Antitubercular study on stem bark of Albizia procera (ROXB.) BENTH using Microplate Alamar Blue assay (MABA)

Albizia procera commonly known as white siris is a large deciduous tree of the family Mimosideae, widely distributed throughout India. Traditionally the plant is used in convulsions, pain, delirium, cancer and septicemia. The decoction of bark is given for rheumatism, hemorrhage and is considered useful in treating pregnancy problems, for stomach ache and sinus.The preliminary phytochemical screening of ethanol extract of Albizia procera shows the presence of active constituents like flavonoids, phenolic compounds and tannins. Earlier studies show the flavonoids and phenolic compounds play major role in antitubercular activity. Based on this, we made an attempt to evaluate the antitubercular potential of this plant. The ethanolic extract and its fractions (Hexane and Ethyl acetate) were investigated for antitubercular activity using Alamar Blue dye method (MABA), in which Mycobacterium tuberculosis was sensitive upto 3.12μg/ml.The extract and fractions show better anti tubercular activity than streptomycin and potentially equal to pyrazinamide and ciprofloxacin. The observed activity may be due to the presence of flavonoids and phenolic compound which is confirmed by HPTLC. This investigation on stem bark of Albizia procera has the potential to be developed further into a natural Anti-TB drug.

New Investigations with Lupane Type A-Ring Azepane Triterpenoids for Antimycobacterial Drug Candidate Design

Twenty lupane type A-ring azepano-triterpenoids were synthesized from betulin and its related derivatives and their antitubercular activity against Mycobacterium tuberculosis, mono-resistant MTB strains, and nontuberculous strains Mycobacterium abscessus and Mycobacterium avium were investigated in the framework of AToMIc (Anti-mycobacterial Target or Mechanism Identification Contract) realized by the Division of Microbiology and Infectious Diseases, NIAID, National Institute of Health. Of all the tested triterpenoids, 17 compounds showed antitubercular activity and 6 compounds were highly active on the H37Rv wild strain (with MIC 0.5 µM for compound 7), out of which 4 derivatives also emerged as highly active compounds on the three mono-resistant MTB strains. Molecular docking corroborated with a machine learning drug-drug similarity algorithm revealed that azepano-triterpenoids have a rifampicin-like antitubercular activity, with compound 7 scoring the highest as a potential M. tuberculosis RNAP potential inhibitor. FIC testing demonstrated an additive effect of compound 7 when combined with rifampin, isoniazid and ethambutol. Most compounds were highly active against M. avium with compound 14 recording the same MIC value as the control rifampicin (0.0625 µM). The antitubercular ex vivo effectiveness of the tested compounds on THP-1 infected macrophages is correlated with their increased cell permeability. The tested triterpenoids also exhibit low cytotoxicity and do not induce antibacterial resistance in MTB strains.

Assessment of the Antimicrobial and Antiproliferative Activities of Chloropyrazine-Tethered Pyrimidine Derivatives: In Vitro, Molecular Docking, and In-Silico Drug-Likeness Studies

Molecular hybridization (MH) of heterocyclic rings has enabled scientists to design and develop novel drugs and drug-like candidates. In our previous work, considering the importance of MH, we synthesized different kinds of chloropyrazine-tethered pyrimidine derivatives (22–40) containing either substituted phenyl or heteroaryl rings at position-6 of the pyrimidine ring and evaluated their antitubercular activity. Herein, we report the antimicrobial and antiproliferative activities of 22–40. The antiproliferative activity of the target hybrids was superior to the antimicrobial activity. However, some compounds showed greater antimicrobial activity than the standard drugs. For instance, among the nineteen derivatives, compound 31 containing a 2″,4″-dichlorophenyl ring, showed the most potent antibacterial and antifungal activities (MIC 45.37 µM), followed by compounds 25 and 30 bearing 4″-nitrophenyl and 2″,4″-difluorophenyl scaffolds with minimum inhibitory concentrations (MIC) values of 48.67 µM and 50.04 µM, respectively. Compound 35, containing a bioisosteric 2″-pyridinyl ring, showed the most potent antiproliferative activity against the prostate cancer cell line (DU-145) with an IC50 value of 5 ± 1 µg/mL. Additional testing of compounds 22–40 on human normal liver cells (LO2) indicated that the compounds were more selective to cancer cell lines over normal cells. Further, molecular docking of the most potent compound 35 against dihydrofolate reductase (DHFR) (PDB ID: 1U72) had a good binding affinity with a docking score of −6.834. The SwissADME program estimated the drug-likeness properties of compound 35. Hybrid 35 is a potential lead molecule for the development of new anticancer drugs, whereas 31 is a promising antimicrobial lead candidate.

