Onion Peel Ethylacetate Fraction and Its Derived Constituent Quercetin 4'-O-β-D Glucopyranoside Attenuates Quorum Sensing Regulated Virulence and Biofilm Formation

Critical review on plant-derived quorum sensing signaling inhibitors in pseudomonas aeruginosa

Pseudomonas aeruginosa, a biofilm-forming organism with complex quorum mechanisms (Las, Rhl, PQS, and IQS), poses an imminent danger to the healthcare sector and renders current treatment options for chemotherapy ineffectual. The pathogen's diverse pathogenicity, antibiotic resistance, and biofilms make it difficult to eradicate it effectively. Quorum sensing, a complex system reliant on cell density, controls P. aeruginosa's pathogenesis. Quorum-sensing genes are key components of P. aeruginosa's pathogenic arsenal, and their expression determines how severe the spread of infection becomes. Over the past ten years, there has been a noticeable increase in the quest for and development of new antimicrobial medications. Quorum sensing may be an effective treatment for infections triggered by bacteria. Introducing quorum-sensing inhibitors as an anti-virulent strategy might be an intriguing therapeutic method that can be effectively employed along with current medications. Amongst the several speculated processes, a unique anti-virulence strategy using anti-quorum sensing and antibiofilm medications for targeting pseudomonal infestations seems to be at the forefront. Due to their noteworthy quorum quenching capabilities, biologically active phytochemicals have become more well-known in the realm of science in this context. Recent research showed how different phytochemical quorum quenching actions affect P. aeruginosa's QS-dependent pathogenicity. This review focuses on the most current data supporting the implementation of plant bio-actives to treat P.aeruginosa-associated diseases, as well as the benefits and future recommendationsof employing them in anti-virulence therapies as a supplementary drug development approach towards conventional antibiotic approaches.

Quercetin-4'-O-β-D-glucopyranoside inhibits podocyte injury by SIRT5-mediated desuccinylation of NEK7

Diabetic kidney disease (DKD) is a complication of diabetic mellitus. New treatments need to be developed. This study aimed to investigate the effects of quercetin-4'-O-β-D-glucopyranoside (QODG) on podocyte injury. Podocytes were cultured in high glucose (HG) medium, treated with QODG, and overexpressing or knocking down SIRT5. Oxidative stress indicators were assessed using corresponding kits. Pyroptosis was detected by flow cytometry and western blot analysis. Succinylation modification was detected using immunoprecipitation (IP) and western blot analysis. The interaction between NEK7 and NLRP3 was determined by co-IP. The results indicated that QODG inhibited oxidative stress and pyroptosis of podocytes induced by HG. Besides, QODG suppressed succinylation levels in HG-induced podocytes, with the upregulation of SIRT5. Knockdown of SIRT5 reversed the effects of QODG on oxidative stress and pyroptosis. Moreover, SIRT5 inhibited the succinylation of NEK7 and the interaction between NLRP3 and NEK7. In conclusion, QODG upregulates SIRT5 to inhibit the succinylation modification of NEK7, impedes the interaction between NEK7 and NLRP3, and then inhibits the pyroptosis and oxidative stress injury of podocytes under HG conditions. The findings suggested that QODG has the potential to treat DKD and explore a novel underlying mechanism of QODG function.

Effect of L-HSL on biofilm and motility of Pseudomonas aeruginosa and its mechanism

Pseudomonas aeruginosa (P. aeruginosa) biofilm formation is a crucial cause of enhanced antibiotic resistance. Quorum sensing (QS) is involved in regulating biofilm formation; QS inhibitors block the QS signaling pathway as a new strategy to address bacterial resistance. This study investigated the potential and mechanism of L-HSL (N-(3-cyclic butyrolactone)-4-trifluorophenylacetamide) as a QS inhibitor for P. aeruginosa. The results showed that L-HSL effectively inhibited the biofilm formation and dispersed the pre-formed biofilm of P. aeruginosa. The production of extracellular polysaccharides and the motility ability of P. aeruginosa were suppressed by L-HSL. C. elegans infection experiment showed that L-HSL was non-toxic and provided protection to C. elegans against P. aeruginosa infection. Transcriptomic analysis revealed that L-HSL downregulated genes related to QS pathways and biofilm formation. L-HSL exhibits a promising potential as a therapeutic drug for P. aeruginosa infection. KEY POINTS: • Chemical synthesis of N-(3-cyclic butyrolactone)-4-trifluorophenylacetamide, named L-HSL. • L-HSL does not generate survival pressure on the growth of P. aeruginosa and can inhibit the QS system. • KEGG enrichment analysis found that after L-HSL treatment, QS-related genes were downregulated.

Quercetin disrupts biofilm formation and attenuates virulence of Aeromonas hydrophila

Aeromonas hydrophila poses significant health and economic challenges in aquaculture owing to its pathogenicity and prevalence. Overuse of antibiotics has led to multidrug resistance and environmental pollution, necessitating alternative strategies. This study investigated the antibacterial and antibiofilm potentials of quercetin against A. hydrophila. Efficacy was assessed using various assays, including antibacterial activity, biofilm inhibition, specific growth time, hemolysis inhibition, autoaggregation, and microscopic evaluation. Additionally, docking analysis was performed to explore potential interactions between quercetin and virulence proteins of A. hydrophila, including proaerolysin, chaperone needle-subunit complex of the type III secretion system, and alpha-pore forming toxin (PDB ID: 1PRE, 2Q1K, 6GRK). Quercetin exhibited potent antibacterial activity with 21.1 ± 1.1 mm zone of inhibition at 1.5 mg mL-1. It also demonstrated significant antibiofilm activity, reducing biofilm formation by 46.3 ± 1.3% at the MIC and attenuating autoaggregation by 55.9 ± 1.5%. Hemolysis was inhibited by 41 ± 1.8%. Microscopic analysis revealed the disintegration of the A. hydrophila biofilm matrix. Docking studies indicated active hydrogen bond interactions between quercetin and the targeted virulence proteins with the binding energy -3.2, -5.6, and -5.1 kcal mol⁻1, respectively. These results suggest that quercetin is an excellent alternative to antibiotics for combating A. hydrophila infection in aquaculture. The multifaceted efficacy of quercetin in inhibiting bacterial growth, biofilm formation, virulence factors, and autoaggregation highlights the potential for aquaculture health and sustainability. Future research should delve into the precise mechanisms of action and explore synergistic combinations with other compounds for enhanced efficacy and targeted interventions.

