title: In-vitro and in-vivo metabolic studies of the candidate chemopreventative pentamethylchromanol using liquid chromatography/tandem mass spectrometry.
abstract: OBJECTIVE
  This study focuses on the in-vitro metabolic profiles of pentamethylchromanol in human, rat, dog and non-human primates, and characterizes the associated metabolic kinetics and specific human isozymes responsible for metabolism. Additional investigations compare in-vitro data with in-vivo metabolic data from rats and dogs.
  
  
  METHODS
  In-vitro metabolites were generated from commercially available microsomes, S9 fractions and cytochrome P450 isozymes. Reaction mixtures were analysed using liquid chromatography/tandem mass spectrometry for metabolite identification, stability, phenotyping and kinetic profiles. Plasma samples were collected from 28-day toxicology studies in rats and dogs, and analysed using the same methodology as for the identification of in-vitro metabolites.
  
  
  RESULTS
  Samples from in-vitro experiments produced a total of eight identified metabolites while five were observed in the in-vivo samples. Kinetic analysis of metabolites in human microsomes generated Michaelis constants (K(M)) ranging from 10.9 to 104.9 mum. Pentamethylchromanol metabolic stability varied by species and multiple isozymes were identified for the observed biotransformation pathways. Pentamethylchromanol is susceptible to multiple metabolic pathways and differential metabolic stability, which is species dependent.
  
  
  CONCLUSIONS
  In-vitro metabolism was not a strong predictor of in-vivo metabolism for the samples assays but showed glucuronidation and sulfation as common biotransformation pathways.
authors.affiliation: Toxicology and Bioanalytical Science Department, Southern Research Institute, Birmingham, AL 35205, USA. gorman@southernresearch.org
authors.forename: Gregory S
authors.initials: GS
authors.lastname: Gorman
authors.forename: Lori
authors.initials: L
authors.lastname: Coward
authors.forename: Corenna
authors.initials: C
authors.lastname: Kerstner-Wood
authors.forename: Lea
authors.initials: L
authors.lastname: Freeman
authors.forename: Charles D
authors.initials: CD
authors.lastname: Hebert
authors.forename: Izet M
authors.initials: IM
authors.lastname: Kapetanovic
mesh_terms: D000818:Animals; D002839:Chromans / Q000493:pharmacokinetics*; D002853:Chromatography, Liquid / Q000379:methods*; D004285:Dogs; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D008658:Inactivation, Metabolic; D007527:Isoenzymes / Q000378:metabolism; D008297:Male; D008862:Microsomes, Liver / Q000378:metabolism; D011323:Primates / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013045:Species Specificity; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D002839:Chromans; D007527:Isoenzymes; C029141:2,2,5,7,8-pentamethyl-1-hydroxychroman