Isolation and Identification of Human Gut Bacteria Capable of Converting Curcumin to Its Hydrogenated Metabolites

Curcumin is widely recognized for its health benefits, though the role of gut microbiota in its metabolic transformation was not well studied. In this study, bacterial strains capable of metabolizing curcumin were isolated from human stool samples. Using 16S rRNA and whole-genome sequencing, two novel strains (<i>Clostridium butyricum</i> UMA_cur1 and <i>Escherichia coli</i> UMA_cur2) were identified. In addition, the metabolic products were analyzed using liquid chromatography-mass spectrometry. These strains efficiently converted curcumin into dihydro-curcumin (DHC) and tetrahydro-curcumin (THC). Notably, <i>E. coli</i> UMA_cur2 also produced hexahydro-curcumin (HHC) and octahydro-curcumin (OHC), marking the first identification of a strain capable of such transformations. The absence of the YncB gene (typically involved in curcumin conversion) in <i>C. butyricum</i> UMA_cur1 suggests an alternative metabolic pathway. Curcumin metabolism begins during the stationary growth phase, indicating that it is not crucial for primary growth functions. Furthermore, <i>E. coli</i> UMA_cur2 produced these metabolites sequentially, starting with DHC and THC and progressing to HHC and OHC. These findings identified two novel strains that can metabolize curcumin to hydrogenated metabolites, which enhance our understanding of the interaction between curcumin and gut microbiota.