New Strategies for Biocontrol of Bacterial Toxins and Virulence: Focusing on Quorum-Sensing Interference and Biofilm Inhibition

The overuse of antibiotics and the emergence of multiple-antibiotic-resistant pathogens are becoming a serious threat to health security and the economy. Reducing antimicrobial resistance requires replacing antibiotic consumption with more biocontrol strategies to improve the immunity of animals and humans. Probiotics and medicinal plants have been used as alternative treatments or preventative therapies for a variety of diseases caused by bacterial infections. Therefore, we reviewed some of the anti-virulence and bacterial toxin-inhibiting strategies that are currently being developed; this review covers strategies focused on quenching pathogen quorum sensing (QS) systems, the disruption of biofilm formation and bacterial toxin neutralization. It highlights the probable mechanism of action for probiotics and medicinal plants. Although further research is needed before a definitive statement can be made on the efficacy of any of these interventions, the current literature offers new hope and a new tool in the arsenal in the fight against bacterial virulence factors and bacterial toxins.

Study on the inhibitory effect of quercetin combined with gentamicin on the formation of Pseudomonas aeruginosa and its bioenvelope

OBJECTIVE

The potential effects of quercetin and gentamicin combination on the bacteriostatic activity and biofilm formation of Pseudomonas aeruginosa (PA) were examined, and the findings provided a theoretical basis for the development of quercetin as a new biofilm inhibitor.

METHODS

The minimum inhibitory concentration (MIC) of eight PAs was determined by microdilution method and the partial inhibitory concentration index (FICI) of the combined drug was analyzed by micro-dilution method. Thereafter, the lowest film inhibitory concentration (MBIC) of quercetin and gentamicin alone and in combination was evaluated by crystal violet staining. Finally, scanning electron microscopy (SEM) and laser confocal microscopy (CLSM) were used to decipher the inhibitory effect of the combination on biofilm formation.

OUTCOME

The antibacterial activity of quercetin alone was relatively weak, but after combination with gentamicin, the antibacterial activity was significantly enhanced, as evident by FICI of 0.28 and 0.53 and manifested as synergistic or additive effect, which indicated that quercetin can enhance gentamicin antibacterial activity. The results of crystal violet staining revealed that quercetin and gentamicin alone exhibited a similar biofilm formation inhibitory effect, but the inhibitory effect was substantially weaker, and the antibiofilm activity was stronger and exhibited a dose-dependent response after the combination of the two with 1/2FICI. The results of scanning electron microscopy and laser confocal microscopy also showed that the treatment of PA biofilm after combining quercetin and gentamicin with 1/2FICI could completely destroy the spatial structure of the complete biofilm, significantly reduce the thickness of bacteria, and markedly reduce the proportion of viable bacteria in the membrane.

CONCLUSION

The combination of quercetin and gentamicin can effectively inhibit the formation of PA as well as its biofilm, and exhibit synergistic and additive effects.

Celecoxib, Glipizide, Lapatinib, and Sitagliptin as potential suspects of aggravating SARS-CoV-2 (COVID-19) infection: a computational approach

COVID-19 caused by SARS-CoV-2 has emerged as a potential threat to human life, especially to people suffering from chronic diseases. In this study, we investigated the ability of selected FDA-approved drugs to inhibit TACE (tumor necrosis factor α converting enzyme), which is responsible for the shedding of membrane-bound ACE2 (angiotensin-converting enzyme2) receptors into soluble ACE2. The inhibition of TACE would lead to an increased population of membrane-bound ACE2, which would facilitate ACE2-Spike protein interaction and viral entry. A total of 50 drugs prescribed in treating various chronic diseases in Saudi Arabia were screened by performing molecular docking using AutoDock4.2. Based on docking energy (≤ -9.00 kcal mol^-1), four drugs (Celecoxib, Glipizide, Lapatinib, and Sitagliptin) were identified as potential inhibitors of TACE, with binding affinities up to 10⁶-10⁷ M^-1. Analysis of the molecular docking suggests that these drugs were bound to TACE's catalytic domain and interact with the key residues such as His405, Glu406, and His415, which are involved in active site Zn²⁺ ion chelation. Molecular dynamics simulation was performed to confirm the stability of TACE-drugs complexes. RMSD (root mean square deviation), RMSF (root mean square fluctuation), Rg (radius of gyration), and SASA (solvent accessible surface area) were within the acceptable limits. Free energy calculations using Prime-MM/GBSA suggest that Celecoxib formed the most stable complex with TACE, followed by Glipizide, Sitagliptin, and Lapatinib. The finding of this study suggests a mechanism for drugs to aggravate SARS-CoV-2 infection and hence high mortality in patients suffering from chronic diseases.Communicated by Ramaswamy H. Sarma.

Effect of samarium oxide nanoparticles on virulence factors and motility of multi-drug resistant Pseudomonas aeruginosa

Biofilm formation and quorum sensing (QS) dependent virulence factors are considered the major causes of the emergence of drug resistance, therapeutic failure and development of Pseudomonas aeruginosa infections. This study aimed to investigate the effects of samarium oxide nanoparticles (Sm₂O₃NPs) on biofilm, virulence factors, and motility of multidrug-resistant P. aeruginosa. Sm₂O₃NPs were synthesized using curcumin and characterized by Transmission Electron Microscopy, X-ray diffractometer, Field Emission Scanning Electron Microscopy, and Energy-dispersive X-ray spectroscopy. Minimum inhibitory concentration (MIC) was determined using broth microdilution method. The antibiofilm potential of Sm₂O₃NPs was also evaluated by crystal violet staining and light microscopy examination. Then, the effect of sub-MICs concentrations of Sm₂O₃NPs on the proteolytic and hemolytic activities of P. aeruginosa was investigated. Finally, the effect of Sm₂O₃NPs on various types of motility including swarming, swimming, and twitching was studied. Our results showed that Sm₂O₃NPs significantly inhibited biofilm formation of P. aeruginosa by 49-61%. Additionally, sub-MICs concentrations of Sm₂O₃NPs effectively decreased virulence factors including pyocyanin (33-55%), protease (24-45%), and hemolytic activity (22-41%). Moreover, swarming, swimming, and twitching motility remarkably was reduced after exposure to the NPs. The findings of this work showed that Sm₂O₃NPs have a high potential in inhibiting QS-dependent virulence of P. aeruginosa, which could be considered for antibacterial chemotherapy after further characterization.

