Growth Inhibition of Mycobacterium bovis, Mycobacterium tuberculosis and Mycobacterium avium In Vitro: Effect of 1-β-d-2‘-Arabinofuranosyl and 1-(2‘-Deoxy-2‘-fluoro-β-d-2‘-ribofuranosyl) Pyrimidine Nucleoside Analogs

Enhancing or Quenching of a Mitochondria-Targeted AIEgens-Floxuridine Sensor by the Regulation of pH-Dependent Self-assembly, Efficient Recognition of Hg2+, and Stimulated Response of GSH

Biocompatible fluorescent probes have emerged as essential tools in life sciences for visualizing subcellular structures and detecting specific analytes. Herein, we report the synthesis and characterization of a novel fluorescent probe (TPE-FdU), incorporated with hydrophilic 2'-fluoro-substituted deoxyuridine and hydrophobic ethynyl tetraphenylethene moieties, which possessed typical aggregation-induced emission (AIE) behavior. In comparison to the TPE-FdU (pKa 7.68) treated in neutral conditions, it performed well at pH 4, exhibiting an enhanced 450 nm emission signal of approximately four times stronger. As the pH value was increased to 10, the fluorescence intensity was completely quenched. The TEM images of TPE-FdU in an acidic environment (nanospherical morphology, AIE enhance, pH = 4) and in a basic environment (microrods, fluorescence quenching, pH = 9) revealed that it was a pH-dependent self-assembled probe, which was also illustrated by the interpretation of the NMR spectrum. Furthermore, the TPE-FdU probe exhibited a specific response to trace Hg2+ ions. Interestingly, the quenched fluorescence of the TPE-FdU probe caused by Hg2+ can be recovered by the addition of GSH due to the formation of the Hg-S bond being released away. MTT assay and CLSM images demonstrated that TPE-FdU was nontoxic and selectively visualized in the intracellular mitochondria. These results contributed to the development of advanced fluorescent probes with diverse applications in cell imaging, environment protection, and biomedical research.

New Flexible Analogues of 8-Aza-7-deazapurine Nucleosides as Potential Antibacterial Agents

A variety of ribo-, 2'-deoxyribo-, and 5'-norcarbocyclic derivatives of the 8-aza-7-deazahypoxanthine fleximer scaffolds were designed, synthesized, and screened for antibacterial activity. Both chemical and chemoenzymatic methods of synthesis for the 8-aza-7-deazainosine fleximers were compared. In the case of the 8-aza-7-deazahypoxanthine fleximer, the transglycosylation reaction proceeded with the formation of side products. In the case of the protected fleximer base, 1-(4-benzyloxypyrimidin-5-yl)pyrazole, the reaction proceeded selectively with formation of only one product. However, both synthetic routes to realize the fleximer ribonucleoside (3) worked with equal efficiency. The new compounds, as well as some 8-aza-7-deazapurine nucleosides synthesized previously, were studied against Gram-positive and Gram-negative bacteria and M. tuberculosis. It was shown that 1-(β-D-ribofuranosyl)-4-(2-aminopyridin-3-yl)pyrazole (19) and 1-(2',3',4'-trihydroxycyclopent-1'-yl)-4-(pyrimidin-4(3H)-on-5-yl)pyrazole (9) were able to inhibit the growth of M. smegmatis mc2 155 by 99% at concentrations (MIC99) of 50 and 13 µg/mL, respectively. Antimycobacterial activities were revealed for 4-(4-aminopyridin-3-yl)-1H-pyrazol (10) and 1-(4'-hydroxy-2'-cyclopenten-1'-yl)-4-(4-benzyloxypyrimidin-5-yl)pyrazole (6). At concentrations (MIC99) of 40 and 20 µg/mL, respectively, the compounds resulted in 99% inhibition of M. tuberculosis growth.

