The present study was performed to evaluate the effect of the methanolic extract of Cissus quadrangularis
(CQE) against free radical damage. The test extract exhibited significant inhibition in DPPH free radical formation, superoxide radical production and lipid peroxide production in erythrocytes. The activities of liver marker enzymes and antioxidant defense enzymes in rat liver homogenate were assessed in control and experimental animals. Carbon tetrachloride (CCl4
) caused a significant increase in aspartate aminotransaminase (AST) and alanine aminotransaminase (ALT), alkaline phosphatase (ALP), and decrease in superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and reduced glutathione (GSH), which was reverted by CQE pretreatment. The results obtained suggest that CQE showed inhibition of lipid peroxidation, free radical production and increase in antioxidant enzymes activities, which reveal its antioxidant property. It can be concluded that the free radical scavenging activity of the plant extract may be responsible for the therapeutic action against tissue damage.