New Charged Cholinesterase Inhibitors: Design, Synthesis, and Characterization.

Triazoles and triazolium salts are very common subunits in the structures of various drugs. Medicaments with a characteristic 1,2,3-triazole core are also being developed to treat neurodegenerative disorders associated with cholinesterase enzyme activity. Several naphtho- and thienobenzo-triazoles from our previous research emerged as being particularly promising in that sense. For this reason, in this research, new naphtho- and thienobenzo-triazoles 23-34, as well as 1,2,3-triazolium salts 44-51, were synthesized and tested. Triazolium salts 44-46 showed excellent activity while salts 47 and 49 showed very good inhibition toward both butyrylcholinesterase (BChE) and acetylcholinesterase (AChE) enzymes. In contrast, neutral photoproducts were shown to be selective towards BChE but with very good inhibition potential as molecules 24-27. The representative of newly prepared compounds, 45 and 50, were stable in aqueous solution and revealed intriguing fluorimetric properties, characterized by a strong Stokes shift of >160 nm. Despite their condensed polycyclic structure shaped similarly to well-known DNA-intercalator ethidium bromide, the studied compounds did not show any interaction with ds-DNA, likely due to the unfavorable steric hindrance of substituents. However, the studied dyes bind proteins, particularly showing very diverse inhibition properties toward AChE and BChE. In contrast, neutral photoproducts were shown to be selective towards a certain enzyme but with moderate inhibition potential. The molecular docking of the best-performing candidates to cholinesterases' active sites identified cation-π interactions as the most responsible for the stability of the enzyme-ligand complexes. As genotoxicity studies are crucial when developing new active substances and finished drug forms, in silico studies for all the compounds synthesized have been performed.

New resveratrol analogs as improved biologically active structures: Design, synthesis and computational modeling.

New analogs of the well-known bioactive trihydroxy-stilbene resveratrol were synthesized to investigate their potential biological activity. The focus was on assessing their ability to inhibit cholinesterase enzymes (ChEs) and their antioxidative properties, which were thoroughly examined. New resveratrol analogs were synthesized through Wittig or McMurry reaction in moderate-to-good yields. In all synthetic pathways, mixtures of cis- and trans-isomers were obtained, then separated by chromatography, and trans-isomers were isolated as targeted structures. The stilbene derivatives underwent evaluation for antioxidant activity (AOA) using DPPH and CUPRAC assay, and their potential to inhibit acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) was also measured. The biological tests have shown that the same compounds exhibited significant antioxidative and butyrylcholinesterase inhibitory potential, as evidenced by lower IC50 values compared to the established standards, trans-resveratrol, and galantamine, respectively. Additionally, molecular docking of the selected synthesized potential inhibitors to the enzyme's active site was performed, followed by assessing the complex stability using molecular dynamics simulation lasting 100 ns. Lastly, the new compounds underwent examination to determine their potential mutagenicity.

Cholinesterase Inhibitory and Anti-Inflammatory Activity of the Naphtho- and Thienobenzo-Triazole Photoproducts: Experimental and Computational Study.

New 1,2,3-triazolo(thieno)stilbenes were synthesized as mixtures of isomers and efficiently photochemically transformed to their corresponding substituted thienobenzo/naphtho-triazoles in high isolated yields. The resulting photoproducts were studied as acetyl- (AChE) and butyrylcholinesterase (BChE) inhibitors without or with interconnected inhibition potential of TNF-α cytokine production. The most promising anti-inflammatory activity was shown again by naphtho-triazoles, with a derivative featuring 4-pentenyl substituents exhibiting notable potential as a cholinesterase inhibitor. To identify interactions between ligands and the active site of cholinesterases, molecular docking was performed for the best potential inhibitors. Additionally, molecular dynamics simulations were employed to assess and validate the stability and flexibility of the protein-ligand complexes generated through docking.

Thieno-Thiazolostilbenes, Thienobenzo-Thiazoles, and Naphtho-Oxazoles: Computational Study and Cholinesterase Inhibitory Activity.

