Synthesis, Crystal Structures and Urease Inhibition of 4-Bromo-N'-(1-(pyridin-2-yl)ethylidene)benzohydrazide and Its Dinuclear Copper(II) Complex.

A new dinuclear copper(II) complex [Cu2(µ-Br)2L2]·0.5MeOH with the benzohydrazone ligand 4-bromo-N'-(1-(pyridin-2-yl)ethylidene)benzohydrazide (HL) has been synthesized and characterized by elemental analysis, IR and UV-Vis spectroscopic studies. Single crystal structures of the complex and the benzohydrazone compound were studied. The Cu atoms in the complex are coordinated by two benzohydrazone ligands and two Br bridging groups, forming square pyramidal coordination. The complex has good inhibitory activity on Jack bean urease, with IC50 value of 1.38 µmol·L-1.

Synthesis and molecular modelling studies of phenyl linked oxadiazole-phenylhydrazone hybrids as potent antileishmanial agents.

Molecular hybridization yielded phenyl linked oxadiazole-benzohydrazones hybrids 6-35 and were evaluated for their antileishmanial potentials. Compound 10, a 3,4-dihydroxy analog with IC50 value of 0.95 ± 0.01 µM, was found to be the most potent antileishmanial agent (7 times more active) than the standard drug pentamidine (IC50 = 7.02 ± 0.09 µM). The current series 6-35 conceded in the identification of thirteen (13) potent antileishmanial compounds with the IC50 values ranging between 0.95 ± 0.01-78.6 ± 1.78 µM. Molecular docking analysis against pteridine reductase (PTR1) were also performed to probe the mode of action. Selectivity index showed that compounds with higher number of hydroxyl groups have low selectivity index. Theoretical stereochemical assignment was also done for certain derivatives by using density functional calculations.

Synthesis of novel benzohydrazone-oxadiazole hybrids as ß-glucuronidase inhibitors and molecular modeling studies.

A series of compounds consisting of 25 novel oxadiazole-benzohydrazone hybrids (6-30) were synthesized through a five-step reaction sequence and evaluated for their ß-glucuronidase inhibitory potential. The IC50 values of compounds 6-30 were found to be in the range of 7.14-44.16µM. Compounds 6, 7, 8, 9, 11, 13, 18, and 25 were found to be more potent than d-saccharic acid 1,4-lactone (48.4±1.25µM). These compounds were further subjected for molecular docking studies to confirm the binding mode towards human ß-d-glucuronidase active site. Docking study for compound 13 (IC50=7.14±0.30µM) revealed that it adopts a binding mode that fits within the entire pocket of the binding site of ß-d-glucuronidase. Compound 13 has the maximum number of hydrogens bonded to the residues of the active site as compared to the other compounds, that is, the ortho-hydroxyl group forms hydrogen bond with carboxyl side chain of Asp207 (2.1Å) and with hydroxyl group of Tyr508 (2.6Å). The other hydroxyl group forms hydrogen bond with His385 side chain (2.8Å), side chain carboxyl oxygen of Glu540 (2.2Å) and Asn450 side-chain's carboxamide NH (2.1Å).

Synthesis of new oxadiazole derivatives as α-glucosidase inhibitors.

Oxadiazole derivatives (6-28) having hydrazone linkage, were synthesized through condensation reaction between benzohydrazide 5 with various benzaldehydes. The oxadiazoles derivatives (6-28) were evaluated for their α-glucosidase inhibitory activity. The IC50 values for inhibition activity vary in the range between 2.64 ± 0.05 and 460.14 ± 3.25 µM. The IC50 values were being compared to the standard acarbose (IC50=856.45 ± 5.60 µM) and it was found that compounds 6-9, 12, 13, 16, 18, 20, 22-28 were found to be more active than acarbose, while other compounds showed no activity. Structure-activity relationship (SAR) studies suggest that oxadiazole benzohydrazones (6-28) inhibitory potential is dependent on substitution of the N-benzylidene part. Compound 18 (IC50=2.64 ± 0.05 µM), which has trihydroxy substitution at C-2', C-4', and C-5' on N-benzylidene moiety, recorded the highest inhibition activity that is three-hundred times more active than the standard drug, acarbose (IC50=856.45 ± 5.60 µM). Compound 23 (IC50=34.64 ± 0.35 µM) was found to be the most active among compounds having single hydroxyl substitution. Shifting hydroxyl from C-2' to C-4' (6) and C-3' (7) reduces inhibitory activity significantly. Compounds with chlorine substituent (compounds 16, 28, and 27) showed potent activities but lower as compared to hydroxyl analogs. Substituent like nitro or methyl groups at any position suppresses enzyme inhibition activity. This reveals the important presence of hydroxyl and halo groups to have enzyme inhibitory potential.

Synthesis, crystal structures, and urease inhibition of an acetohydroxamate-coordinated oxovanadium(V) complex derived from N'-(3-bromo-2-hydroxybenzylidene)-4-methoxybenzohydrazide.

A new benzohydrazone compound N'-(3-bromo-2-hydroxybenzylidene)-4-methoxybenzohydrazide (H2L) was prepared. Reaction of H2L and acetohydroxamic acid (HAHA) with VO(acac)2 in methanol gave the complex [VOL(AHA)]. Both H2L and the oxovanadium complex were characterized by elemental analysis, IR, UV-vis and (1)H NMR spectra, and single crystal X-ray diffraction. H2L was also characterized by high-resolution mass spectrum. Thermal analysis of the oxovanadium complex was carried out. The benzohydrazone ligand, in its dianionic form, coordinates to V atom through the phenolate oxygen, imino nitrogen and enolate oxygen. The acetohydroxamic acid coordinates to V atom through the carbonyl oxygen and deprotonated hydroxyl oxygen. The V atom is in octahedral coordination. H2L, HAHA and the oxovanadium complex were tested for their urease inhibitory activities. The percent inhibition at concentration of 100 µmol·L(-1) on Helicobacter pylori urease is 78% for the oxovanadium complex. The IC50 value for the complex is 36.5 µmol·L(-1). Molecular docking study was performed to study the inhibition.