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Ethnopharmcological Relevance: Microbial biofilm formation, a quorum sensing (QS) regulated process, is one of the major causes of nosocomial and chronic infections, foodborne diseases, and associated deaths. Various approaches have been used to eradicate the menace of biofilm. Ethnomedicinal plants as potent antibiofilm agents are gaining a lot of interest in an era where the drug resistance is increasing and the availability of potent antibiotics is no longer promised. In this context, the methanol extract of Cuphea carthagenensis (CCMD), an ethno-medicinal and culinary herb, was evaluated as an antibiofilm and anti-QS agent against Pseudomonas aeruginosa., Aim of the Study: The aim of the study is to evaluate the antibiofilm and anti-QS activity of an ethnomedicinal plant against a strong biofilm forming microorganism, P. aeruginosa., Methods: Antibiofilm activity of CCMD was demonstrated at different concentrations by Tissue Culture Plate, Test Tube method and other microscopic techniques. The effect of CCMD on QS and QS-related virulence factors viz. Pyocyanin, exopolymeric substance matrix (EPS), total protease, elastase, pyoverdin and swimming motility in P. aeruginosa were also evaluated. Antioxidant activity (DPPH & FRAP), total phenolic and flavonoid content were also checked. In order to determine the composition of the extract HPLC analysis was also performed., Results: In vitro study demonstrated a significant inhibition of biofilm formation (81.88 ± 2.57%) as well as production of QS-dependent virulence factors in P. aeruginosa. The extract also inhibited violacein production (83.31 ± 2.77%) in Chromobacterium violaceum which correlates with the reduction in QS-mediated virulence factors. The extract showed 64.79% ± 0.83% DPPH scavenging activity and reduction of ferricyanide complex (Fe 3+ ) to the ferrous form (Fe 2+ ) in DPPH and FRAP assay, respectively. Furthermore, the extract showed thermal stability and does not have any growth inhibitory effect on P. aeruginosa. The HPLC analysis demonstrated the presence of ellagic acid, ascorbic acid and hippuric acid in the extract., Conclusion: This work is the first to demonstrate that C. carthagenensis can attenuate biofilm formation and QS-mediated virulence factors of P. aeruginosa. Further investigation is required to use this ethnomedicinal plant (CCMD) as an important source of antibiofilm agents., (Copyright © 2020 Elsevier B.V. All rights reserved.)

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., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Ethnopharmacological Relevance: Senegalia nigrescens is used in traditional medicine for the treatment of dysentery and convulsions., Aims of the Study: This study was aimed at identifying bioactive compounds from S. nigrescens and carrying out in vitro and in silico anti-quorum sensing studies on the compounds., Materials and Methods: Extracts of S. nigrescens were chromatographed repeatedly. The isolated compounds were characterised using NMR spectroscopy and mass spectrometry. The anti-quorum sensing potential of S. nigrescens crude extracts and selected phytochemicals was quantified using Chromobacterium violaceum quorum sensing-controlled violacein inhibition assays. Qualitative modulation of quorum sensing activity and signal synthesis was investigated using agar diffusion double ring assays and C. violaceum. Molecular docking was conducted to explore the binding conformations of ent-kaurene diterpenes and flavonoids into the binding sites of quorum sensing regulator proteins, CviR and CviR'., Results: Phytochemical investigation of S. nigrescens resulted in the isolation of a new ent-kaurene diterpenoid (ent-kaur-15-en-18,20-diol) alongside ent-kaur-15-en-18-ol, being isolated for the first time from a plant species. Other compounds isolated included 30-hydroxylup-20(29)-en-3β-ol, 3β-hydroxy-20(29)-en-lupan-30-al, lupeol, stigmasterol, a long chain alcohol (tetracosan-1-ol) and three flavonoids (melanoxetin, quercetin and quercetin-3-O-methyl ether). Structures of isolated compounds were elucidated using different spectroscopic techniques including 1D and 2D NMR. Inhibition of violacein production was concentration-dependent, with 56.52% inhibition being obtained with 200 µg of quercetin-3-O-methyl ether, while 53.38% inhibition was obtained with 600 µg of quercetin. Agar diffusion double ring assays indicated CviI synthase/CviR receptor modulation by S. nigrescens phytochemicals, suggesting that quorum signal synthesis was down-regulated and/or targeting binding of signal to the receptor. The computed binding energy data suggested that the flavonoids had a stronger tendency to inhibit both CviR and CviR' with varying binding affinities., Conclusion: S. nigrescens crude extracts together with the novel ent-kaurenoids and flavonoids demonstrated potential anti-quorum sensing activity. S. nigrescens may thus represent a source of anti-quorum sensing therapeutic candidates for the control of existing and emerging infectious diseases., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Ethnopharmacological Relevance: Nymphaea tetragona is a widely distributed ornamental species with ethnomedicinal uses in the treatment of diarrhea, dysentery, eruptive fevers, and infections. The anti-infectious activities of this herb have already been assessed to clarify its traditional use as a medicine., Aim of Study: In this study, we aimed to verify the inhibitory effects of N. tetragona 50% methanol extract (NTME) on quorum sensing (QS)-controlled virulence factors of bacteria since QS and its virulence factors are novel targets for antimicrobial therapy., Materials and Methods: The antibacterial activity of this extract was evaluated against Chromobacterium violaceum and Pseudomonas aeruginosa. The inhibition of the violacein pigment of C. violaceum by NTME was determined qualitative and quantitative using standard methods. The effects of NTME on swarming motility, biofilm viability, pyocyanin production, and LasA protease activity were evaluated using P. aeruginosa. Finally, the in vitro and in vivo cytotoxicity of NTME were verified by MTT assay and oral administration to rats, respectively., Results: The extract had concentration-dependent antibacterial activity against gram-negative bacteria. NTME at 1/2× minimum inhibitory concentration (MIC), 1× MIC and 2× MIC significantly lowered the levels of violacein of C. violaceum compared to that of the control. The swarming motility of P. aeruginosa was inhibited by ≥70% by treatment with 1/2× MIC of NTME. There were remarkable reductions in pyocyanin production and LasA protease activity in the overnight culture supernatant of P. aeruginosa supplemented with NTME when compared with that of the untreated control. The confocal micrographs of 24h biofilms of P. aeruginosa exposed to NTME exhibited a lower number of live cells than the control. No toxic effect was observed in in vitro and in vivo cytotoxicity assays of NTME., Conclusions: NTME was demonstrated to have significant concentration-dependent inhibitory effects on quorum sensing-mediated virulence factors of bacteria with non-toxic properties, and could thus be a prospective quorum sensing inhibitor., (Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.)

