Synthesis and in vitro antitubercular activity of pyridine analouges against the resistant Mycobacterium tuberculosis

Screening of novel narrow-spectrum benzofuroxan derivatives for the treatment of multidrug-resistant tuberculosis through in silico, in vitro, and in vivo approaches

Tuberculosis remains a serious global health threat, exacerbated by the rise of resistant strains. This study investigates the potential of two benzofuroxan (Bfx) derivatives, 5n and 5b, as targeted treatments for MDR-TB using in silico, in vitro, and in vivo methodologies. In vitro analyses showed that Bfx compounds have significant activity against Mtb H37Rv, with Bfx 5n standing out with a MIC90 of 0.09 ± 0.04 μM. Additionally, their efficacy against MDR and pre-XDR strains was superior compared to commercial drugs. These Bfx compounds have a narrow spectrum for mycobacteria, which helps avoid dysbiosis of the gut microbiota, and they also exhibit high selectivity and low toxicity. Synergism studies indicate that Bfx derivatives could be combined with rifampicin to enhance treatment efficacy and reduce its duration. Scanning electron microscopy revealed severe damage to the morphology of Mtb following treatment with Bfx 5n, showing significant distortions in the bacillary structures. Whole-genome sequencing of the 5n-resistant isolate suggests resistance mechanisms mediated by the Rv1855c gene, supported by in silico studies. In vivo studies showed that the 5n compound reduced the pulmonary load by 3.0 log10 CFU/mL, demonstrating superiority over rifampicin, which achieved a reduction of 1.23 log10 CFU/mL. In conclusion, Bfx derivatives, especially 5n, effectively address resistant infections caused by Mtb, suggesting they could be a solid foundation for future therapeutic developments against MDR-TB.

Modulators targeting protein-protein interactions in Mycobacterium tuberculosis

Tuberculosis (TB) is a chronic infectious disease caused by Mycobacterium tuberculosis (M. tuberculosis), mainly transmitted through droplets to infect the lungs, and seriously affecting patients' health and quality of life. Clinically, anti-TB drugs often entail side effects and lack efficacy against resistant strains. Thus, the exploration and development of novel targeted anti-TB medications are imperative. Currently, protein-protein interactions (PPIs) offer novel avenues for anti-TB drug development, and the study of targeted modulators of PPIs in M. tuberculosis has become a prominent research focus. Furthermore, a comprehensive PPI network has been constructed using computational methods and bioinformatics tools. This network allows for a more in-depth analysis of the structural biology of PPIs and furnishes essential insights for the development of targeted small-molecule modulators. Furthermore, this article provides a detailed overview of the research progress and regulatory mechanisms of PPI modulators in M. tuberculosis, the causative agent of TB. Additionally, it summarizes potential targets for anti-TB drugs and discusses the prospects of existing PPI modulators.

Design and synthesis of some novel hybrid molecules based on 4-thiazolidinone bearing pyridine-pyrazole scaffolds: molecular docking and molecular dynamics simulations of its major constituent onto DNA gyrase inhibition

Due to multidrug resistance, microbial infections have become significant on a global level. As infections caused by several resistant bacteria and fungi severely harm mankind, scientists have developed new antibiotics to combat these infections. In order to develop novel antimicrobial agents, a series of 4-thiazolidinone-based 5-arylidene hybrids (5a-o) have been designed and synthesized to evaluate their antibacterial and antifungal activities. For the determination of the structure of a novel synthesized hybrid, various spectral techniques, e.g., IR, 1H NMR, 13C NMR, and Mass spectroscopy, were used. Two bacterial gram-negative (Escherichia coli and Pseudomonas aeruginosa), two gram-positive strains (Staphylococcus aureus and Streptococcus pyogenes), and one fungal strain (Candida albicans) were used to evaluate antimicrobial activity. Compounds 5c, 5g, and 5i were effective due to their MIC values of 62.5 μg/mL against tested bacterial strains (S. pyogenes (5c), P. aeruginosa (5g), and E. coli (5i), respectively.) and 250 μg/mL against C. albicans fungal strains, respectively. Additionally, molecular docking and 100 ns molecular dynamic simulations were carried out to investigate the stability of molecular contacts and to establish how the newly synthesized inhibitors fit together in the most stable conformations.

