title: Liquorice, a unique "guide drug" of traditional Chinese medicine: a review of its role in drug interactions.
abstract: BACKGROUND
  Liquorice is the root of Glycyrrhiza uralensis Fisch. or Glycyrrhiza glabra L., Leguminosae. It is a widely used herbal medicine native to southern Europe and parts of Asia and has beneficial applications in both the medicinal and the confectionery sectors. Unlike its usage in Europe, liquorice in traditional Chinese medicine is commonly combined with other herbs in a single prescription, as a unique "guide drug" to enhance the effectiveness of other ingredients, to reduce toxicity, and to improve flavor in almost half of Chinese herbal formulas. A review on phytochemical and pharmacological research to explain this unique "guide" effect is suggested for future investigations.
  
  
  METHODS
  The information was collected from scientific journals, books, and pharmacopeia. The studies about the traditional uses, randomized controlled trials, chemical, pharmacological and pharmacokinetic data related to liquorice-herb/drug interaction or combination were included in the review.
  
  
  RESULTS
  According to recent reports, the "guide" effect of liquorice is partially through components transformed in liquorice-drug interaction; altering enzyme activity of P450 isoforms, as evidenced by induction of model probe substrates; and modulation of drug transporter proteins such as intestinal P-glycoprotein.
  
  
  CONCLUSIONS
  The overview and comparison of traditional uses of liquorice with recent pharmacological studies and randomized controlled trials provide new insights into this ancient drug for future investigations and clinical use, especially in drug combination.
authors.affiliation: College of Traditional Chinese Medicine, Tianjin University of Traditional Chinese Medicine, Tianjin 300193, China; Key Laboratory of Pharmacology of Traditional Chinese Medical Formulae, Ministry of Education, Tianjin 300193, China.
authors.forename: Xiaoying
authors.initials: X
authors.lastname: Wang
authors.forename: Han
authors.initials: H
authors.lastname: Zhang
authors.forename: Lili
authors.initials: L
authors.lastname: Chen
authors.forename: Lihua
authors.initials: L
authors.lastname: Shan
authors.forename: Guanwei
authors.initials: G
authors.lastname: Fan
authors.forename: Xiumei
authors.initials: X
authors.lastname: Gao
mesh_terms: D000818:Animals; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D006035:Glycyrrhiza / Q000009:adverse effects / Q000633:toxicity; D041743:Herb-Drug Interactions; D006801:Humans; D008516:Medicine, Chinese Traditional; D026901:Membrane Transport Proteins / Q000378:metabolism
chemical_list: D026901:Membrane Transport Proteins; D003577:Cytochrome P-450 Enzyme System
keywords: CYP; Cytochrome P450; DGLL; Detoxification; Drug interactions; GA; GZ; HSYA; IC(50); Liquorice; P-glycoprotein; P-gp; TCM; Traditional Chinese medicine; cytochrome; diammonium glycyrrhizinate lipid ligand; glycyrrhetic acid; glycyrrhizin; half maximal inhibitory concentration; hydroxysafflor yellow A; traditional Chinese medicine