Comparative anticancer and antioxidant activities of different ingredients of Ginkgo biloba extract (EGb 761).

Flavonoid glycosides are the major constituents of Ginkgo biloba extract (EGb 761) and are well known to be an antioxidant for inhibiting tumor growth. Because it contains several flavonoid glycosides and other bioactive substances, the activities of EGb 761 against cancer in vivo and in vitro remain poorly understood. This situation prompted interest in the compounds for experimental study. We have investigated the anticancer effects of three analogues of EGb 761 samples on sarcoma 108 (S180)-bearing mice and leukemic 1210 (L1210) cell lines. We have also evaluated the changes of endogeneous antioxidant scavenging enzymes, including superoxide dismutase (SOD), glutathione (GST), lipid peroxidation (LPx), and catalase (CAT), in the blood of the S180-bearing mice. The EGb 761, EGb 761-H (containing mainly flavonoid aglycones and terpene trilactones), and EGb 761-DT-H (containing mainly flavonoid aglycones) samples exhibited cytotoxicity and inhibitory activity with IC (50) values of 46.36 +/- 2.43 microM, 10.27 +/- 0.88 microM, and 14.93 +/- 0.73 microM in L1210 cell-based assays, respectively. This resulted in 41.74 %, 60.72 %, and 63.76 % reductions in tumor weight after 10 days of treatment, respectively. In summary, the anticancer activity of EGb 761 can be improved by increasing the concentration of the aglycone form of the flavonoid. Terpene trilactones cannot exert the anticancer effects of flavonoids in vivo. Raising the levels of the free radical scavenger enzymes GST, SOD and CAT may be one of the involved anticancer mechanisms.