Olga G. Serebryakova

Synthesis of organophosphates with fluorine-containing leaving groups as serine esterase inhibitors with potential for Alzheimer disease therapeutics.

Acetylcholinesterase and butyrylcholinesterase inhibitors are potential cognition enhancers in Alzheimer disease. O,O-Dialkylphosphate inhibitors with 1-substituted 2,2,2-trifluoroethoxy leaving groups were synthesized by phosphonate-phosphate rearrangement. Substituents in the 1-position of the leaving group along with the O-alkyl groups modulated potency and selectivity against acetylcholinesterase, butyrylcholinesterase, and carboxylesterase.

Esterase profile and analysis of structure-inhibitor selectivity relationships for homologous phosphorylated 1-hydroperfluoroisopropanols

352 Organophosphorous compounds (OPCs) are widely used not only in agrochemical practice but are also cited in pharmacopoeias of many countries as drugs for treating schistosomiasis, glaucoma, and Alzheimer’s disease [1]. The physiological effect of such compounds is based on competitive interaction with serine esterases including the primary biological targets, such as acetylcholinesterase (AChE) [2], the target enzyme for the acute toxic effect of antiacetylcholinesterase compounds, and the neuropathy target esterase (NTE) [3], the target enzyme for organophosphate-induced delayed neurotoxicity, as well as the secondary biological targets, such as butyrylcholinesterase (BChE) and carboxylesterase (CaE). BChE and CaE are stoichiometric scavengers, interaction with which reduces the content of active phosphoryl compound at the toxicokinetic stage of development of biological response [4, 5]. The preferential binding of anticholinesterase compounds with one or another target esterase largely determines the resultant therapeutic or toxic effect of a given compound as well as the character and degree of expression of this effect.

Conjugates of γ-Carbolines and Phenothiazine as new selective inhibitors of butyrylcholinesterase and blockers of NMDA receptors for Alzheimer Disease

Alzheimer disease is a multifactorial pathology and the development of new multitarget neuroprotective drugs is promising and attractive. We synthesized a group of original compounds, which combine in one molecule γ-carboline fragment of dimebon and phenothiazine core of methylene blue (MB) linked by 1-oxo- and 2-hydroxypropylene spacers. Inhibitory activity of the conjugates toward acetylcholinesterase (AChE), butyrylcholinesterase (BChE) and structurally close to them carboxylesterase (CaE), as well their binding to NMDA-receptors were evaluated in vitro and in silico. These newly synthesized compounds showed significantly higher inhibitory activity toward BChE with IC50 values in submicromolar and micromolar range and exhibited selective inhibitory action against BChE over AChE and CaE. Kinetic studies for the 9 most active compounds indicated that majority of them were mixed-type BChE inhibitors. The main specific protein-ligand interaction is π-π stacking of phenothiazine ring with indole group of Trp82. These compounds emerge as promising safe multitarget ligands for the further development of a therapeutic approach against aging-related neurodegenerative disorders such as Alzheimer and/or other pathological conditions.

Synthesis, molecular docking and biological evaluation of N,N-disubstituted 2-aminothiazolines as a new class of butyrylcholinesterase and carboxylesterase inhibitors

A series of 31 N,N-disubstituted 2-amino-5-halomethyl-2-thiazolines was designed, synthesized, and evaluated for inhibitory potential against acetylcholinesterase (AChE), butyrylcholinesterase (BChE) and carboxylesterase (CaE). The compounds did not inhibit AChE; the most active compounds inhibited BChE and CaE with IC50 values of 0.22-2.3μM. Pyridine-containing compounds were more selective toward BChE; compounds with the para-OMe substituent in one of the two dibenzyl fragments were more selective toward CaE. Iodinated derivatives were more effective BChE inhibitors than brominated ones, while there was no influence of halogen type on CaE inhibition. Inhibition kinetics for the 9 most active compounds indicated non-competitive inhibition of CaE and varied mechanisms (competitive, non-competitive, or mixed-type) for inhibition of BChE. Docking simulations predicted key binding interactions of compounds with BChE and CaE and revealed that the best docked positions in BChE were at the bottom of the gorge in close proximity to the catalytic residues in the active site. In contrast, the best binding positions for CaE were clustered rather far from the active site at the top of the gorge. Thus, the docking results provided insight into differences in kinetic mechanisms and inhibitor activities of the tested compounds. A cytotoxicity test using the MTT assay showed that within solubility limits (<30μM), none of the tested compounds significantly affected viability of human fetal mesenchymal stem cells. The results indicate that a new series of N,N-disubstituted 2-aminothiazolines could serve as BChE and CaE inhibitors for potential medicinal applications.

