Ellagitannins from Conocarpus erectus exhibit anti-quorum sensing activity against Pseudomonas aeruginosa
Quorum sensing (QS) is a key regulator of virulence and biofilm formation in the human opportunistic pathogen Pseudomonas aeruginosa and other medically relevant bacteria. In our previous work [1,2], we have shown a number of medicinal plants, including Conocarpus erectus L. (Combretaceae), to be effective in inhibiting pathogenicity of P. aeruginosa via attenuation of the QS system. In this study, two compounds responsible for anti-QS activity were purified from an aqueous extract of C. erectus. The stereoisomeric C-glycosidic ellagitannins, vescalagin and castalagin, were isolated using bioassay-guided fractionation and HPLC. Structures were confirmed via mass spectrometry and NMR spectroscopy. Both ellagitannins were shown to significantly decrease AHL signal production, QS gene expression, and virulence factor production in P. aeruginosa at a concentration of 40µg/ml. This is the first report of vescalagin and castalagin being isolated from C. erectus, and also the first report of their activity on the QS system of P. aeruginosa.
Acknowledgements: National Institute of General Medical Sciences #R25 GM61347 (A.A.), Cystic Fibrosis Foundation #ADONIZ06H0/07HO (A.A.), National Institute of Health (NCCAM) NRSA #1-T32-AT01060–01 (A.A., and K.M.) and1-R15-AT002626–01 (K.M.), NIAID grants R01 AI072508 and R01 AI064332 (F.M.A.), Monica Pupo, Hanna Milewicz, Tomo Kawate, and Steven Casper
References: 1. Adonizio, A. et al. (2008). Antimicrob. Agents Chemother. 52:198–203.
2. Adonizio, A. L., et al. (2006). J. of Ethnopharmacol. 103:427–435.