Rate of metabolism of eupatorin (10 μM) by recombinant microsomes expressing CYP1A1, CYP1A2, or CYP1B1. (a) Disappearance of eupatorin over time by CYP1 family enzymes. (b) Formation of the metabolite cirsiliol over a 20-minute time period. Experiments were performed in duplicate as described in Materials and methods. Error bars represent mean ± minimum or maximum values for n = 2 determinations.