Prevention and Ameliorating Effects of Garlic Extract on the Formation of 7,12-Dimethylbenz[a]anthracene-Induced DNA Adducts in Cultured Cells

Cultured cell lines were used to detect the inhibitory effects of garlic on the DNA adduct formation induced by chemical carcinogen. Cells were treated with [3H]-7,12-dimethylbenz[a]anthracene ([3H]-DMBA) for 48 h prior or after 0.1% garlic extract treatment and the quantity of resulting DNA adducts was measured by β-scintillation counting. Moreover, [32P]-postlabeling assay and thin layer chromatography (TLC) were used to characterize the alteration and density of individual adducts. The results indicated that adding DMBA to cultures led to its rapid accumulation in live cells and followed by extensive excretion into the culture medium 5 h after treatment. DNA adducts were further revealed by TLC, with distinctive stripe features as compared to the dotted pattern observed in mouse fibroblast cells. From TLC configurations, it was noted that the intensity and the number of adducts from cells treated with garlic first were markedly reduced. On the contrary, only a mediocre reduction in the intensity and the number of adducts was observed when garlic added after [3H]-DMBA, indicating a more significant role in prevention than in amelioration that garlic may play. The present study may also be useful for the identification of interactions between phytochemicals and chemical carcinogen during human carcinogenesis.