Protection against radiation-induced chromosome damage in mouse bone marrow by Ocimum sanctum

The radioprotective effect of the leaf extract of Ocimum sanctum (Ocimum extract, OE) was investigated by taking chromosome aberrations as the end point. Adult Swiss mice were whole-body exposed to 1-6 Gy of gamma radiation with/without pretreatment with 10 mg/kg b.wt. of OE intraperitoneally for 5 consecutive days. Radiation was given 30 min after the last injection. Metaphase plates were prepared from femur marrow on days 1, 2, 7 and 14 post-treatment and the frequency of aberrant cells and individual aberrations were scored. OE alone did not have any significant effect on the chromosomes. Maximum percent of aberrant cells was observed at 24 h in all the exposed groups. The percent aberrant cells showed a linear quadratic increase with radiation dose, in both radiation alone (RT) and OE + RT-treated groups. Exchange (dicentrics and rings) and multiple (pulverized and severely damaged cells) aberrations also showed a similar response. However, the slopes of OE + RT was significantly shallower than RT groups (p < 0.05). A dose-modifying factor of 2.63 was obtained taking percent aberrant cells for 2 Gy as the base. Progressive decline in the percent aberrant cells as well as the number of aberrations with time after irradiation was observed in both RT and OE + RT groups. OE treatment resulted in a faster recovery compared to RT alone group. At doses below 3 Gy, OE pretreatment almost completely eliminated the exchange aberrations from the cell population by day 2. Studies on a chemical system demonstrated that OE significantly reduced the generation of hydroxyl radical; a lower dose of OE (1 mg/ml) was more effective than 5 mg/ml and this effect was more pronounced than that produced by DMSO. These results show that OE affords in vivo protection against radiation-induced cytogenetic damage. Free radical scavenging is a likely mechanism of OE protection.