Amounts and variation in grapefruit juice of the main components causing grapefruit-drug interaction

J Chromatogr B Biomed Sci Appl. 2000 May 12;741(2):195-203. doi: 10.1016/s0378-4347(00)00104-3.


A method for the determination of three furocoumarins containing two new chemicals (GF-I-1 and GF-I-4) in commercially available grapefruit juice and grapefruit itself was developed using high-performance liquid chromatography (HPLC). These components isolated from grapefruit juice have 5-geranyloxyfurocoumarin dimer structures showing extremely high affinities for a form of cytochrome P450 (CYP3A4). Considerable differences were observed on the contents among commercial brands and also batches. The contents were determined to be 321.4+/-95.2 ng/ml GF-I-1, 5641.2+/-1538.1 ng/ml GF-I-2 and 296.3+/-84.9 ng/ml GF-I-4 in twenty-eight white grapefruit juices. These chemicals were not detected in beverages from orange, apple, grape and tangerine, except that trace amount of GF-I-2 and GF-I-4 were found in lemon juice. The average levels of these furocoumarins were lower in the juice from red grapefruit than a white one. The highest level of these components were found in the fruit meat.

MeSH terms

  • Beverages / analysis*
  • Calibration
  • Chromatography, High Pressure Liquid
  • Citrus*
  • Coumarins / analysis*
  • Coumarins / metabolism
  • Cytochrome P-450 CYP3A
  • Cytochrome P-450 Enzyme System / metabolism
  • Food-Drug Interactions*
  • Mass Spectrometry
  • Mixed Function Oxygenases / metabolism
  • Reproducibility of Results
  • Substrate Specificity


  • Coumarins
  • GF I-1
  • GF I-4
  • Cytochrome P-450 Enzyme System
  • Mixed Function Oxygenases
  • CYP3A protein, human
  • Cytochrome P-450 CYP3A
  • CYP3A4 protein, human