Synthesis, antitubercular activity, and molecular docking studies of Benzyl-modified 8-hydroxyquinolines

@#<p><strong>Background:</strong> Infection with Mycobacterium tuberculosis, the causative agent of TB, is responsible for one of the global epidemics. Thus, new drugs are needed that do not confer cross-resistance with currently administered front-line therapeutics. Quinoline-based natural products and synthetic derivatives have been extensively explored for antitubercular activity.<br /><strong>Objective:</strong> The main goal of this study was to prepare a collection of benzylated 8-hydroxyquinoline derivatives through synthesis and assess their antitubercular activity along with a molecular docking study to clarify their biological mechanism of action.<br /><strong>Methodology:</strong> The benzylated 8-hydroxyquinoline derivatives were synthesized using Williamson synthesis methods. Antitubercular activity was assessed against fast replicating M. tuberculosis H??Rv using Microplate Alamar Blue Assay (MABA) and non-replicating cultures using Low-Oxygen Recovery Assay (LORA). Molecular docking studies were carried out against enoyl-acyl carrier protein reductase (InhA).<br /><strong>Results:</strong> Five benzylated 8-hydroxyquinoline derivatives were synthesized in moderate yields and characterized using NMR spectroscopy. MABA and LORA assays indicate compounds 3-5 as the most inhibitory derivatives with MIC90's ranging from 6.38 to 54.28 ?M. Molecular docking against InhA showed modest 90 binding energies for compounds 4 (-8.5 kcal/mol) and 5 (-8.6 kcal/mol).<br /><strong>Conclusion:</strong> Findings suggest a rationale for the further evolution of this promising series of antitubercular quinoline small molecules. Structure-activity analysis shows that an 8-benzyl moiety with chlorine atom/s is important for improved activity against replicating and non-replicating M. tb. H??Rv. This is also supported by our in silico studies.</p>

Increasing pinosylvin production in Escherichia coli by reducing the expression level of the gene fabI-encoded enoyl-acyl carrier protein reductase

Background: The plant secondary metabolite pinosylvin is a polyphenol from the stilbene family, which have positive effects on human health. Biotechnological production is an attractive alternative for obtaining this stilbene. In Escherichia coli, malonyl-CoA is the precursor for both stilbene and fatty acid syntheses. In this study, with the aim of increasing pinosylvin production, we evaluated a novel approach that is based on reducing the expression of the gene fabI, which encodes the enzyme enoyl-acyl carrier protein reductase that is involved in fatty acid synthesis. Results: A recombineering method was employed to eliminate the chromosomal -35 promoter sequence and the upstream region of the gene fabI in E. coli strain W3110. Analysis, employing RT-qPCR, showed that such modification caused a 60% reduction in the fabI transcript level in the mutant strain W3110Δ-35fabI::Cm compared to the wild type W3110. Synthetic genes encoding a mutant version of 4-coumaroyl-CoA ligase from Streptomyces coelicolor A3 with improved catalytic activity employing cinnamic acid as substrate and a stilbene synthase from Vitis vinifera were cloned to generate the plasmid pTrc-Sc4CL(M)-VvSTS. The production performance of strains W3110Δ-35fabI::Cm/pTrc-Sc4CL(M)-VvSTS and W3110/pTrc-Sc4CL(M)- VvSTS was determined in shake flask cultures with Luria-Bertani medium supplemented with 10 g/L glycerol and 3 mM cinnamic acid. Under these conditions, the strain W3110Δ-35fabI::Cm/pTrc-Sc4CL(M)-VvSTS produced 52.67 mg/L pinosylvin, a level 1.5-fold higher than that observed with W3110/pTrc-Sc4CL(M)-VvSTS. Conclusion: A reduction in the transcript level of fabI caused by the elimination of the -35 and upstream promoter sequences is a successful strategy to improve pinosylvin production in E. coli.

Docking studies on novel alkaloid tryptanthrin and its analogues against enoyl-acyl carrier protein reductase (InhA) of Mycobacterium tuberculosis.

Isoniazid resistance is a serious threat in the battle against the treatment of multi-drug resistant tuberculosis (MDR-TB) and extremely drug-resistant tuberculosis (XDR-TB). Isoniazid is an inhibitor of enoyl-acyl carrier protein reductase (InhA) of Mycobacterium tuberculosis, which is an important and functional enzyme of the type II fatty acid synthesis system and important therapeutic target. Natural alkaloid tryptanthrin and its analogues have shown anti-tubercular activity against MDR-TB, but their cellular target is unknown. In this work, in silico molecular docking was performed using docking server in order to see the interaction of tryptanthrin and its 15 analogues with InhA of M. tuberculosis. Results showed that among tryptanthrin and its 15 analogues, tryptanthrin and its two analogues exhibited good affinity to the binding site of InhA with free binding energy of -7.94 kcal/mol and inhibition constant (Ki) of 1.50 µm. Active site residues of InhA interacting with tryptanthrin were Ser13, Thr39, Phe41, Leu63, Asp64, Val65, Ile95, Phe97 and Ile122. In binding mode, polar bond were found between O1 (1) with Asp64 of bond length (3.34 Å) and hydrophobic bonds were found between Leu63 with C15 and C12, Val65 with C7, Val65 with C12 and C4, Ile95 with C6 and C7, Ile95 with C10, C12 and C14. Important pi-pi bonds were found between Phe41 with C2, C5, C7, C12, C4, C6, C8, C9, C13 and Phe97 with C9. These interactions indicated stability of tryptanthrin in active residue and suggested it as a potential drug candidate. Thus, good affinity of tryptanthrin to binding site of InhA may lead to synthesis of anti-tubercular drug capable of combating MDR strains of M. tuberculosis