1-1-diphenyl-2-picrylhydrazyl and violacein

Outbreaks of multidrug-resistant bacteria are increasingly reported at the clinical setting. The antimicrobial, anti-biofilm, anti-quorum sensing, and anti-oxidant activities of four essential oils extracted from Cinnamomum verum, Origanum majorana, Thymus vulgaris, and Eugenia caryophyllata against Gram-positive and Gram-negative multidrug-resistant bacteria were evaluated in vitro.. This study was conducted on 105 multidrug resistant clinical strains. Inhibition diameter zone, minimum inhibitory concentration, and minimum bactericide concentration of the oils were determined using agar disc diffusion method and microdilution. The ability of the 4 essential oils to inhibit the production of bacterial biofilms was tested on polystyrene plates, as well as their inhibitory effect on the production of violacein by Chromobacterium violaceum CV026. The anti-oxidant activity was evaluated by the 2,2-diphenyl-1-picrylhydrazyl scavenging method.. Essential oils of Cinnamomum verum, Thymus vulgaris and Eugenia caryophyllata showed an important antibacterial activity. The inhibition diameter zone was higher than 20 mm for 90.24 %, 85.71 % and 60.95 % of strains respectively. These essential oils have a remarkable anti-biofilm and anti-quorum sensing activities against almost all the species studied. Clove extract revealed the highest anti-oxidant activity (Pourcentage of inhibtion of DPPH = 90.3 %).. These results supported the use of the 4 essential oils as alternative or complementary agents to treat infections caused by multidrug-resistant bacteria, and to prevent biofilm formation and quorum sensing signaling. They might be used as a safe anti-oxidants instead of harmful artificial ones.

Topics: Anti-Bacterial Agents; Antioxidants; Biofilms; Biphenyl Compounds; Cinnamomum zeylanicum; Disk Diffusion Antimicrobial Tests; Drug Evaluation, Preclinical; Drug Resistance, Multiple, Bacterial; Gram-Negative Bacteria; Gram-Positive Bacteria; Indoles; Microbial Sensitivity Tests; Oils, Volatile; Origanum; Picrates; Quorum Sensing; Syzygium; Thymus Plant

Quorum sensing (QS) is a cell density dependent expression of species in bacteria mediated by compounds called autoinducers (AI). Several processes responsible for successful establishment of bacterial infection are mediated by QS. Inhibition of QS is therefore being considered as a new target for antimicrobial chemotherapy. Flavonoid compounds are strong antioxidant and antimicrobial agents but their applications are limited due to their poor dissolution and bioavailability. Our objective was to investigate the effect of kaempferol loaded chitosan nanoparticles on modulating QS mediated by AI in model bioassay test systems. For this purpose, kaempferol loaded nanoparticles were synthesized and characterized in terms of hydrodynamic diameter, hydrogen bonding, amorphous transformation and antioxidant activity. QS inhibition in time dependent manner of nanoparticles was measured in violacein pigment producing using the biosensor strain Chromobacterium violaceum CV026 mediated by AI known as acylated homoserine lactone (AHL). Our results indicated that the average kaempferol loaded chitosan/TPP nanoparticle size and zeta potential were 192.27±13.6nm and +35mV, respectively. The loading and encapsulation efficiency of kaempferol into chitosan/TPP nanoparticles presented higher values between 78 and 93%. Kaempferol loaded chitosan/TPP nanoparticle during the 30 storage days significantly inhibited the production of violacein pigment in Chromobacterium violaceum CV026. The observation that kaempferol encapsulated chitosan nanoparticles can inhibit QS related processes opens up an exciting new strategy for antimicrobial chemotherapy as stable QS-based anti-biofilm agents.

Topics: Acyl-Butyrolactones; Anti-Bacterial Agents; Antioxidants; Biofilms; Biphenyl Compounds; Chitosan; Chromobacterium; Drug Compounding; Hydrogen Bonding; Indoles; Kaempferols; Nanoparticles; Picrates; Quorum Sensing

Violacein, a violet pigment produced by Chromobacterium violaceum, has attracted much attention in recent literature due to its pharmacological properties. In this work, the antioxidant properties of violacein were investigated. The reactivity with oxygen and nitrogen reactive species and 1,1-diphenyl-2-picryl-hydrazyl (DPPH), a stable free radical, was evaluated. EPR studies were carried out to evaluate the reactivity with the hydroxyl radical. The action of violacein against lipid peroxidation in three models of lipid membranes, including rat liver microsomes, Egg and Soy bean phosphathidylcholine liposomes were also evaluated. The compound reacted with DPPH (IC(50)=30microM), nitric oxide (IC(50)=21microM), superoxide radicals (IC(50)=125microM) and decreased the hydroxyl radical EPR signal. The compound protected the studied membranes against peroxidation induced by reactive species in the micromolar range. The reconstitution of violacein into the membranes increased its antioxidant effect. These results indicate that the compound has strong antioxidant potential. Based on these results we suggest violacein plays an important role with the microorganism membrane in defense against oxidative stress.

Topics: Animals; Antioxidants; Biphenyl Compounds; Cell Membrane; Electron Spin Resonance Spectroscopy; Free Radical Scavengers; Hydrazines; Hydroxyl Radical; Indoles; Lipid Peroxidation; Liposomes; Microsomes, Liver; Nitric Oxide; Oxidative Stress; Peroxidase; Phosphatidylcholines; Picrates; Rats; Superoxides