Five new stilbene dimers from the lianas of Gnetum hainanense.

Five new stilbene dimers, gnetuhainins A-E (1-5), were isolated together with resveratrol trans-dehydrodimer (6), resveratrol, oxyresveratrol, and (-)-epsilon-viniferin from the lianas of Gnetum hainanense. Their structures and stereochemistry were determined on the basis of their chemical and spectral data. Compounds 1-5 are dimers formed by a resveratrol unit and an oxyresveratrol unit and belong to a new type of oligostilbenes polymerized from two different stilbene units.