Synthesis, Theoretical, in Silico and in Vitro Biological Evaluation Studies of New Thiosemicarbazones as Enzyme Inhibitors.

Eleven new thiosemicarbazone derivatives (1-11) were designed from nine different biologically and pharmacologically important isothiocyanate derivatives containing functional groups such as fluorine, chlorine, methoxy, methyl, and nitro at various positions of the phenyl ring, in addition to the benzyl unit in the molecular skeletal structure. First, their substituted-thiosemicarbazide derivatives were synthesized from the treatment of isothiocyanate with hydrazine to synthesize the designed compounds. Through a one-step easy synthesis and an eco-friendly process, the designed compounds were synthesized with yields of up to 95 % from the treatment of the thiosemicarbazides with aldehyde derivatives having methoxy and hydroxy groups. The structures of the synthesized molecules were elucidated with elemental analysis and FT-IR, 1 H-NMR, and 13 C-NMR spectroscopic methods. The electronic and spectroscopic properties of the compounds were determined by the DFT calculations performed at the B3LYP/6-311++G(2d,2p) level of theory, and the experimental findings were supported. The effects of some global reactivity parameters and nucleophilic-electrophilic attack abilities of the compounds on the enzyme inhibition properties were also investigated. They exhibited a highly potent inhibition effect on acetylcholinesterase (AChE) and carbonic anhydrases (hCAs) (KI values are in the range of 23.54±4.34 to 185.90±26.16 nM, 103.90±23.49 to 325.90±77.99 nM, and 86.15±18.58 to 287.70±43.09 nM for AChE, hCA I, and hCA II, respectively). Furthermore, molecular docking simulations were performed to explain each enzyme-ligand complex's interaction.

Enzyme inhibition, molecular docking, and density functional theory studies of new thiosemicarbazones incorporating the 4-hydroxy-3,5-dimethoxy benzaldehyde motif.

New Schiff base-bearing thiosemicarbazones (1-13) were obtained from 4-hydroxy-3,5-dimethoxy benzaldehyde and various isocyanates. The structures of the synthesized molecules were elucidated in detail. Density functional theory calculations were also performed to determine the spectroscopic properties of the compounds. Moreover, the enzyme inhibition activities of these compounds were investigated. They showed highly potent inhibition effects on acetylcholinesterase (AChE) and human carbonic anhydrases (hCAs) (KI values are in the range of 51.11 ± 6.01 to 278.10 ± 40.55 nM, 60.32 ± 9.78 to 300.00 ± 77.41 nM, and 64.21 ± 9.99 to 307.70 ± 61.35 nM for AChE, hCA I, and hCA II, respectively). In addition, molecular docking studies were performed, confirmed by binding affinities studies of the most potent derivatives.

Potential thiosemicarbazone-based enzyme inhibitors: Assessment of antiproliferative activity, metabolic enzyme inhibition properties, and molecular docking calculations.

A new series of thiosemicarbazone derivatives (1-11) were prepared from various aldehydes and isocyanates with high yields and practical methods. The structures of these compounds were elucidated by Fourier transform infrared, 1 H-nuclear magnetic resonance (NMR), 13 C-NMR spectroscopic methods and elemental analysis. Cytotoxic effects of target compounds were determined by 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide assay and compound 1 showed significant cytotoxic activity against both MCF-7 and MDA-MB-231 cells, with half-maximal inhibitory concentration values of 2.97 µM and 6.57 µM, respectively. Moreover, in this study, the anticholinergic and antidiabetic potentials of these compounds were investigated. To this aim, the effect of the newly synthesized thiosemicarbazone derivatives on the activities of acetylcholinesterase (AChE) and αglycosidase (α-Gly) was evaluated spectrophotometrically. The title compounds demonstrated high inhibitory activities compared to standard inhibitors with Ki values in the range of 122.15-333.61 nM for α-Gly (Ki value for standard inhibitor = 75.48 nM), 1.93-12.36 nM for AChE (Ki value for standard inhibitor = 17.45 nM). Antiproliferative activity and enzyme inhibition at the molecular level were performed molecular docking studies for thiosemicarbazone derivatives. 1M17, 5FI2, and 4EY6, 4J5T target proteins with protein data bank identification with (1-11) compounds were docked for anticancer and enzyme inhibition, respectively.

