Hydrangdione C, a novel triterpenoid with an unprecedented skeleton from Salvia hydrangea DC. ex Benth

Abstract

The genus Salvia is a rich source of terpenoids with structural diversity. Apart from sesterterpenoids as unusual constituents of Salvia species [1,2], it is a source of di- and triterpenoids with unprecedented carbon skeletons [3]. Aiming at identifying structurally interesting and bioactive metabolites from the Salvia species, we examined the extract of Salvia hydrangea DC. ex Benth. In our search for new bioactive natural products, a novel triterpenoid (hydrangdione C, 1) was isolated from the hexane extract of this plant. The skeletal type displayed by hydrangdione C was noticeable for its unusual carbon ring skeleton with a unique five membered ring D substituted by an acetyl group. This is the first report of a natural triterpenoid with a five-membered ring D. The structure of 1 was established by comprehensive 1D NMR, 2D NMR, and HRMS spectroscopic analysis and subsequently confirmed by a single-crystal X-ray diffraction study.