Hypophyllins A–D, Labdane-Type Diterpenoids with Vasorelaxant Activity from <i>Hypoestes phyllostachya</i> “Rosea”

Abstract

Three rearranged labdane-type diterpenoids, hypophyllins A–C ( 1 – 3 ), and a caged labdane diterpenoid possessing a 8,9-dioxatricyclic[4.2.1.1 3,7 ]decane moiety, hypophyllin D ( 4 ), as well as two new biogenetically related diterpernoids, hypophyllins E ( 5 ) and F ( 6 ), were isolated from the aerial parts of Hypoestes phyllostachya “Rosea”. The absolute configurations of 1 – 4 were determined by X-ray diffraction analysis. The plausible biogenetic pathway for 1 – 4 was also proposed. Compounds 4 and 5 showed potent vasorelaxant activity on endothelium-intact thoracic aorta rings precontracted with KCl.