Oral consumption of curcumin, a natural polyphenol, is associated with reduced incidence of cancer. Yet, a significant amount of the orally dosed compound is eliminated in the feces, and a major fraction of the absorbed compound is metabolized to inactive glucuronides, resulting in poor bioavailability (<1%). It is not known how oral curcumin exhibits chemopreventive activity. We propose curcumin glucuronide is an inflammation-responsive natural prodrug that is converted back to curcumin on demand at the site of action. Our studies show elevated levels of β-glucuronidase, an enzyme that hydrolyzes the glycosidic bond of glucuronides to generate the parent compound, in human breast cancer. Oral administration of curcumin in mouse tumor models generated significant tumor levels of the polyphenol. Intravenous administration of the glucuronide resulted in the formation of curcumin in the tumor tissue. Chronic daily oral curcumin dosing led to tumor accumulation of curcumin and inhibition of tumor growth in tumor models with high β-glucuronidase activity. Overall, the study presented here provides preliminary evidence for a novel mechanism of action for orally administered curcumin.—Liu, G., Khanna, V., Kirtane, A., Grill, A., Panyam, J. Chemopreventive efficacy of oral curcumin: a prodrug hypothesis. FASEB J. 33, 9453–9465 (2019). www.fasebj.org.
Bibliographical noteFunding Information:
The authors acknowledge Prof. Yu-Iin Leu of Chia Nan University of Pharmacy and Science (Tainan, Taiwan) for providing us with near-infrared fluorescent difluoromethylphenol-glucuronide probe. The authors thank Brenda Koniar (University of Minnesota, Minneapolis, MN, USA) for assistance with the animal studies and Jim Fischer (University of Minnesota) for assistance with liquid chromatography?mass spectrometry. Supported by a grant-in-aid award from the University of Minnesota and U.S. National Institutes of Health, National Cancer Institute Grant CA 141996 (to J.P.). The authors declare no conflicts of interest
- cancer prevention
- curcumin glucuronide