Further Investigations on the Antioxidant Activity of Ocimum sanctum Using Different Paradigms of Oxidative Stress in Rats

Objective : To extend the investigations on the reported antioxidant activity of Ocimum sanctum. Materials and methods : The oxidative stress parameters used in rats were the isolated heart ischaemia-reperfusion injury, chronic (28 days) exposure to cigarette smoke, chronic footshock stress (21 days) and iron-overload hepatotoxicity. The parameters of oxidative stress included the estimation of the antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX), and lipid peroxidation (LPO). A standardized extract of O. Sanctum (OS) and vitamin E (VE), a standard antioxidant agent, were used as the test drugs. Results : OS (50 and 100 mg/kg, p.o.) and VE (200 mg/kg, p.o.) administered for 5 days prior to induction of ischaemia-reperfusion reversed the depletion of SOD, CAT and GPX, and the increase in LPO induced in heart by this model of oxidative stress. Likewise, both OS (50 and 100 mg/kg, p.o.) and VE (200 mg/kg, p.o.), administered for 28 days, concomitant with exposure to cigarette smoke (CS) reversed the changes induced by CS in rat heart and lung SOD, CAT, GPX and LPO. A similar effect was noted when these doses of OS and VE were administered for 21 days along with exposure to chronic stress induced oxidative stress in rat brain frontal cortex and striatum. Iron overload induced increase in hepatic lipid peroxidation was attenuated by these doses of OS and VE, administered for 5 days prior to iron overload. Conclusion : OS exhibited significant antioxidant activity against several paradigms of oxidative stress induced by a variety of techniques in different rat tissues, which was comparable to that induced by VE. The results confirm the antioxidant activity of OS and indicate that, like VE, it is not tissue specific. It also provides a basis for the clinical use of OS in several clinical conditions involving oxidative stress.