withalongolide O

Withalongolide O is a naturally occurring withanolide isolated from the plant *Physalis longifolia*. Structurally, it is characterized by a $\Delta^2$-1-oxo- moiety in the A ring, a 5$\beta$,6$\beta$-epoxy group in the B ring, and a lactone ring in its nine-carbon side chain. In preclinical studies, withalongolide O has demonstrated potent anti-proliferative and cytotoxic activity against several human cancer cell lines, including head and neck squamous cell carcinoma (JMAR and MDA-1986) and melanoma (B16F10 and SKMEL-28), as well as normal fetal lung fibroblasts (MRC-5). Its IC50 values in these assays range from 0.15 to 2.95 µM. It was identified during bioactivity-guided isolation efforts aimed at discovering novel chemotherapeutic leads from the Solanaceae family.