ANTIOXIDATIVE ACTIVITY OF GINKGOLIDES AGAINST SUPEROXIDE IN AN APROTIC ENVIRONMENT

The terpene lactones ginkgolide A, ginkgolide B, ginkgolide C, ginkgol ide J and bilobalide, which are components of a standardized extract ( EGb 761) from leaves of Ginkgo biloba, as well as ginkgolide M from ro ots of G. biloba were studied regarding their reaction against superox ide (O-2(-)) and hydroperoxyl radicals (HO2) in dimethyl sulfoxide as an aprotic solvent. It was found that the ginkgolides B, C, J, M as we ll as bilobalide react with superoxide and its protonated form as demo nstrated by EPR and UV/VIS spectroscopy. The initial reaction rate wit h these oxygen-derived radicals is in the order of 100 M-1/s and below . Ginkgolide A does not react with superoxide under these conditions. From these findings it can be suggested that the superoxide scavenging effect of the ginkgolides B, C, J, M and bilobalide contributes to th e antioxidant properties of G. biloba. (C) 1997 Elsevier Science Irela nd Ltd.