Anticlastogenic effects of Ginkgo biloba extract (EGb 761) and some of its constituents in irradiated rats

In a previous study we reported that radiation-induced clastogenic factors (CF) are found in the plasma of Chernobyl accident recovery workers and that their chromosome damaging effects are inhibited by antioxidant treatment with a Ginkgo biloba extract (EGb761). In the present study, we induced CF in rats with a radiation dose of 4.5 Gy. The protective effects of the complete extract were compared to those obtained with the extract devoid of its terpene fraction (CP205), with isolated ginkg,golides A + B and bilobalide at the concentrations present in EGb761. The pretreatment samples were taken at day 22 postirradiation, the posttreatment samples the day following arrest of the 3-week treatment. The adjusted clastogenic score (ACS) were reduced from 11.71 +/- 3.55 to 2.00 +/- 2.83 after treatment with 100 mg/kg and from 13.43 + 2.23 to 4.29 + 2.14 with 50 mg/kg of the complete extract (p < 0.0001). Similar protective effects were observed with CP205, ginkgolides and bilobalide (p < 0.001), while the reduction of ACS in placebo-treated rats was not statistically significant (12.80 +/- 1.79 and 9.20 +/- 2.68). However, if the efficacy of the treatment was compared to placebo, only the complete extract was significantly protective. While all components exerted anticlastogenic effects at the concentrations present in the complete extract, the comparison of the different groups by analysis of variance did not reveal significant differences. This may be due to to the small number of animals available in each treatment group. The complete extract reduced the ACS by 83% at the dose of 100 mg/kg, while the lower dose of 50 mg/kg and the three components reached only 66%-68% reduction. The better protection provided by the complete extract is due to synergistic rather than to additive effects. (C) 1999 Elsevier Science B.V. All rights reserved.