Abstract: Objective: Study on antioxidant activity of different extracts from fruits of Siraitia grosvenori. in vitro. Methods: D-deoxyribose method, reagent box method and spectrophotometry method were used to determine the inhibiting effect on radical activity and hemolysis of red blood cells. Results: 1. Different extracts from fruits of Siraitia grosvenori. all had inhibiting effects on hydroxyl radical (·OH) activity, superoxide anion radical (O·2)activity, MDA and the hemolysis of red blood cells. But antioxidant effects of different extracts were different in different antioxidant systems. 2. Mogrosides were the main components that inhibit MDA and hemolysis of red blood cells, and also had synergetic effect with the other components of extracts on scavenging ·OH and O·2 radicals. Conclusion: Extracts from fruits of Siraitia grosvenori. had antioxidant effects while Mogrosides were the main antioxidant components of the extracts.

Key words: extracts from fruits of Siraitia grosvenori., mogrosides, antioxidant activity