The chemoprevention activity of temu mangga extracts was investigated by determination of antioxidant activity with a peroxidation number method and gluthatione-S-transferase (GST) activity in Chang medium culture and cell lysate (total GST activity). The results indicated that ethanol extract has a strong antioxidant activity. It is caused by the phenolic group in the ethanol extract. Treatment Chang cell culture with 7th and 4th ethanol fractions increased the GST activity when compared to the control. The total GST activity (cytosolic and microsomal) increased when Chang cell culture was treated with H2O2/Fe+2. The decrease of the total GST activity was observed when 7th and 4th ethanol fractions were supplemented with H2O2/Fe+2 compared to the cell culture receiving H2O2/Fe+2 only.