Synthesis, structures, and urease inhibitory activities of oxovanadium(V) complexes with Schiff bases

A series of oxovanadium(V) complexes, [VO2L1]2 (1), [VO2L2]2 (2), [VO2L3]2 (3), [VO2L4]2 (4), [VO(OCH3)L5] (5), and [VO(OCH3)(HOCH3)L6] (6) (HL1 = 2-ethoxy-6-{[2-(2-hydroxyethylamino)ethylimino]methyl}phenol, HL2 = 4-chloro-2-{[2-(2-hydroxyethylamino)ethylimino]methyl}phenol, HL3 = 2-methoxy-6-[(2-methylaminoethylimino)methyl]phenol, HL4 = 4-chloro-2-[(2-methylaminoethylimino)methyl]phenol, HL5 = N′-(2-hydroxy-3-ethoxybenzylidene)-3-hydroxy-2-naphthohydrazide, and HL6 = N′-(2-hydroxy-5-chlorobenzylidene)-3-hydroxy-2-naphthohydrazide), have been prepared and structurally characterized by physico-chemical methods and X-ray diffraction. The inhibition rates (%) with the concentration of 100 μM for the complexes on Helicobacter pylori urease are 18.96 ± 0.44 (1), 33.01 ± 1.80 (2), 35.83 ± 0.78 (3), 48.09 ± 1.23 (4), 45.91 ± 2.09 (5), and 90.72 ± 1.91 (6). The relationship between the structures and urease inhibitory activities indicates that the chloro-substituted complexes have stronger activity than the alkoxy-substituted complexes. It is notable that one of the chloro-substituted complexes has very strong urease inhibitory activity, with IC50 value of 17.35 ± 1.01 μM, which is much lower than that of the acetohydroxamic acid coassayed as a standard urease inhibitor. The kinetic studies reveal that the complex is a mixed-competitive inhibitor of urease. The molecular docking study of the complexes with the Helicobacter pylori urease was performed.