In Vitro Enzyme Inhibition Experiment

Negligible inhibition of UGT in human liver microsomes by mitragynine

Negligible Inhibition was detected.  Cutoff used —

IC50 > 10 μM are low potential inhibitors.
1 μM < IC50 < 10 μM are moderate potential inhibitors. 
IC50 < 1 μM are high potential inhibitors.

4-methylumbelliferone

mitragynine

4-methylumbelliferone glucuronide

  • UGT

Cell fraction Pooled human liver microsomes -7999662

Results

The IC50 values were all greater than the highest concentrations used (IC50 > 100 μM) since inhibition at more than 50% did not occur at the highest concentration.

Concentration of precipitant and % inhibition of pooled human liver microsomes (intermediate values estimated from figure 3) (p < 0.05 for all values)
0.01 μM: 16 ± 3%
0.1 μM: 26 ± 3%
1 μM: 29 ± 3%
10 μM:30 ± 2%
100 μM: See above data

Sample Compound measured Value Measurement Study sequence Additional information N replicates

Experimental Conditions

Pooled human liver microsomes were purchased from Sigma-Aldrich; The enzyme activity assay mixture (250 μL) contained Tris-HCl (100 mM) (pH 7.4), MgCl (5 mM), microsomal protein (0.1 mg/mL), Triton X-100 (0.005%), UDPGA (3 mM), and 4-MU (100 μM).

Tested concentrations of precipitant only up to 100 μM due to limited solubility

Control=no inhibitor

0.1 mg/mL

Commercially available

250 μL

30 min

MgCl2

UDPGA

Not available

Not available

100 μM

0.01-100 μM