Radioprotection of plasmid and cellular DNA and Swiss mice by silibinin.

The radioprotective effect of a non-toxic bioactive component in plant milk thistle, silibinin against genotoxicity induced by gamma-irradiation was investigated in vivo/in vitro. Under in vitro conditions of irradiation, silibinin protected plasmid pBR322 DNA against gamma-radiation-induced strand breaks in a concentration dependent manner (0-200microM). Under cellular conditions of radiation exposure (3Gy), silibinin offered protection to lymphocyte DNA as evidenced from reduction in DNA damage and micronuclei formation, which showed correlation to the extent of intracellular reactive oxygen species reduction. Our extended animal studies suggest that oral administration of silibinin (70mg/kg for 3 days) to mice prior to whole-body gamma-exposure (7.5Gy) resulted in significant protection to radiation-induced mortality and DNA damage in blood leukocytes. However, silibinin treatment after irradiation was not as effective as pre-administration. In conclusion, present study indicated that silibinin has a strong potential to prevent radiation-induced DNA damage under both in vitro and in vivo.