Antibacterial bibenzyl derivatives from the tubers of Bletilla striata.

Ten previously undescribed bibenzyl derivatives (bletistrins A-J), including 5 that have hydroxyl-substituted chiral centres on the aliphatic bibenzyl bridge, along with twelve known bibenzyl derivatives, were isolated from the rhizomes of Bletilla striata. The structures of bletistrins A-J were primarily elucidated on the basis of their 1D and 2D NMR spectroscopic data. The absolute configurations of bletistrins A, D, F, H and I were determined by electronic circular dichroism (ECD) spectroscopic analysis and optical rotation value. Most of the isolated compounds were evaluated for their antibacterial activities against 3 g-positive bacterial strains and 1 g-negative bacterial strain. Bletistrins F, G, and J, bulbocol, shanciguol and shancigusin B showed inhibitory activities, with MICs of (3-28 μg/mL) against S. aureus ATCC 6538.