Antimicrobial constituents from the tubers of Bletilla ochracea.

A new 2-(2-methylpropyl)butanedioic acid derivative, bletillin A ( 1), and a new bibenzyl, bletillin B ( 2), together with seventeen known compounds ( 3- 19), were isolated from the tubers of Bletilla ochracea Schltr. Their structures were established by detailed spectroscopic analyses. Phenanthrenes ( 12- 14) exhibited antibacterial activities against gram-positive bacteria Staphylococcus aureus, S. epidermidis, and Bacillus subtilis, with MIC values of 12.5-25 µg/mL. © Georg Thieme Verlag KG Stuttgart · New York.