Three New Xanthones from Hypericum scabrum and Their Quorum Sensing Inhibitory Activities against Chromobacterium violaceum

Quorum sensing (QS) plays an important role in the production of virulence factors and pathogenicity in pathogenic bacteria and is, therefore, a hopeful target to fight against bacterial infections. During our search for natural QS inhibitors, two new xanthonolignoids (1 and 2), each existing as a racemic mixture, one new simple oxygenated xanthone (7), and eight known analogs (3–6, 8–11) were isolated from Hypericum scabrum Linn. Chiral separation of 1 yielded a pair of enantiomers 1a and 1b. The structures of these compounds were elucidated by spectroscopic analysis and ECD (electrostatic circular dichroism) calculations. All isolates were evaluated for their QS inhibitory activity against Chromobacterium violaceum. Both 9 and 10 exhibited the most potent QS inhibitory effects with minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of 31.25 and 62.5 μM, respectively. Crystal violet staining was used to further evaluate the biofilm inhibition potential of compounds 7, 9 and 10, and the formation of biofilms increased with decreasing drug concentration in a classic dose-dependent manner. The results of a cytotoxicity assay revealed that compounds 7, 9 and 10 exhibited no cytotoxic activity on PC-12 cells at the tested concentration.

The Derived Components of Gnaphalium hypoleucum DC. Reduce Quorum Sensing of Chromobacterium violaceum

Gnaphalium hypoleucum DC. was first recorded in the Chinese National Pharmacopoeia “Yi Plant Medicine”. There is no detailed report on its main components’ activity in suppressing the quorum sensing activity (QS) of bacteria. Our study aimed to screen the main components in extracts of G. hypoleucum DC. in order to measure their effects on bacterial QS activity and to explore specific quorum sensing mechanisms that are affected by G. hypoleucum DC. extracts. Crude extracts of G. hypoleucum DC. contained significant amounts of two compounds shown to inhibit bacterial QS activity, namely apigenin and luteolin. Apigenin and luteolin in crude extracts of G. hypoleucum DC. showed substantial inhibition of pigment formation, biofilm production, and motility in Chromobacterium violaceum ATCC 12472 compared to the effects of other phytochemicals from G. hypoleucum DC. Apigenin and luteolin exhibited a strong QS inhibitory effect on C. violaceum, interfering with the violacein pigment biosynthesis by downregulating the vioB, vioC, and vioD genes. In the presence of signal molecules, the QS effect is prevented, and the selected compounds can still inhibit the production of the characteristic purple pigment in C. violaceum. Based on qualitative and quantitative research using genomics and bioinformatics, we concluded that apigenin and luteolin in crude extracts of G. hypoleucum DC can interfere with the generation of QS in C. violaceum by downregulating the vioB, vioC, and vioD genes. Indeed, G. hypoleucum DC. is used for the treatment of bacterial infections, and this research provides new ideas and potential alternative uses for medicinal plants.

Antimicrobial Activity of Dihydroisocoumarin Isolated from Wadi Lajab Sediment-Derived Fungus Penicillium chrysogenum: In Vitro and In Silico Study

Antibiotic resistance is considered a major health concern globally. It is a fact that the clinical need for new antibiotics was not achieved until now. One of the most commonly prescribed classes of antibiotics is β-Lactam antibiotics. However, most bacteria have developed resistance against β-Lactams by producing enzymes β-Lactamase or penicillinase. The discovery of new β-Lactamase inhibitors as new antibiotics or antibiotic adjuvants is essential to avoid future catastrophic pandemics. In this study, five dihydroisocoumarin: 6-methoxy mellein (1); 5,6-dihydroxymellein (2); 6-hydroxymellein (3); 4-chloro-6-hydroxymellein (4) and 4-chloro-5,6-di-hydroxymellein (5) were isolated from Wadi Lajab sediment-derived fungus Penicillium chrysogenum, located 15 km northwest of Jazan, KSA. The elucidation of the chemical structures of the isolated compounds was performed by analysis of their NMR, MS. Compounds 1–5 were tested for antibacterial activities against Gram-positive and Gram-negative bacteria. All of the compounds exhibited selective antibacterial activity against Gram-positive bacteria Staphylococcus aureus and Bacillus licheniformis except compound 3. The chloro-dihydroisocoumarin derivative, compound 4, showed potential antimicrobial activities against all of the tested strains with the MIC value between 0.8–5.3 μg/mL followed by compound 5, which exhibited a moderate inhibitory effect. Molecular docking data showed good affinity with the isolated compounds to β-Lactamase enzymes of bacteria; NDM-1, CTX-M, OXA-48. This work provides an effective strategy for compounds to inhibit bacterial growth or overcome bacterial resistance.

Mechanisms, Anti-Quorum-Sensing Actions, and Clinical Trials of Medicinal Plant Bioactive Compounds against Bacteria: A Comprehensive Review

Bacterial strains have developed an ability to resist antibiotics via numerous mechanisms. Recently, researchers conducted several studies to identify natural bioactive compounds, particularly secondary metabolites of medicinal plants, such as terpenoids, flavonoids, and phenolic acids, as antibacterial agents. These molecules exert several mechanisms of action at different structural, cellular, and molecular levels, which could make them candidates or lead compounds for developing natural antibiotics. Research findings revealed that these bioactive compounds can inhibit the synthesis of DNA and proteins, block oxidative respiration, increase membrane permeability, and decrease membrane integrity. Furthermore, recent investigations showed that some bacterial strains resist these different mechanisms of antibacterial agents. Researchers demonstrated that this resistance to antibiotics is linked to a microbial cell-to-cell communication system called quorum sensing (QS). Consequently, inhibition of QS or quorum quenching is a promising strategy to not only overcome the resistance problems but also to treat infections. In this respect, various bioactive molecules, including terpenoids, flavonoids, and phenolic acids, exhibit numerous anti-QS mechanisms via the inhibition of auto-inducer releases, sequestration of QS-mediated molecules, and deregulation of QS gene expression. However, clinical applications of these molecules have not been fully covered, which limits their use against infectious diseases. Accordingly, the aim of the present work was to discuss the role of the QS system in bacteria and its involvement in virulence and resistance to antibiotics. In addition, the present review summarizes the most recent and relevant literature pertaining to the anti-quorum sensing of secondary metabolites and its relationship to antibacterial activity.

