Hypargyrin A, a Hemiacetalic Germacrolide from Viguiera hypargyrea (Asteraceae). Biogenetic Implications and Biological Evaluation

Abstract

A new hemiacetalic germacrolide 6, named hypargyrin A, was isolated from the aerial parts of Viguiera hypargyrea, along with the known compounds (8R, 9R)-beta-caryophyllene epoxide, entkaur-16-en-19-oic acid (1), hispidulin (2), 8 beta-epoxyangeloyloxy-14-acetoxy-tithifolin (3), 8 beta-epoxyangeloyloxy-14-hydroxy-tithifolin (4) and budlein B (5). Spectroscopic analysis of 6 allowed the structural correction of a compound isolated from Blainvillea gayana. Budlein B (5) can be considered the biogenetic precursor of 6, and two pathways for its formation are proposed. Hypargyrin A (6) did not display significant anti-inflammatory activity against ear edema in mice induced by TPA, but showed cytotoxic activity against HeLa (IC50 35.1 mu M) and Hep-2 (39.2 mu M) human cells.