Radioprotection by Rhodiola imbricata in mice against whole-body lethal irradiation.

Rhodiola imbricata, an Indian medicinal plant, was investigated for protection against whole-body lethal gamma irradiation (10 Gy)-induced mortality in Swiss albino strain "A" mice. The maximum tolerance dose values for aqueous (RD-I) and aqua-alcoholic (RD-II) extracts were 1,100 and 1,300 mg/kg of body weight, respectively. Pre-irradiation administration of RD-I produced >90% survival, while RD-II produced >83% survival beyond the 30-day observation period. The optimal radioprotective dose for RD-I as well as RD-II was 350 mg/kg of body weight; the aqua-alcoholic extract, however, had an advantage over the aqueous extract at lower as well as at higher doses. The optimal time interval between administration of extract and irradiation was 30 minutes for both RD-I and RD-II. The number of colony-forming units per spleen in irradiated mice was 1.91 +/- 0.15, while in mice given RD-I or RD-II, 30 minutes before irradiation (10 Gy), it increased to 17.3 +/- 0.67 and 15.6 +/- 0.61, respectively. These findings have important implications in the development of a suitable radioprotector of herbal origin.