First identification of isatin-β-thiosemicarbazones as novel inhibitors of New Delhi metallo-β-lactamase-1： Chemical synthesis, biological evaluation and molecular simulation

New Delhi metallo-b-lactmase-1（NDM-1） catalyzes the hydrolysis of b-lactam antibiotics and cleaves the b-lactam ring of the molecule, conferring bacterial resistance against these medicines. In an effort to discover novel agents to treat this superbug, an old drug methisazone was found to be a weak NDM-1 inhibitor, with an IC50 of 297.6 mmol/L. Based on this result, a series of isatin-β-thiosemicarbazones（IBTs）were synthesized and biologically evaluated as novel NDM-1 inhibitors. Nine of the IBT compounds showed IC50 values of 〈10 mmol/L, the best of which was 2.72 mmol/L. Comparative field analysis（Co MFA） contour maps were generated to depict the structural features and molecular docking was performed to understand the possible binding mode of these inhibitors. The present research hereby has provided valuable information for further discovery of NDM-1 inhibitors.

Synthesis, Molecular Structure and Antibacterial Activity of Benzylmethyl-4-Methyl-3-Thiosemicarbazone

A novel Schiff base, benzylmethyl-4-methyl-3-thiosemicarbazone (BMM) de-rived from benzylmethylketone and 4-methylthiosemicarbazide was synthe-sized and characterized by elemental analysis, spectroscopic methods (IR, 1H NMR, 13C NMR) and physical means. The single crystal structure analysis of the Schiff base reveals that it crystallizes in a monoclinic system in the P21/c space group. BMM revealed moderate antibacterial activity on three bacterial strains with diameter zone of inhibition of 16 mm (E. coli), 14 mm (K. pneumonia) and 13 mm (S. epider-midis) compared with the standard drug, ciprofloxacin.

Development of a Highly Sensitive Extractive Spectrophotometric Method for the Determination of Nickel(II) from Environmental Matrices Using 2-Acetylpyridine-4-methyl-3-thiosemicarbazone

Nickel(II) reacts with 2-acetylpyridine-4-methyl-3-thiosemicarbazone (APMT) and forms a yellow colored complex, which was extracted into n-hexanol from sodium acetate and acetic acid buffer at pH 6.0. The absorbance value of the Ni(II)-APMT complex was measured at different intervals of time at 375 nm to ascertain the time stability of the complex. The extraction of the complex into the solvent was instantaneous and stable for more than 72 hrs. The system obeyed Beer’s law in the concentration range of 0.235 - 2.43 μg·ml–1 of nickel(II), with an excellent linearity and a correlation coefficient of 0.999. The molar absorptivity and Sandell’s sensitivity of the extracted species were found to be 2.16 × 104 L mol–1 ·cm–1 and 0.003 μg·cm–2 at 375 nm, respectively. Hence a detailed study of the extraction of nickel(II) with APMT has been undertaken with a view to developing a rapid and sensitive extractive spectrophotometric method for the determination of nickel(II) when present alone or in the presence of diverse ions which are usually associated with nickel(II) in environmental matrices like soil and industrial effluents. Various standard alloy samples (CM 247 LC, IN 718, BCS 233, 266, 253 and 251) have been tested for the determination of nickel for the purpose of validation of the present method. The results of the proposed method are comparable with those from atomic absorption spectrometry and were found to be in good agreement.