Molecular Modeling Study of Quercetin and their Metal Complexes

A chemical behavior of Quercetin as antioxidant and metal chelator has become the subject of intense experimental research. In this paper, we apply a semi empirical approach to study the stability constant of Quercetin with metals like Cd, Pb and Bi. The comparative analysis of the theoretical formation constant of Quercetin-metal complexes with metals with experimental results shows that H-removal from phenolic -OH site during the metal chelation correlated with experimentally determined stability constant by Job's method. The analysis of the theoretical BDE (Bond Dissociation Energy) values, for all OH sites in Quercetin, clearly shows the importance of the B-ring –OH groups. Mulliken spin density distribution for the radicals formed after H-removal on each OH site of Quercetin is also investigated. The results indicate that 3'-O. and 4'-O. (B-ring) Quercetin radical spin density appears to be more delocalized than the other sites present on A-ring.