title: An ex vivo approach to botanical-drug interactions: a proof of concept study.
abstract: BACKGROUND
  Botanical medicines are frequently used in combination with therapeutic drugs, imposing a risk for harmful botanical-drug interactions (BDIs). Among the existing BDI evaluation methods, clinical studies are the most desirable, but due to their expense and protracted time-line for completion, conventional in vitro methodologies remain the most frequently used BDI assessment tools. However, many predictions generated from in vitro studies are inconsistent with clinical findings. Accordingly, the present study aimed to develop a novel ex vivo approach for BDI assessment and expand the safety evaluation methodology in applied ethnopharmacological research.
  
  
  METHODS
  This approach differs from conventional in vitro methods in that rather than botanical extracts or individual phytochemicals being prepared in artificial buffers, human plasma/serum collected from a limited number of subjects administered botanical supplements was utilized to assess BDIs. To validate the methodology, human plasma/serum samples collected from healthy subjects administered either milk thistle or goldenseal extracts were utilized in incubation studies to determine their potential inhibitory effects on CYP2C9 and CYP3A4/5, respectively. Silybin A and B, two principal milk thistle phytochemicals, and hydrastine and berberine, the purported active constituents in goldenseal, were evaluated in both phosphate buffer and human plasma based in vitro incubation systems.
  
  
  RESULTS
  Ex vivo study results were consistent with formal clinical study findings for the effect of milk thistle on the disposition of tolbutamide, a CYP2C9 substrate, and for goldenseal׳s influence on the pharmacokinetics of midazolam, a widely accepted CYP3A4/5 substrate. Compared to conventional in vitro BDI methodologies of assessment, the introduction of human plasma into the in vitro study model changed the observed inhibitory effect of silybin A, silybin B and hydrastine and berberine on CYP2C9 and CYP3A4/5, respectively, results which more closely mirrored those generated in clinical study.
  
  
  CONCLUSIONS
  Data from conventional buffer-based in vitro studies were less predictive than the ex vivo assessments. Thus, this novel ex vivo approach may be more effective at predicting clinically relevant BDIs than conventional in vitro methods.
authors.affiliation: Department of Clinical, Social and Administrative Sciences, University of Michigan College of Pharmacy, Ann Arbor, Michigan, USA.
authors.forename: Xinwen
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Clinical, Social and Administrative Sciences, University of Michigan College of Pharmacy, Ann Arbor, Michigan, USA.
authors.forename: Hao-Jie
authors.initials: HJ
authors.lastname: Zhu
authors.affiliation: Department of Pharmacotherapy and Translational Research, University of Florida, Gainesville, Florida, USA; Center for Pharmacogenomics, University of Florida, Gainesville, Florida, USA.
authors.forename: Juliana
authors.initials: J
authors.lastname: Munoz
authors.affiliation: Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA.
authors.forename: Bill J
authors.initials: BJ
authors.lastname: Gurley
authors.affiliation: Department of Pharmacotherapy and Translational Research, University of Florida, Gainesville, Florida, USA; Center for Pharmacogenomics, University of Florida, Gainesville, Florida, USA. Electronic address: jmarkowitz@cop.ufl.edu.
authors.forename: John S
authors.initials: JS
authors.lastname: Markowitz
mesh_terms: D000328:Adult; D044182:Benzylisoquinolines / Q000097:blood; D001599:Berberine / Q000097:blood; D065729:Cytochrome P-450 CYP2C9 / Q000378:metabolism; D051544:Cytochrome P-450 CYP3A / Q000378:metabolism; D005260:Female; D041743:Herb-Drug Interactions; D006801:Humans; D039321:Hydrastis; D008297:Male; D008862:Microsomes, Liver / Q000378:metabolism; D008874:Midazolam / Q000494:pharmacology*; D020944:Silybum marianum; D010936:Plant Extracts / Q000494:pharmacology*; D000077385:Silybin; D012838:Silymarin / Q000097:blood; D014044:Tolbutamide / Q000494:pharmacology*; D055815:Young Adult
chemical_list: D044182:Benzylisoquinolines; D010936:Plant Extracts; D012838:Silymarin; D001599:Berberine; D000077385:Silybin; C013024:hydrastine; D014044:Tolbutamide; C450260:CYP2C9 protein, human; D065729:Cytochrome P-450 CYP2C9; C510164:CYP3A5 protein, human; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D008874:Midazolam
keywords: Botanical–drug interactions; Cytochrome P450s; Ex-vivo model; Goldenseal; Milk thistle