1,2,3-Triazole substituted phthalocyanine metal complexes as potential inhibitors for anticholinesterase and antidiabetic enzymes with molecular docking studies.

In recent years, acetylcholinesterase (AChE) and α-glycosidase (α-gly) inhibition have emerged as a promising and important approach for pharmacological intervention in many diseases such as glaucoma, epilepsy, obesity, cancer, and Alzheimer's. In this manner, the preparation and enzyme inhibition activities of peripherally 1,2,3-triazole group substituted metallophthalocyanine derivatives with strong absorption in the visible region were presented. These novel metallophthalocyanine derivatives (2-6) effectively inhibited AChE, with Ki values in the range of 40.11 ± 5.61 to 78.27 ± 15.42 µM. For α-glycosidase, the most effective Ki values of compounds 1 and 2 were with Ki values of 16.11 ± 3.13 and 18.31 ± 2.42 µM, respectively. Also, theoretical calculations were investigated to compare the chemical and biological activities of the ligand (1) and its metal complexes (2-6). Biological activities of 1 and its complexes against acetylcholinesterase for ID 4M0E (AChE) and α-glycosidase for ID 1R47 (α-gly) are calculated. Theoretical calculations were compatible with the experimental results and these 1,2,3-triazole substituted phthalocyanine metal complexes were found to be efficient inhibitors for anticholinesterase and antidiabetic enzymes.Communicated by Ramaswamy H. Sarma.

Exploring of antioxidant and antibacterial properties of novel 1,3,4-thiadiazole derivatives: Facile synthesis, structural elucidation and DFT approach to antioxidant characteristics.

In recent years, compounds containing thiophene and 1,3,4-thiadiazole skeletons have become important cyclic compounds, especially in medicinal chemistry. In this manner, we synthesized and isolated seven 1,3,4-thiadiazole derivatives with thiophene groups and fully characterized by elemental analysis and general spectroscopic methods such as 1H NMR, 13C NMR, and FT-IR. Antibacterial activities of the title compounds were investigated by using TLC-Dot blot, macro dilution, well diffusion, and growth curve analysis methods. Compounds 1 and 6 showed inhibitory activities against all tested gram-negative and gram-positive bacteria. TLC-DPPH and DPPH assays, on the other hand, were performed to detect the antioxidant activities of the 1,3,4-thiadiazole derivatives and compound 1 exhibited the highest antioxidant activity at all tested concentrations. QTAIM and NCI calculations were performed as well as structural, electronic, and spectral analyzes using density functional theory (DFT). Calculations were carried out at the B3lyp/6-311 + +g(2d,2p) level of theory, and the data were used to examine the antioxidant activity of the compounds.

Synthesis, spectroscopic studies, and antioxidant activities of novel thio/carbohydrazones and bis-isatin derivatives from terephthalaldehyde.

New bis(isatins-thio/carbohydrazones) based on Schiff bases were prepared from terephthalaldehyde biscarbohydrazone and 5-substituted isatins in the presence of a drop of sulfuric acid under reflux in ethanol. Terephthalaldehyde bis(thio/carbohydrazone) was synthesized by the reaction of (thio)/carbohydrazide and terephthalaldehyde in the presence of a few drops of acetic acid under reflux in ethanol. The structures of these synthesized compounds were determined using IR, 1H NMR, and 13C NMR spectroscopy and elemental analysis. The in vitro antioxidant activity of all the compounds was determined by the 1,1-diphenyl-2-picryl hydrazyl (DPPH.) free radical scavenging method. Compound 2 showed the best antioxidant activity.

Analysis of tautomeric equilibrium in (E)-4,6-dibromo-2-[(4-fluorophenylimino)methyl]-3-methoxyphenol compound.

In this study, the tautomeric equilibrium between the phenol-imine and keto-amine structural forms of (E)-4,6-dibromo-2-[(4-fluorophenylimino)methyl]-3-methoxyphenol compound has been investigated with experimental (XRD, UV-vis and NMR) and theoretical (DFT and TD-DFT) methods. The results clearly show that structural preference of the compound is definitely depended on its state. Namely, the compound exists in phenol-imine form in the solid state while one or both of these forms can be seen in solvent media. For example, the compound prefers phenol-imine form in benzene while both forms exist in EtOH and DMSO solvents. Coexistence of two forms has been quantified with NMR studies, giving a ratio of 11:9 for phenol and keto structures of the compound in acetone-d6 solvent.