Copper 2 sulfate pentahydrate

D-(+)-glucose, sodium polyacrylate, acetic acid 99–100% (glacial), nitric acid (≥65%), hydrogen peroxide 30% (w/w), Triton X-100, sodium tartrate dehydrate, sodium hydrogen carbonate, ascorbic acid and phosphate buffered saline powder were obtained from Sigma-Aldrich (Steinheim, Germany). Copper (II) sulfate-pentahydrate and ethanol were purchased from Merck (Darmstadt, Germany); bicinchoninc acid disodium salt and sodium carbonate decahydrate from Alfa Aesar (Haverhill, MA, USA); and 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) from Enzo Life Science (Farmingdale, NY, USA). The olive oil (a mixture of refined and virgin olive oils) was purchased in a supermarket in Italy. Ultrapure water was obtained from a Milli-Q Plus system (Millipore, Bedford, MA, USA) and was always used freshly prepared.
Brain heart infusion broth (BHI), listeria selective agarb (LSM), and blood agar plates were produced by Biolife, while plate count agar (PCA) was produced by Biokar diagnostics. The reference strain for experimental trials was the American Type Culture Collection (ATCC 19117), which came from a Listeria monocytogenes (serotype 4d) third line culture to prevent the risk of phenotypic alteration.

Curcumin, copper(II) sulfate pentahydrate (CuSO₄·5H₂O), zinc(II) chloride (ZnCl₂) and iron(III) nitrate nonahydrate (Fe(NO₃)₃·9H₂O) were purchased from Merck (Germany). Solvents with highest purity were bought from Merck (Germany) and used without further purifications. The elemental analyses (carbon, hydrogen and nitrogen) of complexes were obtained from a Carlo ERBA Model EA 1108 analyzer. The metal content of the complexes was determined by atomic absorption analysis on a Varian Spectra AA-220 equipment. Fourier transform infrared (FT-IR) spectroscopy was performed using a FT-IR Spectrometer Bruker Tensor 27 as KBr disks. Fresh stock solution of metal-CUR complexes (Cu-CUR, Zn-CUR, Fe-CUR) and free-CUR were prepared in dimethyl sulfoxide (DMSO) at the concentration of 1 mg/ml. N-Acyl-homoserine lactone (C6-HSL) (Sigma-Aldrich) was used at 20 µM in C. violaceum CV026 biosensor bioassay.

Copper (II) sulfate pentahydrate, CuSO₄∙5H₂O (>98.0%); ammonium sulfate, (NH₄)₂SO₄ (99%); calcium chloride, CaCl₂ (99.9%); magnesium sulfate heptahydrate, MgSO₄∙7H₂O (99%); potassium chloride, KCl (99%); potassium phosphate monobasic, K₂HPO₄ (99%); thiamine hydrochloride (99%) sodium citrate dihydrate HOC(COONa)(CH₂COONa)₂∙2H₂O (>99%), and sodium hydroxide anhydrous pellets, NaOH (>98%) were purchased from Merck (Darmstadt, Germany). The citric acid (99.5%), malt extract agar, and yeast extract were supplied by Scharlau (Barcelona, Spain). 2,2′-Azino-bis(3-ethylbenzthiazoline-6-sulfonate), ABTS (>98.0%), 3,5-dinitrosalicylic acid, and DNS (>98.0%) were manufactured from Sigma–Aldrich, St. Louis, MO, USA. D(+)-Glucose anhydrous PA-ACS and sodium acetate anhydrous (99.9%) were obtained from PanReac AppliChem (Barcelona, Spain). Acrylamide and bis-acrylamide solution (30%, 29:1), 0.5 M Tris-HCl, pH 6.8, 1.5 M Tris-HCl, pH 8.8 solutions were provided for Bio-Rad, Alcobendas, Spain.

Copper (II) sulfate pentahydrate (CuSO₄·5H₂O) (99.0–100.5 %) and Potassium sodium tartrate tetrahydrate (C₄H₄KNaO₆·4H₂O, 99.0–102.0 %) were bought from Merck Germany. Commercial ZnO was obtained from Sigma-Aldrich, USA. Dextrose (C₆H₁₂O₆) (extra pure) was purchased from Sisco Research Laboratories Pvt. Ltd. Analytical grade reagents of NaOH (98 %, Labo) and Acid Red114 (C₃₇H₂₈N₄Na₂O₁₀S₃) were used. Throughout the experiment, deionized water was used for washing and solution purification.