Upon metabolism. curcumin undergoes a transformation, either through autoxidation or COX2 catalyzation, creating a quinone methide, according to new pathways proposed by researchers at Vanderbilt University. This reaction, which creates quinone methide, may contribute to curcurmin’s chemopreventive activity.
Previous study of curcumin, the orange-yellow crystalline compound—C21H20O6—that constitutes the coloring of turmeric, has been limited by chemical and metabolic instability. By investigating the compounds oxidative reaction, however, Schneider and colleagues found two pathways by which curcumin transforms into quinone methide and a delocalized radical in the heptadienone chain.
One pathway, autoxidation, was dependent on pH level, with the highest rate at pH 8 (2.2 µm/min). Autoxidation also was associated with stoichiometric uptake of oxygen. The other pathway, catalyzation by recombinant COX2, increased the rate nearly 10-fold with the addition of 300 µm of hydrogen peroxide. Acetaminophen but not indomethacin inhibited the transformation, leading the researchers to propose that oxidation occurs through peroxidase activity.
Introducing the compound in mouse macrophage-like cells resulted in a 1.8-fold increase in bicyclopentadione product in cells activated by LPS.
Their complete findings are published in the January 14 issue of The Journal of Biological Chemistry.