Objective:In this study, the antioxidant and radioprotective efficacy of a semi-purified aquaalcoholic extract of T. cordifolia (RTp) was evaluated in the murine model system. Methods:Free radical scavenging ability was evaluated in chemical system. Radioprotective efficacy of RTp was then evaluated at in vivo level in terms of survival and dose reduction factor. The effect of RTp administration on endogenous defense system in irradiated mice was evaluated in small intestine.Results: RTp contained 47.5 ± 1.09 mg gallic acid equivalent polyphenols and 17.45 ± 1.89 µg quercetin equivalent flavonoids per gram of extract. RTp scavenged both Fenton reaction (IC 50 0.48 mg/ml) and radiation generated (IC 50 0.50 mg/ml) hydroxyl radicals; superoxide anions (IC 50 0.49 mg/ml) and DPPH radicals (IC 50 0.67 mg/ml). RTp (250 mg/kg body weight, i.p., -1 h) rendered 83.3% survival in lethally irradiated mice (DRF = 1.43). It accelerated recovery of radiation-induced decrease in body weight of mice. RTp administration on one hand improved the endogenous defense system by augmenting levels of total thiols, superoxide dismutase (SOD) and catalase and concomitantly decreased lipid peroxidation in mouse small intestine. Conclusion:These results imply that RTp treatment augmented antioxidant defense system which afforded an important mechanism of radioprotection. The bio-molecules present in RTp acting in this direction need to be investigated further.