The inhibitory effect of thiourea-based compounds was evaluated using carbon steel body specimens in hydrochloric acid media. Thiourea derivatives, N-(pyrimidin-2-ylcarbamothioyl)benzamide and N-(6-methylpyridin-2-ylcarbamothioyl)benzamide, were synthesized using a simple route with good yields of approximately 70%. The inhibitory efficiencies were obtained by means of weight-loss experiments and electrochemical techniques (e.g. polarization curves and electrochemical impedance spectroscopy). The presence of a methyl functional group showed a better inhibitory efficiency compared with the derivate inhibitor without such modification. Analyzing Langmuir isotherms, G 0 ads values indicate the chemical Downloaded by [University of Sherbrooke] at 15:32 12 April 2015 ACCEPTED MANUSCRIPT ACCEPTED MANUSCRIPT 2 adsorption of thiourea-based compounds. The E Corr values obtained for the thiourea derivative with the methyl functionality was cathodically shifted by approximately −0.08 V, with an inhibition efficiency of 81%.

Corrosion inhibitors have been used to preserve the integrity of metal components of plant facilities under severe corrosive conditions that would lead to failure or reduction of the operating cycle of essential units. These include risers, columns, wells, pipelines, pressure vessels and distillation towers structures. Several compound classes have been studied as corrosion inhibitors for metallic materials. In special, organic compounds have been tested and applied industrially as corrosion inhibitors due to their low toxicity. Taking into account recent recommendations for eliminating the use of toxic inorganic inhibitors there was a significant increase in studies on the use of natural products as corrosion inhibitors. Natural products are considered environmentally suitable corrosion inhibitors for use on a large scale. Recent studies have shown that black pepper extract is rich in a mixture of alkaloids substances that have excellent anti-corrosion properties in acid conditions. The aim of this study was to investigate the carbon steel corrosion inhibition efficiency of black pepper crude extract and purified piperine (major alkaloid present in the extract) in highly corrosive environment by weight loss measurements. For this reason, weight loss tests were carried out to study the inhibition efficiency. The inhibition efficiencies of different concentrations of the black pepper crude extract was higher than the efficiencies of the same concentrations of pure piperine. The efficiencies were about 97 % for the crude extract and 70 % for the pure piperine.

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Background: Antibacterial resistance is a serious public health problem infecting millions in the global population. Currently, there are few antimicrobials on the market against resistant bacterial infections. Therefore, there is an urgent need for new therapeutic options against these strains. Objective: In this study, we synthesized and evaluated ten Bis(2-hydroxynaphthalene-1,4-dione) against Gram-positive strains, including a hospital Methicillin-resistant (MRSA), and Gram-negative strains. Method: The compounds were prepared by condensation of aldehydes and lawsone in the presence of different L-aminoacids as catalysts in very good yields. The compounds were submitted to antibacterial analysis through disk diffusion and Minimal Inhibitory Concentration (MIC) assays. Result: L-aminoacids have been shown to be efficient catalysts in the preparation of Bis(2- hydroxynaphthalene-1,4-dione) from 2-hydroxy-1,4-naphthoquinones and arylaldehydes in excellent yields of up to 96%. The evaluation of the antibacterial profile against Gram-positive strains (Enterococcus faecalis ATCC 29212, Staphylococcus aureus ATCC 25923, S. epidermidis ATCC 12228) also including a hospital Methicillin-resistant S. aureus (MRSA) and Gram-negative strains (Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853 and Klebsiella pneumoniae ATCC 4352), revealed that seven compounds showed antibacterial activity within the Clinical and Laboratory Standards Institute (CLSI) levels mainly against P. aeruginosa ATCC 27853 (MIC 8-128 µg/mL) and MRSA (MIC 32-128 µg/mL). In addition, the in vitro toxicity showed all derivatives with no hemolytic effects on healthy human erythrocytes. Furthermore, the derivatives showed satisfactory theoretical absorption, distribution, metabolism, excretion, toxicity (ADMET) parameters, and a similar profile to antibiotics currently in use. Finally, the in silico evaluation pointed to a structure-activity relationship related to lipophilicity for these compounds. This feature may help them in acting against Gram-negative strains, which present a rich lipid cell wall selective for several antibiotics. Conclusion: Our data showed the potential of this series for exploring new and more effective antibacterial activities in vivo against other resistant bacteria.