Withanolides from Physalis coztomatl.

Six withanolides (1-6), as well as two known withanolides (physachenolide D 7 and withanoside VI 8), were isolated from the aerial parts of Physalis coztomatl (Solanaceae). Structural elucidations of 1-6 were achieved through 2D NMR and other spectroscopic techniques, while the structure of 1 was confirmed by X-ray crystallographic analysis. In addition, the stereochemical orientation of the 17-hydroxy group in withanolides was discussed in relation to (13)C NMR shifts of C-12, 13, 14 and 16. Such analysis established that coagulansin A contains a 17α-hydroxy moiety rather than the reported 17β-hydroxy functionality, and has been revised accordingly.