Experimental and Molecular Modeling Studies on the Complexation of Chromium(III) with the Angiotensin-Converting Enzyme Inhibitor Captopril

Abstract

Captopril (CPT) is an inhibitor of angiotensin I converting enzyme, used as a medication for the treatment of people with high blood pressure, renal insufficiency, and cardiovascular diseases. It inhibits the angiogenesis process, vasoconstriction, and tumor metastasis. Some metal-captopril complexes exhibit antimicrobial activities. In the current work, the formation of the Cr^III-CPT complex was studied spectrophotometrically and potentiometrically in aqueous solution. Kinetics of Cr^III-CPT complex formation was spectrophotometrically studied over the pH range 3.20-4.20, at an ionic strength of 0.3 M at 30-50 °C. Cr^III-CPT complex formation was potentiometrically studied at 25 °C, where ligand protonation constants and complexes' overall stability constants were calculated. UV-vis absorption spectra were executed to confirm the complex formation. Density functional theory and molecular dynamics simulation were performed to search the geometries of the Cr^III-CPT complex. Atoms in molecules and interaction region indicator calculations are used to investigate intermolecular interactions for the formation of Cr^III-CPT complex. The antimicrobial activity of the CPT ligand and Cr^III-CPT complex on the prevention and control of environmental pathogenic bacteria, as tested on both Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative bacteria Escherichia coli (E. coli) via agar disc diffusion method, assess the ability to use as an antimicrobial agent. CPT had shown good antimicrobial activity against both types of bacteria, which had increased slightly the zone of inhibition in Cr-CPT that indicates the increased efficacy due to Cr(III) antimicrobial activity via its oxidative damage to the bacterial cell wall. No previous study tested the CPT antimicrobial activity against Gram-positive ones such as S. aureus.