@article {Tian552, author = {Dan-Dan Tian and Joshua J. Kellogg and Ne{\c s}e Okut and Nicholas H. Oberlies and Nadja B. Cech and Danny D. Shen and Jeannine S. McCune and Mary F. Paine}, title = {Identification of Intestinal UDP-Glucuronosyltransferase Inhibitors in Green Tea (Camellia sinensis) Using a Biochemometric Approach: Application to Raloxifene as a Test Drug via In Vitro to In Vivo Extrapolation}, volume = {46}, number = {5}, pages = {552--560}, year = {2018}, doi = {10.1124/dmd.117.079491}, publisher = {American Society for Pharmacology and Experimental Therapeutics}, abstract = {Green tea (Camellia sinensis) is a popular beverage worldwide, raising concern for adverse interactions when co-consumed with conventional drugs. Like many botanical natural products, green tea contains numerous polyphenolic constituents that undergo extensive glucuronidation. As such, the UDP-glucuronosyltransferases (UGTs), particularly intestinal UGTs, represent potential first-pass targets for green tea-drug interactions. Candidate intestinal UGT inhibitors were identified using a biochemometrics approach, which combines bioassay and chemometric data. Extracts and fractions prepared from four widely consumed teas were screened (20{\textendash}180 μg/ml) as inhibitors of UGT activity (4-methylumbelliferone glucuronidation) in human intestinal microsomes; all demonstrated concentration-dependent inhibition. A biochemometrics-identified fraction rich in UGT inhibitors from a representative tea was purified further and subjected to second-stage biochemometric analysis. Five catechins were identified as major constituents in the bioactive subfractions and prioritized for further evaluation. Of these catechins, (-)-epicatechin gallate and (-)-epigallocatechin gallate showed concentration-dependent inhibition, with IC50 values (105 and 59 μM, respectively) near or below concentrations measured in a cup (240 ml) of tea (66 and 240 μM, respectively). Using the clinical intestinal UGT substrate raloxifene, the Ki values were \~{}1.0 and 2.0 μM, respectively. Using estimated intestinal lumen and enterocyte inhibitor concentrations, a mechanistic static model predicted green tea to increase the raloxifene plasma area under the curve up to 6.1- and 1.3-fold, respectively. Application of this novel approach, which combines biochemometrics with in vitro-in vivo extrapolation, to other natural product-drug combinations will refine these procedures, informing the need for further evaluation via dynamic modeling and clinical testing.}, issn = {0090-9556}, URL = {https://dmd.aspetjournals.org/content/46/5/552}, eprint = {https://dmd.aspetjournals.org/content/46/5/552.full.pdf}, journal = {Drug Metabolism and Disposition} }