Synthesis and characterization of a proton transfer salt between dipicolinic acid and 2-amino-6-methylbenzothiazole and its complexes, and their inhibition studies on carbonic anhydrase isoenzymes

Abstract

A novel proton transfer compound (HMeABT)(+)(HDPC)(-)center dot H2O (1) obtained from 2-amino-6-methylbenzothiazole (MeABT) and dipicolinic acid (H2DPC) and its Fe(III), Fe(II), Co(II), Ni(II) and Cu(II) complexes (2-6) have been prepared and characterized by elemental, spectral (H-1 NMR, IR and UV-Vis) and thermal analyses, magnetic measurement and molar conductivity. Additionally, single crystal X-ray diffraction techniques were applied to all complexes. All compounds, including acetazolamide (AAZ) as the control compound, were also evaluated for their in vitro inhibition effects on human carbonic anhydrase isoenzymes (hCA I and hCA II) for their hydratase and esterase activities. Although there is no inhibition for hydratase activities, all compounds have inhibited the esterase activities of hCA land II. The comparison of the inhibition studies of 1-6 to parent compounds, MeABT and H2DPC, indicates that 1-6 have more inhibitory effects. The inhibition effects of 2-6 are also compared to the simple metal complexes of MeABT and H2DPC, and the complexes from proton transfer salt (2-6) have shown better inhibition effects. Nevertheless, all the studied compounds have less inhibition effects than AAZ