Effect of Bromination on the Quorum Sensing-Inhibiting Properties of Indole-3-Carboxaldehydes in Chromobacterium violaceum AHL System

Abstract

Quorum sensing (QS) is a form of bacterial communication involved in the production of virulence factors in many species. As a result, inhibition of quorum sensing may be of use in mitigating pathogenesis. The signaling molecule indole is currently being investigated as a target for quorum sensing inhibition (QSI) and the indole derivative indole-3-carboxaldehyde (ICA) has been shown to inhibit quorum sensing-mediated behaviors in Escherichia coli. In this study, we investigate bromination as a method of increasing the QSI capabilities of indole carboxaldehydes. The IC50 values of three monobrominated indole carboxaldehydes (5-bromoindole-3-carboxaldehyde, 6-bromoindole-3-carboxaldehyde, and 7-bromoindole-3-carboxaldehyde) were determined and compared to the IC50 value of ICA. The bromination of these indole carboxaldehydes reduced the IC50 values between 2- and 13-fold, indicating that bromination significantly increases the potency of these indole carboxaldehydes.