Occurrence of C-glucoside of resveratrol oligomers in Hopea parviflora.

Investigation of the highly polar chemical constituents in the stem of Hopea parviflora (Dipterocarpaceae) resulted in the isolation of four new resveratrol derivatives, hopeasides A and B (1, 2) (resveratrol pentamers), C (3) (resveratrol trimer), and D (4) (resveratrol dimer) together with nine known resveratrol oligomers (5—13). The new structures have a common partial structure of the 1-hydroxy-1-(3,5-dihydroxy-2-C-glucopyranosylphenyl)-2-(4-hydroxyphenyl)ethane-2-yl group after oxidative condensation of (E)-resveratrol-10-C-β-glucopyranoside (14). The structures were determined by spectroscopic analysis including 2D-NMR and computer-aided molecular modeling. The biogenetic relationship of the isolates and NMR characteristics caused by steric hindrance are also discussed in this paper.