Inhibition Of Violacein Production Research Articles

Anti-biofilm and anti-quorum sensing activities of extract, fractions and compounds from the leaves of Cassia alata L. against yeast pathogens

BackgroundCassia alata or Senna alata, also known as “ringworm bush” because of its very effective fungicidal properties, is commonly used in African traditional medicine to treat fungal infections. Despite extensive phytochemical and pharmacological studies previously reported on C. alata, the antibiofilm activity against pathogenic yeast as well as the related anti-quorum sensing mechanism of some active constituents has not yet been elucidated. The aim of the study was to isolate the bioactive constituents from the methanol extract of the leaves of C. alata (CAExt) using antibiofilm-guided fractionation against yeast fungal pathogens and then to investigate the anti-quorum sensing activity of the active constituents by assessing their ability to inhibit violacein production in Chromobacterium violaceum. MethodsChromatographic methods were used to isolate the constituents of CAExt, and spectroscopic methods were used to elucidate the chemical structures of the isolated compounds. The broth microdilution assay was used to evaluate the antifungal activity against Candida albicans and C. parapsilosis, while crystal violet staining was used for the inhibition of biofilm formation and the disruption of preformed biofilm. The biosensor strain C. violaceum ATCC 12472 was used to investigate the anti-quorum sensing activity of the most active constituents. ResultsThe crude extract exhibited biofilm inhibition and eradication activities against the tested pathogenic yeast. The biofilm inhibition percentages ranged from 53.22 % to 75.38 %, while the biofilm eradication percentages ranged from 23.21 % to 64.25 %. The ethyl acetate fraction demonstrated high biofilm inhibition and eradication activities against the tested microorganisms. The biofilm inhibition percentages ranged from 58.19 % to 79.30 %, while the biofilm eradication percentages ranged from 34.105 % to 69.54 %. The purification of subfractions led to the identification of six compounds: stigmasterol (1), sitosterol (2), lupeol (3), emodin (4), kaempferol (5) and stigmasterol glycoside (6), two of which (4 and 5) showed potent biofilm inhibition and eradication activities. Both compounds demonstrated significantly lower MBIC50 values of 70.81 µg/mL and 65.65 µg/mL against Candida albicans and MBEC50 values of 63.65 µg/mL and 82.66, respectively, against C. albicans and C. parapsilosis. The crude extract and compounds (4) and (5) also demonstrated quorum sensing inhibitory activity, as indicated by the MQSIC value of 1024 µg/mL for the crude extract and 128 µg/mL for the two compounds. Moreover, compounds (4) and (5) displayed significant inhibitory effects on violacein production, as indicated by their low IC50 values of 28.08 µg/mL and 26.44 µg/mL, respectively. ConclusionsData obtained in this study not only support the traditional use of C. alata in the treatment of fungal infections but also reveal C. alata extract, as well as the two isolated bioactive compounds emodin (4) and kaempferol (5), as a potential source for developing antibiofilm alternative agents against biofilm-associated yeast infections. List of compounds studiedstigmasterol (1), sitosterol (2), lupeol (3), emodin (4), kaempferol (5), stigmasterol glycoside (6)

Linalool Reduces Virulence and Tolerance to Adverse Conditions of Listeria monocytogenes.

Listeria monocytogenes, a foodborne pathogen causing listeriosis, poses substantial societal, economic, and public health challenges due to its resistance, persistence, and biofilm formation in the food industry. Exploring subinhibitory concentrations of compounds to target virulence inhibition and increase susceptibility to adverse conditions presents a promising strategy to mitigate its impact of L. monocytogenes and unveils new potential applications. Thus, this study aims to explore the effect of linalool on virulence factors of L. monocytogenes and potential use in the reduction in its tolerance to stressful conditions. This action was analysed considering the use of two sub-inhibitory concentrations of linalool, 0.312 and 0.625 mg/mL. We found that even with the lowest tested concentrations, a 65% inhibition of violacein production by Chromobacterium violaceum, 55% inhibition in biofilm formation by L. monocytogenes and 62% reduction on haemolysis caused by this bacterium were observed. In addition to its impact on virulence factors, linalool diminished the tolerance to osmotic stress (up to 4.3 log reduction after 24 h with 12% NaCl), as well as to high (up to 3.8 log reduction after 15 min at 55 °C) and low temperatures (up to 4.6 log reduction after 84 days with 12% NaCl at 4 °C). Thus, this study paves the way to further investigation into the potential utilization of linalool to mitigate the threat posed by L. monocytogenes in the field of food safety and public health.

