Evaluation of genotoxicity and mutagenicity of aqueous extracts of Rhazya stricta Decne. and Thymus vulgaris L.

Traditional herbal medicines have been part of human healthcare systems since ancient times. The studies on herbal medicines have mainly focused on their beneficial aspects and hence their harmful effects have been usually overlooked. Throughout Middle East and South Asia, Rhazya stricta Decne. and Thymus vulgaris L. are used as traditional medicines for various diseases. We evaluated R. stricta and T. vulgaris aqueous extracts for their genotoxicity and mutagenicity through comet assay and Ames Salmonella mutagenicity test respectively. An overall treatment effect (p < 0.0001) showed higher genotoxicity of T. vulgaris extract indicated by increased tail moments in comet assay compared to the extract of R. stricta and the combined extract. Further, an overall dose effect (p < 0.0001) showed higher genotoxicity at 1 mg/ml which further increased at 5 mg/ml doses of the extracts compared to 0 mg/ml. The genotoxicity did not show any further increase at 10 mg/ml. The extracts were also tested for their mutagenicity through Ames Salmonella test. R. stricta and T. vulgaris were not mutagenic to TA100 and TA98 when extracts tested separately. However, combined extracts of R. stricta and T. vulgaris was weakly mutagenic to TA98 with number of revertants 92 ± 8 at the highest concentration tested. This study implies that the herbal medicines should be used cautiously as they may cause long term harmful effects along with the intended beneficial activity.