The antioxidant properties of ethanol extracts and their solvent-partitioned fractions from various green seaweeds.

The antioxidant activities of the ethanol (EtOH) extracts from the green seaweeds Enteromorpha compressa, Capsosiphon fulvescens, Chaetomorpha moniligera, and Ulva pertusa, as well as their solvent-partitioned fractions, were investigated, and their antioxidant activities were correlated with total phenolic and flavonoid contents. The EtOH extracts and their solvent-partitioned fractions showed 2,2-diphenyl-1-picrylhydrazyl (DPPH) and hydroxyl (OH•) radical scavenging activities with strong reducing ability. The most effective antioxidant properties were observed from the EtOH extracts of E. compressa and C. fulvescens. Among the solvent-partitioned fractions obtained with n-hexane, chloroform (CF), and ethyl acetate, the CF fractions from E. compressa and C. fulvescens exhibited higher radical scavenging activities and stronger reducing ability than other fractions. The OH• radical scavenging capacity and reducing power of these fractions were comparable to those of a positive control, α-tocopherol, at concentrations of 0.06-1.0 mg/mL. Total phenolic contents showed little correlation (r²=0.22-0.42) with the antioxidant properties; however, significant correlation (r² =0.73-0.96) was observed with flavonoid contents, implying that the flavonoid constituents contribute substantially to the antioxidant properties of the extracts. The overall results suggested that the green seaweeds (E. compressa and C. fulvescens), especially their CF fractions, could be good sources of natural antioxidants and of highly beneficial ingredients for healthcare products, such as nutraceuticals, supplements, and cosmeceuticals.