Jpn. J. Pharmacol. 85 (4), 399-408 (2001)

Inhibitory Potential of Herbal Medicines on Human Cytochrome P450-Mediated Oxidation: Properties of Umbelliferous or Citrus Crude Drugs and Their Relative Prescriptions

Lian-Qing Guo1,4, Masahiko Taniguchi2, Qiao-Yun Chen3, Kimiye Baba2 and Yasushi Yamazoe1,*

1Division of Drug Metabolism and Molecular Toxicology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai 980-8578, Japan
2Division of Pharmacognosy, Osaka University of Pharmaceutical Sciences, Takatsuki 569-1094, Japan
Departments of 3Pharmacy and 4Clinical Pharmacology, Jinling Hospital, Nanjing 210002, China

*Corresponding author. FAX: +81-22-217-6826, E-mail:

Abstract: To investigate the possible drug interaction with herbal medicine, hot water decoctions or 40% ethanol infusions of several Umbelliferous or Citrus crude drugs and their prescriptions were examined in vitro for their abilities to inhibit human cytochrome P450 3A (CYP3A). Addition of each decoction or infusion from Baizhi (Angelica dahurica and varieties), Qianghuo (Notopterygium incisum or N. forbesii), Duhuo (Angelica biserrata), Fangfeng (Saposhnikovia divaricata), Danggui (Angelica sinensis), Zhishi or Zhiqiao (Citrus aurantium) resulted in various degrees of human CYP3A inhibition as determined by microsomal testosterone 6β-hydroxylation. The inhibitory potency was consistent with the abundance of the hydrophobic components for each sample. Experiments on the infusion of a Japanese Baizhi (BZ1) showed the major role of furanocoumarins on human CYP3A inhibition. Some of the crude drugs and a related prescription showed increased inhibition after the preincubation, suggesting the involvement of a mechanism-based inhibition. Some formulated prescriptions, however, showed intense inhibition with their hydrophobic fractions rather than with their hydrophobic fractions, suggesting that components other than furanocoumarins in herbal prescriptions may also cause CYP3A inhibition. These results indicate the necessity of intensive investigations on the possible drug interaction with traditional medicines.

Keywords: Furanocoumarin, Crude drug, Traditional prescription, Cytochrome P450 3A, Inhibition
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