Curcumin is the chemical part of tumeric which is most active. It prevents cancer in rodents, particularly in the intestines. However curcumin is poorly absorbed when given by mouth. Very little gets into the bloodstream. So these researchers wondered if metabolites of curcumin where really causing the beneficial affects attributed to curcumin. Metabolites are the products made through the metabolism of a chemical in the body. First, they found that isolated liver cells of rats and humans produced two metabolites, hexahydrocurcumin and hexahydrocurcuminol. Rats given curcumin by injection mostly made curcumin glucuronide and curcumin sulfate. They made little hexahydrocurcumin, hexahydrocurcuminol, and hexahydrocurcumin glucuronide. They then studied the effect of these metabolites on an enzyme important in the prevention of cancer, cyclooxygenase-2 (COX-2). They compared how much four metabolites blocked COX-2 activity in cells from the surface the human large intestine. Curcumin complete inhibited COX-2. Tetrahydrocurcumin, hexahydrocurcumin, and curcumin sulfate, only weakly inhibited COX-s. Tetrahydrocurcumin has been shown to be metabolite of curcumin in mice. Hexahydrocurcuminol had no effect. These scientists concluded that the live rats made different curcumin metabolites than did liver cells in a test tube. The metabolites studied inhibit COX-2 had less than curcumin. When curcumin is given by mouth, the cells on the surface of the intestine are directly exposed to curcumin, not metabolites. Therefore they advise studying curcumin as a treatment in colon and rectal cancer.
Characterization of metabolites of the chemopreven…[Cancer Res. 2001]