naphthoquinones and Tuberculosis--Multidrug-Resistant

Mycobacterium tuberculosis (Mtb) causes one of the most grievous pandemic infectious diseases, tuberculosis (TB), with long-term morbidity and high mortality. The emergence of drug-resistant Mtb strains, and the co-infection with human immunodeficiency virus, challenges the current WHO-TB stewardship programs. The first-line anti-TB drugs, isoniazid (INH) and rifampicin (RIF), have become extensively obsolete in TB control from chromosomal mutations during the last decades. However, based on clinical trial statistics, the production of well-tolerated anti-TB drug(s) is miserably low. Alternately, semi-synthesis or structural modifications of first-line obsolete antitubercular drugs remain as the versatile approach for getting some potential medicines. The use of any suitable phytochemicals with INH in a hybrid formulation could be an ideal approach for the development of potent anti-TB drug(s). The primary objective of this review was to highlight and analyze available INH-phytochemical hybrid research works. The utilization of phytochemicals through chemical conjugation is a new trend toward the development of safer/non-toxic anti-TB drugs.

Topics: Antitubercular Agents; Benzaldehydes; Drug Development; Glycosides; Humans; Indoles; Isoniazid; Molecular Structure; Mycobacterium tuberculosis; Naphthoquinones; Phytochemicals; Steroids; Structure-Activity Relationship; Terpenes; Tuberculosis; Tuberculosis, Multidrug-Resistant

Topics: Antitubercular Agents; Cells, Cultured; Humans; Microbial Sensitivity Tests; Mycobacterium tuberculosis; Naphthoquinones; Tuberculosis, Multidrug-Resistant

Mycobacterium tuberculosis remains a global health threat largely due to the lengthy duration of curative antibiotic treatment, contributing to medical nonadherence and the emergence of drug resistance. This prolonged therapy is likely due to the presence of M. tuberculosis persisters, which exhibit antibiotic tolerance. Inorganic polyphosphate [poly(P)] is a key regulatory molecule in the M. tuberculosis stringent response mediating antibiotic tolerance. The polyphosphate kinase PPK1 is responsible for poly(P) synthesis in M. tuberculosis, while the exopolyphosphatases PPX1 and PPX2 and the GTP synthase PPK2 are responsible for poly(P) hydrolysis. In the present study, we show by liquid chromatography-tandem mass spectrometry that poly(P)-accumulating M. tuberculosis mutant strains deficient in ppx1 or ppk2 had significantly lower intracellular levels of glycerol-3-phosphate (G3P) and 1-deoxy-xylulose-5-phosphate. Real-time PCR revealed decreased expression of genes in the G3P synthesis pathway in each mutant. The ppx1-deficient mutant also showed a significant accumulation of metabolites in the tricarboxylic acid cycle, as well as altered arginine and NADH metabolism. Each poly(P)-accumulating strain showed defective biofilm formation, while deficiency of ppk2 was associated with increased sensitivity to plumbagin and meropenem and deficiency of ppx1 led to enhanced susceptibility to clofazimine. A DNA vaccine expressing ppx1 and ppk2, together with two other members of the M. tuberculosis stringent response, M. tuberculosis rel and sigE, did not show protective activity against aerosol challenge with M. tuberculosis, but vaccine-induced immunity enhanced the killing activity of isoniazid in a murine model of chronic tuberculosis. In summary, poly(P)-regulating factors of the M. tuberculosis stringent response play an important role in M. tuberculosis metabolism, biofilm formation, and antibiotic sensitivity in vivo.

Topics: Acid Anhydride Hydrolases; Animals; Antitubercular Agents; Biofilms; Citric Acid Cycle; Clofazimine; Disease Models, Animal; Drug Resistance, Bacterial; Gene Expression; Glycerophosphates; Isoenzymes; Isoniazid; Meropenem; Mice; Mycobacterium tuberculosis; Naphthoquinones; Phosphotransferases (Phosphate Group Acceptor); Polyphosphates; Thienamycins; Tuberculosis Vaccines; Tuberculosis, Multidrug-Resistant; Vaccines, DNA; Xylose