Synthesis and testing of trifluoromethyl-containing phosphonate-peptide conjugates as inhibitors of serine hydrolases

A modification of novel fluorinated organophosphorous compounds containing terminal alkyne group by different azidopeptides via Cu(I)-catalyzed click chemistry has been described. The inhibitor activity of trifluoromethyl-containing methylphosphonates and their peptide-conjugates towards acetylcholinesterase, butyrylcholinesterase, and carboxylesterase has been investigated. It was shown that the incorporation of peptide fragments significantly modulates the esterase profile of starting methylphosphonates.

Further studies toward a mouse model for biochemical assessment of neuropathic potential of organophosphorus compounds

Inhibition and aging of neuropathy target esterase (NTE) by neuropathic organophosphorus (OP) compounds triggers OP compound‐induced delayed neuropathy (OPIDN), whereas inhibition of acetylcholinesterase (AChE) produces cholinergic toxicity. The neuropathic potential of an OP compound is defined by its relative inhibitory potency toward NTE vs. AChE assessed by enzyme assays following dosing in vivo or after incubations of direct‐acting compounds or active metabolites with enzymes in vitro. The standard animal model of OPIDN is the adult hen, but its large size and high husbandry costs make this species a burdensome model for assessing neuropathic potential. Although the mouse does not readily exhibit clinical signs of OPIDN, it displays axonal lesions and expresses brain AChE and NTE. Therefore, the present research was performed as a further test of the hypothesis that inhibition of mouse brain AChE and NTE could be used to assess neuropathic potential using mouse brain preparations in vitro or employing mouse brain assays following dosing of OP compounds in vivo. Excellent correlations were obtained for inhibition kinetics in vitro of mouse brain enzymes vs. hen brain and human recombinant enzymes. Furthermore, inhibition of mouse brain AChE and NTE after dosing with OP compounds afforded ED50 ratios that agreed with relative inhibitory potencies assessed in vitro. Taken together, results with mouse brain enzymes demonstrated consistent correspondence between in vitro and in vivo predictors of neuropathic potential, thus adding to previous studies supporting the validity of a mouse model for biochemical assessment of the ability of OP compounds to produce OPIDN. Copyright