CHEMICAL COMPOSITION AND BIOACTIVITIES OF ESSENTIAL OIL FROM AN ENDEMIC SALVIA ABSCONDITIFLORA GREUTER & BURDET

Objective: The study aimed to determine the chemical composition and antibacterial, antibiofilm, and anti-quorum sensing activities of the essential oil of Salvia absconditiflora Greuter & Burdet (an endemic species) growing wildly in Türkiye. Material and Method: The essential oil from the aerial parts of the plant was obtained by hydro-distillation (0.4%) and analyzed by GC-FID and GC-MS. In addition, the broth microdilution method was used to determine antibacterial activity. The crystal violet assay was performed for antibiofilm activity, and the reporter bacteria Chromobacterium violaceum ATCC 12472 was used in the anti-quorum sensing activity test. Result and Discussion: The major components of the essential oil were identified as 1,8-cineole (32.2%), camphor (13.6%), α-pinene (7.6%), camphene (5.5%), and viridiflorol (5.1%). The essential oil showed the best antibacterial activity against Gram-positive test bacteria, with a minimum inhibitory concentration (MIC) of 0.0078 (v/v) against Staphylococcus aureus strains. The percentage biofilm inhibition value of the essential oil was determined as 84.4%. The inhibition of violacein production by the essential oil in Chromobacterium violaceum ATCC 12472 indicated the possibility of anti-quorum sensing activity. The results of this study show that the essential oil of S. absconditiflora could be a promising alternative in fighting bacterial infections.

Green synthesis and characterization of silver nanoparticles from Ducrosia flabellifolia Boiss. aqueous extract: Anti-quorum sensing screening and antimicrobial activities against ESKAPE pathogens.

Biosynthesis of silver nanoparticles using natural compounds derived from plant kingdom is currently used as safe and low-cost technique for nanoparticles synthesis with important abilities to inhibit multidrug resistant microorganisms (MDR). ESKAPE pathogens, especially MDR ones, are widely spread in hospital and intensive care units. In the present study, AgNPs using Ducrosia flabellifolia aqueous extract were synthesized using a reduction method. The green synthesized D. flabellifolia-AgNPs were characterized by UV-Vis spectrophotometer, Scanning electron microscopy (SEM), and X-ray diffraction assays. The tested D. flabellifolia aqueous extract was tested for its chemical composition using Liquid Chromatography-Electrospray Ionization-Mass Spectrometry (LC-ESI-MS). Anti-quorum sensing and anti-ESKAPE potential of D. flabellifolia-AgNPs was also performed. Results from LC-ESI-MS technique revealed the identification of chlorogenic acid, protocatechuic acid, ferulic acid, caffeic acid, 2,5-dihydroxybenzoic acid, and gallic acid as main phytoconstituents. Indeed, the characterization of newly synthetized D. flabellifolia-AgNPs revealed spherical shape with mean particle size about 16.961±2.914 nm. Bio-reduction of silver was confirmed by the maximum surface plasmon resonance of D. flabellifolia-AgNPs at 430 nm. Newly synthetized D. flabellifolia-AgNPs were found to possess important anti-ESKAPE activity with low minimal inhibitory concentrations (MICs) ranging from 0.078 to 0.312 mg/mL, and low minimal bactericidal concentrations (MBCs) varying from 0.312 to 0.625 mg/mL. Moreover, D. flabellifolia-AgNPs were active against Candida utilis ATCC 9255, C. tropicalis ATCC 1362, and C. albicans ATCC 20402 with high mean diameter of growth inhibition at 5 mg/mL, low MICs, and minimal fungicidal concentrations values (MFCs). The newly synthetized D. flabellifolia-AgNPs were able to inhibit violacein production in Chromobacterium violaceum, pyocyanin in Pseudomonas aeruginosa starter strains. Hence, the newly synthesized silver nanoparticles using D. flabellifolia aqueous extract can be used as an effective alternative to combat ESKAPE microorganisms. These silver nanoparticles can attenuate virulence of Gram-negative bacteria by interfering with the quorum sensing system and inhibiting cell-to-cell communication.

