Triuracils – 1,3-Bis[ω-(N-methyluracil-1-yl)alkyl]thymines and Their 5,5′-Cyclic Counterparts

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.

Novel slow-binding reversible acetylcholinesterase inhibitors based on uracil moieties for possible treatment of myasthenia gravis and protection from organophosphate poisoning

A series of new compounds in which uracil and 3,6-dimethyluracil moieties are bridged with different spacers were prepared and evaluated in vitro for the acetyl- and butyrylcholinesterase (AChE and BChE) inhibitory activities. These bisuracils are shown to be very effective inhibitors of AChE, inhibiting the enzyme at nano- and lower molar concentrations with extremely high selectivity for AChE vs. BChE. Kinetic analysis showed that the lead compound 2h acts as a slow-binding inhibitor of AChE and possess a long drug-target residence time (τ = 1/k_off = 18.6 ± 7.5 min). Moreover, compound 2h ameliorated muscle weakness in myasthenia gravis rat model with a lower effective dose and longer lasting effect than pyridostigmine bromide. Besides, it was shown that compound 2h has an effect of increasing efficiency of antidotal therapy as a pretreatment for poisoning by organophosphates.

Novel Acetylcholinesterase Inhibitors Based on Uracil Moiety for Possible Treatment of Alzheimer Disease

In this study, novel derivatives based on 6-methyluracil and condensed uracil were synthesized, namely, 2,4-quinazoline-2,4-dione with ω-(ortho-nitrilebenzylethylamino) alkyl chains at the N atoms of the pyrimidine ring. In this series of synthesized compounds, the polymethylene chains were varied from having tetra- to hexamethylene chains, and secondary NH, tertiary ethylamino, and quaternary ammonium groups were introduced into the chains. The molecular modeling of the compounds indicated that they could function as dual binding site acetylcholinesterase inhibitors, binding to both the peripheral anionic site and active site. The data from in vitro experiments show that the most active compounds exhibit affinity toward acetylcholinesterase within a nanomolar range, with selectivity for acetylcholinesterase over butyrylcholinesterase reaching four orders of magnitude. In vivo biological assays demonstrated the potency of these compounds in the treatment of memory impairment using an animal model of Alzheimer disease.

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.