CD-g-CS nanoparticles for enhanced antibiotic treatment of Staphylococcus xylosus infection

Staphylococcus xylosus (S. xylosus)-induced cow mastitis is an extremely serious clinical problem. However, antibiotic therapy does not successfully treat S. xylosus infection because these bacteria possess a strong biofilm formation ability, which significantly reduces the efficacy of antibiotic treatments. In this study, we developed ceftiofur-loaded chitosan grafted with β-cyclodextrins (CD-g-CS) nanoparticles (CT-NPs) using host-guest interaction. These positively charged nanoparticles improved bacterial internalization, thereby significantly improving the effectiveness of antibacterial treatments for planktonic S. xylosus. Moreover, CT-NPs effectively inhibited biofilm formation and eradicated mature biofilms. After mammary injection in a murine model of S. xylosus-induced mastitis, CT-NPs significantly reduced bacterial burden and alleviated inflammation, thereby achieving optimized therapeutic efficiency for S. xylosus infection. In conclusion, this treatment strategy could improve the efficiency of antibiotic therapeutics and shows great potential in the treatment of S. xylosus infections.

Chemical constituents and medicinal properties of Allium species

Allium species, belonging to Alliaceae family, are among the oldest cultivated vegetables used as food. Garlic, onions, leeks and chives, which belong to this family, have been reported to have medicinal properties. The Allium species constituents have been shown to have antibacterial and antioxidant activities, and, in addition, other biological properties. These activities are related to their rich organosulfur compounds. These organosulfur compounds are believed to prevent the development of cancer, cardiovascular, neurological, diabetes, liver diseases as well as allergy and arthritis. There have also been reports on toxicities of these compounds. The major active compounds of Allium species includes, diallyl disulfide, diallyl trisulfide, diallyl sulfide, dipropyl disulfide, dipropyl trisulfide, 1-propenylpropyl disulfide, allyl methyl disulfide and dimethyl disulfide. The aim of this review is to focus on a variety of experimental and clinical reports on the effectiveness, toxicities and possible mechanisms of actions of the active compounds of garlic, onions, leek and chives.

Recent Advances in Bioactive Compounds, Health Functions, and Safety Concerns of Onion (Allium cepa L.)

Onion (Allium cepa L.) is a common vegetable, widely consumed all over the world. Onion contains diverse phytochemicals, including organosulfur compounds, phenolic compounds, polysaccharides, and saponins. The phenolic and sulfur-containing compounds, including onionin A, cysteine sulfoxides, quercetin, and quercetin glucosides, are the major bioactive constituents of onion. Accumulated studies have revealed that onion and its bioactive compounds possess various health functions, such as antioxidant, antimicrobial, anti-inflammatory, anti-obesity, anti-diabetic, anticancer, cardiovascular protective, neuroprotective, hepatorenal protective, respiratory protective, digestive system protective, reproductive protective, and immunomodulatory properties. Herein, the main bioactive compounds in onion are summarized, followed by intensively discussing its major health functions as well as relevant molecular mechanisms. Moreover, the potential safety concerns about onion contamination and the ways to mitigate these issues are also discussed. We hope that this paper can attract broader attention to onion and its bioactive compounds, which are promising ingredients in the development of functional foods and nutraceuticals for preventing and managing certain chronic diseases.

Quercetin Inhibits Biofilm Formation by Decreasing the Production of EPS and Altering the Composition of EPS in Staphylococcus epidermidis

Staphylococcus epidermidis is an opportunistic pathogen, and its biofilm formation ability is an important virulent factor. Quercetin, a typical flavonoid ubiquitously used in dietary supplementation, is known for its antioxidant property, but its anti-biofilm activity against S. epidermidis remains unknown. In this study, the anti-biofilm activity of quercetin was investigated using S. epidermidis ATCC35984, a strong biofilm-positive strain. An attempt was made to disclose the mechanisms of the anti-biofilm activity of quercetin. S. epidermidis exhibited a less cell surface hydrophobicity after quercetin treatment. Also, quercetin effectively inhibited S. epidermidis cells from adhering to the glass slides. Quercetin downregulated the intercellular adhesion (ica) locus and then polysaccharide intercellular adhesin (PIA) production was reduced. Therefore, S. epidermidis cells became less hydrophobic, which supported quercetin’s anti-biofilm effect. Our study suggests that quercetin from plants be given further attention as a potential anti-biofilm agent against the biofilm formation of S. epidermidis, even biofilm infections of other bacteria.

Attenuation of quorum sensing mediated virulence factors production and biofilm formation in Pseudomonas aeruginosa PAO1 by Colletotrichum gloeosporioides HM3

Signal dependent microbial communication in Pseudomonas aeruginosa PAO1 is a typical phenomenon mediated by acyl homo-serine lactone molecules that helps in developing biofilm and enhance antibiotic resistance. Microbial sources provide insight to the hidden treasure of secondary metabolites, and these structurally diversified chemical motifs can be used as antimicrobial and anti-infective agents. In the present study, endophytic fungus, Colletotrichum gloeosporioides HM3 isolated from Carica papaya leaves was explored for anti-infective potential against P. aeruginosa PAO1. The crude extract of C. gloeosporioides HM3 displayed bacteriostatic effect on P. aeruginosa PAO1 growth at 750 μg/ml concentration. A significant decline was observed in the production of quorum sensing regulated virulence factors, i.e. 56.32%, 62.54%, and 66.67% of pyocyanin, chitinase, and elastase enzyme, respectively. A drastic reduction in pathogenic determinant behaviour after treatment with crude extract of C. gloeosporioides HM3 i.e. EPS, rhamnolipid, and HCN production was noted. Light microscopy and CLSM analysis revealed that fungal extract treatment has reduced bacterial ability to form dense biofilm architecture. In silico analysis demonstrated the binding efficiency of bioactive compound, 4-(2,3-dimethoxybenzylidene)-3-methyl-1-(4-nitrophenyl)-2-pyrazolin-5-one, which is equipotent to the natural ligand and displayed a docking score of -5.436 kcal/mol with QS transcriptional regulator (LasR). Whereas the compound Acetamide, n-[tetrahydro-3-(phenylmethyl) thieno [3,4-d]thiazol-2 (3 h)-ylidene]-, s,s-dioxide exhibits a docking score of -4.088 kcal/mol (LasR) and -1.868 kcal/mol (RhlR) with cognate receptor proteins. Henceforth, the research report suggests C. gloeosporioides HM3 derived metabolites could be considered as a potential inhibitors of QS regulated virulence factors and biofilm production in P. aeruginosa PAO1.