In vitro biological activities of Combretum molle R.Br. ex G. Don (Combretaceae) against mastitis-causing organisms

Bovine mastitis, caused mostly by Staphylococcus species, has gained global importance owing to the increasing prevalence of multi-drug resistant bacteria, which comprise a risk to food security and public health. In this study, the antibacterial, anti-biofilm and quorum quenching activities of six leaf extracts of Combretum molle R.Br. ex G. Don prepared using different solvents were assessed against clinical isolates of Staphylococcus aureus and two Staphylococcus ATCC strains (S. aureus ATCC 29213 and S. epidermidis ATCC 35984). The antioxidant and anti-inflammatory activity and cytotoxicity of the extracts was also evaluated. The antibacterial and anti-biofilm potential of the extracts was determined via serial microdilution and crystal violet and INT assays. Quorum quenching activity was ascertained via inhibition of violacein production in Chromobacterium violaceum ATCC 12472. The antioxidant activity was determined using in vitro chemical assays. The 15-lipoxygenase enzyme inhibition and the nitric oxide inhibition assays were utilized to ascertain the anti-inflammatory activity of the extracts. The tetrazolium-based colorimetric (MTT) reduction assay was used to determine the cytotoxicity of the extracts against Vero African green monkey kidney cells. The antibacterial activity of the extracts was moderate to good, with minimum inhibitory concentration (MIC) values of 0.02–0.63 mg/mL. The extracts had promising biofilm inhibition (≥50 %) against four of the test strains. The effects of the extracts on the metabolic activity of the test strains showed ≥ 50 % inhibition in most of the test strains at the different test times. All extracts had moderate to excellent quorum quenching activity at different concentrations with an inhibition ranging between 32.81- 96.32 %. The methanol and cold water extracts had the best antioxidant activity against the 2, 2-diphenyl-1-picrylhydrazyl (DPPH) and 2, 2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radicals with IC50 of 7.79 and 2.34 µg/mL, respectively. The hot water extract (AQH) had the best anti-inflammatory activity in terms of 15-lipoxygenase enzyme inhibition with 85.26 % inhibition, while the methanol extract had the best nitric oxide inhibition in LPS-induced RAW 264.7 macrophages with inhibition of 96.75 % at 100 µg/mL. Selectivity index values of the extracts were as high as 50. Combretum molle, therefore, offers promising potential as a source of antibiofilm and anti-quorum sensing agents with the ability to disrupt microbial virulence factors. Additionally, the extract had good antioxidant and anti-inflammatory properties, supporting further research into its use in preventing and treating bovine mastitis.

Evaluation of anti-quorum sensing and antibiofilm effects of secondary metabolites from Gambeya lacourtiana (De Wild) Aubr. & Pellegr against selected pathogens

BackgroundMicrobial infections cause serious health problems especially with the rising antibiotic resistance which accounts for about 700,000 human deaths annually. Antibiotics which target bacterial death encounter microbial resistance with time, hence, there is an urgent need for the search of antimicrobial substances which target disruption of virulence factors such as biofilm and quorum sensing (QS) with selective pressure on the pathogens so as to avoid resistance.MethodsNatural products are suitable leads for antimicrobial drugs that can inhibit bacterial biofilms and QS. Twenty compounds isolated from the medicinal plant Gambeya lacourtiana were evaluated for their antibiofilm and anti-quorum sensing effects against selected pathogenic bacteria.ResultsMost of the compounds inhibited violacein production in Chromobacterium violaceum CV12472 and the most active compound, Epicatechin had 100% inhibition at MIC (Minimal Inhibitory Concentration) and was the only compound to inhibit violacein production at MIC/8 with percentage inhibition of 17.2 ± 0.9%. Since the bacteria C. violaceum produces violacein while growing, the inhibition of the production of this pigment reflects the inhibition of signal production. Equally, some compounds inhibited violacein production by C. violaceum CV026 in the midst of an externally supplied acylhomoserine lactone, indicating that they disrupted signal molecule reception. Most of the compounds exhibited biofilm inhibition on Staphyloccocus aureus, Escherichia coli and Candida albicans and it was observed that the Gram-positive bacteria biofilm was most susceptible. The triterpenoids bearing carboxylic acid group, the ceramide and epicatechin were the most active compounds compared to others.ConclusionSince some of the compounds disrupted QS mediated processes in bacteria, it indicates that this plant is a source of antibiotics drugs that can reduce microbial resistance.

