Beta-Glucuronidase Catalyzes Deconjugation and Activation of Curcumin-Glucuronide in Bone.
Level 5 - mechanism / opinion, no new human data
Preclinical animal and in vitro laboratory study
PubMed 30794412 · doi:10.1021/acs.jnatprod.8b00873
What was done
Researchers evaluated whether inactive curcumin-glucuronide undergoes site-specific enzymatic activation in bone via β-glucuronidase (GUSB). They tested the effects of aglycone versus glucuronidated curcumin on RANKL-stimulated osteoclastogenesis in cell culture. They also measured curcumin metabolites in the serum and bone marrow of curcumin-treated C57BL/6J mice and tested ex vivo deconjugation in marrow from wild-type mice, GUSB-deficient mouse models (C3H/HeJ and mps/mps), and marrow treated with the GUSB inhibitor saccharolactone.
What was found
The abstract reports directional findings without numerical values. Aglycone curcumin inhibited RANKL-stimulated osteoclastogenesis, whereas glucuronidated curcumin did not. In C57BL/6J mice, the proportion of active aglycone relative to total curcumin was higher in bone marrow than in serum, though it remained a minor component. Ex vivo, marrow hydrolyzed the majority of in vivo delivered curcumin-glucuronide into the aglycone; this hydrolysis was blocked by saccharolactone and was reduced or absent in GUSB-deficient mice.
Why it matters
This study provides a plausible mechanism resolving the paradox of curcumin's bone-protective actions despite poor systemic bioavailability. Local deconjugation by β-glucuronidase in bone marrow suggests a target metabolic pathway that could also apply to other glucuronidated dietary polyphenols.
Limits
This is preclinical animal and in vitro research, so findings cannot be directly extrapolated to humans. The abstract does not report sample sizes, specific drug dosages, or quantitative statistical measures. Furthermore, ex vivo deconjugation required artificial conditions to prevent degradation of the unstable aglycone.
Cited by
- supports Glucuronidated curcumin is completely biologically inactive.