Abstract: The protective effect and mechanism of (-)-epigallocatechin gallate (EGCG) combined with carmustine on the DNA damage of Chang liver cells were evaluated by MTT assay, flow cytometric assay and Comet assay respectively. The results showed that EGCG can prevent the growth inhibition caused by carmustine, the 50% inhibitory concentration (IC₅₀) of carmustine to Chang liver cells was 43.31 μg/ml, while it is combined with EGCG(25 μg/ml and 50 μg/ml, the concentration under which EGCG has no growth inhibition to Chang liver cells), the IC₅₀ to Chang liver cells increased to 52.46 μg/ml and 46.65 μg/ml respectively. EGCG also decreased carmustine-induced DNA damage in Chang liver cells according to Comet assay results. The Olive tail moment decreased from 9.07±5.48 to 6.02±2.46. EGCG also decreased the apoptosis percentages of Chang liver cells caused by carmustine. After Chang liver cells treated with EGCG(25 μg/ml) and carmustine (20 μg/ml) for 4 h, 6 h and 24 h, the apoptosis percentage decrease from 4.53±0.64（%）、6.01±0.14（%）、2.27±0.32（%）to 3.04±0.47（%）、5.61±0.10（%）、1.14±0.23（%）respectively. These results suggest that EGCG can protect the human normal liver cells from the lethal action by carmustine. The mechanism is the EGCG possess the activity of decreasing the DNA damage caused by these agents and the apoptosis percentage caused by carmustine.

Key words: EGCG, carmustine, DNA damage, comet assay, flow cytometric assay, apoptosis, IC₅₀