Four new stilbenoids from the lianas of Gnetum montanum f. megalocarpum

From the lianas of Gnetum montanum Markgr. f. megalocarpum Markgr., four new stilbenoids, gnetumontanins A - D ( 1 - 4) were obtained together with 16 known compounds. Gnetumontanin A ( 1) is the first oligostilbene dimerized from two oxyresveratrol units, gnetumontanin B ( 2) is a new stilbene trimer oligomerized from two oxyresveratrol and one resveratrol units, gnetumontanin C ( 3) is a new stilbenoid with a novel skeleton having a delta-lactone moiety and gnetumontanin D ( 4) is a glucoside of 3. Their structures were determined by means of spectroscopic evidence, especially 2D NMR techniques. Gnetumontanin B showed potent inhibition of TNF-alpha with an inhibitory ratio of 58.1 % (P < 0.05) at a concentration of 10 ( - 5) mol L (-1) and the IC (50) was 1.49 x 10 ( - 6) mol L (-1).