Conjugates of nucleobases with triazole-hydroxamic acids for the reactivation of acetylcholinesterase and treatment of delayed neurodegeneration induced by organophosphate poisoning.

A series of new uncharged conjugates of adenine, 3,6-dimetyl-, 1,6-dimethyl- and 6-methyluracil with 1,2,4-triazole-3-hydroxamic and 1,2,3-triazole-4-hydroxamic acid moieties were synthesized and studied as reactivators of organophosphate-inhibited cholinesterase. It is shown that triazole-hydroxamic acids can reactivate acetylcholinesterase (AChE) inhibited by paraoxon (POX) in vitro, offering reactivation constants comparable to those of pralidoxime (2-PAM). However, in contrast to 2-PAM, triazole-hydroxamic acids demonstrated the ability to reactivate AChE in the brain of rats poisoned with POX. At a dose of 200 mg/kg (i.v.), the lead compound 3e reactivated 22.6 ± 7.3% of brain AChE in rats poisoned with POX. In a rat model of POX-induced delayed neurodegeneration, compound 3e reduced the neuronal injury labeled with FJB upon double administration 1 and 3 h after poisoning. Compound 3e was also shown to prevent memory impairment of POX-poisoned rats as tested in a Morris water maze.

Thymine-Modified Nanocarrier for Doxorubicin Delivery in Glioblastoma Cells.

Brain tumor glioblastoma is one of the worst types of cancer. The blood-brain barrier prevents drugs from reaching brain cells and shields glioblastoma from treatment. The creation of nanocarriers to improve drug delivery and internalization effectiveness may be the solution to this issue. In this paper, we report on a new nanocarrier that was developed to deliver the anticancer drug doxorubicin to glioblastoma cells. The nanocarrier was obtained by nanoemulsion polymerization of diallyl disulfide with 1-allylthymine. Diallyl disulfide is a redox-sensitive molecule involved in redox cell activities, and thymine is a uracil derivative and one of the well-known bioactive compounds that can enhance the pharmacological activity of doxorubicin. Doxorubicin was successfully introduced into the nanocarrier with a load capacity of about 4.6%. Biological studies showed that the doxorubicin nanocarrier composition is far more cytotoxic to glioblastoma cells (T98G) than it is to cancer cells (M-HeLa) and healthy cells (Chang liver). The nanocarrier improves the penetration of doxorubicin into T98G cells and accelerates the cells' demise, as is evident from flow cytometry and fluorescence microscopy data. The obtained nanocarrier, in our opinion, is a promising candidate for further research in glioblastoma therapy.

Novel Uracil-Based Inhibitors of Acetylcholinesterase with Potency for Treating Memory Impairment in an Animal Model of Alzheimer's Disease.

Novel derivatives based on 6-methyluracil and condensed uracil, 2,4-quinazoline-2,4-dione, were synthesized with terminal meta- and para-benzoate moieties in polymethylene chains at the N atoms of the pyrimidine ring. In the synthesized compounds, the polymethylene chains were varied from having tris- to hexamethylene chains and quaternary ammonium groups; varying substituents (ester, salt, acid) at benzene ring were introduced into the chains and benzoate moieties. In vivo biological experiments demonstrated the potency of these compounds in decreasing the number of ß-amyloid plaques and their suitability for the treatment of memory impairment in a transgenic model of Alzheimer's disease.

The First 5'-Phosphorylated 1,2,3-Triazolyl Nucleoside Analogues with Uracil and Quinazoline-2,4-Dione Moieties: A Synthesis and Antiviral Evaluation.

A series of 5'-phosphorylated (dialkyl phosphates, diaryl phosphates, phosphoramidates, H-phosphonates, phosphates) 1,2,3-triazolyl nucleoside analogues in which the 1,2,3-triazole-4-yl-ß-D-ribofuranose fragment is attached via a methylene group or a butylene chain to the N-1 atom of the heterocycle moiety (uracil or quinazoline-2,4-dione) was synthesized. All compounds were evaluated for antiviral activity against influenza virus A/PR/8/34/(H1N1). Antiviral assays revealed three compounds, 13b, 14b, and 17a, which showed moderate activity against influenza virus A (H1N1) with IC50 values of 17.9 µM, 51 µM, and 25 µM, respectively. In the first two compounds, the quinazoline-2,4-dione moiety is attached via a methylene or a butylene linker, respectively, to the 1,2,3-triazole-4-yl-ß-D-ribofuranosyl fragment possessing a 5'-diphenyl phosphate substituent. In compound 17a, the uracil moiety is attached via the methylene unit to the 1,2,3-triazole-4-yl-ß-D-ribofuranosyl fragment possessing a 5'-(phenyl methoxy-L-alaninyl)phosphate substituent. The remaining compounds appeared to be inactive against influenza virus A/PR/8/34/(H1N1). The results of molecular docking simulations indirectly confirmed the literature data that the inhibition of viral replication is carried out not by nucleoside analogues themselves, but by their 5'-triphosphate derivatives.

