Design of novel water-soluble isoxazole-based antimicrobial agents and evaluation of their cytotoxicity and acute toxicity

Based on the readily available 3-organyl-5-(chloromethyl)isoxazoles, a number of previously unknown water-soluble conjugates of isoxazoles with thiourea, amino acids, some secondary and tertiary amines, and thioglycolic acid were synthesized. The bacteriostatic activity of aforementioned compounds has been studied against Enterococcus durans B-603, Bacillus subtilis B-407, Rhodococcus qingshengii Ac-2784D, and Escherichia coli B-1238 microorganisms (provided by All-Russian Collection of Microorganisms, VKM). The influence of the nature of the substituents in positions 3 and 5 of the isoxazole ring on the antimicrobial activity of the obtained compounds has been determined. It is found that the highest bacteriostatic effect is observed for compounds containing 4-methoxyphenyl or 5-nitrofuran-2-yl substituents in position 3 of the isoxazole ring as well as methylene group in position 5 bearing residues of l-proline or N-Ac-l-cysteine (5a-d, MIC 0.06-2.5 µg/ml). The leading compounds showed low cytotoxicity on normal human skin fibroblast cells (NAF1nor) and low acute toxicity on mice in comparison with the well-known isoxazole-containing antibiotic oxacillin.

Synthesis and Characterization of 2-Di-methyl Amino Ethyl Laurate Betaine Surfactant

The growing need for sustainable natural-based surfactants from green chemistry has led to syntheses of surfactants without the use of solvents and without the generation of by-products when milder manufacturing processes are used. The zwitterionic betaine ester surfactants are derived from natural renewable sources and are biodegradable. In this research, the betaine ester surfactant 2-di-methylaminoethyllaurate betaine was synthesized from 2-di-methylaminoehanol and lauric acid derived from coconut oil in a three-step chemo-enzymatic esterification reaction. The enzymatic process was optimized in terms of operating parameters such as temperature, time, molar ratio and enzyme concentration, resulting in a yield of 87.91%. Structural analysis of the intermediate 2-di-methylaminoethyl laurate as well as the final product 2-di-methylaminoethyl laurate betaine was carried out with FTIR and 1H NMR. The surfactant properties of the betaine were also determined and showed that the betaine can be used as a co-surfactant in many cosmetic and personal care products.

Novel Quaternary Ammonium Derivatives of 4-Pyrrolidino Pyridine: Synthesis, Structural, Thermal, and Antibacterial Studies

Six novel quaternary ammonium derivatives of 4-pyrrolidino pyridine were prepared and isolated via a facile one-pot synthesis and a simple purification procedure. The purity and the molecular structure of the 4-pyrrolidino pyridine derivatives were confirmed with 1H and 13C NMR spectroscopy and powder X-ray diffraction techniques. The crystal structures of the compounds were characterized by single crystal X-ray diffraction (SCXRD) and their thermal properties were studied by Differential Scanning Calorimetry (DSC) analyses. The antibacterial properties of the title compounds against five bacterial strains were evaluated using Kirby–Bauer disk diffusion susceptibility test. The compounds crystallize in the monoclinic or orthorhombic crystal systems (space groups: P21/c, P21/n, or P212121) and their crystal structures are stabilized by a combination of intra- and intermolecular halogen bonding interactions, short contacts and π-π interactions. Above interactions, they contribute to the thermal stability and lack of phase transition effects up to 350 °C. Two of the compounds possess antibacterial effect against E. coli or S. aureus bacterial strains—similar or better than the kanamycin reference.