Modulation of glutathione and antioxidant enzymes by Ocimum sanctum and its role in protection against radiation injury.

Aqueous extract (OE) of the leaves of Ocimum sanctum, the Indian holy basil, has been found to protect mouse against radiation lethality and chromosome damage and to possess significant antioxidant activity in vitro. Therefore a study was conducted to see if OE protects against radiation induced lipid peroxidation in liver and to determine the role, if any, of the inherent antioxidant system in radioprotection by OE. Adult Swiss mice were injected intraperitoneally (i.p.) with 10 mg/kg of OE for 5 consecutive days and exposed to 4.5 Gy of gamma radiation 30 min after the last injection. Glutathione (GSH) and the antioxidant enzymes glutathione transferase (GST), reductase (GSRx), peroxidase (GSPx) and superoxide dismutase (SOD), as well as lipid peroxide (LPx) activity were estimated in the liver at 15 min, 30 min, 1, 2, 4 and 8 hr post-treatment. LPx was also studied after treatment with a single dose of 50 mg/kg of OE with/without irradiation. OE itself increased the GSH and enzymes significantly above normal levels whereas radiation significantly reduced all the values. The maximum decline was at 30-60 min for GSH and related enzymes and at 2 hr for SOD. Pretreatment with the extract checked the radiation induced depletion of GSH and all the enzymes and maintained their levels within or above the control range. Radiation significantly increased the lipid peroxidation rate, reaching a maximum value at 2 hr after exposure (approximately 3.5 times that of control). OE pretreatment significantly (P < 0.0001) reduced the lipid peroxidation and accelerated recovery to normal levels. The results indicate that Ocimum extract protects against radiation induced lipid peroxidation and that GSH and the antioxidant enzymes appear to have an important role in the protection.

Radioprotective effect of leaf extract of Indian medicinal plant Ocimum sanctum.

Water or aqueous ethanol extract of O. sanctum was given ip, either as a single dose or multiple doses, before a whole-body exposure to 11 Gy(LD100/30) of 60Co gamma radiation in albino mice. The water extract was more effective and less toxic than the aqueous ethanol extract. An optimum ip dose of 50 mg/kg (< 1/100 LD50) of the water extract, at 10 mg/kg/day for 5 consecutive days, gave the maximum survival. Increasing the dose per treatment or the number of treatments did not increase protection. Intraperitoneal administration gave the best protection (70% survival). Other routes (im, iv and po) were less effective and produced 37-47% survival. The optimum dose (ip) gave a dose modifying factor of 1.28. Since the extract may contain a number of chemical compounds, it is not possible to attribute the observed protection to any particular compound at present.