Dereplication strategy for antimicrobial metabolite using thin-layer chromatography-bioautography and LC-PDA-MS analysis

Rapid identification of known compounds, i.e., dereplication, has become a strategically important area for the natural-product chemists involved in bioprospecting of microbes for novel bioactive metabolites. Among microbial biodiversity, endophytic fungi represent an abundant and dependable source of structurally diverse bioactive metabolites. During the course of screening for antimicrobial secondary metabolites from endophytic fungi, an antimicrobial metabolite was identified from the ethyl acetate extract obtained from the culture broth of Xylaria sp., an endophytic fungus from Ficus pumila Linn. (Moraceae) that exhibited a broad spectrum of antimicrobial activity against human and phytopathogenic bacteria and fungi. Chemical investigation of the ethyl acetate fraction using thin-layer chromatography (TLC) bioautography and LC-hyphenated techniques led to the identification of a known benzoic acid derivative. Here, we describe the application of analytical strategies (TLC-bioautography) and hyphenated spectroscopic techniques (liquid chromatography-photodiode array detector-mass spectrometry LC-PDA-MS) for the dereplication of antimicrobial metabolites

Synthesis of new 1, 2, 4-triazole derivatives and their anticorrosion properties on mild steel in hydrochloric acid medium

New 1, 2, 4-triazole derivatives have been synthesized and their anticorrosion properties established. The structures of these compounds were confirmed by spectral studies. The corrosion inhibition of mild steel in 0.5 M HCl by the three derivatives at 0.01-0.05 g L-1 was studied using mass loss and electrochemical techniques. Corrosion inhibition mechanism was proposed based on activation and adsorption thermodynamic parameters. Scanning electron microscopy exhibited the film formed on the metal surface. The electronic properties of the inhibitors were obtained from Hyperchem 7.5 package program. Excellent correlation was found between theoretical and experimental results. (C) 2015 Elsevier B.V. All rights reserved

Dereplication strategy for antimicrobial metabolite using thin-layer chromatography-bioautography and LC-PDA-MS analysis

Rapid identification of known compounds, i.e., dereplication, has become a strategically important area for the natural-product chemists involved in bioprospecting of microbes for novel bioactive metabolites. Among microbial biodiversity, endophytic fungi represent an abundant and dependable source of structurally diverse bioactive metabolites. During the course of screening for antimicrobial secondary metabolites from endophytic fungi, an antimicrobial metabolite was identified from the ethyl acetate extract obtained from the culture broth of Xylaria sp., an endophytic fungus from Ficus pumila Linn. (Moraceae) that exhibited a broad spectrum of antimicrobial activity against human and phytopathogenic bacteria and fungi. Chemical investigation of the ethyl acetate fraction using thin-layer chromatography (TLC) bioautography and LC-hyphenated techniques led to the identification of a known benzoic acid derivative. Here, we describe the application of analytical strategies (TLC-bioautography) and hyphenated spectroscopic techniques (liquid chromatography-photodiode array detector-mass spectrometry LC-PDA-MS) for the dereplication of antimicrobial metabolites

Implication of PKS type I gene and chromatographic strategy for the biodiscovery of antimicrobial polyketide metabolites from endosymbiotic Nocardiopsis prasina CLA68

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

Inhibition activity of new thiazole hydrazones towards mild steel corrosion in acid media by thermodynamic, electrochemical and quantum chemical methods

The mild steel anti-corrosion potential by newly synthesized thiazole hydrazones, 4-(4-methoxy-phenyl)-thiazole-2-carboxylic acid benzylidene-hydrazide (TH-1), 4-(4-methoxy-phenyl)-thiazole-2-carboxylic acid (3-hydroxy-benzylidene)-hydrazide (TH-2) and 4-(4-methoxy-phenyl)-thiazole-2-carboxylic acid (4-hydroxy-benzylidene)-hydrazide (TH-3) in 0.5M hydrochloric acid was studied by gravimetric and electrochemical techniques. Thermodynamic parameters were evaluated for activation and adsorption processes. Adsorption of the inhibitors followed Langmuir isotherm. Electrochemical measurements showed that addition of inhibitors simultaneously decreased corrosion current density and double layer capacitance but increased charge transfer resistance. Potentiodynamic polarization studies revealed that thiazole hydrazones effectively suppressed both the anodic and cathodic processes of mild steel corrosion in acid solution and hence acted as mixed-type inhibitors. Quantum chemical parameters like EHOMO, ΔE, softness and hardness were very well correlated with experimental data. SEM characterized the film formed on the mild steel

Application of bioassay-guided fractionation coupled with a molecular approach for the dereplication of antimicrobial metabolites

A systematically delineated dereplication approach was described based on genome mining and bioassay-guided fractionation using endophytic fungus Xylaria psidii FPL-52(S) isolated from leaves of Ficus pumila Linn., (Moraceae). A polyketide synthase gene-based molecular screening strategy by a degenerate oligonucleotide primer polymerase chain reaction technique coupled with a bioinformatic phylogenomic approach revealed the presence of an iterative polyketide synthase gene within the genome of Xylaria psidii FPL-52(S). Chemical dereplication of ethyl acetate extract derived from a submerged fermentation culture broth of Xylaria psidii FPL-52(S) by bioassay-guided chromatographic and hyphenated analytical spectroscopic techniques led to the identification of polyketide mycoalexin 3-O-methylmellein. Antimicrobial profiling and minimal inhibitory concentration values for 3-O-methylmellein were determined by disc diffusion and microbroth dilution techniques. Gram-positive bacteria, dermatophytic and phytopathogenic fungi were susceptible in terms of inhibition zone and minimum inhibitory concentration values when compared to co-assayed standards. Herein, we highlight and demonstrate an improved approach which facilitates efficient dereplication and effect-guided fractionation of antimicrobial metabolite(s). The present work flow serves as a promising dereplication tool to survey the biosynthetic potential of endophytic fungal diversity, thereby identifying the most promising strains and prioritizing them for novel polyketide-derived antimicrobial metabolite discovery