Antioxidant activities and antioxidative components in the surf clam, Mactra veneriformis

Aqueous (ET1) and alcoholic (ET2) extracts from Mactra veneriformis were studied for their antioxidant potentials using various in vitro assays. The ET2 was fractioned into four parts according to the polarity of the extractive medium, viz. ET2-p (petroleum ether), ET2-e (ethyl acetate), ET2-n (n-butanol) and ET2-w (water). Among the four fractions, ET2-w showed the strongest reducing power, and highest 2,2 diphenyl-1-picrylhydrazyl (DPPH) scavenging and metal chelating activities, while the ET2-p possessed higher hydroxyl radical scavenging activities. It was found that ET2-w had large amounts of free amino acids and oligosaccharides, while ET2-p contained a large amount of unsaturated fatty acids. We conclude that amino acids, oligosaccharides and unsaturated fatty acids all contribute to the antioxidant activity of M. veneriformis. In order to elucidate the above, antioxidative components involved in the antioxidant activities were also detected. It was found that amino acids and carbohydrates were the major components of ET2-w. The amino acids were Tau (0.26%), Tyr (0.38%), Met (0.31%), Cys (0.38%), Arg (1.79%) and so on, while carbohydrates were oligosaccharides that were composed of disaccharides and trisaccharides. The unsaturated fatty acids were the major components of ET2-p, which contained a high amount of docosahexaenoic acid (9.03%) and eicosapentaenoic acid (18.49%).