[The isolation and identification of PAF inhibitors from Piper wallichii (Miq.) Hand-Mazz and P. hancei Maxim].

Platelet activating factor (PAF) is a highly potent endogenous phospholipid mediator, involved in various inflammatory and cardiovascular disorders. As part of a research program dealing with PAF inhibitors isolated from Piper plant species, we have isolated kadsurenone (I), denudatin B (II), and N-isobutyl-deca-trans-2-trans-4-dienamide (III) from Piped wallichii (Miq.) Hand-Mazz. and P. hancei Maxim. In a continuing search for potential PAF inhibitor from plants, using PAF induced platelet aggregation as a guide, a new neolignan named hancinone D (IV) was isolated from P. hancei maxim. By X-ray analysis it was identified as a racemate. The X-ray analysis led to a revision of the previously made structure assignment of hancinone C. Another new neolignan named wallichinine (V), which was identified as an analogue of (IV), along with the known compounds hancinone C (VI), galgravin (VII), dihydropiperlonguminine (VIII) and crotepoxide (IX) were isolated from P. wallichii (Miq.) Hand-Mazz. The structure determination was based upon spectroscopic analysis. All of the compounds were for the first time obtained from both plants. In the test of platelet aggregation caused by PAF, I, II, V, VI, VII showed inhibitory activity, whereas III, IV, VII, IX showed no activity.