Inhibition of biofilm formation, quorum sensing and other virulence factors in Pseudomonas aeruginosa by polyphenols of Gynura procumbens leaves

Abstract

Quorum sensing (QS) enables virulence factors in bacteria for biofilm formation and pathogenic invasion. Therefore, quorum quenching (QQ), disruption of QS circuit, becomes an alternative antimicrobial therapy. In this study, leaf extract of Gynura procumbens (GP) was used to inhibit biofilm and virulent factors in Pseudomonas aeruginosa. The extract inhibited the biofilm production (p ≤ 0.05) in P. aeruginosa strains MZ2F and MZ4A. The minimum biofilm eradication concentration (MBEC) was recorded at 250 and 500 μg/ml while total activity was found at 288 and 144 ml/g, respectively. Moreover, a significant reduction of virulence factors (p ≤ 0.05) at sub-MBEC without affecting the growth implies the QQ action of the extract. The bioactive fractions were rich in polyphenols and tentatively identified as quercetin and myricetin (R_f=0.53-0.60). Furthermore, we employed computational methods to validate our findings and their interactions with QS receptors (LasR and RhlR). Interestingly, docking studies have also shown that quercetin and myricetin are the promising anti-QS agents out of 31 GP compounds. Notably, their binding affinity ranged between −9.77 and −10.52 kcal/mol for both QS receptors, with controls ranging from −5.40 to −8.97 kcal/mol. Besides, ΔG of quercetin and myricetin with LasR was −71.56 and −74.88 kcal/mol, respectively. Moreover, compounds were suitable drug candidates with stable binding interactions. Therefore, the anti-QS activity of GP leaves and the identified polyphenols can be used in developing QQ-based therapeutics.

Communicated by Ramaswamy H. Sarma

Keywords:

• Quorum sensing
• biofilm formation
• Pseudomonas aeruginosa
• Gynura procumbens
• polyphenols
• microbial virulence
• antimicrobial resistance

Acknowledgements

Authors extend their gratitude towards the Department of Biotechnology and Genetic Engineering, Islamic University, Bangladesh for providing laboratory support. A bunch of thanks goes to Raihan Rahman, Shakil Ahmed Khan, and Moinuddin Sheam for their unconditional supports in some experiments. Special thanks to Dr Nilufa Akhter Banu for her contribution in the identification of the collected plant.

Disclosure statement

The authors declare no conflict of interest.

Author contributions

M.M.K and Z.N conceived and designed the study; Z.N, M.M.K, M.A.I, and F.J.M performed the wet-lab experiments; Z.N conducted the dry-lab investigations; Z.N and M.M.K analyzed and interpreted the data; Z.N wrote the manuscript draft and prepared the graphical interpretations; S.B.S helped in column chromatography and draft preparation; Z.N, M.M.K, M.R.I, and H.A critically revised and finalized the manuscript; M.M.K supervised the whole work. All authors approved the final version of the manuscript.

Additional information

Funding

This study was partially funded by University Grant Commission (UGC) research fund (Grant No. 4829) and National Science and Technology (NST) Fellowship from Ministry of Science and Technology, Government of the Peoples’ Republic of Bangladesh.