The cell wall of Mycobacterium tuberculosis interacts with the host counterpart during the pathogenesis of tuberculosis. L-rhamnosyl (L-Rha) residue, a linker connects the arabinogalactan and peptidoglycan moieties in the bacterial cell wall. The biosynthesis of L-rhamnose utilizes four successive enzymes RmlA, RmlB, RmlC and RmlD. Neither rhamnose nor the genes responsible for its synthesis are observed in humans. Thus, drugs inhibiting enzymes of this pathway are unlikely to interfere with metabolic pathways in humans. The adverse drug effects of first and second line drugs along with the development of multi-drug resistance tuberculosis have stimulated the research in search of new therapeutic drugs. Thus, it is attractive to hypothesize that inhibition of the biosynthesis of L-Rha would be lethal to the mycobacteria. Nature provides innumerable secondary metabolites with novel structural architectures with reported activity against M. tuberculosis. Combination of structure based virtual screening with physicochemical and pharmacokinetic studies against rhamnose pathway enzymes identified potential leads. The crucial screening studies recognized four phytocompounds butein, diospyrin, indicanine, and rumexneposide A with good binding affinity towards the rhamnose pathway proteins. Furthermore, the high throughput screening methods recognized butein, a secondary metabolite from Butea monosperma with strong anti-tubercular bioactive spectrum. Butein displayed promising anti-mycobacterial activity which is validated by Microplate alamar blue assay (MABA). The focus on novel agents like these phytocompounds which exhibit preference toward the successive enzymes of a single pathway can prevent the development of bacterial resistance.

Topics: Antitubercular Agents; Bacterial Proteins; Biosynthetic Pathways; Chalcones; Humans; Molecular Docking Simulation; Mycobacterium tuberculosis; Naphthoquinones; Rhamnose; Tuberculosis, Multidrug-Resistant

The recent emergence of multidrug-resistant (MDR), extensively drug-resistant (XDR), and totally drug-resistant (TDR) Mycobacterium tuberculosis (MTB) strains have further complicated the control of tuberculosis (TB). There is an urgent need of new molecules candidates to be developed as novel, active, and less toxic anti-tuberculosis (anti-TB) drugs. Medicinal plants have been an excellent source of leads for the development of drugs, particularly as anti-infective agents. In previous studies, the non-polar extract of Diospyros anisandra showed potent anti-TB activity, and three monomeric and five dimeric naphthoquinones have been obtained. In this study, we performed bioguided chemical fractionation and the isolation of eight naphthoquinones from D. anisandra and their evaluation of anti-TB and cytotoxic activities against mammalian cells.. The n-hexane crude extract from the stem bark of the plant was obtained by maceration and liquid-liquid fractionation. The isolation of naphthoquinones was carried out by chromatographic methods and identified by gas chromatography and mass spectroscopy data analysis. Anti-TB activity was evaluated against two strains of MTB (H37Rv) susceptible to all five first-line anti-TB drugs and a clinical isolate that is resistant to these medications (pan-resistant, CIBIN 99) by measuring the minimal inhibitory concentration (MIC). Cytotoxicity of naphthoquinones was estimated against two mammalian cells, Vero line and primary cultures of human peripheral blood mononuclear (PBMC) cells, and their selectivity index (SI) was determined.. Plumbagin and its dimers maritinone and 3,3'-biplumbagin showed the strongest activity against both MTB strains (MIC = 1.56-3.33 μg/mL). The bioactivity of maritinone and 3,3'-biplumbagin were 32 times more potent than rifampicin against the pan-resistant strain, and both dimers showed to be non-toxic against PBMC and Vero cells. The SI of maritinone and 3,3'-biplumbagin on Vero cells was 74.34 and 194.11 against sensitive and pan-resistant MTB strains, respectively.. Maritinone and 3,3'-biplumbagin possess a very interesting potential for development as new drugs against M. tuberculosis, mainly resistant profile strains.

Topics: Animals; Antitubercular Agents; Cells, Cultured; Chlorocebus aethiops; Diospyros; Gas Chromatography-Mass Spectrometry; Humans; Leukocytes, Mononuclear; Male; Microbial Sensitivity Tests; Middle Aged; Mycobacterium tuberculosis; Naphthoquinones; Plant Bark; Plant Extracts; Plant Stems; Rifampin; Tuberculosis, Multidrug-Resistant; Vero Cells

The recent increase in the incidence of tuberculosis with the emergence of multi-drug resistant (MDR) cases has lead to the search for new drugs that are effective against MDR strains of Mycobacterium tuberculosis (M. tb) and can augment the potential of existing drugs against tuberculosis. In the present study a series of naphthalene-1,4-dione derivatives were synthesized and evaluated for their in vitro antimycobacterial activity against M. tb H37Rv strain. Preliminary results indicated that most of the compounds demonstrated significant antimycobacterial activities. The most effective compounds of the series 7, 8 and 10 have MIC values of 3.13 microg/mL and growth inhibition of 99%. Compound 7 has an IC50 value of 0.49 microg/mL. Compounds 1, 3 and 18 with MIC values of 3.13 microg/mL also showed 96-98% growth inhibition. The objective of our study is to generate new leads through different mode of action and to optimize their structure to display the potent efficacy.

Topics: Anti-Bacterial Agents; Microbial Sensitivity Tests; Mycobacterium tuberculosis; Naphthoquinones; Structure-Activity Relationship; Tuberculosis, Multidrug-Resistant