Synthesis of 5-methyl-2,4-dihydro-3H-1,2,4-triazole-3-one's aryl Schiff base derivatives and investigation of carbonic anhydrase and cholinesterase (AChE, BuChE) inhibitory properties.

Carbonic anhydrase enzymes (EC 4.2.1.1, CAs) are metalloenzyme families that catalyze the rapid conversion of H2O and CO2 to HCO3- and H+. CAs are found in different tissues where they participate in various significant biochemical processes such as ion transport, carbon dioxide respiration, ureagenesis, lipogenesis, bone resorption, electrolyte secretion, acid-base balance, and gluconeogenesis. In such processes, many CAs are significant therapeutic targets because of their inhibitory potentials especially in the treatment of some diseases such as edema, glaucoma, obesity, cancer, epilepsy, and osteoporosis. Acetylcholinesterase (AChE) and Butyrylcholinesterase (BuChE) inhibitors are also valuable compounds for different therapeutic applications including Alzheimer's disease. In this work, we report a fast and effective synthesis of 5-methyl-2,4-dihydro-3H-1,2,4-triazole-3-one's aryl Schiff base derivatives and also their CA and cholinesterases inhibitory properties. Our findings showed that these Schiff base derivatives, with triazole ring, found as strong CA and cholinesterases inhibitors.

Synthesis and glutathione reductase inhibitory properties of 5-methyl-2,4-dihydro-3H-1,2,4-triazol-3-one's aryl Schiff base derivatives.

Glutathione reductase (GR) is responsible for the existence of the reduced glutathione (GSH) molecule, a crucial antioxidant against oxidative stress reagents. The antimalarial activities of some redox active compounds are attributed to their inhibition of antioxidant flavoenzyme GR, and inhibitors are therefore expected to be useful for the treatment of malaria. In this work, a fast and effective synthesis and the GR inhibitory properties of 5-methyl-2,4-dihydro-3H-1,2,4-triazol-3-one's aryl Schiff base derivatives are reported. For this aim, the triazol nucleus was obtained, which was substituted with identical groups: ester, hydrazide, and Schiff base system at the N-2 and N-4 nitrogen atoms. The majority of the reactions were carried out by utilizing both microwave and conventional methods in order to compare their yields and reaction times. Beside this, the occuring E/Z geometrical isomers from the CN double bond and the cis/trans amide conformers at the CONH single bond were studied. In the biological activity section of this work, it was found that all synthesized compounds have better inhibitory activity than N,N-bis(2-chloroethyl)-N-nitrosourea against GR; especially, two molecules, 6e and 6f, are the best among them. The evidence indicates that these Schiff base derivatives, with triazole ring, are strong GR inhibitors and novel antimalaria candidates.

Synthesis and biological evaluation of novel bromophenol derivatives as carbonic anhydrase inhibitors.

Here, we provide an alternative synthesis of the natural bromophenol 3,4-dibromo-5-(2,3-dibromo-4,5-dihydroxybenzyl)-6-(ethoxymethyl)benzene-1,2-diol (3) and the first synthesis of (4,5-dihydroxy-2-methylphenyl)(3,4-dihydroxyphenyl)methanone (18) and its brominated derivatives 19-21. The compounds were characterized and tested against the two most studied members of the pH regulatory enzyme family, carbonic anhydrase (CA). The inhibitory potencies of the novel compounds and two natural bromophenols 2, 3 were analyzed at the human isoforms hCA I and hCA II as targets and the KI values were calculated. The KI values of the novel compounds were measured in the range of 13.7-32.7 mM for the hCA I isozyme and 0.65-1.26 mM for the hCA II isozyme. The structurally related compound 14 was also tested in order to understand the structure­activity relationship, and the clinically used sulfonamide acetazolamide (AZA)was tested for comparison reasons. All of the compounds exhibited competitive inhibition with 4-nitrophenylacetate as substrate. The compounds showed strong inhibitory activity against hCA I, being more effective as compared to the clinically used AZA (KI: 36.2 mM), but rather less activity against hCA II.

Synthesis and carbonic anhydrase inhibitory properties of novel bromophenols including natural products.

