Anti-quorum sensing of Galla chinensis and Coptis chinensis on bacteria

Abstract

This study was to develop the quorum sensing (QS) inhibitors from Traditional Chinese Medicinal Plants (TCMs). The water extracts of twenty-nine plants were screened for quorum sensing inhibitory (QSI) activity using two biomonitor strains, Chromobacterium violaceum CV026 (CV026), Agrobacterium tumefaciens A136 (A136). Two of the plants, Galla chinensis and Coptis chinensis, showed a good QS inhibition capacity far below their MIC values, and no effect on their growths. The inhibition zones were 5.16 mm and 12.50 mm for CV026 respectively, and the production of violacein were decreased by 34.5% and 50.44% at 100 μg/mL respectively. QS-mediated β-galactosidase activity in A136 was inhibited strongly of 33.20% at 100 μg/mL by Galla chinensis while Coptis chinensis showed no inhibition. The QS-regulated virulence factors, including swarming motility and biofilm on Pseudomonas aeruginosa PAO1 were inhibited significantly at 10, 50 and 100 μg/mL respectively (P < 0.05). The higher the sub-MIC concentration, the greater the inhibitory effect on the production of violacein, β-galactosidase activity, swarming motility or biofilm formation, showing a good dose-dependent manner (r = 0.9286–0.9999). These findings may be helpful to provide a new aspect regarding the treatment of bacterial infections under a lower concentration of the TCMs.