Caffeoyl arbutin and related compounds from the buds of Vaccinium dunalianum.

Dunalianosides A-I (1-9), esters of arbutin and related phenolic glucosides, were isolated from the buds of Vaccinium dunalianum Wight (Ericaceae) together with 20 known compounds, and their structures were established on the basis of 1- and 2D NMR spectroscopic evidence. Dunalianosides F-H were dimers of p-hydroxyphenyl 6-O-trans-caffeoyl-beta-D-glucopyranoside (10). The latter was obtained in extraordinary high yield (22% of dry weight), and dunalianoside I (9) was found to be a conjugate of arbutin with an iridoid glucoside.