Ethnopharmacological Relevance: An alternative approach to antibiotics is the development of anti-pathogenic agents to control the bacterial virulome. Such anti-pathogenic agents could target a phenomena known as quorum sensing (QS)., Materials and Methods: Six bacterial N-acyl-homoserine lactone (AHL)-dependent bioreporter strains were used to evaluate if bee hive glue also known as propolis contains constituents capable of inhibiting QS-controlled AHL signaling. In addition, the effect of propolis on the QS-dependent swarming motility was evaluated with the opportunisitic pathogen, Pseudomonas aeruginosa., Results: Differences in the propolis tincture samples were identified by physiochemical profiles and absorption spectra. Propolis tinctures at 0.0005% (v/v) that do not affect bacteria biosensor growth or the reporter system monitored were exposed to biosensors with and without the addition an AHL. No AHL signal mimics were found to be present in the propolis tinctures. However, when propolis and an inducer AHL signal were together exposed to five Escherichia coli and a Chromobacterium violaceum biosensor, propolis disrupted the QS bacterial signaling system in liquid- and agar-based bioassays and in C(18) reverse-phase thin-layer plate assays. Swarming motility in the opportunistic pathogen, Pseudomonas aeruginosa PAO1 and its AHL-dependent LasR- and RhlR-based QS behaviors were also inhibited by propolis., Conclusions: Together, we present evidence that propolis contain compounds that suppress QS responses. In this regard, anti-pathogenic compounds from bee harvested propolis could be identified and isolated and thus will be valuable for the further development of therapeutics to disrupt QS signaling systems which regulate the virulome in many pathogenic bacteria., (Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.)

Aim of the Study: The study aimed to test the activity of Terminalia catappa L. against bacterial quorum sensing (QS) in order to provide a potential scientific basis for the traditional use of leaf extracts of this plant as an antiseptic., Materials and Methods: The anti-QS activity of the methanolic leaf extract of Terminalia catappa was detected through the inhibition of the QS-controlled violacein pigment production in Chromobacterium violaceum. Fractions resulting from size-exclusion chromatography were assayed. The most active fraction was characterized through qualitative phytochemical detection methods. The effect of this fraction on known QS-controlled phenotypes in test strains was assessed., Results: The fraction with the highest activity (labeled as TCF12) was characterized to be tannin-rich. It specifically inhibited QS-controlled violacein production in Chromobacterium violaceum with 50% reduction achieved at 62.5 μg mL(-1) without significantly affecting growth up to about 962 μg mL(-1). The assessment of its effects on LasA activity of Pseudomonas aeruginosa ATCC 10145 found that the production of this virulence determinant is reduced in a concentration dependent manner with about 50% reduction at 62.5 μg mL(-1). Furthermore, it was found that TCF12 was able to inhibit the maturation of biofilms of Pseudomonas aeruginosa, a phenotype that has also been known to be QS-regulated., Conclusion: Therefore, tannin-rich components of Terminalia catappa leaves are able to inhibit certain phenotypic expression of QS in the test strains used., (Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.)