Curcumin metabolism by human intestinal bacteria in vitro

We tried to isolate metabolite in curcumin by incubation with human feces in vitro for the better understanding of curcumin activity in vivo. One group containing some bacteria, referred as 1C, produced a metabolite other than tetrahydrocurcumin. Structural analysis revealed that this new metabolite was 3-hydroxy-1,7-bis(3,4-dihydroxyphenyl)heptane by comparing it to the reported optically active compound rubranol, which has 3R stereochemistry. In order to determine the absolute stereochemistry of the secondary alcohol of this metabolite, we synthesized its racemic tetramethyl derivative. From HPLC analysis that separate the synthetic sample to two peaks, this metabolite was optically active and was primarily an enantiomer of rubranol. We also compared the activities of curcumin and the metabolite using monocyte chemoattractant protein-1 (MCP-1) which is produced in vitro by murine adipocytes. The metabolite exhibited an inhibition effect associated with the production of MCP-1, which was similar to that of curcumin with attenuated cytotoxicity.