Assessment of Morita-Baylis-Hillman adducts as novel modulators of quorum sensing phenotypes in Chromobacterium CV026 by targeting CviR

This work presents Morita-Baylis-Hillman adducts (MBHA) as new modulators of the violacein biosynthesis in the biosensor strain Chromobacterium CV026. Seven adducts displayed violacein reduction higher than 50±1% when tested at concentrations lower than 625 μM. The most active MBHA inhibited hydrolysis of chitin concomitantly with inhibition of violacein production in CV026, suggesting the disruption of its QS machinery. One MBHA induced the violacein biosynthesis in CV026 in the absence of the cognate AI, also supporting its role as a QS modulator of this QS system. Further, RT-qPCR and competition experiments characterize these two molecules as transcriptional modulators of the QS-regulated operon vioABCDE. Blind docking studies for MBHA showed a strong preference for adducts positioned within the CviR autoinducer-binding domain (AIBD). Our results show MBHA as a promising chemical scaffold for the development of novel QS inhibitors affecting LuxR/LuxI-systems.

Metabolomic Analysis of the Effect of Lippia origanoides Essential Oil on the Inhibition of Quorum Sensing in Chromobacterium violaceum.

Bacteria can communicate through quorum sensing, allowing them to develop different survival or virulence traits that lead to increased bacterial resistance against conventional antibiotic therapy. Here, fifteen essential oils (EOs) were investigated for their antimicrobial and anti-quorum-sensing activities using Chromobacterium violaceum CV026 as a model. All EOs were isolated from plant material via hydrodistillation and analyzed using GC/MS. In vitro antimicrobial activity was determined using the microdilution technique. Subinhibitory concentrations were used to determine anti-quorum-sensing activity by inhibition of violacein production. Finally, a possible mechanism of action for most bioactive EOs was determined using a metabolomic approach. Among the EOs evaluated, the EO from Lippia origanoides exhibited antimicrobial and anti-quorum activities at 0.37 and 0.15 mg/mL, respectively. Based on the experimental results, the antibiofilm activity of EO can be attributed to the blockage of tryptophan metabolism in the metabolic pathway of violacein synthesis. The metabolomic analyses made it possible to see effects mainly at the levels of tryptophan metabolism, nucleotide biosynthesis, arginine metabolism and vitamin biosynthesis. This allows us to highlight the EO of L. origanoides as a promising candidate for further studies in the design of antimicrobial compounds against bacterial resistance.

The Antimicrobial Peptide Octopromycin Suppresses Biofilm Formation and Quorum Sensing in Acinetobacter baumannii

Acinetobacter baumannii is an opportunistic bacterial pathogen that causes severe infections in immunocompromised individuals. A. baumannii forms biofilm and produces extracellular matrix, which supports bacteria to survive under harsh conditions and be resistant to antibacterial treatments. In the present study, we investigated the biofilm and quorum-sensing inhibitory effects of antimicrobial peptide, octopromycin in A. baumannii. Field emission-scanning electron microscopy results clearly showed significantly reduced biofilm mass and caused a collapse in biofilm architecture at the minimum inhibitory concentration (50 µg/mL) and minimum bactericidal concentration (200 µg/mL) of octopromycin. Antibiotic-resistant persister cells of A. baumannii were successfully killed by octopromycin treatment, and it inhibited violacein production in Chromobacterium violaceum in a concentration-dependent manner. Octopromycin also inhibited alginate production, surface movements (swarming and swimming), and twitching motility of A. baumannnii, confirming its anti-quorum-sensing activity. Multiple metabolic pathways, two-component regulation systems, quorum-sensing, and antibiotic synthesis-related pathways in A. baumannii biofilms were strongly affected by octopromycin treatment. The collective findings indicate that the antibacterial peptide octopromycin may control A. baumannii biofilms through multi-target interactions. Octopromycin could be a desirable therapeutic option for the prevention and control of A. baumannii infections.