(2-Bromo-3,4-dimethoxyphenyl) (3,4-dimethoxyphenyl)methanone (10) and its derivatives with Br, one dibromide and isomeric three tribromides, were synthesized. Demethylation of these compounds afforded a series of new bromophenols. Inhibition of human cytosolic carbonic anhydrase II (hCA II) isozyme by these new bromophenols and naturally occurring 3,4,6-tribromo-5-(2,5-dibromo-3,4-dihydroxybenzyl)benzene-1,2-diol (3), and 5,5'-methylenebis(3,4,6-tribromo-benzene-1,2-diol) (4) was investigated. The synthesized compounds showed carbonic anhydrase inhibitory capacities with IC(50) values in the range of 0.7-372 µM against hCA II. Some bromophenols investigated here showed effective hCA II inhibitory activity and might be used as leads for generating novel carbonic anhydrase inhibitors which are valuable drug candidates for the treatment of glaucoma, epilepsy, gastric and duodenal ulcers, neurological disorders, or osteoporosis.

Inhibition of human carbonic anhydrase isozymes I, II and VI with a series of bisphenol, methoxy and bromophenol compounds.

Carbonic anhydrase inhibitors (CAI) are valuable molecules as they have several therapeutic applications, including anti-glaucoma activity. In this study, inhibition of three human carbonic anhydrase (hCA, EC 4.2.1.1) isozymes I, II and VI with a series of bisphenol and bromophenol derivatives was investigated. Molecular docking studies of a set of such inhibitors within CA I and II were also performed. K(I) values of the molecules 2-9 were in the range of 10.025-892.109 µM for hCA I, 1.437-59.107 µM for hCA II and 11.143-919.182 µM for hCA VI, respectively. Reported inhibitory activities of molecules 2-9 will assist in better understanding of structure-activity relationship studies of CAI.

Kinetic and docking studies of phenol-based inhibitors of carbonic anhydrase isoforms I, II, IX and XII evidence a new binding mode within the enzyme active site.

Carbonic anhydrases (CAs, EC 4.2.1.1) are inhibited by sulfonamides, inorganic anions, phenols, coumarins (acting as prodrugs) and polyamines. A novel class of CA inhibitors (CAIs), interacting with the CA isozymes I, II (cytosolic) and IX, XII (transmembrane, tumor-associated) in a different manner, is reported here. Kinetic measurements allowed us to identify hydroxy-/methoxy-substituted benzoic acids as well as di-/tri-methoxy benzenes as submicromolar-low micromolar inhibitors of the four CA isozymes. Molecular docking studies of a set of such inhibitors within CA I and II allowed us to understand the inhibition mechanism. This new class of inhibitors binds differently compared to all other classes of inhibitors known to date: they were found between the phenol-binding site and the coumarin-binding site, filling thus the middle of the enzyme cavity. They exploit different interactions with amino acid residues and water molecules from the CA active site compared to other classes of inhibitors, offering the possibility to design CAIs with an interesting inhibition profile compared to the clinically used sulfonamides/sulfamates.

Synthesis and antioxidant properties of diphenylmethane derivative bromophenols including a natural product.

Bromination of bis(3,4-dimethoxyphenyl)methanone (5) gave four products (6-9) with mono, di, tri, and tetra Br under different conditions. Reduction and demethylation reactions of product 9 with tetra Br were performed, consecutively and a natural product, 5,5'-methylene bis(3,4-dibrombenzene-1,2-diol) (1), was obtained with a 53% yield. Five derivatives, (13-17) (bromophenols), of 1 were also synthesised. The antioxidant and radical scavenging activities of bromophenols 1 and 13-17 were determined by employing various in vitro assays such as 1,1-diphenyl-2-picryl-hydrazyl free radical (DPPH(*)), 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid (ABTS(*+)), N,N-dimethyl-p-phenylenediamine dihydrochloride radical cation (DMPD(*+)), and superoxide anion radical (O(2)(*-)) scavenging, reducing ability determination by the Fe(3+)-Fe(2+) and Cu(2+)-Cu(+) cupric reducing antioxidant capacity (CUPRAC) transformation methods, hydrogen peroxide scavenging, and ferrous ion (Fe(2+)) chelating activities. Moreover, these activities were compared to those of synthetic standard antioxidant compounds such as butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), alpha-tocopherol, and trolox. The results showed that the synthesised bromophenols had effective antioxidant power.