The (ROS) and antioxidant defenses[6]. ROS are mostly removed

The function of antioxidants
in cells as a protective mechanism during oxidative stress and apoptotic cell
death has been offered. Oxidative stress illustrates an imbalance state between
the generation of Reactive oxygen species (ROS) and antioxidant defenses6. ROS are mostly removed by endogenous antioxidants such as
superoxide dismutase (SOD), which converts O2 to H2O2, glutathione peroxidase
(GPx) and catalase (CAT) which in turn convert H2O2 to water7. Moreover, exogenous antioxidants including ascorbic acid, ?-tocopherol, ?-carotene,
vitamin A prevent excessive generation, of free radicals by combining with
them. Indeed when the redox balance is disrupted, creating an oxidative stress situation
8. Treatment of some cancers depends on oxidative stress situation. Several
chemotherapy drugs used in cancer therapy represent their effectiveness by the generation
of reactive oxygen species (ROS) and free radicals, which are part of their metabolic activity 9.  

Thiosemicarbazone based metal complexes
are compounds that possess antitumor, antioxidant, antibacterial, antifungal and
antiviral properties10. Antitumor activity of thiosemicarbazones is often linked to the coordination of metal ions 11. Presently, the significant known effects linked to their anticancer
activity are, in order of discovery, ribonucleotide reductase inhibition, generation
of reactive oxygen species (ROS), topoisomerase II inhibition, mitochondria disruption
and also multidrug resistance protein (MDR1) inhibition10. Such possible medical activities are owing to the powerful chelating
ability of thiosemicarbazones with biologically important metal ions including Ni,
Fe, Cu and their reductive capacities Nickel(II) complexes comprising sulphur and
nitrogen donor ligands are many significant, since several carbon monoxide
dehydrogenases  and hydrogenases comprise
such nickel ion as their active site12.

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