Novel Steroidal[17,16-d]pyrimidines Derived from Epiandrosterone and Androsterone: Synthesis, Characterization and Configuration-Activity Relationships

Two series of novel steroidal[17,16-d]pyrimidines derived from natural epiandrosterone and androsterone were designed and synthesized, and these compounds were screened for their potential anticancer activities. The preliminary bioassay indicated that some of these prepared compounds exhibited significantly good cytotoxic activities against human gastric cancer (SGC-7901), lung cancer (A549), and hepatocellular liver carcinoma (HepG2) cell lines compared with 5-fluorouracil (5-FU), epiandrosterone, and androsterone. Especially the respective pairs from epiandrosterone and androsterone showed significantly different inhibitory activities, and the possible configuration-activity relationships have also been summarized and discussed based on kinase assay and molecular docking, which indicated that the inhibition activities of these steroidal[17,16-d]pyrimidines might obviously be affected by the configuration of the hydroxyl group in the part of the steroidal scaffold.

Analogues of Pyrimidine Nucleosides as Mycobacteria Growth Inhibitors

Tuberculosis (TB) is the oldest human infection disease. Mortality from TB significantly decreased in the 20th century, because of vaccination and the widespread use of antibiotics. However, about a third of the world’s population is currently infected with Mycobacterium tuberculosis (Mtb) and the death rate from TB is about 1.4–2 million people per year. In the second half of the 20th century, new extensively multidrug-resistant strains of Mtb were identified, which are steadily increasing among TB patients. Therefore, there is an urgent need to develop new anti-TB drugs, which remains one of the priorities of pharmacology and medicinal chemistry. The antimycobacterial activity of nucleoside derivatives and analogues was revealed not so long ago, and a lot of studies on their antibacterial properties have been published. Despite the fact that there are no clinically used drugs based on nucleoside analogues, some progress has been made in this area. This review summarizes current research in the field of the design and study of inhibitors of mycobacteria, primarily Mtb.

New Derivatives of 5-Substituted Uracils: Potential Agents with a Wide Spectrum of Biological Activity

Pyrimidine nucleoside analogues are widely used to treat infections caused by the human immunodeficiency virus (HIV) and DNA viruses from the herpes family. It has been shown that 5-substituted uracil derivatives can inhibit HIV-1, herpes family viruses, mycobacteria and other pathogens through various mechanisms. Among the 5-substituted pyrimidine nucleosides, there are not only the classical nucleoside inhibitors of the herpes family viruses, 2'-deoxy-5-iodocytidine and 5-bromovinyl-2'-deoxyuridine, but also derivatives of 1-(benzyl)-5-(phenylamino)uracil, which proved to be non-nucleoside inhibitors of HIV-1 and EBV. It made this modification of nucleoside analogues very promising in connection with the emergence of new viruses and the crisis of drug resistance when the task of creating effective antiviral agents of new types that act on other targets or exhibit activity by other mechanisms is very urgent. In this paper, we present the design, synthesis and primary screening of the biological activity of new nucleoside analogues, namely, 5'-norcarbocyclic derivatives of substituted 5-arylamino- and 5-aryloxyuracils, against RNA viruses.

Synthesis of acyclic nucleoside phosphonates targeting flavin-dependent thymidylate synthase in Mycobacterium tuberculosis

Flavin-Dependent Thymidylate Synthase (FDTS) encoded by ThyX gene was discovered as a new class of thymidylate synthase involved in the de novo synthesis of dTMP named only in 30 % of human pathogenic bacteria. This target was pursed for the development of new antibacterial agents against multiresistant pathogens. We have developed a new class of ANPs based on the mimic of two natural's cofactors (dUMP and FAD) as inhibitors against Mycobacterium tuberculosis ThyX. Several synthetic efforts were performed to optimize regioselective N1-alkylation, cross-coupling metathesis and Sonogashira cross-coupling. Compound 19c showed a poor 31.8% inhibitory effect on ThyX at 200 μM.

