Phytochemistry and Pharmacology of Withania somnifera: An Updated Review

Abstract

Withania somnifera, known in Ayurveda as ashwagandha, is among the most widely used medicinal plants of South Asia, and its roots and leaves have attracted steady laboratory interest over several decades. This narrative review brings together published work on its chemistry and pharmacology and asks how far the reported activities can be trusted as evidence for use in people. The plant is rich in withanolides, steroidal lactones of which withaferin A and withanolide A are the best studied, together with withanosides, sitoindosides and a minor alkaloid fraction, and the profile differs between roots and leaves and between populations. Cell and animal studies describe effects on stress responses, neuronal growth, inflammation, immune function and cancer cell survival, and a few small human studies point in similar directions. Most of this work rests on crude extracts of uncertain composition, on concentrations that are hard to relate to doses taken by people, and on trials that are short and small. The review concludes that the chemistry is well characterised, that the pharmacology is plausible but unevenly supported, and that standardised extracts, reported composition and adequately sized controlled trials are the main gaps. It reports no new data.