The influence of three newly synthesized oxadiazole derivatives on the corrosion inhibition of mild steel in 0.5 M HCl solution was studied using mass loss and electrochemical techniques. The corrosion rate decreased with increasing concentration of inhibitors and increased with increase in temperature of the medium. Adsorption of the all the three inhibitors obeyed the Langmuir isotherm model. Polarization curves indicated that the inhibitors are of mixed type. Electrochemical impedance spectroscopy measurements explained the mechanism of action of inhibitors. Various activation and adsorption thermodynamic parameters were calculated. The surface adsorbed film was characterized by scanning electron microscopy (SEM) and energy dispersive analysis of X-ray (EDAX). The electronic properties of the inhibitors were obtained from AM1 semiempirical quantum chemical approach. Excellent correlation was found between theoretical and experimental results.

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Advanced approach in probing for polyketide antimicrobials requires novel genomics and chromatographic strategies. An endophytic strain CLA68 was isolated from the root of Combretum latifolium Blume (Combretaceae) collected from the Western Ghats of Southern India. Strain CLA68 was then identified as Nocardiopsis prasina by its characteristic culture morphology and analysis of 16S rRNA gene sequence. Biosynthetic polyketide synthase genes were investigated using two pairs of degenerate primers. Ethyl acetate extract of CLA68 exhibited broad spectrum activity against a panel of test human pathogens. PKS type-I gene detection and chromatographic strategy yielded a robust polyketide antimicrobial compound which identified as nocapyrone E. Minimum inhibitory concentration of the purified compound against MRSA and other human pathogens ranged between 25 and 100 μg/ml. The present work highlights the utility of N. prasina CLA68 as potential source for antimicrobial polyketide nocapyrone E which could help to combat multidrug-resistant pathogens. This study demonstrates feasibility of PKS type-I gene-based molecular approach and chemical investigation by chromatographic approach is the best method for prediction and rapid discovery of novel polyketides from endosymbiotic actinomycetes. The sequence data of this endosymbiotic actinomycete is deposited in GenBank under the accession no. KP269077.

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In the postgenomic era, a new strategy for chemical dereplication of polyketide anti-infective drugs requires novel genomics and chromatographic strategies. An endosymbiotic fungal strain CLB38 was isolated from the root tissue of Combretum latifolium Blume (Combretaceae) which was collected from the Western Ghats of India. The isolate CLB38 was then identified as Emericella variecolor by its characteristic stellate ascospores culture morphology and molecular analysis of ITS nuclear rDNA and intervening 5.8S rRNA gene sequence. ITS2 RNA secondary structure modeling clearly distinguished fungal endosymbiont E. variecolor CLB38 with other lifestyles in the same monophyletic clade. Ethyl acetate fraction of CLB38 explored a broad spectrum of antimicrobial activity against multidrug resistant pathogens. Biosynthetic PKS type-I gene and chromatographic approach afford two polyketide antimicrobial compounds which identified as evariquinone and isoindolones derivative emerimidine A. MIC of purified compounds against test microorganisms ranged between 3.12 μg/ml and 12.5 μg/ml. This research highlights the utility of E. variecolor CLB38 as an anticipate source for anti-infective polyketide metabolites evariquinone and emerimidine A to combat multidrug resistant microorganisms. Here we demonstrates a chemogenomics strategy via the feasibility of PKS type-I gene and chromatographic approach as a proficient method for the rapid prediction and discovery of new polyketides compounds from fungal endosymbionts.

Alcoholic extracts of Spinach (SP) leaves was studied as corrosion inhibitor for mild steel in 0.5 M HCl using weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy techniques. The results of the study revealed that SP extracts inhibit mild steel corrosion through adsorption process following Langmuir adsorption isotherm. The protection efficiency increased with increase in inhibitor concentration and decreased with temperature. Polarization measurements indicated that the SP behaves as mixed type of inhibitor. EIS measurements showed that the charge transfer resistance increases with increase in the concentration of SP extracts. Various thermodynamic parameters such as activation energy, activation enthalpy and activation entropy were evaluated. Adsorption thermodynamic parameters were also computed and SEM was used to analyze the surface adsorbed film.