpa racemosa var. macrophysa (0.04 ±0.002% mg/gm dry wt.). The partial characterization of the extract which contents the highest activity was done by UV-Visible Spectrophotometer, FTIR, and NMR. The functional groups and all the possible compounds present in the extract were partially characterized. It can be concluded from this study, that some seaweed extract can be used for natural antioxidant production, after further characterization to negotiate the side effect of synthetic, market available antioxidants.