Glucuronidation dynamics of curcumin and tetrahydrocurcumin for differential structures and chemical reactivities in human liver microsome and uridine diphosphate glucuronosyltransferase 2B7

THC is the main metabolite of curcumin with better bioactivity. This study aimed to explore the factors that cause differences in the bioactivity of curcumin and THC. We analyzed the metabolic activities of curcumin and THC and the factors responsible for the differences in their activities by glucuronidation activity assay, LC-MS, HPLC, homologous sequence comparisons, and molecular docking. Curcumin has higher metabolic activity than THC in HLM and UGT2B7, while the keto-enol isomers of curcumin and THC were distinctly different under different pH, and their structural transformations were hypothesized. Furthermore, UGT1A and UGT2B are differential sequences of curcumin and THC in UGTs. The binding sites and patterns of curcumin and THC in UGT2B7 are markedly different. In summary, the difference in keto-enolic interconversion isomerism between curcumin and THC is the main factor causing the difference in their activities, which provides a scientific basis for the development of curcumin.