Potent inhibition of bacterial neuraminidase activity by pterocarpans isolated from the roots of Lespedeza bicolor

Abstract

Bacterial neuraminidase has been highlighted as a key enzyme for pathogenic infection and sepsis. Six pterocarpans displaying significant levels of neuraminidase inhibitory activity were isolated from the root bark of Lespedeza bicolor. The isolated compounds were identified as three new pterocarpans (1-3) together with known compounds erythrabyssin 11 (4), lespebuergine G4 (5), and 1-methoxyerythrabyssin 11 (6). The new compounds were characterized as bicolosin A (1), bicolosin B (2), and bicolosin C (3). All compounds inhibited bacterial neuraminidase in a dose-dependent manner with significant inhibition (IC50 = 0.09-3.25 mu M). All neuraminidase inhibitors screened were found to exhibit noncompetitive kinetics. The three most potent neuraminidase inhibitors (1,3 and 6) feature a methoxy substitution on C-1. (C) 2011 Elsevier Ltd. All rights reserved.