Naringin inhibits the biofilms of metallo-β-lactamases (MβLs) producing Pseudomonas species isolated from camel meat

Food producing animals harbouring bacteria carrying drug resistance genes especially the metallo-beta-lactamase (MBL) pose high risk for the human population. In addition, formation of biofilm by these drug resistant pathogens represents major threat to food safety and public health. In this study, metallo-β-lactamases (MβLs) producing Pseudomonas spp. from camel meat were isolated and assessed for their biofilm formation. Further, in vitro and in silico studies were performed to study the effect of flavone naringin on biofilm formation against isolated Pseudomonas spp. A total of 55% isolates were found to produce metallo-β-lactamase enzyme. Naringin mitigated biofilm formation of Pseudomonas isolates up to 57%. Disturbed biofilm architecture and reduced the colonization of bacteria on glass was observed under scanning electron microscope (SEM) and confocal laser scanning microscope (CLSM). The biofilm related traits such as exopolysaccharides (EPS) and alginate production was also reduced remarkably in the presence of naringin. Eradication of preformed biofilms (32–60%) was also observed at the respective 0.50 × MICs. Molecular docking revealed that naringin showed strong affinity towards docked proteins with binding energy ranging from −8.6 to −8.8 kcal mol⁻¹. Presence of metallo-β-lactamase producers indicates that camel meat could be possible reservoir of drug-resistant Pseudomonas species of clinical importance. Naringin was successful in inhibiting biofilm formation as well as eradicating the preformed biofilms and demonstrated strong binding affinity towards biofilm associated protein. Thus, it is envisaged that naringin could be exploited as food preservative especially against the biofilm forming food-borne Pseudomonas species and is a promising prospect for the treatment of biofilm based infections.

Okanin in Coreopsis tinctoria Nutt is a major quorum-sensing inhibitor against Chromobacterium violaceum

ETHNOPHARMACOLOGICAL RELEVANCE

Coreopsis tinctoria Nutt has various medical and functional properties and its flower is widely used as health-care tea to decrease blood glucose and to lower blood lipids. However, the quorum sensing (QS) inhibition activity of Coreopsis tinctoria Nutt flower remains unclear.

AIM OF THE STUDY

To assess inhibitory activity against quorum sensing by Chromobacterium violaceum, to identify the chemical composition of the extracts and to disclose the action mechanism of separated compound.

MATERIAL AND METHODS

Violacein inhibition assays were performed in 96-wells microplates. The compounds extracted from Coreopsis tinctoria Nutt flower were separated and purified by various chromatography techniques. Respectively, thin layer chromatography (TLC, GF254), mass spectrometer (Agilent 1100 Series LC/MSD Trap SL), Medium-pressure automatic purification system (Buscisepacore C 620, Switzerland), High performance liquid chromatography (HPLC, Shimadzu LC-20AD, Japan), Liquid preparation Chromatography (Waters2545, USA). The chemical structures were identified by nuclear magnetic resonance (NMR, Bruker AV-500, Germany) technique. The inhibitory mechanism of okanin against C. violaceum quorum sensing was detected by quantitative real-time PCR (qRT-PCR).

RESULTS

Quorum sensing regulates production of bacterial virulence factors, thereby making it an intriguing target for attenuating bacterial pathogenicity. In this study, anti-QS activity of Coreopsis tinctoria Nutt methanol fraction (CTM) was investigated against C. violaceum ATCC12472. CTM showed an inhibitory effect on the QS-mediated virulence factors production such as violacein in C. violaceum without effect on growth rate. Also, okanin was isolated from CTM and its potential of anti-QS was confirmed after observing a significant reduction of violacein production in C. violaceum. An attempt was made to assess the effect of okanin on vioABCDE expression in C. violaceum to disclose acting mechanisms.

CONCLUSIONS

The results of this study contribute to validate an inhibitory effect of Coreopsis tinctoria Nutt flower on quorum sensing by Chromobacterium violaceum and to determine the compound responsible for inhibition. Also, the inhibitory effect was achieved in tandem with the down-regulation of vio operon.

Allium Flavonols: Health Benefits, Molecular Targets, and Bioavailability

Allium species are revered worldwide as vegetables, condiments, and spices as well as the therapeutic agents in traditional medicine. The bioactive compounds in alliums mainly include organosulfur compounds, polyphenols, dietary fibers, and saponins. Flavonoids, particularly flavonols from alliums, have been demonstrated to have the antioxidant, anticancer, hypolipidemic, anti-diabetic, cardioprotective, neuroprotective, and antimicrobial activities. However, flavonols are mostly characterized from onions and have not been comprehensively reviewed across different species. This article therefore focuses on flavonol profiles from different Allium species, their health effects, underlying molecular mechanisms, and bioavailability. Intriguingly, the functional health effects of flavonols were mainly ascribed to their antioxidant and anti-inflammatory activities involving a cascade of multiple signaling pathways. Although the Allium-derived flavonols offer tremendous potential in preventing chronic disease risks, in-depth studies are needed to translate their clinical application.

Antioxidant, anti-quorum sensing, biofilm inhibitory activities and chemical composition of Patchouli essential oil: in vitro and in silico approach

The interest in naturally occurring essential oils from medicinal plants has increased extremely over the last decade markedly because they possess antimicrobial and antioxidant protective properties against different chronic diseases. Extensive survival of drug-resistant infectious bacteria depends on quorum sensing (QS) signaling network which raises the need for alternative antibacterial compounds. The aim of this study was to examine the phytochemical compounds of patchouli essential oil (PEO) and to assess its antioxidant activity. Antioxidant studies estimated by 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging method showed that the PEO has effective antioxidant activity (IC₅₀ 19.53 µg/mL). QS inhibitory activity of PEO was examined by employing the biosensor strain, Chromobacterium violaceum CV12472. At sub-lethal concentrations, PEO potentially reduced the QS regulated violacein synthesis in CV12472 without inhibiting its cell proliferation. Moreover, it also effectively reduced the production of some QS regulated virulence factors and biofilm development in P. aeruginosa PAO1 without hindering its growth. Phytochemical analysis of PEO was done by GC/MS technique. Molecular docking of PEO major compounds with QS (LasR and FabI) and biofilm regulator proteins (MvfR and Sialidase) of PAO1 was evaluated. These phytocompounds showed potential hydrogen binding interactions with these proteins. The overall results, in vitro and in silico, suggest that PEO could be applied as biocontrol agent against antibiotic resistance pathogens. Communicated by Ramaswamy H. Sarma.

