Dihydrostilbenes from Indigofera pulchra

Abstract

A mixture of two new dihydrostilbenes, 3-methoxy-4,5-methylenedioxy- 4′-O-(2ξ,3-dihydroxy-3-methylbutyl)-dihydrostilbene (1) and 3,5-dimethoxy-4′-O-(2ξ,3-dihydroxy-3-methylbutyl)-dihydrostilbene (2), was isolated from Indigofera pulchra as an inseparable mixture. Several isolation strategies, including multiple preparative TLC, SPE and finally HPLC were undertaken in an attempt to separate these metabolites, but to no avail. Structure elucidation on the mixture was conducted and we were able to establish the structures of these compounds unambiguously by MS and a series of 1D and 2D-NMR analyses. The mixture of these dihydrostilbenes was analyzed by NMR spectroscopy and 1 and 2 were in a ratio of 52:48, respectively, and this was evaluated against a panel of methicillin-resistant Staphylococcus aureus (MRSA) and multidrug-resistant variants of this organism, including a strain over-expressing the NorA efflux pump; weak activity was observed.