In vitro antioxidant activities of three selected brown seaweeds of India

In vitro antioxidant activities of three selected Indian brown seaweeds – viz., Sargassum marginatum, Padina tetrastomatica and Turbinaria
conoides – were investigated. Total phenolic content and reducing power of crude methanolic extract were also investigated. The
activity of total methanolic extract and five different fractions (viz., petroleum ether (PE), ethyl acetate (EA), dichloromethane (DCM),
butanol (BuOH) and aqueous) were studied using total antioxidant activity, DPPH radical scavenging and deoxyribose assays. EA fraction
of S. marginatum exhibited higher total antioxidant activity of 39.62 mg ascorbic acid equivalent/g extract (or 0.31 mg ascorbic acid
equivalent/g seaweed on dry weight basis) among the all the fractions. Among the fractions obtained from different seaweeds, EA fraction
of S. marginatum showed higher DPPH scavenging activity of 23.16%; while PE fraction of T. conoides exhibited lower deoxyribose
activity of 47.81%. Higher phenolic content (49.16 mg gallic acid equivalent/g extract or 0.86 mg GAE/g of seaweed on dry weight basis)
was noticed in aqueous fraction of T. conoides. Reducing power of crude methanolic extract increased with increasing concentration.
Reducing power of T. conoides and P. tetrastomatica were higher compared to standard antioxidant (a-tocopherol). Among the seaweeds,
total methanolic extract of T. conoides had significantly higher phenol content (P < 0.05) compared to the other two species.
In vitro antioxidant activity of methanolic extracts from all the three seaweeds showed an increase with increasing concentration indicating
the dose dependency of these properties.