Browsing by Author "Alemu, Yemataw Addis"
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- Synthesis, characterization and biological evaluation of zinc(ii) complexes with phenanthroline derivatives and s-methyl dithiocarbazate schiff basesPublication . Alemu, Yemataw Addis; Cavaco, Isabel; Correia, IsabelThe discovery of novel active compounds with new mechanisms of action, higher efficacy and improved selectivity is a matter of urgency to multi drug resistance and toxicity problems associated with many therapeutic drugs. In the current work S-methyl dithiocarbazate Schiff base: SalSmdt, Mp(Smdt)2, VanSmdt, PySmdt and their Zn(II) complexes: Zn[(SalSmdt)(H2O)]0.5H2O, Zn2[(Mp(Smdt)2)(CH3COO)], Zn[(VanSmdt)(H2O)] and Zn[(PySmdt)(CH3COO)]1.5H2O were synthesized. The Schiff bases were obtained by condensation of S-methyl dithiocarbazate (smdt) with different aromatic aldehydes: salicylaldehyde (sal), o-vanillin (van), pyridoxal (py) and 2,6-diformyl-4-methylphenol (Mp). Additionally, Zn[(phen)2(NO3)2]2H2O, Zn[(aminophen)2(NO3)2]1.5H2O and Zn[(Mephen)2(NO3)2]3.5H2O complexes were developed by reaction of Zn(II) with 1,10- phenanthroline (phen), 4,7-dimethyl-1,10-phenanthroline (Mephen) and 5-amino-1,10- phenanthroline (aminophen). All compounds were characterized by elemental analysis, FTIR, UV-Vis, NMR, MS and fluorescence spectroscopies. The characterization suggests that the Schiff base ligands coordinate the metal ion through the phenolate–O, the imine-N and the sulfur atom in the thiol form (except in Zn[(PySmdt)(CH3COO)] for which the thione is proposed). The stability of the compounds in buffered aqueous media (5 % DMSO and 95 % PBS, pH 7.4) was evaluated and all compounds are stable at least for three hours. The antioxidant potential was tested using the 2,2-diphenyl-1-picrylhydrazyl assay. All S-methyl dithiocarbazate Schiff bases showed moderate antioxidant activity but the Zn(II) complexes, with the exception of Zn[(PySmdt)(CH3COO)], are inactive. The Zn-phenanthroline complexes were tested for their DNA binding ability by fluorescence spectroscopy. The results indicate that there is interaction between the complexes and calf thymus DNA. Cytotoxicity studies with several tumor cell lines (PC-3, MCF-7 and CACO-2) are ongoing. The results obtained for the Schiff bases are promising since the IC50 values ranged from 4.41 to 28.99 μM. The phenanthroline ligands and their corresponding Zn complexes showed very high cytotoxicity towards A2780 ovarian cancer cells, with the Zn complexes showing slightly higher activity than the ligands.