Phenylisoxazole-3/5-Carbaldehyde Isonicotinylhydrazone Derivatives: Synthesis, Characterization, and Antitubercular Activity

Eight new phenylisoxazole isoniazid derivatives, 3-(2′-fluorophenyl)isoxazole-5-carbaldehyde isonicotinylhydrazone (1), 3-(2′-methoxyphenyl)isoxazole-5-carbaldehyde isonicotinylhydrazone (2), 3-(2′-chlorophenyl)isoxazole-5-carbaldehyde isonicotinylhydrazone (3), 3-(3′-clorophenyl)isoxazole-5-carbaldehyde isonicotinylhydrazone (4), 3-(4′-bromophenyl)isoxazole-5-carbaldehyde isonicotinylhydrazone (5), 5-(4′-methoxiphenyl)isoxazole-3-carbaldehyde isonicotinylhydrazone (6), 5-(4′-methylphenyl)isoxazole-3-carbaldehyde isonicotinylhydrazone (7), and 5-(4′-clorophenyl)isoxazole-3-carbaldehyde isonicotinylhydrazone (8), have been synthesized and characterized by FT-IR, 1H-NMR, 13C-NMR, and mass spectral data. The 2D NMR (1H-1H NOESY) analysis of 1 and 2 confirmed that these compounds in acetone-d6 are in the trans(E) isomeric form. This evidence is supported by computational calculations which were performed for compounds 1–8, using DFT/B3LYP level with the 6-311++G(d,p) basis set. The in vitro antituberculous activity of all the synthesized compounds was determined against the Mycobacterium tuberculosis standard strains: sensitive H37Rv (ATCC-27294) and resistant TB DM97. All the compounds exhibited moderate bioactivity (MIC = 0.34–0.41 μM) with respect to the isoniazid drug (MIC = 0.91 μM) against the H37Rv sensitive strain. Compounds 6 (X = 4′-OCH3) and 7 (X = 4′-CH3) with MIC values of 12.41 and 13.06 μM, respectively, were about two times more cytotoxic, compared with isoniazid, against the resistant strain TB DM97.

Design, Synthesis and Biological Investigation of Some Novel Quinazolin-4(3H)-One Tethered 1, 3, 4-Thiadiazole-Thiol Motifs as Direct Enoyl Acyl Carrier Protein Reductase Inhibitors