Synthesis, antitubercular profile and molecular docking studies of quinazolinone-based pyridine derivatives against drug-resistant tuberculosis

The promising quinazolinone-based pyridine derivatives (4a-j) were synthesized and subsequently tested for their antimycobacterial activities against the various drug-sensitive and drug-resistant Mycobacterium tuberculosis (Mtb) strains to combat infectious diseases and address growing concerns about the devastating effects of tuberculosis (TB). Utilizing 1H NMR, 13C NMR, and mass spectra, the structural and molecular confirmation of the synthesized compounds were deciphered. With minimum inhibitory concentration (MIC) values ranging from 0.31 to 19.13 μM, the results showed that compounds 4e and 4f showed promise anti-TB action against both drug-sensitive and drug-resistant TB strains. To study the cytotoxicity of synthesized molecules, normal Vero and mouse macrophage (RAW264.7) cell lines were utilized. Remarkably, it was revealed that at the highest concentration tested, none of the newly synthesized molecules were toxic to the Vero cell line. The binding patterns of the potent compounds 4b, 4e and 4f in the active site of the mycobacterial membrane protein Large 3 (MmpL3) protein are also revealed by molecular docking studies, which has contributed to the development of a structural rationale for Mtb inhibition. The physicochemical characteristics of the compounds were then predicted using theoretical calculations. Overall, the molecular docking results, physiochemical properties, and observed antimycobacterial activity all point to compound 4e with trifluoromethyl and compound 4f with nitro moiety as potential quinazolinone linked pyridine-based MmpL3 inhibitors.Communicated by Ramaswamy H. Sarma.

Design, synthesis and biological evaluation of novel oxindole analogs as antitubercular agents

Aim: To design, synthesize and evaluate oxindole derivatives for antitubercular activity. Methodology: We synthesized the derivatives, confirmed their structures by 1H/13C NMR and mass spectrometry, and evaluated them for antitubercular activity against Mycobacterium tuberculosis H37Rv strain using the microplate alamarBlue™ assay. Results: Among all the synthesized derivatives, OXN-1, -3 and -7 exhibited excellent antitubercular activity (minimum inhibitory concentration [MIC]: 0.78 μg/ml). Compounds with a MIC ≤1.56 were tested for cytotoxicity against human embryonic kidney cells and were found to be relatively nontoxic. Molecular docking analysis of OXN-1, -3 and -7 was performed to determine their binding patterns at the active site of DNA topoisomerase II (PDB-5BS8). In drug combination studies, OXN-1, 3 and 7 showed synergism with isoniazid. Conclusion: The obtained results reveal that oxindole derivatives exhibit potent antitubercular activity.

Bis(pyridine)enaminone as a Precursor for the Synthesis of Bis(azoles) and Bis(azine) Utilizing Recent Economic Green Chemistry Technology: The Q-Tube System

We reported herein efficient economic high-pressure synthesis procedures for the synthesis of bis(azoles) and bis(azines) by utilizing the bis(enaminone) intermediate. Bis(enaminone) reacted with hydrazine hydrate, hydroxylamine hydrochloride, guanidine hydrochloride, urea, thiourea, and malononitrile to form the desired bis azines and bis azoles. A combination of elemental analyses and spectral data was used to confirm the structures of the products. Compared with conventional heating, the high-pressure Q-Tube method promotes reactions in a short period of time and provides high yields.

Synthesis and Structure-Activity Relationship of 2,6-Disubstituted Thiosemicarbazone Derivatives of Pyridine as Potential Antituberculosis Agents

In this study, six new 2,6-disubstituted thiosemicarbazone derivatives of pyridine were synthesized (4−9), and their tuberculostatic activity was evaluated. All of them showed two- to eightfold higher activity (minimum inhibitory concentration (MIC) 0.5−4 µg/mL) against the resistant strain compared with the reference drug. Compounds 5 and 7, which contained the most basic substituents—pyrrolidine and piperidine—in their structure, strongly inhibited the growth of the standard strain (MIC 2 µg/mL). Furthermore, the same derivatives exhibited activity comparable to that of the reference drugs against some types of Gram-positive bacteria (MIC 0.49 µg/mL) and showed no cytotoxicity (IC50 > 50 µg/mL) in HaCaT cells. The zwitterionic structure of each compound was determined using X-ray crystallography. Absorption, distribution, metabolism, and excretion analyses showed that all compounds are good drug candidates. Thus, compounds 5 and 7 were identified as leading structures for further research on antituberculosis drugs with extended effects.

Recent updates in natural terpenoids as potential anti-mycobacterial agents

Tuberculosis is considered as a leading health issue globally. Even though, the todays first line anti-mycobacterial treatments used in the hospital have low deaths, multidrug-resistance forms of the ailment have now spread globally and become a major issue. The wide-ranging biodiversity of medicinal plants, ocean animals have gained considerable attention for drug discovery in previous spans, and the emergence of TB drug resistance has inspired interest in judging natural products (NPs) to cure this disease. Till now, several compounds have been isolated from natural sources with anti-mycobacterial activity, few of which demonstrate significant activity and have the potential for further development. Worldwide huge natural flora and fauna are existing, this flora and fauna must be investigated for new potent lead against infectious TB. This review systematically surveys various classes of terpenoid molecules obtained from different medicinal plants, fungi, sponges, and sea plumes with anti-TB activity, which could be useful for further optimization and development in this field.

