Anti-tubercular agents. Part 3. Benzothiadiazine as a novel scaffold for anti-Mycobacterium activity

In Silico Drug Design of Benzothiadiazine Derivatives Interacting with Phospholipid Cell Membranes

The use of drugs derived from benzothiadiazine, a bicyclic heterocyclic benzene derivative, has become a widespread treatment for diseases such as hypertension, low blood sugar or the human immunodeficiency virus, among others. In this work we have investigated the interactions of benzothiadiazine and four of its derivatives designed in silico with model zwitterionic cell membranes formed by dioleoylphosphatidylcholine, 1,2-dioleoyl-sn-glycero-3-phosphoserine and cholesterol at the liquid–crystal phase inside aqueous potassium chloride solution. We have elucidated the local structure of benzothiadiazine by means of microsecond molecular dynamics simulations of systems including a benzothiadiazine molecule or one of its derivatives. Such derivatives were obtained by the substitution of a single hydrogen site of benzothiadiazine by two different classes of chemical groups, one of them electron-donating groups (methyl and ethyl) and another one by electron-accepting groups (fluorine and trifluoromethyl). Our data have revealed that benzothiadiazine derivatives have a strong affinity to stay at the cell membrane interface although their solvation characteristics can vary significantly—they can be fully solvated by water in short periods of time or continuously attached to specific lipid sites during intervals of 10–70 ns. Furthermore, benzothiadiazines are able to bind lipids and cholesterol chains by means of single and double hydrogen-bonds of characteristic lengths between 1.6 and 2.1 Å.

An insight into antimycobacterial and antioxidant potentials of INH-Schiff base complexes and in silico targeting of MtKasB receptor of M. tuberculosis

Isoniazid Schiff base complexes synthesized by the molecular hybridization strategy revealed enhanced anti-tubercular (100% killing of M. tb strain) and antioxidant activities.

Synthesis and biological activity of novel 3-heteroaryl-2H-pyrido[4,3-e][1,2,4]thiadiazine and 3-heteroaryl-2H-benzo[e][1,2,4]thiadiazine 1,1-dioxides

ABSTRACT

A series of novel 1,2,4-thiadiazine 1,1-dioxides were synthesized by condensation of 2-chlorobenzenesulfonamide and 4-chloropyridine-3-sulfonamide with heterocyclic methyl carbimidates obtained from heterocyclic carbonitriles and used at the time of their creation. Substituted amidines were isolated as the intermediates in the reaction with 2-chlorobenzenesulfonamide. Those intermediates were successfully cyclized to corresponding 1,2,4-thiadiazine 1,1-dioxides in pyridine with the addition of DBU. The newly synthesized compounds were evaluated for their tuberculostatic and anticancer activities. Eight compounds were able to inhibit the growth of some renal and non-small cell lung cancer cell lines.

GRAPHICAL ABSTRACT

Recent advances in the design and synthesis of heterocycles as anti-tubercular agents

Due to the unusual structure and chemical composition of the mycobacterial cell wall, effective tuberculosis (TB) treatment is difficult, making many antibiotics ineffective and hindering the entry of drugs. With approximately 33% of infection, TB is still the second most deadly infectious disease worldwide. The reasons for this are drug-resistant TB (multidrug resistant and extensively drug resistant), persistent infection (latent TB) and synergism of TB with HIV; furthermore no new chemical entity has emerged in last 40 years. New data available from the recently sequenced genome of the mycobacterium and the application of methods of modern drug design promise much for the fight against this disease. In this review, we present an introduction to TB, followed by an overview of new heterocyclic anti-tubercular moieties published during the last decade.

Antimycobacterial activity of two natural alkaloids, vasicine acetate and 2-acetyl benzylamine, isolated from Indian shrub Adhatoda vasica Ness. leaves

In folk medicine, Adhatoda vasica Ness. (Acanthaceae) is used to treat asthma and cough. The leaves of A. vasica were powdered and extracted with hexane, ethyl acetate and methanol. The hexane extract showed 97 percent reduction in colony-forming units (CFU) at 100 microg/ml. The hexane extract was subjected to column chromatography. Two natural compounds, vasicine acetate and 2-acetyl benzylamine, were isolated from it. They were bioassayed against Mycobacterium tuberculosis. The two compounds showed strong antimycobacterial activity. Vasicine acetate and 2-acetyl benzylamine isolated from hexane extract of A. vasica leaves, significantly inhibited M. tuberculosis and one multi-drug-resistant (MDR) strain and one sensitive strain at 200 and 50 microg/ml, respectively. Our study demonstrated that both the compounds, vasicine acetate and 2-acetyl benzylamine, could be evaluated further for developing a drug to control M. tuberculosis.