Anti-quorum sensing effects of batatasin III: in vitro and in silico studies

The spread of multidrug resistant bacteria has fueled the development of new antibiotics to combat bacterial infections. Disrupting the quorum sensing (QS) mechanism with biomolecules is a promising approach against bacterial infections. Plants used in Traditional Chinese Medicine (TCM) represent a valuable resource for the identification of QS inhibitors. In this study, the in vitro anti-QS activity of 50 TCM-derived phytochemicals against the biosensor Chromobacterium violaceum CV026 was tested. Among the 50 phytochemicals, 7-methoxycoumarin, flavone, batatasin III, resveratrol, psoralen, isopsoralen, and rhein inhibited violacein production and showed good QS inhibitory effects. Batatasin III was selected as the best QS inhibitor based on drug-likeness, physicochemical properties, toxicity, and bioactivity score prediction analyses using SwissADME, PreADMET, ProtoxII, and Molinspiration. At 30 μg/ mL, Batatasin III inhibited violacein production and biofilm formation in C. violaceum CV026 by more than 69% and 54% respectively without affecting bacterial growth. The in vitro cytotoxicity evaluation by MTT assay demonstrated that batatasin III reduced the viability of 3T3 mouse fibroblast cells to 60% at 100 μg/mL. Furthermore, molecular docking studies showed that batatasin III has strong binding interactions with the QS-associated proteins CViR, LasR, RhlR, PqsE, and PqsR. Molecular dynamic simulation studies showed that batatasin III has strong binding interactions with 3QP1, a structural variant of CViR protein. The binding free energy value of batatasin III-3QP1 complex was −146.295 ± 10.800 KJ/mol. Overall results suggested that batatasin III could serve as a lead molecule that could be developed into a potent QS inhibitor. Communicated by Ramaswamy H. Sarma

α-Alkylidene δ-lactones inhibit quorum sensing phenotypes in Chromobacterium strain CV026 showing interaction with the CviR receptor.

Disruption of bacterial quorum sensing (QS) is presented as a promising strategy to overcome clinically relevant and phytopathogenic bacteria. This work presents α-alkylidene δ-lactones as new chemical scaffolds that inhibit the biosynthesis of violacein in the biosensor strain Chromobacterium CV026. Three molecules displayed higher than 50% violacein reduction when tested at concentrations lower than 625 µM. The most active α-alkylidene δ-lactone inhibited the hydrolysis of chitin concomitantly with the inhibition of violacein production in CV026, suggesting the disruption of its QS machinery. Further, RT-qPCR and competition experiments showed this molecule to be a transcriptional inhibitor of the QS-regulated operon vioABCDE. Docking calculations suggested a good correlation between binding affinity energies and inhibition effects, with all molecules positioned within the CviR autoinducer-binding domain (AIBD). The most active lactone yielded the best binding affinity energy, most probably due to its unprecedented binding with the AIBD. Our results show α-alkylidene δ-lactones as promising chemical scaffolds for the development of new QS inhibitors affecting LuxR/LuxI-systems.

Anti-Biofilm, Anti-Quorum Sensing, and Anti-Proliferative Activities of Methanolic and Aqueous Roots Extracts of <i>Carica papaya</i> L. and <i>Cocos nucifera</i> L.

Objective: This study focused on the antibacterial and anti-proliferative activity of extracts from Carica papaya and Cocos nucifera roots. Methodology: The minimum inhibitory concentration and the minimum bactericidal concentration of the extracts on Escherichia coli, Pseudomonas aeruginosa, Streptococcus mutans, and Staphylococcus aureus were deduced by the microdilution method. The anti-biofilm activity was determined on all four strains and anti-quorum sensing activity by inhibition of violacein production in Chromobacterium violaceum. Anti-proliferative activity on prostate cultured cancer cells was evaluated by MTT assay. Sterols and triterpenes were also assayed in this study. Results: The methanolic extract of Carica papaya showed the best anti-biofilm effect with a percentage inhibition of 66.10 ± 1.79. The methanolic extract of Cocos nucifera had the strongest inhibition on the production of quorum sensing (61.42 ± 0.28). In addition, the methanolic extract of Cocos nucifera roots showed the best cytotoxic effect on prostate cancer LNCaP cell lines (IC50 = 26.98 ± 2.6 μg/mL) and Carica papaya on the PC-3 lines (IC50 = 127.20 ± 5.99 μg/mL). The extracts were also rich in triterpenes and sterols. Conclusion: This study provides support for the ethnomedical use of Carica papaya and Cocos nucifera roots as an antimicrobial and anticancer.