Synthesis, Molecular Modeling Study, and Quantum-Chemical-Based Investigations of Isoindoline-1,3-diones as Antimycobacterial Agents

The condensation of phthalic anhydride afforded structurally modified isoindoline-1,3-dione derivatives with selected amino-containing compounds. The title compounds (2-30) have been characterized by thin-layer chromatography (TLC), infrared spectroscopy, ¹H and ¹³C NMR spectroscopy, and mass spectroscopy. All of the compounds were assessed for their antimycobacterial activity toward the H37Rv strain by a dual read-out assay method. Among the synthesized compounds, compound 27 possessed a significant IC₅₀ of 18 μM, making it the most potent compound of the series. The InhA inhibitory (IC₅₀) activity of compound 27 was 8.65 μM in comparison to Triclosan (1.32 μM). Computational studies like density functional theory (DFT) study, molecular docking, and dynamic simulation studies illustrated the reactivity and stability of the synthesized compounds as InhA inhibitors. A quantum-mechanics-based DFT study was carried out to investigate the molecular and electronic properties, reactivities, and nature of bonding present in the synthesized compounds and theoretical vibrational (IR) and isotropic value (¹H and ¹³C NMR) calculations.

Antitubercular activity assessment of fluorinated chalcones, 2-aminopyridine-3-carbonitrile and 2-amino-4H-pyran-3-carbonitrile derivatives: In vitro, molecular docking and in-silico drug likeliness studies

A series of newer previously synthesized fluorinated chalcones and their 2-amino-pyridine-3-carbonitrile and 2-amino-4H-pyran-3-carbonitrile derivatives were screened for their in vitro antitubercular activity and in silico methods. Compound 40 (MIC~ 8 μM) was the most potent among all 60 compounds, whose potency is comparable with broad spectrum antibiotics like ciprofloxacin and streptomycin and three times more potent than pyrazinamide. Additionally, compound 40 was also less selective and hence non-toxic towards the human live cell lines-LO2 in its MTT assay. Compounds 30, 27, 50, 41, 51, and 60 have exhibited streptomycin like activity (MIC~16–18 μM). Fluorinated chalcones, pyridine and pyran derivatives were found to occupy prime position in thymidylate kinase enzymatic pockets in molecular docking studies. The molecule 40 being most potent had shown a binding energy of -9.67 Kcal/mol, while docking against thymidylate kinase, which was compared with its in vitro MIC value (~8 μM). These findings suggest that 2-aminopyridine-3-carbonitrile and 2-amino-4H-pyran-3-carbonitrile derivatives are prospective lead molecules for the development of novel antitubercular drugs.

Pyridine: the scaffolds with significant clinical diversity

The nitrogen-bearing heterocycle pyridine in its several analogous forms occupies an important position as a precious source of clinically useful agents in the field of medicinal chemistry research. This privileged scaffold has been consistently incorporated in a diverse range of drug candidates approved by the FDA (Food and Drug Administration). This moiety has attracted increasing attention from several disease states owing to its ease of parallelization and testing potential pertaining to the chemical space. In the next few years, a larger share of novel pyridine-based drug candidates is expected. This review unifies the current advances in novel pyridine-based molecular frameworks and their unique clinical relevance as reported over the last two decades. It highlights an inclination to the use of pyridine-based molecules in drug crafting and the subsequent emergence of several potent and eligible candidates against a range of diversified diseases.

The nitrogen-bearing heterocycle pyridine in its several analogous forms occupies an important position as a precious source of clinically useful agents in the field of medicinal chemistry research.

Biological and Biochemical Evaluation of Isatin-Isoniazid Hybrids as Bactericidal Candidates against Mycobacterium tuberculosis

Tuberculosis remains a leading cause of mortality among infectious diseases worldwide, prompting the need to discover new drugs to fight this disease. We report here the design, synthesis, and antimycobacterial activity of isatin-mono/bis-isoniazid hybrids. Most of the compounds exhibited very high activity against Mycobacterium tuberculosis, with MICs in the range of 0.195 to 0.39 μg/ml, and exerted a more potent bactericidal effect than the standard antitubercular drug isoniazid (INH). Importantly, these compounds were found to be well tolerated at high doses (>200 μg/ml) on Vero kidney cells, leading to high selectivity indices. Two of the most promising hybrids were evaluated for activity in THP-1 macrophages infected with M. tuberculosis, among which compound 11e was found to be slightly more effective than INH. Overexpression of InhA along with cross-resistance determination of the most potent compounds, selection of resistant mutants, and biochemical analysis, allowed us to decipher their mode of action. These compounds effectively inhibited mycolic acid biosynthesis and required KatG to exert their biological effects. Collectively, this suggests that the synthesized isatin-INH hybrids are promising antitubercular molecules for further evaluation in preclinical settings.