N,N-disubstituted 2-aminothiazolines as new inhibitors of serine esterases

209 Recently, N,SScontaining heterocyclic comm pounds, especially the derivatives of 22aminoo1,33thii azole, draw increasing attention due to their chemical properties as well as a wide spectrum of biological activity. It is known that many compounds containing the thiazoline (4,55dihydroo1,33thiazole) fragment exhibit antibacterial, anticancer, antifungal, and other types of activities [1–3]. However, information about the inhibition of serine esterases by compounds conn taining the thiazoline fragment is practically absent in the literature. The ability to reversibly inhibit cholinestt erases was shown for only some 22substituted thiazoo lines and imidazo[2,11b]thiazole derivatives [4, 5]. Since it is known that the inhibition of serine esterases can have different pharmacological effects, the search and design of new inhibitors of these enzymes is of interest. In particular, inhibitors of acee tylcholinesterase (AChE, EC 3.1.1.7) contribute to the improvement of cognitive functions in dementia of various origins [6]. Inhibitors of butyrylcholinesterase (BChE, EC 3.1.1.8) also improve cognitive function, which is especially important for severe stages of Alzheimers disease, when the activity of AChE is decreased and its function (hydrolysis of acetylchoo line) is implemented by BChE. In contrast to AChE inhibitors, BChE inhibitors do not have a dangerous side effect such as acute cholinergic toxicity and other adverse effects characteristic of AChE inhibitors [7]. Carboxylesterase (CaE, EC 3.1.1.1) and BChE hydroo lyze many therapeutically important drugs containing ester groups; in view of this, selective inhibitors of these enzymes are important for modulating the metabolism and pharmacokinetics of these drugs [8]. Researchers of the Institute of Physiologically Active Compounds, Russian Academy of Sciences, have developed and widely use an approach including the determination of the esterase profile of compounds with a comparative evaluation of their inhibitory activv ity with respect to several esterases [9–11]. This approach provides a more comprehensive picture of the biological effects of compounds and thus makes it possible to assess the therapeutic potential and possii ble side effects of test compounds. The purpose of this study was to search for new effective inhibitors of serine esterases in the 22amii nothiazoline series. We synthesized both the comm pounds described in the literature and the original N,NNdisubstituted 55iodomethyll22aminothiazolines 1–8 of the general formula and analyzed their esterase profile. For this purpose, we studied the inhibitory activity of these compounds with respect to human erythrocyte AChE, horse serum BChE, and porcine liver CaE. 55Iodomethyll22aminothiazolines 1–8 were syn thesized by the reaction of allyl isothiocyanate with appropriate amines …

Molecular design of N , N -disubstituted 2-aminothiazolines as selective carboxylesterase inhibitors

Selective carboxylesterase inhibitors are employed as modulators of hydrolytic metabolism of ester or amide-containing drugs. Using the Molecular Field Topology Analysis (MFTA), the models for the relationships between the structures and inhibitory activities of 5-halomethyl-2-aminothiazolines against acetylcholinesterase, butyrylcholinesterase, and carboxylesterase were built, the molecular design was performed, and a focused library of potentially active and selective carboxylesterase inhibitors was proposed.

1,2,4-Thiadiazoles as promising multifunctional agents for treatment of neurodegenerative diseases

Detailed studies of properties of new 3-substituted 5-anilino-1,2,4-thiadiazoles containing different substituents at position 3 of the thiadiazole ring were carried out, in particular, their esterase profile and antioxidant properties. It was found that the presence in the molecule of 2-aminopropyl fragment determines an efficient and selective inhibition of butyrylcholinesterase as compared to acetylcholinesterase and carboxylesterase, with radical-scavenging activity being weak. The compounds containing a 2-aminopropenyl fragment possess a high radicalscavenging activity, weakly inhibit cholinesterases, and exhibit anticarboxylesterase activity. A wide spectrum of activity of 3-substituted 5-anilino-1,2,4-thiadiazoles as inhibitors of cholinesterases and highly efficient scavengers of free radicals gives a basis for the optimization of structure and development in this series of original agents for therapy of neurodegenerative diseases.

Synthesis, molecular docking, and biological activity of 2-vinyl chromones: Toward selective butyrylcholinesterase inhibitors for potential Alzheimer's disease therapeutics

We investigated the biological activity of a series of substituted chromeno[3,2-c]pyridines, including compounds previously synthesized by our group and novel compounds whose syntheses are reported here. Tandem transformation of their tetrahydropyridine ring under the action of activated alkynes yielding 2-vinylsubstituted chromones was used to prepare nitrogen-containing derivatives of a biologically active chromone system. The inhibitory activity of these chromone derivatives against acetylcholinesterase (AChE), butyrylcholinesterase (BChE) and carboxylesterase (CaE) was investigated using the methods of enzyme kinetics and molecular docking. Antioxidant (antiradical) activity of the compounds was assessed in the ABTS assay. The results demonstrated that a subset of the studied chromone derivatives selectively inhibit BChE but do not exhibit antiradical activity. In addition, the results of molecular docking effectively explained the observed features in the efficacy, selectivity, and mechanism of BChE inhibition by the chromone derivatives.