Phenolic profiles, antioxidant, antiquorum sensing, antibiofilm and enzyme inhibitory activities of selected Acacia species collected from Benin

Gum arabica is a local commercial nutraceutical and food preservative collected mostly from acacia plants. HPLC-DAD analysis identified gallic acid, syringic acid, ferulic acid, coumarin, rutin and rosmarinic acid in hydroethanol extracts of all three acacia species with ferulic acid being the most abundant component in Acacia ataxacantha (45.25 ± 0.33 mg/g) Acacia sieberiana (130.3 ± 0.65 mg/g) and Acacia nilotica (125.50 ± 0.51 mg/g). Extracts displayed good antioxidant capacities in β-carotene-linoleic acid, DPPH•, ABTS•+, CUPRAC and metal chelating assays and extracts were more active than the standards used in the DPPH•, ABTS•+ and CUPRAC assays. Extracts inhibited violacein production in Chromobacterium violaceum CV12472 at MIC and sub-MIC concentrations as well as quorum sensing in C. violaceum CV026 under externally supplied acylhomoserine lactone. The extracts showed antimicrobial activity with MIC values ranging from 0.1562 mg/mL to 2.5 mg/mL on Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeruginosa, Salmonella Typhi, Escherichia coli and Candida albicans with excellent biofilm inhibition at MIC and sub-MIC concentrations especially against E. coli. Extracts showed inhibitions on some enzymes with A. Sieberiana and A. Nilotica having very good anticholinesterase, antidiabetic (α-glucosidase and α-amylase) and antiurease activities. The results indicate the relevance of acacia in food applications.

Antibacterial, Antibiofilm, and Anti-Quorum Sensing Potential of Novel Synthetic Compounds Against Pathogenic Bacteria Isolated From Chronic Sinusitis Patients.

Quorum sensing (QS) is a major controller of virulence and biofilm formation in pathogenic bacteria. The aim of the research was to screen novel synthetic compounds (18) from 2 series (Pyrazole and Diene dione) for quorum sensing and biofilm inhibitory potential against resistant pathogens isolated from patients with chronic sinusitis. Most of the compounds have documented zone of inhibition against Gram positive strains Staphylococcus aureus, Enterococcus faecalis and moderate activity against Gram negative Klebseilla pneumoniae and Proteus mirabilis in comparison with standard antibiotic. Compounds Q1 and Q7 have given the maximum zone of inhibition 18 and 20 mm with MICs 0.312 mg/mL and .156 mg/mL against S aureus and E faecalis, respectively. Some compounds were equally potent at inhibiting the formation of biofilm which later established by phase contrast microscopy. Regarding quorum sensing inhibition, the tested concentration of synthetic compound UA3 0.313 mg/mL inhibited violacein production without decreasing Chromobacterium pseudoviolaceum count which was significantly lower than determined MIC’s. It was depicted from the results that selected compounds exhibited low level of cytotoxicity toward human red blood cells. Hence, these findings revealed that most novel compounds were effective antibacterial, whereas compound UA3 has shared significant anti-quorum sensing potential against Chromobacterium pseudoviolaceum.

Anti-Biofilm, Antibacterial, and Anti-Quorum Sensing Activities of Selected South African Plants Traditionally Used to Treat Diarrhoea.

