Synthesis, characterization and chemiluminescence study of quercetin and its metal complexes

Quercetin is one of the most common flavonoid present in nature that has attracted the attention of many researchers because of its biological properties. It is a strong natural antioxidant and having free radical scavenging activity along with potent metal chelator [1]. As transition metal ions play a vital role in the initiation of free radical processes (via the Fenton reaction), metal chelation is widely considered as a mechanism of the antioxidant activity of flavonoids. The interaction of flavonoids with metal ions may change the antioxidant properties and some biological effects of the flavonoids [2].In the present work we synthesized three metal(II) complexes with quercetin (M = Cu, Ni and Co). The complex formation was examined by analytical techniques including UV-Vis, IR, thermal gravimetric and elemental analyses. Reaction of luminol with hydroxyl radicals produces a chemiluminescence (CL) signal which is influenced by specific radical scavengers, so luminol chemiluminescence was used to evaluate radical scavenging of quercetin and its metal complexes. CL intensity was measured with different concentrations of ligand and complexes. This method can serve as a screening test for the antioxidant properties of substances [3].