Abstract: Orthogonal array design method was applied to optimize the microwave-assisted water extraction of polysaccharides from Ginggo biloba leaves (GBLP) in order to maximize polysaccharide yield. Meanwhile, the antioxidant activity in vitro of polysaccharides from Ginggo biloba leaves was assessed by DPPH, hydroxyl and superoxide anion free radical scavenging assays and compared with vitamin C. The results showed that the optimal extraction conditions were microwave power of 480 W, material-to-liquid ratio of 1:30 (g/mL), and microwave treatment time of 8 min. Under these conditions, the extraction yield of polysaccharides was up to 14.70%. The extract obtained had a powerful scavenging activity against DPPH and hydroxyl free radicals in a concentration-dependent manner but a weak superoxide anion free radical scavenging activity with no significant concentration-dependent relationship.

Key words: microwave-assisted extraction, polysaccharides from Gingko biloba leaves, antioxidant activity