The development of resistance of microorganisms to conventional antibiotics is a major global health concern; hence, there is an increasing interest in medicinal plants as a therapeutic option. This study aimed to evaluate the antibacterial, anti-biofilm, and anti-quorum activities of crude extracts prepared using various solvents of nine indigenous South African plants used locally for the treatment of diarrhoea. The minimum inhibitory concentration (MIC) was determined using the broth microdilution method and the crystal violet assay was used to test the anti-biofilm activity of the extracts against a panel of bacteria. Anti-quorum sensing activity of the extracts was assessed via inhibition of violacein production in Chromobacterium violaceum ATCC 12472. Preliminary screening of extracts against E. coli ATCC 25922 revealed that the acetone extracts had significant activity, with MIC values ranging from 0.04 to 0.63 mg/mL. Further screening against a panel of bacterial pathogens showed that the acetone extract of Bauhinia bowkeri was the most active with MIC of 0.01 mg/mL against Salmonella enteritidis, followed by Searsia lancea with MIC of 0.03 mg/mL against Bacillus cereus. All the plant extracts prevented the attachment of biofilms by more than 50% against at least one of the tested bacteria. However, only the mature biofilm of B. cereus was susceptible to the extracts, with 98.22% eradication by Searsia pendulina extract. The minimum quorum sensing inhibitory concentration of the extracts ranged from 0.08 to 0.32 mg/mL with S. lancea having the most significant activity. The extract of S. lancea had the best violacein production inhibitory activity with IC50 value of 0.17 mg/mL. Overall, the results obtained indicate that acetone extracts of S. leptodictya, S. lancea, S. batophylla, S. pendulina, B. galpinii, and B. bowkeri possess antibacterial and anti-biofilm activities and can modulate quorum sensing through the inhibition of violacein production. Therefore, these results signify the potential of the selected plant extracts in treating diarrhoea through inhibition of bacterial growth, biofilm formation inhibition, and quorum sensing antagonism, supporting their medicinal use.

Synthesis and characterization of bismuth(III) complex with an EDTA-based phenylene ligand and its potential as anti-virulence agent

A new acyclic bismuth complex (Bi-edtabz) was synthesized from a mixture of solutions of the ligand (EDTA-based phenylene) and bismuth under acidic conditions. Its anti-virulence properties were evaluated against Escherichia coli O157: H7, Listeria monocytogenes, Pseudomonas aeruginosa, Salmonella enterica sub. enterica serovar Typhimurium and Staphylococcus aureus. The bismuth complex was characterized by NMR, UV-Vis, FTIR, ESI/MS and TG. Furthermore, Bi-edtabz complex at 0.25–1 mM presented better antibiofilm properties against E. coli O157: H7 and S. aureus with values of biomass reduction of 30.1–57.1% and 37.8–55.5%, respectively, compared with the ligand edtabz. While biofilm formation of L. monocytogenes, P. aeruginosa and Salmonella Typhimurium was most impaired by edtabz (biomass reduction of 66.1–100%, 66.4–88.0% and 50.9–67.1%), respectively. Additionally, Bi-edtabz inhibited the swimming motility of E. coli O157: H7 (12.5%) and colony spread of S. aureus (47.2%) at 1 mM and inhibited violacein production, a quorum-sensing related pigment of the biosensor strain Chromobacterium violaceum. Hence, edtabz and the Bi-edtabz complex can be used as novel anti-virulence agents against pathogenic bacteria.

Physicochemical Composition and Characterization of Bioactive Compounds of Mulberry (Morus indica L.) Fruit During Ontogeny.

Mulberry fruit is well recognized as one of the richest sources of bioactive compounds. We investigated the physicochemical composition and characterized the bioactive compounds during different ripening stages of mulberry (Morus indica) fruit and evaluated their anti-quorum sensing activity on Chromobacterium violaceum. The proximate components such as carbohydrates, proteins and lipids were found to be high in the ripe fruit compared to unripe and mid-ripe fruit. The ripe fruit contained higher content of total phenolics and flavonoids (336.05 and 282.55mg/100g fresh weight (FW), respectively). Epicatechin and resveratrol were the major polyphenols detected in the fruit with the range 5.13-19.46 and 4.07-14.45mg/100g FW, respectively. Chlorogenic acid and myricetin were predominant in the unripe and mid-ripe fruit (7.14 and 1.84mg/100g FW, respectively). The fruit was found to be an excellent source of anti-diabetic compound 1-deoxynojirimycin. The highest content of 1-deoxynojirimycin was present in the mid-ripe fruit, with a content of 2.91mg/100g FW. Furthermore, fruit extracts exhibited anti-quorum sensing activity against Chromobacterium violaceum by effectively inhibiting violacein production. Ripe fruit extracts showed the highest activity of 76.30% at 1mg/mL and thus, could be used as a potent anti-quorum sensing agent. The results could be promising in the selection of appropriate developmental stages for M. indica fruit commercial exploitation inthe food formulations rich in potential health components.

