Preparation, analysis and antioxidant evaluation of the controlled product of polysaccharide from Mactra veneriformis by mild acid hydrolysis

The polysaccharides from Mactra veneriformis (MVPS) were degraded by controlled mild acid hydrolysis to produce active oligosaccharides. MVPS can easily be hydrolyzed by H2SO4 or HCl. The hydrolyzing process was investigated in acid addition and reaction time by evaluating the producing content of reducing sugar. Hydrolysis with 1 M HCl to MVPS can generate a time-depended behavior that is mild and controllable. HPLC analysis monitored the change of oligosaccharides composition in hydrolyzing. Total nine oligosaccharides are recognizable in the HPLC profile, and their content showed a regular transformation in hydrolysis. Those nine ingredients were identified as glucooligosaccharides with DP from 1 to 7 by MS analysis. Antioxidant activities of the typical hydrolyzates as well as MVPs were further tested in assays of DPPH and hydroxyl radicals scavenging, and reducing power. It was found that HCl hydrolyzate exhibited stronger antioxidant effects than MVPS and H2SO4 hydrolyzate due to its higher content of oligosaccharides.