Lack of the cytochrome P450 3A interaction of methanolic extract of Withania somnifera, Withaferin A, Withanolide A and Withanoside IV

Abstract

Aims: Withania somnifera is widely employed as a rejuvenator and expected to promote physical health and increase longevity. The aim of the present research work was to evaluate Cytochrome P450 3A (CYP3A) interaction of Withania somnifera . Materials and Methods: In vitro CYP3A interaction of methanolic extract of Withania somnifera (WS) and its principal phytoconstituents: Withaferin-A (WA), Withanolide-A (WL-A) and Withanoside-IV (WS-IV) were investigated in rat and human liver microsomes. In vivo CYP3A interaction potential was investigated by administering methanolic extract of WS orally at a dose of 500 mg/kg in female Wistar rats. Sildenafil citrate was used to index the activity of CYP3A. Results: IC 50 values of methanolic extract of Withania somnifera, WA, WL-A, WS-IV were found to be 200 μg/ml, >20 μM, >64 μM and >64 μM for CYP3A both in rats and humans, respectively. When sildenafil citrate was orally co-administered with methanolic extract of WS and compared with orally administered sildenafil citrate alone, the area under plasma concentration time (AUC) curve and C max did not significantly differ as compared to the group which received rifampicin orally (positive control). Conclusions: Results suggested that methanolic extract of WS, WA, WL-A, WS-IV showed no in vitro CYP3A inhibition in rats and humans. Methanolic extract of WS did not significantly alter the pharmacokinetics of sildenafil citrate in rats; indicating its safety when co-administered with other drugs that are substrates of CYP3A. Thus the results indicate the lesser likelihood of drug herb interactions when concomitantly administered with CYP3A substrates.