Curcumin, the polyphenolic yellow pigment from the turmeric plant, exhibits anti-inflammatory, antioxidant, and anticancer effects in vitro and in animal models. More than one hundred molecular targets of curcumin have been elucidated using in vitro cell culture assays. Very little, however, is known about the chemical-molecular mechanism whereby curcumin affects its targets, or how so many diverse targets can be affected by one single molecule. Furthermore, although curcumin shows beneficial effects in animal models of inflammatory diseases, the tissue levels detected after oral administration are in many cases below the concentrations required to elicit the corresponding effects in cell culture models. We have discovered that curcumin undergoes a previously unrecognized autoxidative and enzymatic transformation to generate novel metabolites. Oxidative transformation of curcumin occurs via reactive intermediates to form a novel bicyclopentadione derivative as the final, stable product. I have detected the final bicyclopentadione product of curcumin oxidative transformation in human and mouse plasma after oral administration of curcumin, indicating that this transformation is relevant in vivo. I will test the hypothesis that he oxidative metabolites are the direct mediators of some of the effects of curcumin. Finding that metabolites are the ultimate mediators of curcumin's activity would resolve many unanswered questions on how curcumin is acting - some of which are stated above. Preliminary data in the lab strongly supports a role for curcumin oxidative metabolites as mediators of some of curcumin's effects: the oxidative metabolites of curcumin include reactive species that adduct to peptides/proteins at cysteine residues to potentially alter cellular signaling;a mixture of these oxidative metabolites was shown to be more potent than curcumin at inhibiting Parathyroid Hormone related Peptide (PTHrP) secretion in a breast cancer cell line;we have shown that oxidative transformation of curcumin is required for its topoisomerase II poisoning activity. I propose to further study these metabolites and their biological effects in three Specific Aims: (1) To assess the biological consequences of oxidative transformation of curcumin. (2) To define the products and mechanism of oxidative transformation of curcumin. (3) To define the pharmacokinetics and tissue distribution of oxidized curcumin. The novel concept of oxidative bioactivation of curcumin could result in a paradigm shift in understanding the structure and function of curcumin. Important implications for clinical and therapeutic application of curcumin as a CAM natural agent are imminent.
Increasing biochemical and clinical evidence supports the use of dietary supplement curcumin for prevention of cancer and other diseases. The goal of this application is determine if novel metabolites formed during curcumin'oxidative transformation are involved in its biological activity.
