TABLE 2

IC50 values for inhibition by curcuminoid extract and piperine of P450 selective activities measured in human liver microsomes Functional activities evaluated included triazolam 1′-hydroxylation (CYP3A), flurbiprofen hydroxylation (CYP2C9), S-mephenytoin hydroxylation (CYP2C19), phenacetin de-ethylation (CYP1A2), dextromethorphan demethylation (CYP2D6), chlorzoxazone hydroxylation (CYP2E1), and bupropion hydroxylation (CYP2B6). IC50 values were generated by nonlinear regression curve fitting using Prism software. Also shown are IC50 values for control inhibitors that are known to be relatively specific for each of the P450 isoforms evaluated measured in the same set of human liver microsomes. Shown are the mean ± S.E. of triplicate determinations using HLM from three different individuals.


Isozyme

IC50 Curcuminoid Extract

IC50 Piperine

IC50 Control Inhibitor

Control Inhibitor
μM μM μM
CYP3A 25.3 ± 1.3 5.5 ± 0.7 0.10 ± 0.04 Ketoconazole
CYP2C9 13.5 ± 1.4 40.7 ± 4.1 0.44 ± 0.03 Sulfaphenazole
CYP2D6 63.6 ± 4.8 >50 0.13 ± 0.01 Quinidine
CYP2C19 7.4 ± 1.2 >50 6.5 ± 1.3 Omeprazole
CYP1A2 95.4 ± 17.1 29.8 ± 3.6 0.10 ± 0.02 α-Naphthoflavone
CYP2E1 >200 >50 5.8 ± 0.8 Diethyldithiocarbamate
CYP2B6
9.4 ± 1.9
>50
5.0 ± 0.5
thio-TEPA