Chinese medicinal herbs modulate mutagenesis, DNA binding and metabolism of benzo[a]pyrene

Abstract

AbstractOldenlandia diffusa (OD) and Scutellaria barbata (SB) have been used in traditional Chinese medicine for treating liver, lung and rectal tumours while Astragalus membranaceus (AM) and Ligustrum lucidum (LL) are often used as an adjunct in cancer therapy. In this study, we determined the effects of aqueous extracts of these four herbs on benzo[a]pyrene (BaP)‐induced mutagenesis using Salmonella typhimurium TA100 as the bacterial tester strain and rat liver 9000 × g supernatant as the metabolic activation system. The effects of these herbs on [3H]BapP binding to calf thymus DNA and formation of BaP‐DNA adducts were assessed. Organosoluble and water‐soluble metabolites of BaP were extracted and analysed by high performance liquid chromatography (HPLC) and alumina column liquid chromatography. Mutagenesis assays revealed that all four herbs produced a significant concentration‐dependent inhibition of His+ revertants induced by BaP. At a concentration of 1.5 mg/plate, SB and OD in combination exhibited an additive effect, whereas AM and LL in combination demonstrated an antagonistic effect. The trend of inhibition of these four herbs on BaP‐induced mutagenesis was: SB > LL > OD > AM. LL, OD and SB significantly inhibited BaP binding to DNA. LL and SB significantly reduced BaP‐DNA adduct formation and SB significantly decreased formation of organosoluble metabolites of BaP. Our data suggest that these Chinese medicinal herbs possess cancer chemopreventive properties.