Synthesis and characterization of a novel amino salicylato salt and its Cu(II) complex and their inhibition studies on carbonic anhydrase isoenzymes

A novel amino salicylato salt, 2-amino-6-methylpyridinium 2-hydroxy-5-sulfonatobenzoate (1), and its Cu(II) complex, 2-ammonio-6-methylpyridinium bis(μ6-5-sulfonatosalicylatoaquacopper(II)) (2), have been synthesized from free ligands, namely 5-sulfosalicylic acid (H3ssa) and 2-amino-6-methylpyridine (amp). Compounds 1 and 2 have been characterized by elemental, spectral (1H NMR, IR and UV–Vis) and thermal analyses. Additionally, magnetic measurements and the single crystal X-ray diffraction technique have been applied to compound 2. Compound 2 crystallizes in the triclinic P1¯ space group. In the symmetric unit, the Cu(II) ion exhibits a distorted square planar configuration, coordinated by two carboxylate oxygen atoms (O2 and O2i), one phenolic oxygen atom (O1) of the ssa3− anion and a water molecule (O1w). The free ligands H3ssa and amp, and the products 1 and 2, and acetazolamide (AAZ) as a control compound have been also evaluated for their in vitro inhibitor effects on human carbonic anhydrase isoenzymes (hCA I and hCA II), purified from the erythrocyte cell by affinity chromatography for their hydratase and esterase activities. In relation to esterase activities, the inhibition equilibrium constants (Ki) have also been determined. A comparison of the inhibition studies of the newly synthesized compounds 1 and 2 with the parent compounds H3ssa and amp, and to AAZ, indicates that 1 and 2 have an effective inhibitory activity on hCA I and II, and can be used as potential inhibitors.

Graphical abstractA newly synthesized amino salicylato salt and its Cu(II) complex have effective inhibitory activity on hCAI and II. The Cu(II) complex crystallizes in the triclinic P1¯ space group with a distorted square planar configuration.Figure optionsDownload full-size imageDownload as PowerPoint slideResearch highlights► A novel amino salicylato salt and its Cu(II) complex have been synthesized. ► They have been characterized by elemental, spectral and thermal analyses. ► The single crystal X-ray diffraction technique have been applied to complex compound. ► These novel compounds have effective inhibitory activity on hCA I and II. ► They might be considered as prospective medicines for glaucoma.