Controlled Fermentation Using Autochthonous Lactobacillus plantarum Improves Antimicrobial Potential of Chinese Chives against Poultry Pathogens

Chinese chives (CC) are rich in several antimicrobial constituents including organosulfur compounds, phenolics, and saponins, among others. Herein, we fermented CC juice using an autochthonous isolate, Lactobacillus plantarum having antimicrobial effects against poultry pathogens toward formulating an antimicrobial feed additive. Following 24 h of fermentation, the antimicrobial and antiviral activities of CC juice were significantly enhanced against poultry pathogens. However, the antioxidant activity of CC juice was significantly decreased following fermentation. Meanwhile, the compositional changes of CC juice following fermentation were also investigated. The total polyphenol, thiol, and allicin contents were significantly decreased in L. plantarum 24 h-fermented CC juice (LpCC) extract; however, total flavonoids increased significantly following fermentation. The untargeted metabolite profiling of nonfermented CC juice (NCC) and LpCC extracts was carried out using the ultra-high-performance liquid chromatography-linear trap quadrupole-orbitrap-tandem mass spectrometry (UHPLC-LTQ-Orbitrap-MS/MS) followed by multivariate analyses. The score plots of principal component analysis (PCA) and orthogonal partial least squares-discriminant analysis (OPLS-DA) based on UHPLC-LTQ-Orbitrap-MS/MS datasets displayed a clear segregation between the LpCC and NCC samples, which suggests their marked metabolomic disparity. Based on the multivariate analysis, we selected 17 significantly discriminant metabolites belonging to the different chemical classes including alkaloid, flavonols, saponins, fatty acids, amino acids, and organic acids. Notably, the flavonols including the glycosides of quercetin, kaempferol, and isorhamnetin as well as the saponins displayed significantly higher relative abundance in LpCC as compared with NCC. This study provides useful insights for the development of a fermented CC juice based antimicrobial feed additive to combat poultry infections.

Identifying novel inhibitor of quorum sensing transcriptional regulator (SdiA) of Klebsiella pneumoniae through modelling, docking and molecular dynamics simulation

In this study, attempts have been made to identify novel inhibitor(s) of SdiA (a homolog of LuxR transcription regulator) of Klebseilla pneumoniae using various computational techniques. 4LFU was used as a template to model the structure of SdiA. ProCheck, Verify3D, Ramachandran plot scores and ProSA-Web confirmed the good quality of the model as the root mean square deviation (RMSD) between SdiA model, and 4LFU template was estimated to be 0.21 Å. The secondary structural contents of SdiA model were predicted using PDBsum. The only binding site of SdiA was identified (area = 523.083 Ų and volume = 351.044 ų) using CASTp. Molecular docking at three different levels [high throughput virtual screening, standard-precision (SP) and extra-precision (XP) dockings] with increasingly stringent conditions was performed using Glide on Selleck's express pick library (L3600). A total of 61 ligands were found to bind with high affinities to the active site of SdiA. Further, the effect of solvent on protein-ligand interaction was evaluated by performing molecular mechanics-general born surface area (Prime/MM-GBSA). On the basis of Prime/MM-GBSA score, molecular dynamics simulation (50 ns) was performed on the ligand (WAY-390139-A) showing lowest binding energy to confirm the stability of protein-ligand complex. Docking energy and the corresponding binding affinity of WAY-390139-A towards SdiA were estimated to be -13.005 kcal mol^-1 and 3.46 × 10⁹ M^-1, respectively. Our results confirm that WAY-390139-A binds at the autoinducer binding site of SdiA with high affinity and stability and can be further exploited as potential drug against K. pneumoniae after experimental validation.Communicated by Ramaswamy H. Sarma.

Calpurnia aurea (Aiton) Benth Extracts Reduce Quorum Sensing Controlled Virulence Factors in Pseudomonas aeruginosa

Pseudomonas aeruginosa is the causative agent of several life-threatening human infections. Like many other pathogens, P. aeruginosa exhibits quorum sensing (QS) controlled virulence factors such as biofilm during disease progression, complicating treatment with conventional antibiotics. Thus, impeding the pathogen's QS circuit appears as a promising alternative strategy to overcome pseudomonas infections. In the present study, Calpurnia aurea were evaluated for their antibacterial (minimum inhibitory concentrations (MIC)), anti-quorum sensing/antivirulence (AQS), and antibiofilm potential against P. aeruginosa. AQS and antivirulence (biofilm formation, swimming, and swarming motility) activities of plant extracts were evaluated against Chromobacterium violaceum and P. aeruginosa, respectively. The in vitro AQS potential of the individual compounds were validated using in silico molecular docking. Acetone and ethanolic extracts of C. aurea showed MIC at 1.56 mg/mL. The quantitative violacein inhibition (AQS) assay showed ethyl acetate extracts as the most potent at a concentration of 1 mg/mL. GCMS analysis of C. aurea revealed 17 compounds; four (pentadecanol, dimethyl terephthalate, terephthalic acid, and methyl mannose) showed potential AQS through molecular docking against the CviR protein of C. violaceum. Biofilm of P. aeruginosa was significantly inhibited by ≥60% using 1-mg/mL extract of C. aurea. Confocal laser scanning microscopy correlated the findings of crystal violet assay with the extracts significantly altering the swimming motility. C. aurea extracts reduced the virulence of pseudomonas, albeit in a strain- and extract-specific manner, showing their suitability for the identification of lead compounds with QS inhibitory potential for the control of P. aeruginosa infections.

Food color 'Azorubine' interferes with quorum sensing regulated functions and obliterates biofilm formed by food associated bacteria: An in vitro and in silico approach

Quorum sensing (QS) plays a crucial role in different stages of biofilm development, virulence production, and subsequently to the growth of bacteria in food environments. Biofilm mediated spoilage of food is one of the ongoing challenge faced by the food industry worldwide as it incurs substantial economic losses and leads to various health issues. In the present investigation, we studied the interference of quorum sensing, its regulated virulence functions, and biofilm in food-associated bacteria by colorant azorubine. In vitro bioassays demonstrated significant inhibition of QS and its coordinated virulence functions in Chromobacterium violaceum 12472 (violacein) and Pseudomonas aeruginosa PAO1 (elastase, protease, pyocyanin, and alginate). Further, the decrease in the production EPS (49–63%) and swarming motility (61–83%) of the pathogens was also recorded at sub-MICs. Azorubine demonstrated broad-spectrum biofilm inhibitory potency (50–65%) against Chromobacterium violaceum, Pseudomonas aeruginosa, E. coli O157:H7, Serratia marcescens, and Listeria monocytogenes. ROS generation due to the interaction between bacteria and azorubine could be responsible for the biofilm inhibitory action of the food colorant. Findings of the in vitro studies were well supported by molecular docking and simulation analysis of azorubine and QS virulence proteins. Azorubine showed strong binding to PqsA as compared to other virulent proteins (LasR, Vfr, and QscR). Thus, it is concluded that azorubine is a promising candidate to ensure food safety by curbing the menace of bacterial QS and biofilm-based spoilage of food and reduce economic losses.

