Table 2

Inhibition of human P450 1A1, 1A2, and 1B1 by various hydroxystilbene compounds

CompoundIC50Ratio (1A2/1A1)Ratio (1B1/1A1)
1A11A21B1
μM
Rhapontigenin0.4160940023
3,5-Dihydroxy 4′-methoxystilbene0.4351883
Oxyresveratrol1515034102
3,4′-Dimethoxy-5-hydroxystilbene0.180.1801
3,4′,5-Trimethoxystilbene0.60.60.410.7
Piceid480>2000>1000
Rhaponticin2001661450.80.7

P450 concentrations for determination of catalytic activities were 5, 10, and 10 nM for P450 1A1, 1A2, and 1B1, respectively. Control activities (means of triple determinations) in the absence of chemicals were 12.5, 5.4, and 2.5 nmol of resorufin formed min−1 nmol of P450−1 for P450 1A1, 1A2, and 1B1.