Chemical analysis and antioxidant activities in vitro of polysaccharide extracted from Opuntia ficus indica Mill. cultivated in China

The polysaccharide of Opuntia ficus indica Mill. was isolated by water, and purified by Sephacryl S-400 HR column. The purity of polysaccharide was evaluated by HPLC coupled with gel permeation chromatography. Results showed that the neutral monosaccharide composition of O. ficus indica polysaccharide was rhamnose, arabinose, and glucose in a molar ratio of 1.00:2.98:2.57, with an average molecular weight of about 172,591 Da. Further, its antioxidant capacities in vitro were respectively evaluated by the assays of inhibition of pyrogallol autoxidation, scavenging hydroxyl radical, and liver lipid peroxidation inhibiting. The crude water-soluble polysaccharide and purified polysaccharide showed notable free radical scavenging activity and hydroxyl radical-induced liver lipid peroxidation inhibiting ability, suggesting that O. ficus indica polysaccharide may be considered as a potential candidate for the natural antioxidants and possible health-promoting functional foods.