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

A method for the determination of three furocoumarins containing two new ch emicals (GF-I-1 and GF-I-4) in commercially available grapefruit juice and grapefruit itself was developed using high-performance liquid chromatograph y (HPLC). These components isolated from grapefruit juice have 5-geranyloxy furocoumarin 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 determ ined 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 chemic als 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. T he average levels of these furocoumarins were lower in the juice from red g rapefruit than a white one. The highest level of these components were foun d in the fruit meat. (C) 2000 Elsevier Science B.V. All rights reserved.