Browsing by Author "Tekamo, Israel Alemayehu"
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- Evaluation of schiff bases and its metal complexes with potential therapeutic applicationsPublication . Tekamo, Israel Alemayehu; Correia, Isabel; Cavaco, IsabelMetal-based drugs have drawn significant attention over the past few decades due to their advanced properties and benefits in biomedical therapeutic and diagnostic systems. In the current work two Schiff bases, 4-methyl-2,6-bis-(pyridin-2-yl-hydrazonomethyl)-phenol (L1), and methyl-phenol-di-S-methyl dithiocarbazate (L2), and their corresponding zinc complexes, [Zn2(L1)(OAc)3] (C1) and [Zn2(L2)(OAc)] (C2) (OAc: CH3COO−) were synthesized. All compounds were characterized by elemental analyses, FTIR, UV–Vis and NMR spectroscopies and ESI-MS spectrometry. The stability of the compounds was evaluated under physiological conditions (5 % DMSO and 95 % PBS, pH 7.4). The interaction of Schiff bases and their corresponding Zn(II) complexes with biomolecules namely, bovine serum albumin (BSA) and calf thymus DNA (ctDNA) was investigated using UV-Vis, circular dichroism (CD) and fluorescence spectroscopies under physiological pH and 298 K. Fluorescence quenching of BSA upon interaction with the compounds was analysed using the Stern-Volmer formalism which revealed moderate to strong binding to serum albumin with binding constant values of KB=2.36x103 and 2.38x105M−1, for C1 and C2 respectively. These results reveal good binding propensity in comparison with the ligands. Changes in the secondary structure of BSA are imposed by the Schiff base ligands and Zn(II) complexes as revealed by CD spectroscopy. Additionally, hypochromicity in the UV-Vis absorption spectra of the complexes upon addition of BSA further corroborates interaction between the protein and the complex. The complexes were tested for their DNA binding ability by UV-Vis and CD spectroscopy and the results indicate that there is interaction between the complexes and DNA where C1 has better binding tendency toward DNA than C2. Cytotoxic activity of L1 and L2 studied with several tumour cell lines (Caco-2, MCF-7 and PC-3) and normal cell, NHDF, showed that the compounds are cytotoxic to all cell lines tested, without selectivity towards cancer cells. Overall, the IC50 values are comparable with the ones obtained for the positive control, fluorouracil. The two ligands and one complex were tested against several strains of bacteria and fungi and promising results were obtained, where L1 is active against L. monocytogenes, L2 is active against K. pneumoniae, A. baumannii and S. aureus and C1 against L. monocytogenes and S. aureus. L2 showed better activity against the tested microorganisms compared to L1 and the metal complex.