Tin(II)–quercetin complex: Synthesis, spectral characterisation and antioxidant activity

The complex formation between quercetin (Q) and stannous chloride (SnCl2·2H2O) was studied using UV–visible, IR and 1H NMR spectroscopic techniques. Spectroscopic data suggest that Q can chelate stannous cations through both 3-hydroxy-4-carbonyl and the 3′,4′-dihydroxyl (catechol) chelation sites. The antioxidant activity of the complex was evaluated using 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2′-azinobis 3-ethylbenzothiazoline-6-sulphonic acid (ABTS) diammonium salt and ferric reducing antioxidant power (FRAP) methods. It was shown that radical scavenging activity and ferric reducing potential of free Q was decreased after chelation of stannous cation.