Anticlastogenic effects of Ginkgo biloba extract (EGb 761) and some of itsconstituents 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 tha t 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 comp lete 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 tak en at day 22 postirradiation, the posttreatment samples the day following a rrest of the 3-week treatment. The adjusted clastogenic score (ACS) were re duced from 11.71 +/- 3.55 to 2.00 +/- 2.83 after treatment with 100 mg/kg a nd 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, ginkgolid es and bilobalide (p < 0.001), while the reduction of ACS in placebo-treate d 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 t he complete extract was significantly protective. While all components exer ted anticlastogenic effects at the concentrations present in the complete e xtract, 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 a nd the three components reached only 66%-68% reduction. The better protecti on provided by the complete extract is due to synergistic rather than to ad ditive effects. (C) 1999 Elsevier Science B.V. All rights reserved.