Naphtho-triazoles and thienobenzo-triazoles have so far proven to be very potent inhibitors of the enzyme butyrylcholinesterase (BChE). Based on these results, in this work, new thienobenzo-thiazoles were designed and synthesized, and their potential inhibitory activity was tested and compared with their analogs, naphtho-oxazoles. The synthesis was carried out by photochemical cyclization of thieno-thiazolostilbenes obtained in the first reaction step. Several thienobenzo-thiazoles and naphtho-oxazoles have shown significant potential as BChE inhibitors, together with the phenolic thiazolostilbene being the most active of all tested compounds. These results are significant as BChE has been attracting growing attention due to its positive role in the treatment of Alzheimer's disease. Computational examination based on the DFT approach enabled the characterization of the geometry and electronic structure of the studied molecules. Furthermore, the molecular docking study, accompanied by additional optimization of complexes ligand-active site, offered insight into the structure and stabilizing interactions in the complexes of studied molecules and BChE.

New Thienobenzo/Naphtho-Triazoles as Butyrylcholinesterase Inhibitors: Design, Synthesis and Computational Study.

This study aims to test the inhibition potency of new thienobenzo/naphtho-triazoles toward cholinesterases, evaluate their inhibition selectivity, and interpret the obtained results by molecular modeling. The synthesis of 19 new thienobenzo/naphtho-triazoles by two different approaches resulted in a large group of molecules with different functionalities in the structure. As predicted, most prepared molecules show better inhibition of the enzyme butyrylcholinesterase (BChE), considering that the new molecules were designed according to the previous results. Interestingly, the binding affinity of BChE for even seven new compounds (1, 3, 4, 5, 6, 9, and 13) was similar to that reported for common cholinesterase inhibitors. According to computational study, the active thienobenzo- and naphtho-triazoles are accommodated by cholinesterases through H-bonds involving one of the triazole's nitrogens, π-π stacking between the aromatic moieties of the ligand and aromatic residues of the active sites of cholinesterases, as well as π-alkyl interactions. For the future design of cholinesterase inhibitors and search for therapeutics for neurological disorders, compounds with a thienobenzo/naphtho-triazole skeleton should be considered.

Photochemical Transformations of Diverse Biologically Active Resveratrol Analogs in Batch and Flow Reactors.

Previous biological tests have shown that some resveratrol analogs exhibited significant antioxidative and cholinesterase inhibitory potential, as evidenced by lower IC50 values compared to the established standards, resveratrol and galantamine, respectively. Photochemical transformations were made in parallel on these compounds in the presence of porphyrin photocatalysts in batch and microreactor, showing the significant advantage of flow photochemistry concerning productivity, selectivity, and yields. In this research, the products of photocatalysis and direct irradiation (photolysis) of resveratrol analogs were compared to elucidate how the types and ratios of the products depend on the excitation energy, to reveal the effects of the substituent on the photoinduced reactions and to rationalize experimentally and computationally the nature and ratio of the obtained products. Thus, two main paths were computed in agreement with the experimental results: isomerization with the participation of triplet state intermediates to yield the experimentally detected cis-isomers and subsequent cyclization following a pathway not available for the trans-isomers. The investigation of five model compounds confirmed the advantages of the flow photoreactor in the photochemical reactions of heterocyclic resveratrol analogs.

Resveratrol-Maltol and Resveratrol-Thiophene Hybrids as Cholinesterase Inhibitors and Antioxidants: Synthesis, Biometal Chelating Capability and Crystal Structure.

New resveratrol-thiophene and resveratrol-maltol hybrids were synthesized as cholinesterase inhibitors and antioxidants. As with photostability experiments, biological tests also found remarkable differences in the properties and behavior of thiophene and maltol hybrids. While resveratrol-thiophene hybrids have excellent inhibitory and antioxidant properties (similar to the activity of reference drug galantamine), maltols have been proven to be weaker inhibitors and antioxidants. The molecular docking of selected active ligands gave insight into the structures of docked enzymes. It enabled the identification of interactions between the ligand and the active site of both cholinesterases. The maltols that proved to be active cholinesterase inhibitors were able to coordinate Fe3+ ion, forming complexes of 1:1 composition. Their formation constants, determined by spectrophotometry, are very similar, lgK = 11.6-12.6, suggesting that Fe3+ binds to the common hydroxy-pyranone moiety and is hardly affected by the other aromatic part of the ligand. Accordingly, the characteristic bands in their individual absorption spectra are uniformly red-shifted relative to those of the free ligands. The crystal structures of two new resveratrol-maltol hybrids were recorded, giving additional information on the molecules' intermolecular hydrogen bonds and packing. In this way, several functionalities of these new resveratrol hybrids were examined as a necessary approach to finding more effective drugs for complicated neurodegenerative diseases.

