Green tea (Camellia sinensis)
Inhibitory effects of commonly used herbal extracts on UGT1A1 enzyme activity. CSV JSON

A panel of nine commonly used herbal supplements were screened for their potential to inhibit UGT1A1 activity using human liver microsomes. The result of green tea constituient epigallocatechin gallate (EGCG) was entered. Based on the in vitro findings, inhibition of  UGT1A1 by EGCG is plausible, particularly in the intestine where higher extract concentrations are anticipated. Further clinical studies are warranted.



1 . EGCG inhibition of UGT1A1 (id=NPDI-r41Z9w)

In Vitro Enzyme Inhibition Experiment

Inhibition was detected.  Cutoff used — > 20% inhibition at the highest tested concentrations


epigallocatechin gallate 19058494


  • UGT1A1 40782950

Cell fraction Pooled human liver microsomes -7999662

Concentrations of herbal extracts in screening incubations represent the recommended daily intake (RDI) of each extract dissolved in 53 L, 5.3 L, and 0.53 L. For EGCG, inhibition at the represented RDI was compared with the recommended daily dose (250 mg) of EGCG. The value per dose index (VDI) value was 32.1 L, which is the highest value of all extracts tested, indicating the highest potential for inhibition.


Sample Compound measured Value Measurement Study sequence Additional information N replicates

Experimental Conditions

Precipitant concentrations were estimated from Fig. 2.

0.5 mg/mL

Commercially available

250 µL

30 min


Not available

Not available

25 µM

0.05-500 µg/mL