Arsenic is a well-established environmental toxin, which damages various organs of the body. A triterpenoid saponin, arjunolic acid (AA) has been isolated from the bark of Terminalia arjuna. The present study was conducted to investigate the preventive role of AA against arsenic-induced cytotoxicity in isolated murine hepatocytes. Sodium arsenite (NaAsO(2)) was chosen as the source of arsenic. Incubation of the hepatocytes with NaAsO(2) (1 mM) for 2 h caused reduction in the cell viability and activities of the intracellular enzymatic as well as non-enzymatic antioxidants. Treatment of NaAsO(2) enhanced lipid peroxidation and also increased the activities of the membrane leakage enzymes. Administration of AA (100 microg/ml) before and with the toxin almost normalized the altered activities of antioxidant indices. AA possesses free radical scavenging activity and could enhance the cellular anti-oxidant capability against NaAsO(2)-induced cyto-toxicity. The cytoprotective activity of AA was found to be comparable to that of a known antioxidant, vitamin C. Experimental results, therefore, suggest that AA protects arsenic-induced cytotoxicity in murine hepatocytes.