[46] Antioxidant action of Ginkgo biloba extract EGb 761

Extracts of Ginkgo biloba leaves (EGb 761) are complex titrated, standardized mixtures of active ingredients introduced into medical practice as polyvalent therapeutic agents. This chapter discusses the radical scavenging properties of EGb 761, in several in vitro systems. The interaction of EGb 761 with superoxide and hydroxyl radicals generated by using the water radiolysis method is presented in the chapter. The method of radiolysis is useful because it specifically generates superoxide and hydroxyl radicals in known quantities, thus reducing the risk of possible interferences. To evaluate the role of terpenes contained in EGb 761, a comparative study is described using CP 202, a similar mixture lacking the terpene fraction. The interaction of EGb 761 with peroxyl radicals is assayed by a chemiluminescent method. The interaction of EGb 761 with nitric oxide is assessed by two different spectrophotometric methods. Finally, the effect of EGb 761 on xanthine oxidase activity is described.