Novel 5'-Norcarbocyclic Pyrimidine Derivatives as Antibacterial Agents

A series of novel 5'-norcarbocyclic derivatives of 5-alkoxymethyl or 5-alkyltriazolyl-methyl uracil were synthesized and the activity of the compounds evaluated against both Gram-positive and Gram-negative bacteria. The growth of Mycobacterium smegmatis was completely inhibited by the most active compounds at a MIC99 of 67 μg/mL (mc²155) and a MIC99 of 6.7⁻67 μg/mL (VKPM Ac 1339). Several compounds also showed the ability to inhibit the growth of attenuated strains of Mycobacterium tuberculosis ATCC 25177 (MIC99 28⁻61 μg/mL) and Mycobacterium bovis ATCC 35737 (MIC99 50⁻60 μg/mL), as well as two virulent strains of M. tuberculosis; a laboratory strain H37Rv (MIC99 20⁻50 μg/mL) and a clinical strain with multiple drug resistance MS-115 (MIC99 20⁻50 μg/mL). Transmission electron microscopy (TEM) evaluation of M. tuberculosis H37Rv bacterial cells treated with one of the compounds demonstrated destruction of the bacterial cell wall, suggesting that the mechanism of action for these compounds may be related to their interactions with bacteria cell walls.

Nucleoside analogs and tuberculosis: new weapons against an old enemy

Purine and pyrimidine nucleoside and nucleotide analogs have been extensively studied as anticancer and antiviral agents. In addition to this, they have recently shown great potential against Mycobacterium Tuberculosis, the causative agent of TB. TB ranks as the tenth most common cause of death in the world. The current treatment for TB infection is limited by side effects and cost of the drugs and most importantly by the development of resistance to the therapy. Therefore the development of novel drugs, capable of overcoming the drawbacks of the existing treatments, has become the focus of many research programs. In parallel to that, a tremendous effort has been made to elucidate the unique metabolism of this pathogen with the aim to identify new possible targets. This review presents the state of the art in nucleoside and nucleotide analogs in the treatment of TB. In particular, we report on the inhibitory activity of this class of compounds, both in enzymatic and whole-cell assays, providing a brief insight to which reported target these novel compounds are hitting.

Synthesis and antimicrobial properties of 5,5′-modified 2′,5′-dideoxyuridines

An effective method of synthesis of 5,5′-modified 2′,5′-dideoxyuridine derivatives is based on sequential 5′-iodination and azidation of 5-[4-(1-decyl)-1,2,3-triazol-1-yl]methyl-2′-deoxyuridine followed by 1,3-dipolar cycloaddition of the intermediate azide with an olefin under the catalysis of Cu(I) resulting in 75–85% yield of 5′-[4-substituted (1,2,3-triazol-1-yl]-5-[4-(1-decyl)-1,2,3-triazol-1-yl]methyl-2′,5′-dideoxyuridine. The compounds were shown to possess low cytotoxicity in Vero, A549 cells and Jurkat cell cultures and did not demonstrate noticeable antimicrobial activity.

Significance and biological importance of pyrimidine in the microbial world

Microbes are unique creatures that adapt to varying lifestyles and environment resistance in extreme or adverse conditions. The genetic architecture of microbe may bear a significant signature not only in the sequences position, but also in the lifestyle to which it is adapted. It becomes a challenge for the society to find new chemical entities which can treat microbial infections. The present review aims to focus on account of important chemical moiety, that is, pyrimidine and its various derivatives as antimicrobial agents. In the current studies we represent more than 200 pyrimidines as antimicrobial agents with different mono-, di-, tri-, and tetrasubstituted classes along with in vitro antimicrobial activities of pyrimidines derivatives which can facilitate the development of more potent and effective antimicrobial agents.

Inhibition of Mycobacterium tuberculosis strains H37Rv and MDR MS-115 by a new set of C5 modified pyrimidine nucleosides

Two sets of pyrimidine nucleoside derivatives bearing extended alkyloxymethyl or alkyltriazolidomethyl substituents at position 5 of the nucleobase were synthesized and evaluated as potential antituberculosis agents. The impact of modifications at 3'- and 5'-positions of the carbohydrate moiety on the antimycobacterial activity and cytotoxicity was studied. The highest effect was shown for 5-dodecyloxymethyl-2'-deoxyuridine, 5-decyltriazolidomethyl-2'-deoxyuridine, and 5-dodecyltriazolidomethyl-2'-deoxycytidine. They effectively inhibited the growth of two Mycobacterium tuberculosis strains in vitro, laboratory H37Rv (MIC99=20, 10, and 20μg/mL, respectively) and clinical MDR MS-115 resistant to five top antituberculosis drugs (МIC99=50, 10, and 10μg/mL, respectively).

