Affiliations: Department of Nutritional Science, Faculty of Applied
Bioscience, Tokyo University of Agriculture, 1-1-1 Sakuragaoka, Setagaya-ku,
Tokyo 156-8502, Japan | Institute for Preventive Medicine, Nutrition and
Cancer, Folkh\"alsan Research Center, Division of Clinical Chemistry, PB 60,
FIN-00014, University of Helsinki, Helsinki, Finland
Note: [] Department of Nutritional Science, Faculty of Applied
Bioscience, Tokyo University of Agriculture, 1-1-1 Sakuragaoka, Setagaya-ku,
Tokyo 156-8502, Japan. Tel.: +81 3 5477 2444; Fax: +81 3 5477 2658; E-mail:
[email protected][email protected]
Abstract: Time-resolved fluoroimmunoassays (TR-FIA), with europium labeled
phytoestrogens as tracers, were developed for the quantitative measurement of
genistein, daidzein and enterolactone in plasma and urine for the purpose of
screening large populations and studies on possible correlation between the
values in biological fluids and the risk of western diseases. The mean values of the three phytoestrogens in plasma as determined
by TR-FIA were similar to those obtained by gas chromatography-mass
spectrometry (GC-MS). The urinary excretion levels of total individual
phytoestrogens were higher than those obtained by GC-MS, with the exception of
the daidzein values. However, comparing the assay results obtained by the
present method and those obtained by GC-MS, a strong correlation was evident
(r=0.87-0.99, p<0.001). We measured plasma levels of genistein, daidzein and enterolactone
in 111 healthy Japanese women. The mean and median levels of genistein were
406.8 and 306.3 nmol/l, respectively, and those of daidzein were 118.4 and
76.8 nmol/l, respectively. These levels are higher than those reported for
Americans and Western Europeans. Isoflavone intake as calculated from dietary
records (genistein: mean, 86.5 \mumol/day and daidzein:
mean, 57.4 \mumol/day) was correlated with the plasma
concentrations observed (genistein: r=0.287, p<0.01 and
daidzein: r=0.313, p<0.01). Plasma enterolactone levels were
low in Japanese women (mean, about 10 nmol/l). The levels of urinary excretions
of genistein, daidzein were also measured and it was found that, in the
majority, the levels ranged between 5--25 and 5--50
\mumol/24 h, respectively. In contrast, healthy Finnish
women showed very low values of isoflavones (below 10~nmol/l in plasma
(n=87) and below 0.6 \mumol/24~h in urine
(n=126) for both compounds) and high levels of enterolactone
in both plasma and urine (plasma: mean, 25~nmol/l and urine: majority range,
1--7 \mumol/24 h).
Journal: BioFactors, vol. 12, no. 1-4, pp. 217-225, 2000
