Novel labdane diterpenoids from the aerial parts of Leonurus japonicus

Three new labdane diterpenoids, leojapones A-C (1-3), along with a new artifactual analogue (4) and four known terpenoids, were isolated from the EtOAc extract of the aerial parts of Leonurus japonicus Houtt. Their structures were elucidated by spectroscopic analyses and physicochemical evidences. The effects of new compounds against the abnormal increase in platelet aggregation induced by adenosine diphosphate were examined. But instead of inhibiting the abnormal platelet aggregation, compounds 1-3 boosted it significantly.