In vitro antioxidant activities of some Re(I) metal carbonyls synthesized from isatin derivatives

Abstract

Isatin is a natural indole found in some plants, brains, and human tissues, which possesses numerous medicinal applications. Rhenium complexes of different Schiff bases have multiple biological applications like anti-tumour, anti-microbial and antioxidant activities. Little information exist in literature on the Re(I) metal carbonyls of isatin derivatives and their biological significance. Therefore, the aim was to determine the antioxidant capacities of Re(I) complexes of the Schiff bases of isatin with aniline (C14H10N2O) and isatin with sulphanilamide (C14H11N3O3S) using three antioxidant assays to facilitate further plausible biological and medicinal applications. 2,2-diphenyl-1picrylhydrazyl (DPPH) and hydrogen peroxide radical scavenging activities of the Re(I) isatin derivative complexes and their reducing power were evaluated. Complex 1 was [Re(C14H10N2O)(CO)3Cl], Complex 2 was [Re(C14H10N2O)(CO)3Br] and complex 3 was [Re(C14H11N3O3S)(CO)3Br]. It was observed that Complexes 2 and 3, which contain bromine in their coordination spheres, had better DPPH scavenging activities than Complex 3, which had chlorine in its coordination sphere. Although [Re(C14H10N2O)(CO)3Br] has better DPPH and hydrogen peroxide radical scavenging abilities than [Re(C14H11N3O3S)(CO)3Br], it was observed that [Re(C14H11N3O3S)(CO)3Br] was a better reducing agent than [Re(C14H10N2O)(CO)3Br]. These results showed good antioxidant properties of the complexes, recommendable for further applications such as anti-tumor or cell imaging known with isatin derivatives and Re(I) compounds. Also, this might arouse the interest to study the structure to function relationships in aniline and sulphanilamide-containing complexes, which could be of great medicinal significance.