Protection of mouse bone marrow against radiation-induced chromosome damage and stem cell death by the ocimum flavonoids orientin and vicenin.

In a previous study, orientin and vicenin, the water-soluble plant flavonoids, protected mice against radiation lethality (Uma Devi et al., Radiat. Res. 151, 74-78, 1999). To study bone marrow protection, adult Swiss mice were exposed to 0-6 Gy 60Co gamma rays 30 min after an intraperitoneal injection of 50 microg/ kg body weight of orientin/vicenin. Chromosomal aberrations in bone marrow were studied at 24 h postirradiation. Stem cell survival was studied using the exogenous spleen colony (CFU-S) assay. Radiation produced a dose-dependent increase in aberrant cells as well as in the yield of the different types of aberrations (breaks, fragments, rings and dicentrics) and a decrease in CFU-S. Pretreatment with either flavonoid significantly reduced the aberrant cells and different aberrations and increased the number of CFU-S compared to the respective radiation-alone groups. The dose modification factors for 50% reductions in the number of CFU-S were 1.6 for orientin and 1.7 for vicenin. The present finding that very low nontoxic doses of orientin and vicenin provide efficient protection against bone marrow damage at clinically relevant radiation doses suggests their potential for protection of normal tissues in radiotherapy.