Structures of Oligostilbenoids in Dipterocarpaceaeous Plants and Their Biological Activities

Stilbenoids such as resveratrol (3,5,4'-trihydroxystilbene) have drawn much attention due to the diversity of structures and biological activities. These compounds are typically found as oligomers in a few plant families, such as Dipterocarpaceae, Vitaceae, Leguminosae, Cyperaceae, and Gnetaceae. The rich structural variation and multifunctional bioactivity make stilbenoid oligomers interesting targets for detailed phytochemical investigations. The oligomeric stilbenoids in Dipterocarpaceaeous plants have been my main focus of extensive structural investigation for the past decade. The tetramers of a resveratrol such as (-)-hopeaphenol, vaticanol B, and vaticanol C are widespread and present in large quantities in Dipterocarpaceaeous plants. These are of special interest due to the large number of stereoisomers resulting from many asymmetric carbons and the various frameworks when a resveratrol is homogeneously oligomerized. The structural variations in Vatica, Vateria, Upuna, Cotylelobium, Dipterocarpus, Shorea, and Hopea genera have been examined and about 120 new resveratrol oligomers isolated to date. A detailed structural determination based on comprehensive spectral study has solved the difficulties in elucidation caused by the complicated stereochemistry that comprises diastereomers, epimers, enantiomers, and rotamers. The isolates bear a structural variation of fused cyclic frameworks including heterocyclic and bicyclo ring systems, and have been developed as a chemical library for drug discovery and chemical biology probes for the first time.