Abstract

The antioxidant activities of Tabebuia impetiginosa methanolic extract (TIME) were examined with its serial solvent extracts using hexane, chloroform and ethyl acetate against hydrogen peroxide (H₂O₂)-induced oxidative stress in NIH3T3 cells. The three serial extracts were selected for the study of regeneration on antioxidant enzyme activities because butanol and water extracts significantly affected cell survival. Treatment of hydrogen peroxide on the cells showed a dramatic repression on superoxide dismutase (SOD) and cytosolic NADPH⁺-dependent isocitrate dehydrogenase (IDPc) activities with the remaining activities of 56.1 and 37.5%, respectively. The three extracts significantly regenerated SOD activity with the range of 103 to 178% when compared to the control, and IDPc activity with the range of 34.4 to 42.2%. The three extracts also regenerated catalase and glucose-6-phosphate dehydrogenase activities with the range of 91.6 to 139% in comparison to the control. Hydrogen peroxide did not change intracellular glutathione content. The three serial extracts of TIME enhanced intracellular glutathione concentration, protected proteins from the oxidative attack by H₂O₂ and also decreased malonaldehyde formation in the cells. Taken together, the non-polar extracts of TIME protect NIH3T3 cells from the H₂O₂-induced oxidative stress.

Key words: Tabebuia impetiginosa, NIH3T3, antioxidant activity, hydrogen peroxide (H₂O₂), lipid peroxidation.