Effects of selected flavonolignans and 7-O-methylated analogues on CYP3A-mediated midazolam 1′-hydroxylation in human intestinal microsomes (HIM). Incubation mixtures consisted of HIM (0.05 mg/ml), midazolam (4 μM), flavonolignan or 7-O-methylated analogue (10 or 100 μM; hatched and solid bars, respectively), and potassium phosphate buffer (0.1 M, pH 7.4) supplemented with magnesium chloride (3.3 mM). Reactions were initiated by the addition of NADPH (1 mM) and were terminated after 4 min with ice-cold acetonitrile containing alprazolam as internal standard. Activity in the presence of vehicle control (0.1% DMSO, v/v) was 700 ± 100 pmol/min/mg microsomal protein. Bars and error bars denote means and SDs, respectively, of triplicate incubations. *p <0.05, 10 versus 100 μM; #p < 0.05, flavonolignan versus 7-O-methylated analogue at 100 μM (two-way ANOVA with Bonferroni adjustment).