Virulence attenuating combination therapy: a potential multi-target synergy approach to treat Pseudomonas aeruginosa infections in cystic fibrosis patients

The World Health Organization considers the discovery of new treatments for P. aeruginosa a top priority. Virulence attenuating combination therapy (VACT) is a pragmatic strategy to improve bacterial clearance, repurpose outmoded antibiotics, improve drug efficacy at lower doses, and reduce the evolution of resistance. In vitro and in vivo studies have shown that adding a quorum sensing inhibitor or an extracellular polymeric substance repressor to classical antibiotics synergistically improves antipseudomonal activity. This review highlights why VACT could specifically benefit cystic fibrosis patients harboring chronic P. aeruginosa infections, outlines the current landscape of synergistic combinations between virulence-targeting small-molecules and anti-pseudomonal drugs, and suggests future directions for VACT research.

Structure-based Druggability Assessment of Anti-virulence Targets from Pseudomonas aeruginosa

Antimicrobial Resistance (AMR) represents a serious threat to health and the global economy. However, interest in antibacterial drug development has decreased substantially in recent decades. Meanwhile, anti-virulence drug development has emerged as an attractive alternative to fight AMR. Although several macromolecular targets have been explored for this goal, their druggability is a vital piece of information that has been overlooked. This review explores this subject by showing how structure- based freely available in silico tools, such as PockDrug and FTMap, might be useful for designing novel inhibitors of the pyocyanin biosynthesis pathway and improving the potency/selectivity of compounds that target the Pseudomonas aeruginosa quorum sensing mechanism. The information provided by hotspot analysis, along with binding site features, reveals novel druggable targets (PhzA and PhzS) that remain largely unexplored. However, it also highlights that in silico druggability prediction tools have several limitations that might be overcome in the near future. Meanwhile, anti-virulence drug targets should be assessed by complementary methods, such as the combined use of FTMap/PockDrug, once the consensus druggability classification reduces the risk of wasting resources on undruggable proteins.

In vitro activity and In vivo efficacy of Isoliquiritigenin against Staphylococcus xylosus ATCC 700404 by IGPD target

Staphylococcus xylosus (S. xylosus) is a type of coagulase-negative Staphylococcus, which was previously considered as non-pathogenic. However, recent studies have linked it with cases of mastitis in cows. Isoliquiritigenin (ISL) is a bioactive compound with pharmacological functions including antibacterial activity. In this study, we evaluated the effect of ISL on S. xylosus in vitro and in vivo. The MIC of ISL against S. xylosus was 80 μg/mL. It was observed that sub-MICs of ISL (1/2MIC, 1/4MIC, 1/8MIC) significantly inhibited the formation of S. xylosus biofilm in vitro. Previous studies have observed that inhibiting imidazole glycerol phosphate dehydratase (IGPD) concomitantly inhibited biofilm formation in S. xylosus. So, we designed experiments to target the formation of IGPD or inhibits its activities in S. xylosus ATCC 700404. The results indicated that the activity of IGPD and its histidine content decreased significantly under 1/2 MIC (40 μg/mL) ISL, and the expression of IGPD gene (hisB) and IGPD protein was significantly down-regulated. Furthermore, Bio-layer interferometry experiments showed that ISL directly interacted with IGPD protein (with strong affinity; KD = 234 μM). In addition, molecular docking was used to predict the binding mode of ISL and IGPD. In vivo tests revealed that, ISL significantly reduced TNF-α and IL-6 levels, mitigated the destruction of the mammary glands and reversed the production of inflammatory cells in mice. The results of the study suggest that, ISL may inhibit S. xylosus growth by acting on IGPD, which can be used as a target protein to treat infections caused by S. xylosus.

The anti-hepatitis B virus therapeutic potential of anthraquinones derived from Aloe vera

Although the approved hepatitis B virus (HBV)-polymerase inhibitors (e.g., lamivudine) often lead to drug-resistance, several natural products have shown promising efficacies. Though Aloe vera (AV) gel and its constituents are shown inhibitors of many viruses, their anti-HBV activity still remains elusive. We therefore, tested the anti-HBV potential of AV extract and its anthraquinones in hepatoma cells, including molecular docking, high-performance thin layer chromatography (HPTLC), and cytochrome P450 (CYP3A4) activation analyses. Our anti-HBV assays (HBsAg/HBeAg Elisa) showed maximal inhibition of viral antigens production by aloe-emodin (~83%) > chrysophanol (~62%) > aloin B (~61%) > AV extract (~37%) in HepG2.2.15 cells. Interestingly, the effect of aloe-emodin was comparable with lamivudine (~86%). Moreover, sequential treatment with lamivudine (pulse) followed by aloe-emodin (chase) enhanced the efficacy of monotherapy by ~12%. Docking (AutoDock Vina) of the anthraquinones indicated strong interactions with HBV-polymerase residues that formed stable complexes with high Gibbs's free energy. Further, identification of aloe-emodin and aloin B by validated HPTLC in AV extract strongly endorsed its anti-HBV potential. In addition, our luciferase-reporter gene assay of transfected HepG2 cells showed moderate induction of CYP3A4 by aloe-emodin. In conclusion, this is the first report on anti-HBV potential of AV-derived anthraquinones, possibly via HBV-polymerase inhibition. Of these, although aloin B exhibits novel antiviral effect, aloe-emodin appears as the most promising anti-HBV natural drug with CYP3A4 activating property towards its enhanced therapeutic efficacy.

