Screening of rhizomes of Rheum emodi Wall. Ex. Meissen for antimutagenic potential employing Ames assay

Rheum emodi Wall. Ex. Meissen is an important food and medicinal plant growing wild in western Himalayas. The current endeavor was undertaken to carry out bioassay guided fractionation and isolation of antimutagenic principle(s) present in the rhizomes of Rheum emodi. The antimutagenicity assay was performed to check the recuperating effect of 80% aqueous methanol extract of rhizomes of R. emodi and its fractions i.e. n-hexane, chloroform, ethyl acetate, n-butanol and water fractions, against 4-nitro-o-phenylenediamine (NPD), sodium azide, and 2AF-induced mutagenicity in TA98 and TA100 strains using the Ames Salmonella his+ reversion assay. The crude 80% aqueous methanol extract and ethyl acetate fraction exhibited strong antimutagenicity. The antimutagenic potential of the extracts and fractions was markedly enhanced when indirect acting mutagen was used in both the tester strains of Salmonella typhimurium. In an effort to identify the molecules responsible for the antimutagenic effect displayed by R. emodi, four anthraquinones i.e. aloe-emodin, chrysophanol, emodin and rhein detected in the ethyl acetate fraction by HPLC analysis were also tested for their antimutagenic potential in both the tester strains. It was found that the anthraquinones in their pure form showed lower antimutagenicity than the mother fraction from which they were isolated. The results point towards a synergistic effect of the principles present in the mother fraction.