A withanolide that is 5,6:22,26-diepoxyergosta-2,24-diene-1,26-dione substituted by hydroxy groups at positions 4 and 27 (the 4β,5β,6β,22<i>R</i> stereoisomer). Isolated from <em>Physalis longifolia</em>, it exhibits cytotoxic activity. ChEBI: Withaferin A is a withanolide that is 5,6:22,26-diepoxyergosta-2,24-diene-1,26-dione substituted by hydroxy groups at positions 4 and 27 (the 4beta,5beta,6beta,22R stereoisomer). Isolated from Physalis longifolia, it exhibits cytotoxic activity. It has a role as an antineoplastic agent and an apoptosis inducer. It is an epoxy steroid, a primary alcohol, a delta-lactone, a secondary alcohol, a 27-hydroxy steroid, an ergostanoid, an enone, a 4-hydroxy steroid and a withanolide.