Isolation and identification of phase 1 metabolites of curcuminoids in rats.

Curcuminoids are natural food coloring additives with anti-inflammatory, antioxidant, and anticarcinogenic activity, which contain mainly three diarylheptanoids: curcumin, demethoxycurcumin, and bisdemethoxycurcumin. In this paper, the metabolites of curcuminoids in the feces and urine of rats after oral administration by gavage were investigated. Four new metabolites, 3-hydroxy-[1-(4-hydroxyphenyl)-7-(3-hydroxyphey)] heptane-A (M1), 3-hydroxy-[1-(4-hydroxyphenyl)-7-(3-hydroxyphey)] heptane-B (M2), 3-hydroxy-1,7-bis(3-hydroxyphenyl) heptane-A (M3) and 3-hydroxy-1,7-bis(3-hydroxyphenyl) heptane-B (M4), along with five known metabolites (M5-M9), were isolated from the feces of male Wistar-derived rats and nine known metabolites (M5-M8, M10-M14) were isolated from the urine. Their structures were elucidated by extensive spectroscopic analysis. The finding that the metabolites occurred as several pairs of enantiomers was confirmed by chiral column chromatography. Based on the metabolites' profiles, possible metabolic pathways of the curcuminoids in rats are proposed.