Structural characterization and physicochemical properties of quercetin-Pb complex

Flavonoids are a large group of ubiquitous molecules synthesized by plants. These molecules possess antioxidant activities which prevent free radical damage to biological molecules and can also be metal chelators. This article describes the synthesis of a Pb(II)-quercetin complex and characterization by UV-visible, infrared, H-1 nuclear magnetic resonance spectroscopy, thermogravimetric analysis, and differential thermal analysis. The formation of quercetin and Pb(II) complex ratio 1 : 1 was confirmed by UV-visible spectroscopy. The composition of the complex does not change with pH. Antimicrobial activities were evaluated by using Gram-positive and Gram-negative bacteria. The antioxidant properties of quercetin and the complex was evaluated by using 2,2'-diphenyl-1-picrylhydrazyl radical scavenging method. The quercetin-Pb complex was less effective than quercetin in antimicrobial and antioxidant activity.