Two new withanolides, 2,3-dihydrotrechonolide A 1 and 2,3-dihydro-21-hydroxytrechonolide A 2, were isolated along with two known withanolides, trechonolide A 3 and jaborosalactone 39 4, from the aerial parts of Jaborosa caulescens Gillies & Hook (Solanaceae). Their structures were elucidated through 2D NMR and other spectroscopic techniques. In addition, the structure of 1 was confirmed by X-ray crystallographic analysis.