Update on carbohydrate-containing antibacterial agents

BACKGROUND

Since the first known use of antibiotics > 2,500 years ago, a research field with immense importance for the welfare of mankind has been developed. After a decrease in interest in this topic by the end of the 20th century the occurrence of (poly-)resistant strains of bacteria induced a revival of antibiotics research. Health systems have been seeking viable and reliable solutions to this dangerous and expansive threat.

OBJECTIVE

This review will focus on carbohydrate-containing antibiotics and will give an outline of recently published novel isolated, semisynthetic as well as synthetic structures, their mechanism of action, if known, and the strategies for the design of compounds with potential by improved antibacterial properties.

METHODS

The literature between 2000 and 2008 was screened with main focus on recent examples of novel structures and strategies for the lead finding of exclusively antibacterial agents.

RESULTS/CONCLUSION

With the explanation of the role of the carbohydrate moieties in the respective antibacterial agents together with better synthetic strategies in carbohydrate chemistry as well as improvements in assay development for high throughput screening methods, carbohydrate-containing antibiotics can be used for the finding of potential drug leads that contribute to the fight against infections and diseases caused by (resistant) bacterial pathogens.

Chemotherapeutic interventions against tuberculosis

Tuberculosis is the second leading cause of infectious deaths globally. Many effective conventional antimycobacterial drugs have been available, however, emergence of multidrug-resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB) has overshadowed the effectiveness of the current first and second line drugs. Further, currently available agents are complicated by serious side effects, drug interactions and long-term administration. This has prompted urgent research efforts in the discovery and development of new anti-tuberculosis agent(s). Several families of compounds are currently being explored for the treatment of tuberculosis. This review article presents an account of the existing chemotherapeutics and highlights the therapeutic potential of emerging molecules that are at different stages of development for the management of tuberculosis disease.

Discovery of novel 5-(ethyl or hydroxymethyl) analogs of 2'-'up' fluoro (or hydroxyl) pyrimidine nucleosides as a new class of Mycobacterium tuberculosis, Mycobacterium bovis and Mycobacterium avium inhibitors

Discovery of novel antimycobacterial compounds that work on distinctive targets and by diverse mechanisms of action is urgently required for the treatment of mycobacterial infections due to the emerging global health threat of tuberculosis. We have identified a new class of 5-ethyl or hydroxy (or methoxy) methyl-substituted pyrimidine nucleosides as potent inhibitors of Mycobacterium bovis, Mycobacterium tuberculosis (H37Ra, H37Rv) and Mycobacterium avium. A series of 2'-'up' fluoro (or hydroxy) nucleosides (1, 2, 4-6, 9, 10, 13, 16, 18, 21, 24) was synthesized and evaluated for antimycobacterial activity. Among 2'-fluorinated compounds, 1-(3-bromo-2,3-dideoxy-2-fluoro-β-d-arabinofuranosyl)-5-ethyluracil (13) exhibited promising activity against M. bovis and Mtb alone, and showed synergism when combined with isoniazid. The most active compound emerging from these studies, 1-(β-d-arabinofuranosyl)-4-thio-5-hydroxymethyluracil (21) inhibited Mtb (H37Ra) (MIC(50)=0.5 μg/mL) and M. bovis (MIC(50)=0.5 μg/mL) at low concentrations, and was ten times more potent against Mtb (H37Ra) than cycloserine (MIC(50)=5.0 μg/mL), a second line drug. It also showed an additive effect when combined with isoniazid. Compound 21 retained sensitivity against a rifampicin-resistant (H37Rv) strain of Mtb (MIC(50)=1 μg/mL) at concentrations similar to that for a rifampicin-sensitive (H37Rv) strain, suggesting that it has no cross-resistance to a first-line anti-TB drug. In addition, the replication of M. avium was also inhibited by 21 (MIC(50)=10 μg/mL). No cellular toxicity of 13 or 21 was observed up to the highest concentration tested (CC(50)>100 μg/mL). These observations offer promise for a new drug treatment regimen to augment and complement the current chemotherapy of TB.

