Pleurocins A and B: Unusual 11(9 → 7)-abeo-Ergostanes and Eringiacetal B: A 13,14-seco-13,14-Epoxyergostane from Fruiting Bodies of Pleurotus eryngii and Their Inhibitory Effects on Nitric Oxide Production.

Two novel 11(9 → 7)-abeo-ergostane-type steroids, named pleurocins A (1) and B (2), a 13,14-seco-13,14-epoxy ergostane, named eringiacetal B (3), and an ergostane steroid (4) were isolated from the fruiting bodies of Pleurotus eryngii (Pleurotaceae). Their structures were determined by spectroscopic data and X-ray crystallography. A possible biogenesis pathway for 1-3 was also described. Compounds 1-3 exhibited inhibitory activities against NO production with almost no cytotoxicity at concentrations lower than 30 µM.