Objective: To study the aglycone from Rhei Radix et Rhizoma(AR) on liver microsomal P450 isozymes/cytochrome P450 (CYP450) CYP1A2 activity in rats by enzyme assays. Method: Sixty SD rats were randomly divided into the control group

the phenobarbital sodium (PB) group (75 mg·kg-1 0.5% sodium carboxyl methyl cellulose

CMC-Na)

the dexamethasone (DEX) group (80 mg·kg-1)

the beta-naphthoflavone(β-NF) group (75 mg·kg-1)

the ketoconazole(KET) group (82.5 mg·kg-1) and the different doses of AR groups (7.08

14.40

30.82

46.55

51.63

61.63

100.07 mg·kg-1). The experiment was performed in the liver microsome and the phenacetin was taken as the probe drug. The acetaminophen concentrations were determined by HPLC and the relationship between CYP1A2 activity and the dosage was conducted. Result: Compared with CMC-Na group and the KET group

the production of acetaminophen was very different in the AR groups at 61.63

30.82

14.40 mg·kg-1 (P<0.05). The induce effect was much weaker than three kinds of induction agents

and it was enhanced with the increasing of the dosage. Conclusion: The AR could induce the activity of CYP1A2 in a dose-dependent manner.