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BackgroundA powdered ethanolic extract of Glycyrrhiza aspera root exhibits antimutagenic activity against N-methyl-N-nitrosourea (MNU) based on the Ames assay with Salmonella typhimurium TA1535. The aim of this study was to identify the antimutagenic components of the powdered ethanolic extract of G. aspera root.ResultsThe powdered ethanolic extract of G. aspera root was sequentially suspended in n-hexane, carbon tetrachloride, dichloromethane, ethyl acetate, and ethanol, and each solvent soluble fraction and the residue were assayed for antimutagenic activity against MNU in S. typhimurium TA1535. The dichloromethane soluble fraction exhibited the highest antimutagenicity and was fractionated several times by silica gel chromatography. The fraction with the highest antimutagenic activity was further purified using HPLC, and the fractions were assayed for antimutagenicity against MNU in S. typhimurium TA1535. Finally, five components with antimutagenic activity against MNU were identified as glyurallin A, glyasperin B, licoricidin, 1-methoxyphaseollin, and licoisoflavone B.ConclusionsThe five components were demonstrated to possess an antigenotoxic effect against carcinogenic MNU for the first time. It is important to prevent DNA damage by N-nitrosamines for cancer chemoprevention.Electronic supplementary materialThe online version of this article (doi:10.1186/s41021-016-0068-2) contains supplementary material, which is available to authorized users.

N-Nitroso compounds are suspected to be causative agents for human cancer. N-Methyl-N-nitrosourea (MNU) is a typical direct acting mutagen with alkylation activity of DNA, and has been reported to be formed in vivo. Therefore, it is important for cancer chemoprevention toˆnd some compounds to inhibit mutagenicity induced by MNU. The inhibitory eŠect of plant extracts against the mutagenicity of MNU was evaluated using the Ames assay with Salmonella typhimurium TA1535. Among 43 extracts derived from medicinal and edible plant assayed, Glycyrrhiza aspera ethanolic extract, Glycine max extract with 40% iso‰avone aglycone (ISOMAX AG40) and Zingiber o‹cinale ethanolic extract at the range 0.01-1.0 mg/plate inhibited MNU-induced mutagenicity in S. typhimurium TA1535. No cytotoxicity of the three extracts were observed in Salmonella typhimuirum TA1535, indicating that inhibition of MNU-induced mutagenicity was apparently due to the antimutagenic potency of Glycyrrhiza aspera ethanolic extract, ISOMAX AG40 and Zingiber o‹cinale ethanolic extract. Therefore, the results of relative mutagenicity showed that Glycyrrhiza aspera ethanolic extract and ISOMAX AG40 decreased the mutagenic eŠects to 5.4% and 2.6%, respectively, whereas Zingiber o‹cinale ethanolic extract decreased it to 45%.

Antimutagenesis against N-nitroso compounds contribute to prevention of human cancer. We have found that Glycyrrhiza aspera ethanolic extract exhibits antimutagenic activity against N-methyl-N-nitrosourea (MNU) using the Ames assay with Salmonella typhimurium TA1535. In the present study, eight purified components from Glycyrrhiza, namely glabridin, glycyrrhetinic acid, glycyrrhizin, licochalcone A, licoricesaponin H2, licoricesaponin G2, liquiritigenin and liquiritin were evaluated for their antimutagenicity against MNU in the Ames assay with S. typhimurium TA1535. Glycyrrhetinic acid, glycyrrhizin, licoricesaponin G2, licoricesaponin H2 and liquiritin did not show the antimutagenicity against MNU in S. typhimurium TA1535. Glabridin, licochalcone A and liquiritigenin reduced revertant colonies derived from MNU in S. typhimurium TA1535 without showing cytotoxic effects, indicating that these compounds possess antimutagenic activity against MNU. The inhibitory activity of glabridin and licochalcone A was more effective than that of liquiritigenin. Thus, Glycyrrhiza contains antimutagenic components against DNA alkylating, direct-acting carcinogens.

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