Browsing by Author "Pessoa, João Costa"
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- Antimicrobial and antitumor activity of S-methyl dithiocarbazate Schiff base zinc(II) complexesPublication . Ramilo-Gomes, Filipa; Alemu, Yemataw; Tekamo, Israel; Cavaco, Isabel; Campos, Débora L.; Pavan, Fernando R.; Gomes, Clara S.B.; Brito, Vanessa; Santos, Adriana O.; Domingues, Fernanda; Luís, Ângelo; Marques, M. Matilde; Pessoa, João Costa; Ferreira, Susana; Silvestre, Samuel; Correia, IsabelSchiff bases (SB) obtained from S-methyl dithiocarbazate and aromatic aldehydes: salicylaldehyde (H2L1), o-vanillin (H2L2), pyridoxal (H2L3) and 2,6-diformyl-4-methylphenol (H3L4), and their corresponding Zn(II)-complexes (1-4), are synthesized. All compounds are characterized by elemental analyses, infrared, UV-Vis, nuclear magnetic resonance spectroscopy and mass spectrometry. The structures of H2L2 and [Zn2(L1)2(H2O)(DMF)] (1a) (DMF = dimethylformamide) are solved by single crystal X-ray diffraction. The SB coordinates the metal center through the Ophenolate, Nimine and Sthiolate atoms. The radical scavenging activity is tested using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, with all ligand precursors showing IC50 values ~40 μM. Cytotoxicity studies with several tumor cell lines (PC-3, MCF-7 and Caco-2) as well as a non-tumoral cell line (NHDF) are reported. Interestingly, 1 has relevant and selective antiproliferative effect against Caco-2 cells (IC50 = 9.1 μM). Their antimicrobial activity is evaluated in five bacterial strains (Klebsiella pneumoniae, Acinetobacter baumannii, Listeria monocytogenes, Pseudomonas aeruginosa and Staphylococcus aureus) and two yeast strains (Candida albicans and Candida tropicalis) with some compounds showing bacteriostatic and fungicidal activity. The minimal inhibitory concentration (MIC90) of HnL against Mycobacterium tuberculosis is also reported, with H2L2 and H3L4 showing very high activity (MIC90 < 0.6 μg/mL). The ability of the compounds to bind bovine serum albumin (BSA) and DNA is evaluated for H3L4 and [Zn2(L4)(CH3COO)] (4), both showing high binding constants to BSA (ca. 106 M-1) and ability to bind DNA. Overall, the reported compounds show relevant antitumor and antimicrobial properties, our data indicating they may be promising compounds in several fields of medicinal chemistry.
- Binding of oxovanadium(IV) complexes to blood serum albuminsPublication . Cobbina, Enoch; Mehtab, Sameena; Correia, Isabel; Gonçalves, Gisela; Tomaz, Isabel; Cavaco, Isabel Maria Palma Antunes; Jakusch, Tamás; Eneyedi, Eva; Kiss, Tamás; Pessoa, João CostaIn this work the binding of VIVO2+ and VIVO-complexes to serum albumins {human serum albumin (HSA), bovine serum albumin (BSA) and porcine serum albumin (PSA)} are studied using circular dichroism (CD), electron paramagnetic resonance (EPR) and visible absorption spectroscopy. The results confirm previous findings that VIVO2+ occupies at least two types of binding sites on albumin: ‘the strong vanadium binding site’ (designated by VBS1) and ‘the weak vanadium binding sites’ (designated by VBS2). VBS1 binds 1 mol equivalent of VIVO2+. On the other hand VBS2 correspond to binding of several mol equivalents of VIVO, and studies done with PSA in the presence of excess ZnII ions indicate that VSB2 corresponds to two distinct types of sites. The hyperfine coupling constant Az for VIVO2+ binding at VBS2 on HSA and BSA are all very similar (~168 × 10-4 cm-1) but differ slightly on PSA (~166 × 10-4 cm-1) due to differences in the binding sets. When (VIVO)-HSA systems are titrated with maltol ternary species of (maltol)m(VIVO)mHSA and (maltol)2m(VIVO)mHSA stoichiometry form which are clearly distinguishable from the binary (VIVO)-HSA system by the type and intensity of the CD spectra recorded. Changes are also observable in the intensity of the X-band EPR spectra, but not much in the hyperfine coupling constants Az, which are all in the range 166-167 × 10-4 cm-1. The results further demonstrate that the presence of maltol may enhance the binding of VIVO to albumin.
- DNA cleavage activity of VIVO(acac)2 and derivativesPublication . Butenko, Nataliya; Tomaz, Ana Isabel; Nouri, Ofelia; Escribano, Esther; Moreno, Virtudes; Gama, Sofia; Ribeiro, Vera; Telo, João Paulo; Pessoa, João Costa; Cavaco, Isabel Maria Palma AntunesThe DNA cleavage activity of several b-diketonate vanadyl complexes is examined. Vanadyl acetylacetonate,VIVO(acac)2, 1, shows a remarkable activity in degrading plasmid DNA in the absence of any activating agents, air and photoirradiation. The cleaving activity of several related complexes VIVO(hd)2(2, Hhd = 3,5-heptanedione), VIVO(acac-NH2)2 (3, Hacac-NH2 = acetoacetamide) and VIVO(acac-NMe2)2(4, Hacac-NMe2 = N,N-dimethylacetoacetamide) is also evaluated. It is shown that 2 exhibits an activity similar to 1, while 3 and 4 are much less efficient cleaving agents. The different activity of the complexes is related to their stability towards hydrolysis in aqueous solution, which follows the order 1 2 3 4.The nature of the pH buffer was also found to be determinant in the nuclease activity of 1 and 2. In a phosphate buffered medium DNA cleavage by these agents is much more efficient than in tris, hepes,mes or mops buffers. The reaction seems to take place through a mixed mechanism, involving the formation of reactive oxygen species (ROS), namely OH radicals, and possibly also direct cleavage at phosphodiester linkages induced by the vanadium complexes.