In Vitro Enzyme Inhibition Experiment

Inhibition was detected.  Cutoff used — 50% inhibition vs. control

4-methylumbelliferone

4-methylumbelliferone glucuronide

  • UGT

Cell fraction Pooled human intestinal microsomes -7999663

Standard reference material of green tea leaves T26 (No. 3254) was obtained from the National Institute of Standards and Technology (NIST). Methanol extracts and (sub)fractions (five fractions obtained using a 4 g silica gel column and a hexane-chloroform-methanol mobile phase at 18 mL/min; normal phase chromatography) from T26 were used.

Results

Extracts, fractions, and subfractions from T26 inhibited intestinal UGT activity in a concentration-dependent manner (by 30-100% relative to vehicle control, estimated from Fig. 3). The UGT inhibitory constituents tended to reside in the more hydrophilic subfractions of the fraction prepared from the representative extract. (−)-Epigallocatechin gallate (EGCG) and (−)-epicatechin gallate (ECG), two abundant catechins contained in green tea, were identified as major UGT inhibitors in these subfractions.

Compound measured Measurement Value Study sequence Additional information N replicates

Experimental Conditions

Green tea T26 extracts, fractions, and subfractions were tested as inhibitors of UGT enzymes as described in Gufford et al., 2014 (Drug Metab Dispos. 2014 Oct;42(10):1675-83); information regarding incubation volume, time, and protein linearity were obtain therein.
Bovine serum albumin (0.05%) was added into the incubation system.

0.2 mg/mL

Commercially available

1410074

150 µL

20 min

UDPGA

Available

Not available

100 µM

20, 60, and 180 µg/mL