Synthesis and Antiviral Evaluation of Nucleoside Analogues Bearing One Pyrimidine Moiety and Two D-Ribofuranosyl Residues.

A series of 1,2,3-triazolyl nucleoside analogues in which 1,2,3-triazol-4-yl-ß-d-ribofuranosyl fragments are attached via polymethylene linkers to both nitrogen atoms of the heterocycle moiety (uracil, 6-methyluracil, thymine, quinazoline-2,4-dione, alloxazine) or to the C-5 and N-3 atoms of the 6-methyluracil moiety was synthesized. All compounds synthesized were evaluated for antiviral activity against influenza virus A/PR/8/34/(H1N1) and coxsackievirus B3. Antiviral assays revealed three compounds, 2i, 5i, 11c, which showed moderate activity against influenza virus A H1N1 with IC50 values of 57.5 µM, 24.3 µM, and 29.2 µM, respectively. In the first two nucleoside analogues, 1,2,3-triazol-4-yl-ß-d-ribofuranosyl fragments are attached via butylene linkers to N-1 and N-3 atoms of the heterocycle moiety (6-methyluracil and alloxazine, respectively). In nucleoside analogue 11c, two 1,2,3-triazol-4-yl-2',3',5'-tri-O-acetyl-ß-d-ribofuranose fragments are attached via propylene linkers to the C-5 and N-3 atoms of the 6-methyluracil moiety. Almost all synthesized 1,2,3-triazolyl nucleoside analogues showed no antiviral activity against the coxsackie B3 virus. Two exceptions are 1,2,3-triazolyl nucleoside analogs 2f and 5f, in which 1,2,3-triazol-4-yl-2',3',5'-tri-O-acetyl-ß-d-ribofuranose fragments are attached to the C-5 and N-3 atoms of the heterocycle moiety (6-methyluracil and alloxazine respectively). These compounds exhibited high antiviral potency against the coxsackie B3 virus with IC50 values of 12.4 and 11.3 µM, respectively, although both were inactive against influenza virus A H1N1. According to theoretical calculations, the antiviral activity of the 1,2,3-triazolyl nucleoside analogues 2i, 5i, and 11c against the H1N1 (A/PR/8/34) influenza virus can be explained by their influence on the functioning of the polymerase acidic protein (PA) of RNA-dependent RNA polymerase (RdRp). As to the antiviral activity of nucleoside analogs 2f and 5f against coxsackievirus B3, it can be explained by their interaction with the coat proteins VP1 and VP2.

Synthesis of 1,2,3-triazolyl nucleoside analogues and their antiviral activity.

Based on the fact that a search for influenza antivirals among nucleoside analogues has drawn very little attention of chemists, the present study reports the synthesis of a series of 1,2,3-triazolyl nucleoside analogues in which a pyrimidine fragment is attached to the ribofuranosyl-1,2,3-triazol-4-yl moiety by a polymethylene linker of variable length. Target compounds were prepared by the Cu alkyne-azide cycloaddition (CuAAC) reaction. Derivatives of uracil, 6-methyluracil, 3,6-dimethyluracil, thymine and quinazolin-2,4-dione with ω-alkyne substituent at the N1 (or N5) atom and azido 2,3,5-tri-O-acetyl-D-ß-ribofuranoside were used as components of the CuAAC reaction. All compounds synthesized were evaluated for antiviral activity against influenza virus A/PR/8/34/(H1N1) and coxsackievirus B3. The best values of IC50 (inhibiting concentration) and SI (selectivity index) were demonstrated by the lead compound 4i in which the 1,2,3-triazolylribofuranosyl fragment is attached to the N1 atom of the quinazoline-2,4-dione moiety via a butylene linker (IC50 = 30 µM, SI = 24) and compound 8n in which the 1,2,3-triazolylribofuranosyl fragment is attached directly to the N5 atom of the 6-methyluracil moiety (IC50 = 15 µM, SI = 5). According to theoretical calculations, the antiviral activity of the 1,2,3-triazolyl nucleoside analogues 4i and 8n against H1N1 (A/PR/8/34) influenza virus can be explained by their influence on the functioning of the polymerase acidic protein (PA) of RNA-dependent RNA polymerase (RdRP).

6-Methyluracil derivatives as peripheral site ligand-hydroxamic acid conjugates: Reactivation for paraoxon-inhibited acetylcholinesterase.

New uncharged conjugates of 6-methyluracil derivatives with imidazole-2-aldoxime and 1,2,4-triazole-3-hydroxamic acid units were synthesized and studied as reactivators of organophosphate-inhibited cholinesterase. Using paraoxon (POX) as a model organophosphate, it was shown that 6-methyluracil derivatives linked with hydroxamic acid are able to reactivate POX-inhibited human acetylcholinesterase (AChE) in vitro. The reactivating efficacy of one compound (5b) is lower than that of pyridinium-2-aldoxime (2-PAM). Meanwhile, unlike 2-PAM, in vivo study showed that the lead compound 5b is able: (1) to reactivate POX-inhibited AChE in the brain; (2) to decrease death of neurons and, (3) to prevent memory impairment in rat model of POX-induced neurodegeneration.