Synthesis and evaluation of 5-substituted 2'-deoxyuridine monophosphate analogues as inhibitors of flavin-dependent thymidylate synthase in Mycobacterium tuberculosis

A series of 5-substituted 2'-deoxyuridine monophosphate analogues has been synthesized and evaluated as potential inhibitors of mycobacterial ThyX, a novel flavin-dependent thymidylate synthase in Mycobacterium tuberculosis. A systematic SAR study led to the identification of compound 5a, displaying an IC(50) value against mycobacterial ThyX of 0.91 μM. This derivative lacks activity against the classical mycobacterial thymidylate synthase ThyA (IC(50) > 50 μM) and represents the first example of a selective mycobacterial FDTS inhibitor.

Synthesis, reactivity and biological activity of 5-alkoxymethyluracil analogues

This review article summarizes the results of a long-term investigation of 5-alkoxymethyluracil analogues and is aimed, in particular, at methods of syntheses. Most of the presented compounds were synthesized in order to evaluate their biological activity, therefore, a brief survey of biological activity, especially antiviral, cytotoxic and antibacterial, is also reported.

Design, synthesis and antimycobacterial activities of 1-methyl-2-alkenyl-4(1H)-quinolones

A series of 23 new 1-methyl-2-alkenyl-4(1H)quinolones have been synthesized and evaluated in vitro for their antimycobacterial activities against fast growing species of mycobacteria, such as Mycobacterium fortuitum, M. smegmatis and M. phlei. The compounds displayed good to excellent inhibition of the growth of the mycobacterial test strains with improved antimycobacterial activity compared to the hit compound, evocarpine. The most active compounds, which possessed chain length of 11-13 carbons at position-2 displayed potent inhibitory effects with an MIC value of 1.0mg/L. In a human diploid embryonic lung cell line, MRC-5 cytotoxicity assay, the alkaloids showed weak to moderate cytotoxic activity. Biological evaluation of these evocarpine analogues on the less pathogenic fast growing strains of mycobacteria showed an interesting antimycobacterial profile and provided significant insight into the structure-activity relationships.

Synthesis and antiviral evaluation of 2'-C-methyl analogues of 5-alkynyl- and 6-alkylfurano- and pyrrolo[2,3-d]pyrimidine ribonucleosides

A series of novel 2'-C-methylribonucleosides, involving 5-iodo and 5-alkynyl uridine analogues as well as related bicyclic furano- and pyrrolo[2,3-d]pyrimidinone compounds, has been synthesized and evaluated for their inhibitory effect on replication of the hepatitis C virus (HCV). The new nucleoside analogues did not show meaningful anti-HCV activity.

Synthesis of methyl 5-S-alkyl-5-thio-D-arabinofuranosides and evaluation of their antimycobacterial activity

The emergence of drug resistant tuberculosis necessitates a search for new antimycobacterial compounds. The antigen 85 (ag85) complex is a family of mycolyl transferases involved in the synthesis of trehalose-6,6'-dimycolate and the mycolated hexasaccharide motif found at the terminus of the arabinogalactan in mycobacterium. Enzymes involved in the synthesis of cell wall structures like these are potential targets for the development of new antiinfectives. To potentially inhibit the ag85 complex, methyl 5-S-alkyl-5-thio-arabinofuranoside analogues were designed based on docking studies with ag85C derived from Mycobacterium tuberculosis. The target arabinofuranosides were then synthesized and the antibacterial activity evaluated against Mycobacterium smegmatis ATCC 14468. Two of the compounds, 5-S-octyl-5-thio-alpha-d-arabinofuranoside (8) and 5-S-octyl-5-thio-beta-d-arabinofuranoside (11), showed MICs of 256 and 512microg/mL, respectively. Attempts to directly evaluate acyltransferase inhibitory activity of the arabinofuranosides against ag85C are also described. In conclusion, a new class of antimycobacterial arabinofuranosides has been discovered.