Effect of Quercetin Rich Onion Extracts on Bacterial Quorum Sensing

Quorum sensing (QS) regulates bacterial gene expression and studies suggest quercetin, a flavonol found in onion, as a QS inhibitor. There are no studies showing the anti-QS activity of plants containing quercetin in its native glycosylated forms. This study aimed to evaluate the antimicrobial and anti-QS potential of organic extracts of onion varieties and its representative phenolic compounds quercetin aglycone and quercetin 3-β-D-glucoside in the QS model bacteria Chromobacterium violaceum ATCC 12472, Pseudomonas aeruginosa PAO1, and Serratia marcescens MG1. Three phenolic extracts were obtained: red onion extract in methanol acidified with 2.5% acetic acid (RO-1), white onion extract in methanol (WO-1) and white onion extract in methanol ammonium (WO-2). Quercetin 4-O-glucoside and quercetin 3,4-O-diglucoside were identified as the predominant compounds in both onion varieties using HPLC-DAD and LC-ESI-MS/MS. However, quercetin aglycone, cyanidin 3-O-glucoside and quercetin glycoside were identified only in RO-1. The three extracts showed minimum inhibitory concentration (MIC) values equal to or above 125 μg/ml of dried extract. Violacein production was significantly reduced by RO-1 and quercetin aglycone, but not by quercetin 3-β-D-glucoside. Motility in P. aeruginosa PAO1 was inhibited by RO-1, while WO-2 inhibited S. marcescens MG1 motility only in high concentration. Quercetin aglycone and quercetin 3-β-D-glucoside were effective at inhibiting motility in P. aeruginosa PAO1 and S. marcescens MG1. Surprisingly, biofilm formation was not affected by any extracts or the quercetins tested at sub-MIC concentrations. In silico studies suggested a better interaction and placement of quercetin aglycone in the structures of the CviR protein of C. violaceum ATCC 12472 than the glycosylated compound which corroborates the better inhibitory effect of the former over violacein production. On the other hand, the two quercetins were well placed in the AHLs binding pockets of the LasR protein of P. aeruginosa PAO1. Overall onion extracts and quercetin presented antimicrobial activity, and interference on QS regulated production of violacein and swarming motility.

β-Sitosterol derived compound from onion husks non-polar fraction reduces quorum sensing controlled virulence and biofilm production

Quorum sensing is an important regulatory factor of P. aeruginosa virulence induction such as BF, motility, formations of proteases, pyocyanin, and some toxins. The aim of the current study is to detect the effect of the pet.ether extract from onion husk and compound drive from it on quorum sensing and virulence formations of P. aeruginosa. Quorum sensing inhibiting effect of the pet.ether extract of onion husk and a compound drive from it, was evaluated by C. violaceum reporter using dilution method as well as an antioxidant by using DPPH. The efficacious of: Quorum sensing inhibiting on pet.ether fraction and compound derived from it, were investigated for their activities toward biofilm and pyocyanin synthesis as well as motility from P. aeruginosa. The pet.ether fraction and compound derived from it of onion husk exhibited potent antimicrobial, antioxidant and Quorum sensing inhibiting effects. The pet.ether fraction and compound derived from it possesses significant reduction on pyocyanin and biofilm induction of P. aeruginosa. Moreover, they significantly inhibited swimming motilities of P. aeruginosa. For the first time, our study showed the medical importance of Allium cepa L. as antimicrobial, antioxidant as well as Quorum sensing inhibiting and virulence suppressors of P. aeruginosa. Thus, these might emphasized on Allium cepa L as a natural source for attenuating toxins of the Pseudomonas.

Plant-derived antiviral drugs as novel hepatitis B virus inhibitors: Cell culture and molecular docking study

Despite high anti-HBV efficacies, while the nucleoside analogs (e.g., lamivudine) lead to the emergence of drug-resistance, interferons (e.g., IFN-α causes adverse side-effects. Comparatively, various natural or plant products have shown similar or even better efficacy. Hence, new antiviral strategies must focus not only on synthetic molecules but also on potential natural compounds. In this report, we have combined the in vitro cell culture and in silico molecular docking methods to assess the novel anti-HBV activity and delineate the inhibitory mechanism of selected plant-derived pure compounds of different classes. Of the tested (2.5-50 μg/ml) twelve non-cytotoxic compounds, ten (10 μg/ml) were found to maximally inhibit HBsAg production at day 5. Compared to quercetin (73%), baccatin III (71%), psoralen (67%), embelin (65%), menisdaurin (64%) and azadirachtin (62%) that showed high inhibition of HBeAg synthesis, lupeol (52%), rutin (47%), β-sitosterol (43%) and hesperidin (41%) had moderate efficacies against HBV replication. Further assessment of quercetin in combination with the highly active compounds, enhanced its anti-HBV activity up to 10%. Being the most important drug target, a 3-D structure of HBV polymerase (Pol/RT) was modeled and docked with the active compounds, including lamivudine as standard. Docking of lamivudine indicated strong interaction with the modeled HBV Pol active-site residues that formed stable complex (∆G = -5.2 kcal/mol). Similarly, all the docked antiviral compounds formed very stable complexes with HBV Pol (∆G = -6.1 to -9.3 kcal/mol). Taken together, our data suggest the anti-HBV potential of the tested natural compounds as novel viral Pol/RT inhibitors.

Seed Extract of Psoralea corylifolia and Its Constituent Bakuchiol Impairs AHL-Based Quorum Sensing and Biofilm Formation in Food- and Human-Related Pathogens

The emergence of multi-drug resistance in pathogenic bacteria in clinical settings as well as food-borne infections has become a serious health concern. The problem of drug resistance necessitates the need for alternative novel therapeutic strategies to combat this menace. One such approach is targeting the quorum-sensing (QS) controlled virulence and biofilm formation. In this study, we first screened different fractions of Psoralea corylifolia (seed) for their anti-QS property in the Chromobacterium violaceum 12472 strain. The methanol fraction was found to be the most active fraction and was selected for further bioassays. At sub-inhibitory concentrations, the P. corylifolia methanol fraction (PCMF) reduced QS-regulated virulence functions in C. violaceum CVO26 (violacein); Pseudomonas aeruginosa (elastase, protease, pyocyanin, chitinase, exopolysaccharides (EPS), and swarming motility), A. hydrophila (protease, EPS), and Serratia marcescens (prodigiosin). Biofilm formation in all the test pathogens was reduced significantly (p ≤ 0.005) in a concentration-dependent manner. The β-galactosidase assay showed that the PCMF at 1,000 μg/ml downregulated las-controlled transcription in PAO1. In vivo studies with C. elegans demonstrated increased survival of the nematodes after treatment with the PCMF. Bakuchiol, a phytoconstituent of the extract, demonstrated significant inhibition of QS-regulated violacein production in C. violaceum and impaired biofilm formation in the test pathogens. The molecular docking results suggested that bakuchiol efficiently binds to the active pockets of LasR and RhlR, and the complexes were stabilized by several hydrophobic interactions. Additionally, the molecular dynamics simulation of LasR, LasR-bakuchiol, RhlR, and RhlR-bakuchiol complexes for 50 ns revealed that the binding of bakuchiol to LasR and RhlR was fairly stable. The study highlights the anti-infective potential of the PCMF and bakuchiol instead of bactericidal or bacteriostatic action, as the extract targets QS-controlled virulence and the biofilm.