11-oxo-mogroside V is a natural sweetener, isolated from the fruits of Momordica grosvenori, exhibits strong antioxidant activity. It exhibits significant inhibitory effects on reactive oxygen species (O₂^-, H₂O₂ and *OH) with EC₅₀ of 4.79, 16.52, and 146.17 μg/mL, respectively. IC50 & Target: EC50: 4.79 μg/mL (O₂^-), 16.52 μg/mL (H₂O₂), 146.17 μg/mL (*OH)^[1] In Vitro: 11-oxo-mogroside V shows a higher scavenging effect on O₂- (concentration at which 50% of chemiluminescence intensity is inhibited [EC₅₀]=4.79 μg/mL) and H₂O₂ (EC₅₀=16.52 μg/mL) than those of mogroside V. 11-oxo-mogroside V exhibits a remarkable inhibitory effect on *OH-induced DNA damage with EC₅₀=3.09 μg/mL^[1].11-oxo-mogroside V, a natural sweetener, isolated from the fruits of Momordica grosvenori, exhibits strong inhibitory effect on the primary screening test indicated by the induction of Epstein-Barr virus early antigen (EBV-EA) by a tumor promoter, 12-O-tetradecanoylphorbol-13-acetate (TPA). 11-oxo-mogroside V exhibits strong inhibitory effect on EBV-EA induction (91.2, 50.9 and 21.3% inhibition at 1000, 500 and 100 mol ratio/TPA concentration, respectively)^[2]. In Vivo: In the group treated with DMBA, TPA and 11-oxo-mogroside V, only 26.6 and 53.3% of mice bore papillomas even at 10 and 15 weeks of promotion, respectively, and only 1.0 3.3 and 4.7 papillomas are formed per mouse at 10, 15 and 20 weeks of promotion^[2].