Abstract: BACKGROUND ＆ AIM: To investigate the antioxidative action of the ethanol and water extract of Rhodiola and their dose relationship. MATERIAL AND METHODS: Sprague-Dawley rats were killed and the livers were removed to isolate the microsomes by calcium ion precipitation. The ethanol and water of Rhodiola were extracted by recirculating and boiling. Four LPO models were built which were stimulated by Vc/Fe2＋,CHP, CCl4/NADP and NADPH-ADP／Fe2＋. Two different extracts were added into four models and titrated to final concentrations of 25 mg/ml,12.5 mg/ml,6.25 mg/ml,3.13 mg/ml and 1.56 mg/ml. Then the contents of malondialdehyde (MDA) were measured to assess the antioxidative action of Rhodiola extracts in the first three models.The electrode oxygraph was used to determine the inhibition rate of oxygen consumption in NADPH-ADP／Fe2＋ model. RESULTS: In CHP model, compared with control group, the content of MDA in group 6.25,12.5 and 25.00 mg/ml of water extract decreased significantly (P<0.05). In the Vc/Fe2＋、CHP and CCl4/NADP models, the content of MDA in those groups with different dosages of the two extracts decreased significantly(P<0.01)，and there was dose-dependent relationship between the final concentration and the inhibition rate of MDA to some extent.In NADPH-ADP／Fe2＋ model，the inhibition rates of the highest concentration of the ethanol and water extracts reached 76％ and 43％,respectively. CONCLUSION: The two extracts of Rhodiola had good antioxidative effects. The ethanol extract had comparatively stronger effect in the models containing enzymes.

Key words: rhodiola, antioxidative, lipid peroxidation, electrode oxygraph