Plant-Derived Natural Products as Sources of Anti-Quorum Sensing Compounds

Bacteria communicate with one another by using chemical signalling molecules which is termed as quorum sensing (QS). This process involves producing, releasing, detecting and responding to small hormone like molecules called as autoinducer (Christopher and Bassler, 2005). These regulate a diverse array of physiological activities such as bioluminescence, sporulation, competence, biofilm formation and virulence factor secretion (Rutherford and Bassler, 2012).There are three kinds of autoinducers molecules such as Acyl-homoserine lactones (AHLs) (Galloway et al., 2011), Autoinducer peptides (AIPs) (Sturme et al., 2002; Thoendel et al., 2011) and Autoinducer-2 (AI-2) (Lowery et al., 2008). These are play major role in QS. To overcome quorum sensing (QS) by inhibition and degradation of autoinducer by using Anti-QS compounds. These have the ability to prohibit bacterial quorum sensing and pathogenicity. These are novel microbial disease-controlling compounds including plant extracts and secondary metabolites of  plants (Asfour, 2018).

Demet et al. (2018) studied the anti-quorum sensing activities of quercetin and resveratrol compounds, which have antioxidant property without damaging to host, have been determined via using biosensor bacteria: Chromobacterium violaceum ATCC 12472 and Chromobacterium violaceum CV026. As quorum sensing inhibitors, quercetin and resveratrol's cutting off the bacterial communication will prevent the treatment failures caused by the development of bacterial resistance. The development of layered drugs with antioxidant compounds such as quercetin and resveratrol will pave the way for new horizons for new therapeutic strategies.

Gene expression and behaviour changes in gram negative bacteria are regulated in a population density-dependent fashion by N-acyl homoserine lactone (AHL) signal molecules were studied by Teplitski et al. (2000). Exudates from pea (Pisum sativum) seedlings were found to contain several separable activities that mimicked AHL signals in well-characterized bacterial reporter strains, stimulating AHL-regulated behaviour in some strains. Various species of higher plants in addition to pea were found to secrete AHL mimic activities.

Vasavi et al. (2016) evaluated the anti-QS activity of the ethanolic extract of the traditional herb Centella asiatica by the biosensor bioassay using Chromobacterium violaceum CV026. The effect of ethyl acetate fraction (CEA) from the bioassay-guided fractionation of ethanol extract on QS-regulated violacein production in C. violaceum ATCC12472 and pyocyanin production, proteolytic and elastolytic activities, swarming motility, and biofilm formationin P. aeruginosa PAO1.

Use of plant extracts is common in folk medicine for the treatment of bacterial infection. They have a great activity in inhibiting the bacterial QS systems and thereby mitigate bacterial pathogenesis. The mechanisms of action of these compounds as QSI are variable. Plant extracts constitute a promising tool for the management of bacterial pathogenesis through modulation of bacterial virulence genes. They have a vital role on the down regulation of the QS-related genes. Hence, inhibition of QS can be considered a promising novel strategy to deal with bacterial pathogens.

SELECTED REFERENCES:

DEMET, E., RAD, A.Y. AND AKSOZ, N., 2018, Anti-Quorum sensing potential of antioxidant quercetin and resveratrol. Braz. Arch. Biol. Technol., 61: 1-9.

TEPLITSKI, M., ROBINSON, J. B., AND BAUER, W. D., 2000, Plants secrete substances that mimic bacterial N-acyl homoserine lactone signal activities and affect population density-dependent behaviours in associated bacteria. Mol. Plant Microbe Interact., 13(6): 637-648.

VASAVI, H. S., ARUN, A. B. AND REKHA. P.D., 2016, Anti-quorum sensing activity of flavonoid rich fraction from Centella asiatica L. against Pseudomonas aeruginosa PAO1. J. Microbiol Immun. Infect., 49: 8-15.