Aims: In this study was two noteworthy pharmacophores quinazolin-4(3H)-one and 1,3,4-thiadiazole through methylene bridge were utilized to design, synthesize and characterize some novel 2-methyl quinazolin-4(3H)-one and 6-chloro-2-methyl quinazolin-4(3H)-one tethered S-substituted-1,3,4-thiadiazole-thiol structural analogs respectively as direct Mycobacterium Tuberculosis (MTB) enoyl acyl carrier protein reductase (InhA) inhibitors. Study Design: Design of structural analogs of quinazolin-4(3H)-one tethered 1,3,4-thiadiazole-thiol through methylene bridge by functional group modifications in core scaffold followed by computational studies to select promising compounds. Synthesis of some novel compounds, structural characterization and screening of biological activity of the same. Methodology: The molecular docking of designed compunds was carried out using schrodinger Glide XP into the active site of MTB InhA with protein data bank code (PDB ID: 2H7M). The interactions were evaluated based on the glide G score compared with reference standard isoniazid. Ten new compounds 7(A1-A10) were synthesized, characterized and screened for their in-vitro antitubercular activity by Microplate Almar Blue Assay (MABA) method followed by cytotoxicity evaluation of compounds 7A4 and 7A10 using Vero cell line. Results: All the designed compounds of series 7(A1-A10) had drug-like characteristics and were non-toxic to normal cells. In the molecular docking studies, compounds 7A4, 7A5, and 7A10 demonstrated strong binding affinity in the active region of MTB InhA protein and retained necessary amino acid interaction, similar to co-crystal 2H7M. Synthesized compounds 7(A1-A10) were found to have good antitubercular activity. Out of the series the compounds 7A4 and 7A10 were found to possess excellent antitubercular activity equipotent to reference standard streptomycin with minimum inhibitory concentration (MIC) value of 6.25µg/ml. The cytotoxic potential of compounds 7A4 and 7A10 showed remarkable selectivity index against Vero cell line. Conclusion: The findings of this study highlights the importance of tethering two pharmacophoric motifs in one compound to develop novel antitubercular agents that can be exploited as promising leads as direct InhA inhibitors.

Synthesis, Characterization of Novel Schiff’s Bases of 2-(1H-tetrazol-5-yl) Pyridine and Evaluation of their Antitubercular Activity

This study aimed to prepare some new 2-(1H-tetrazol-5-yl) pyridine derivatives from Pyridine Nitrile as a starting materials and to evaluate the antitubercular activity against Mycobacterium Tuberculosis. The first step involves the reaction of 2-(1H-tetrazol-5-yl) pyridine with ethyl chloroacetate to form ethyl [5-(pyridin-2-yl)-1H-tetrazol-1-yl] acetate (A). In step II it was further treated with hydrazine hydrate to form 2-[5-(pyridin-2-yl)-1H-tetrazol-1-yl] acetohydrazide (B). The compound B was treated with different aromatic aldehyde to form N'-[(E)-substituted phenylmethylidene]-2-[5-(pyridin-2-yl)-1H-tetrazol-1-yl] acetohydrazide (Schiff Bases) (C1–C10). The compounds obtained were identified by spectral data. The antitubercular activity of synthesized compounds were evaluated against Mycobacterium Tuberculosis. The compound C4 and C10 was found to possess potent activity while compounds C2 and C3 shows moderate activity.

Isoniazid-Isatin Hydrazone Derivatives: Synthesis, Antitubercular Activity and Molecular Docking Studies

This study examined the synthesis of isoniazid-isatin hydrazone derivatives 5-7, followed by an investigation on the in vitro antitubercular activity against Mycobacterium tuberculosis H37Rv, and molecular docking. A yield of 81 - 92 % of these compounds was achieved, with structural characterization by spectroscopic methods (FTIR, NMR, HRMS). The in vitro antitubercular activity was evaluated against M. tuberculosis H37Rv, and the highest effect was observed in compound 7, with a minimum inhibitory concentration (MIC) of 0.017 mM, lower than rifampicin (MIC 0.048 mM), which served as the positive control. In addition, the molecular docking of 5-7 was performed to visualize the interaction of isoniazid-isatin hydrazone derivatives with the active site of InhA receptor, which was in agreement with the experimental data. The hydrogen bonding with Ser94 and pi-pi interaction with Phe41 and/or Phe97 on the InhA active site was pivotal for the antitubercular activity. HIGHLIGHTS Tuberculosis caused by Mycobacterium tuberculosis is one of the top ten leading causes of death globally The first and second lines of antituberculosis drugs are the prevalent treatment for this disease, but they show several drawbacks and are exacerbated by the occurrence of drug resistance The isoniazid-isatin hydrazone derivatives were designed through molecular hybridization and synthesized effectively and exhibited moderate to high activity against tuberculosis H37Rv Molecular docking study demonstrated that the hydrogen bonding with Ser94 and the pi-pi interaction with Phe41 and/or Phe97 are important for antitubercular activity GRAPHICAL ABSTRACT