Antiviral, Antibacterial and Anti-Quorum Sensing Activities of a Lyophilized Aqueous Pine Resin Extract

This work aimed to evaluate antiviral, antibacterial and anti-quorum sensing effects of a lyophilized aqueous pine resin extract. The pine resin toxicity was evaluated by a crystal violet assay at 492 nm for Hep-2 cells and the trypan blue method for P3HR1. The cytotoxicity expressed in CC50 was 12.5 mg/ml and 0.23 mg/ml on Hep-2 and P3HR1 cells, respectively. The antiviral effect was obtained at 4 mg/ml against coxsackievirus B4 (CVB4). Using the diffusion method discs for the antibacterial activity, the extract was more active against Gram+ than Gram−. Inhibition zones of 22 mm were obtained at a 275 mg/ml concentration. Inhibition of violacein production by pine resin extract was tested usingChomobacterium violaceum026 (CV026) in a medium supplemented with acyl-homoserine lactone (AHL); cytotoxicity was evaluated toward Artemia and its protecting effect againstVibrio harveyiBB120 and then AHL degradation was studied. Results showed that pine resin inhibited violacein production by CV026, was not toxic for Artemia and protected it againstVibrio harveyiBB120; AHL was degraded with inhibition areas from 9.6, 11.03 and 10.26 to 12.34 mm at the contact times of the mixtures “resin-AHL” respectively at 0 h, 4 h 24 h and 72 h. This study constitutes a confirmation of aqueous extract pine resin as antibacterial, by anti-quorum sensing pathway and antiviral efficacy.

Exploring the quorum sensing inhibition of isolated chrysin from Penicillium chrysogenum DXY-1

We recently and for the first time reported that ethyl acetate extracts isolated from Penicillium chrysogenum DXY-1 exhibited anti-quorum sensing (anti-QS) activity. Herein, another active molecule in the extracts was identified as chrysin by NMR and MS. A 20 μg/mL dose of chrysin inhibited violacein production regulated by QS in C. violaceum CV026 by 31.6%. A 40 μg/mL dose of chrysin suppressed pyocyanin production, elastase activity, proteolytic activity, and biofilm formation regulated by QS in P. aeruginosa PA01 by 41.4%, 13.8%, 8.3%, and 42.4%, respectively. And chrysin could inhibit the swarming activity of P. aeruginosa PA01. Further, molecular docking and CD analysis were used to address the mechanism of chrysin's activity in C. violaceum. Molecular docking results revealed that chrysin suppresses QS system by competing with the natural signal molecule C6HSL for binding to the same pocket of CviR receptor. At the same time, CD results also showed that chrysin could change the secondary structure composition of CviR, which greatly prevented the binding of C6HSL/CviR, and further playing its role on inhibiting bacterial QS system. All these data demonstate that chrysin may be used as a potential QS inhibitor to tackle increasing drug resistance.

Quorum sensing modulatory and biofilm inhibitory activity of Plectranthus barbatus essential oil: a novel intervention strategy.

The essential oil (EO) from the roots of Plectranthus barbatus Andr. (Syn. Coleus forskohlii Briq.) was evaluated for quorum sensing (QS) inhibitory activity. P. barbatus EO was screened for inhibition of QS regulated violacein production in Chromobacterium violaceum (ATCC 12472) wild-type strain. At inhibitory (6.25% v/v) and sub-inhibitory concentrations (3.125% v/v) of the EO, dose-dependent response in the inhibition of violacein production was observed in C. violaceum. Similarly, sub-MIC (6.25% v/v) of P. barbatus EO disrupted QS regulated biofilm formation by 27.87% and inhibited swarming and twitching motility in Pseudomonas aeruginosa PA01 implying its anti-infective and QS modulatory activity. Fluorescence microscopy studies confirmed the disruption of biofilm formation by EO in P. aeruginosa PAO1. Promising antibacterial activity was recorded at concentrations as low as 3.12% v/v for Listeria monocytogenes (ATCC 13932) and at 6.25% v/v for both Salmonella enterica subsp. enterica serovar Typhimurium (ATCC 25241) and Escherichia coli (ATCC 11775). Furthermore, significant dose-dependent inhibition was observed for biofilm formation and motility in all the tested pathogens in different treated concentrations. GC-MS analysis revealed α-pinene, endo-borneol, bornyl acetate, 1-Hexyl-2-Nitrocyclohexane as the major phytoconstituents. P. barbatus EO or its constituent compounds with QS modulatory, antimicrobial and biofilm inhibitory property could be potential new-age dietary source based intervention and preservation technologies.