QUANTITATIVE-DETERMINATION OF LIGNANS AND ISOFLAVONOIDS IN PLASMA OF OMNIVOROUS AND VEGETARIAN WOMEN BY ISOTOPE-DILUTION GAS-CHROMATOGRAPHYMASS-SPECTROMETRY

The first quantitative method for the determination of both lignans an d isoflavonoid phytoestrogens in plasma is presented. Using ion-exchan ge chromatography the diphenols are separated into two fractions 1) th e biologically ''active'' fraction containing the free compounds + mon o- and disulfates and 2) the biologically ''inactive'' fraction contai ning the mono- and diglucuronides and the sulfoglucuronides. After hyd rolysis the fractions are further purified by solid phase extraction a nd ion exchange chromatography. Losses during the complete procedure a re corrected for using radioactive estrogen conjugates during the firs t steps and later by adding deuterated internal standards of all compo unds measured (matairesinol, enterodiol, enterolactone, daidzein, O-de smethylangolensin, equol, and genistein). The final determination is c arried out by isotope dilution gas chromatography-mass spectrometry in the selected ion monitoring mode (GC/MS/SIM). The diphenols may be me asured at concentrations as low as 0.2 to 1.0 nmol/l. Results of plasm a analyses of all compounds in 27 pre- and postmenopausal omnivorous a nd vegetarian women are presented for the first time. The most importa nt findings are that the free+sulfate fraction is low for genistein (3 .8% of total), but as much as 21-25% of enterolactone and enterodiol o ccurs in this fraction. A good correlation between plasma and urine va lues was found. Total concentrations of individual compounds vary grea tly between the subjects (from pmol/l to mumol/l), the vegetarians hav ing higher values, particularly one vegan subject. The highest total e nterolactone concentration value exceeded 1 mumol/l. It is concluded t hat a highly specific method for the assay of 3 lignans and 4 isoflavo noids in plasma has been developed. This method will be useful in futu re studies of lignan and isoflavonoid metabolism..