New naphtho/thienobenzo-triazoles with interconnected anti-inflammatory and cholinesterase inhibitory activity.

New 1,2,3-triazolo(thieno)stilbenes were synthesized by Wittig reaction and photochemically transformed to corresponding substituted thienobenzo/naphtho-triazoles in high isolated yields. They were prepared to study the acetyl- and butyrylcholinesterase inhibition associated with the inhibition of TNFα cytokine production and anti-inflammatory activity. The best experimental results were achieved with the allyl-thienobenzotriazole and isopropyl, p-methoxybenzyl, and hydroxybutyl substituted naphthotriazoles bearing additional chloro or methoxy groups. The allyl-thienobenzotriazole photoproduct is twice as potent an inhibitor of eqBChE compared to the standard galantamine. At the same time, this compound strongly inhibited TNFα production in PBMCs in response to the LPS stimulus. The complexes between selected compounds with the active site of BChE and AChE are assessed by docking, providing insight into the stabilizing interactions between the potential inhibitor and the active site.

Synthesis, photochemistry and computational study of novel 1,2,3-triazole heterostilbenes: Expressed biological activity of their electrocyclization photoproducts.

New 1,2,3-triazolostilbenes were synthesized and photochemically transformed to substituted naphthotriazoles as electrocyclization products in high isolated yields for studying the acetyl- and butyrylcholinesterase inhibitory and anti-inflammatory activity. The best experimental results showed the naphthotriazole photoproducts providing interesting observation on cholinesterase inhibition associated with the inhibition of TNFα cytokine production. The geometries of synthesized triazolostilbenes were computationally examined using Density Functional Theory (DFT), followed by time-dependent DFT calculations to obtain insight into electronic properties observed by UV-Vis spectroscopy. The complexes between selected compounds with the active site of AChE are assessed by docking. A quantum mechanical cluster approach was utilized to optimize their structures, thus providing insight into the stabilizing interactions between the potential inhibitor and the active site.

Synthesis, Photochemistry, Computational Study and Potential Application of New Styryl-Thiophene and Naphtho-Thiophene Benzylamines.

In this research, the synthesis, photochemistry, and computational study of new cis- and trans-isomers of amino-thienostilbenes is performed to test the efficiency of their production and acid resistance, and to investigate their electronic structure, photoreactivity, photophysical characteristics, and potential biological activity. The electronic structure and conformations of synthesized thienostilbene amines and their photocyclization products are examined computationally, along with molecular modeling of amines possessing two thiophene rings that showed inhibitory potential toward cholinesterases. New amino-styryl thiophenes, with favorable photophysical properties and proven acid resistance, represent model compounds for their water-soluble ammonium salts as potential styryl optical dyes. The comparison with organic dyes possessing a trans-aminostilbene subunit as the scaffold shows that the newly synthesized trans-aminostilbenes have very similar absorbance wavelengths. Furthermore, their functionalized cis-isomers and photocyclization products are good candidates for cholinesterase inhibitors because of the structural similarity of the molecular skeleton to some already proven bioactive derivatives.

Alteration in the Chemical Composition of Immortelle, Silver Fir and Prickly Juniper Essential Oils Induced by Light.

The objective of this study was to evaluate impact of light and available oxygen on the chemical composition of three selected essential oils. Aliquots of immortelle (Helichrysum italicum), silver fir (Abies alba) and prickly juniper (Juniperus oxycedrus) essential oils were exposed to UV-A irradiation in the presence of atmospheric oxygen as well as in the presence of inert gas. The compositions of fresh and irradiated samples were studied by GC/MS. Each oil showed an individual response to the applied conditions. In immortelle oil, dominant process was phototransformation of g-curcumene to italicene, isoitalicene and ?-curcumene. Since g-curcumene is one of the major components of immortelle essential oil, exposure of this oil to light can cause significant changes in primary composition and thus quality. In silver fir and prickly juniper oil irradiation caused only slight changes among sesquiterpenes that are present as minor components. Both oils were found to be photostabile and insensitive to the presence of atmospheric oxygen.