Pharmacophoric model building for antitubercular activity of the individual Schiff bases of small combinatorial library

Synthesis and evaluation of anti-TB activity of individual compounds of Schiff bases combinatorial library were done against Mycobacterium tuberculosis H(37)Rv at a single concentration of 6.25mug/mL according to the protocol of TAACF. Compounds 2C and 3D produced 99% inhibitory activity on the investigated organism, while the other tested compounds showed lower activity ranging from 35 to 84%. It was found that there are no relation between the anti-TB activity of the tested compounds and their lipophilicity expressed by ClogP of these compounds. A 3D pharmacophoric model has been generated by Molecular Operating Environment (MOE) using a training set of 10 reported anti-TB compounds and testing the synthesized compounds (1A, 1B, 1D, 1E, 2C, 3A, 3C, 3D, 3E and 4A-4E). The generated pharmacophoric features include, F1: hydrogen bond donors (Don), F2: aromatic rings (Aro), F3: hydrogen bond acceptors (Acc)/metal ligator (ML), F4: Aro/hydrophobic (Hyd). In all hit set, it was found that the amidic nitrogen CONH-NC fitted the region of the Don, F1, while the amidic carbonyl group fitted the region of the Acc/ML, F3. The distances bridging F1 to F2, F3 and F4 were essential for anti-TB activity in the developed pharmacophore model, as it was confirmed from model validation procedure.

Review of knowledge for rational design and identification of anti-tubercular compounds

BACKGROUND

The synergy between tuberculosis and the AIDS epidemic, along with the surge of multi-drug resistant isolates of Mycobacterium tuberculosis, has reaffirmed tuberculosis as a primary public health threat. Discovery of novel anti-tubercular entities is a highly complex and, therefore, more rational design strategies based on our increasing understanding of the fundamental principles of protein-ligand interactions are required. The combination of available knowledge of several 3D protein structures with thousands of anti-tubercular small-molecules have attracted the attention of scientists from all over the world for the application of structure- and ligand-based drug design approaches.

OBJECTIVE

In this review, an outline of the recent knowledge concerning rational design that chemists and biomedical scientists are currently using to rapidly identify and design novel anti-tubercular agents is presented. The recent successes in rational design of anti-tubercular agents mentioned in the review could give insights into the wide range of possibilities of using rational drug design methodologies.

CONCLUSION

The key conclusion is that future research through the aid of combined ligand and receptor-based design and chemo-bioinformatics will bring not only new hope, but also create a new class of anti-tubercular drugs that will help millions of patients.

Anti-tubercular agents. Part IV: Synthesis and antimycobacterial evaluation of nitroheterocyclic-based 1,2,4-benzothiadiazines

In continuation of our earlier work on benzothiadiazines, we have prepared a series of nitrofuran, nitrothiophene and arylfuran coupled benzothiadiazines and evaluated them for antimycobacterial and antibacterial activities. One of the compounds 2f has shown good in vitro antimycobacterial activity. All the synthesized compounds have shown moderate to good antibacterial activity.

Synthesis, structure analysis, and antibacterial activity of some novel 10-substituted 2-(4-piperidyl/phenyl)-5,5-dioxo[1,2,4]triazolo[1,5-b][1,2,4]benzothiadiazine derivatives

A new series of 10-substituted 5,5-dioxo-5,10-dihydro[1,2,4]triazolo[1,5-b]-[1,2,4]benzothiadiazine arylsulfonamide derivatives (10a-j and 13a-f) was synthesized. The structures of these compounds were confirmed on the basis of spectral data, elemental analysis, X-ray analysis, and quantum chemical calculations. These compounds were evaluated for their efficacy as antibacterial agents against various Gram-positive and Gram-negative strains of bacteria. Amongst these compounds 10f and 10i were the most active compounds against Escherichia coli and 13e against E. coli as well as Bacillus subtilis. Moreover, other compounds also showed potent inhibitory activity in comparison to the standard drugs.

Antituberculosis drugs: ten years of research

Tuberculosis is today amongst the worldwide health threats. As resistant strains of Mycobacterium tuberculosis have slowly emerged, treatment failure is too often a fact, especially in countries lacking the necessary health care organisation to provide the long and costly treatment adapted to patients. Because of lack of treatment or lack of adapted treatment, at least two million people will die of tuberculosis this year. Due to this concern, this infectious disease was the focus of renewed scientific interest in the last decade. Regimens were optimized and much was learnt on the mechanisms of action of the antituberculosis drugs used. Moreover, the quest for original drugs overcoming some of the problems of current regimens also became the focus of research programmes and many new series of M. tuberculosis growth inhibitors were reported. This review presents the drugs currently used in antituberculosis treatments and the most advanced compounds undergoing clinical trials. We then provide a description of their mechanism of action along with other series of inhibitors known to act on related biochemical targets. This is followed by other inhibitors of M. tuberculosis growth, including recently reported compounds devoid of a reported mechanism of action.

Effect of substituents on diarylmethanes for antitubercular activity

Aminoalkyl derivatives of diarylmethanes were prepared using Grignard, Friedel-Crafts arylation and aminohydrochloride chain formation reactions. These series of compounds were evaluated against Mycobacterium tuberculosis H(37)R(v) and showed the activity in the range of 6.25-25 microg/mL. Effect of heteroaryl, anthracenyl and phenanthrene groups on diarylmethane pharmacophores for antitubercular activity is described.