A comparative study of radioprotection by Ocimum flavonoids and synthetic aminothiol protectors in the mouse

The radioprotective effect of two flavonoids, orientin (Ot) and vicenin (Vc), obtained from the leaves of Ocimum sanctum, and the synthetic compounds WR-2721 and MPC (2-mercaptopropionyl glycine) have been compared by examining chromosome aberration in cells of bone marrow in irradiated mice. Healthy adult Swiss mice were injected intraperitoneally (ip) with 50 mu g kg(-1) body weight of Ot or Vc; 20 mg kg(-1) of MPG; 150 mg kg(-1) of WR-2721 or double distilled water (DDW). They were exposed to whole body irradiation of 2.0 Gy gamma radiation 30 min later. After 24 h, chromosomal aberrations were studied in the bone marrow of the femur by routine metaphase preparation after colchicine treatment. Radiation (2 Gy) increased the number of aberrant cells from less than 1% in controls to almost 20%. Pre-treatment with all the protective compounds resulted in a significant reduction in the percentage of aberrant metaphases as well as in the different types of aberration scored. Vc produced the maximum reduction in percent aberrant cells while MPG was the least effective; Ot and WR-2721 showed an almost similar effect. However, WR-2721 was the most effective against reduction of complex aberrations, followed by Vc. Neither flavonoids had any systemic toxicity, even at 200 mg kg(-1) body weight. Considering the low dose needed for protection and the high margin between the effective and toxic doses, the ocimum flavonoids may be promising for human radiation protection.