Figure 4: Inhibition of CYP3A4 activities by dihydrotanshinone I and danshen ethanol extract in human liver microsomes. Reactions were performed in the presence of midazolam (3.5 μM) at various concentrations of danshen ethanol extract (0.2–100.0 μg/mL) (a) and dihydrotanshinone I (0.5–100.0 μM) (b), in the microsomes (0.2 mg/mL) and NADPH in a 100 mM phosphate buffer, pH 7.4 in a final volume of 200 μL at 37°C for 5 min. Each point represents the mean of three separate experiments performed in triplicate, and the bar represents S.D.