Chemico-Physical Properties of Metal-Flavonoid

Cheng, Francis

Abstract

Flavonoids are recognized as an important class of nutrient that may be responsible for the chemoprevention of a myriad of degenerative diseases. This action is attributed to their putative antioxidant action. Many investigators have recognized that metal chelation is an important determinate in the prediction of the antioxidant action of flavonoids. However, there is a paucity of data accumulated concerning the chemico-physico properties of metal-flavonoid complexes. A previous investigation from this laboratory has found that four flavonoids, baicilein, luteolin, naringenin, and quercetin, chelate pro-oxidant iron ions into a complex that is not Fenton Reaction active. Another plant-borne product, salicylate has been the subject of previous investigations from this laboratory and found to chelate pro-oxidant iron into a form that is again not Fenton Reaction active. The proposed investigations will study the similarity of action between the four aforementioned flavonoids and salicylate, i.e. the ability to bind pro-oxidant metals both as free ions and in low molecular-weight complexes. The pro-oxidant metals of concern in this study are Fe, Cu, and Mn ions and also in complexed forms with EDTA, ATP/ADP and in porphyrins. The redox potential of each metal complex will predict the antioxidant characteristics in terms of Fenton Reaction activity, other redox-dependent actions such as superoxide dismutase and catalase activity. Metal-flavonoid binding constants will aid in determining if the flavonoids are effective in vivo chelation agents. These data will be derived by potentiometric titrations augmented with UV-vis absorbance. The four flavonoids chosen for this study will give insights into structure-activity relationships. It is hoped that the subject of this investigation will give a new paradigm for the design, and discovery of antioxidants, and anti-inflammatory agents.