One‐Pot Synthesis of Flavonol Esters and Benzamides via Unusual Base Catalyzed Partial Ring‐Opening‐Esterification and Amidation of Flavonols

Assessing the antibiofilm activity of flavonol esters against Pseudomonas aeruginosa PAO1 biofilm: an in vitro, molecular docking, and molecular dynamics study

Pseudomonas aeruginosa is one of the opportunistic pathogens that may cause serious health problems and can produce several virulence factors, which are responsible for various infections, particularly in immunocompromised patients. They are responsible for producing infections on indwelling medical devices by attaching on to them and forming a biofilm. Antibiofilm, antivirulence, and gene expression studies of P. aeruginosa biofilm treated with esters of flavonols were evaluated. Pyocyanin, cell surface hydrophobicity, LasA protease estimation, rhamnolipid estimation, and pyoverdine estimation were performed to evaluate the antivirulence activities of the test compounds against P. aeruginosa. Previous studies on the antivirulence activity of flavonoids against P. aeruginosa demonstrate that even if they can inhibit bacterial growth, relatively high concentrations of the compound are generally required for the inhibition of virulence factors. The esters showed more than 40% inhibition in all the tested virulence factors at their sub minimum inhibitory concentration. The gene expression studies of selected esters toward lasB and rhlA genes show downregulation of rhlA which suggests the inhibition in biofilm formation through rhamnolipid inhibition, quorum sensing inhibition, or biofilm formation inhibition.Communicated by Ramaswamy H. Sarma.

Attenuation of Quorum Sensing Mediated Virulence Factors and Biofilm Formation in Pseudomonas Aeruginosa PAO1 by Substituted Chalcones and Flavonols

Flavonoids epitomize structural scaffolds in many biologically active synthetic and natural compounds. They showcase a diverse spectrum of biological activities including anticancer, antidiabetic, antituberculosis, antimalarial, and antibiofilm activities. The antibiofilm activity of a series of new chalcones and flavonols against clinically significant Pseudomonas aeruginosa PAO1 strain was studied. Antivirulence activities were screened by analysing the effect of compounds on the production of virulence factors like pyocyanin, LasA protease, cell surface hydrophobicity, and rhamnolipid. The best ligands towards the quorum sensing proteins LasR, RhlR, and PqsR were recognised using a molecular docking study. The gene expression in P. aeruginosa after treatment with test compounds was evaluated on quorum sensing genes including rhlA, lasB, and pqsE. The antibiofilm potential of chalcones and flavonols was confirmed by the efficient reduction in the production of virulence factors and downregulation of gene expression.

Synthesis and study of antibiofilm and antivirulence properties of flavonol analogues generated by palladium catalyzed ligand free Suzuki-Miyaura coupling against Pseudomonas aeruginosa PAO1

The Suzuki-Miyaura coupling is one of the ubiquitous method for the carbon-carbon bond-forming reactions in organic chemistry. Its popularity is due to its ability to undergo extensive coupling reactions to generate a broad range of biaryl motifs in a straightforward manner displaying a high level of functional group tolerance. A convenient and efficient synthetic route to arylate different substituted flavonols through the Suzuki-Miyaura cross-coupling reaction has been explained in this study. The arylated products were acquired by the coupling of a variety of aryl boronic acids with flavonols under Pd(OAc)2 catalyzed reaction conditions in a ligand-free reaction strategy. Subsequently, the antibiofilm and antivirulence properties of the arylated flavonols against Pseudomonas aeruginosa PAO1 were studied thoroughly. The best ligands for quorum sensing proteins LasR, RhlR, and PqsR were identified using molecular docking study. These best fitting ligands were then studied for their impact on gene expression level of P. aeruginosa by RT-PCR towards quorum sensing genes lasB, rhlA, and pqsE. The downregulation in the gene expression with the effect of synthesized flavonols endorse the antibiofilm efficiency of the compounds.

Co-assembly Behaviors of Flavonol Derivatives Induced by a Pyridine Derivative on HOPG via Hydrogen Bonding and Van der Waals Forces

In this paper, two new flavonol derivatives, 2-(4-(dodecyloxy)phenyl)-3-hydroxyflavone (DHF) and 2-(3,5-bis(dodecyloxy)phenyl)-3-hydroxyflavone (BDHF), were synthesized to investigate the respective self-assembly behaviors at the liquid/solid interface by scanning tunneling microscopy. In addition, a linear pyridine derivative with acetylene groups called BisPy was added to regulate the assembly of DHF and BDHF, individually. However, only BDHF molecules successfully co-assembled into grid structures with BisPy molecules. Furthermore, the assembly and co-assembly behavior mechanism of flavonol derivatives and BisPy molecules were further studied by density functional theory calculations. This work will lay a foundation for investigating the self-assembly of flavonol derivatives and the co-assembly regulated by pyridine derivatives at the liquid-solid interface.