Pharmacokinetics of the soybean isoflavone daidzein in its aglycone and glucoside form: a randomized, double-blind, crossover study.

Abstract

BACKGROUND:

There are conflicting results in the literature on the bioavailability of isoflavones in the aglycone and the glucoside forms.

OBJECTIVE:

The objective was to investigate the pharmacokinetics of the soy isoflavone daidzein (DAI) on oral administration of both the aglycone and glucoside form in a human intervention study. In addition, the pharmacokinetics of the bacterial and oxidative metabolites of DAI was assessed.

DESIGN:

Seven German men aged 22-30 y participated in a randomized, double-blind study in a crossover design. After ingestion of pure DAI or pure daidzein-7-O-beta-d-glucoside (DG) (1 mg DAI aglycone equivalent/kg body weight), blood samples were drawn before isoflavone administration and 1, 2, 3, 4.5, 6, 8, 10, 12, 24, and 48 h after the dose. Urine was collected before and 0-6, 6-12, and 12-24 h after the intake of the isoflavones. The concentrations of DAI and its major bacterial and oxidative metabolites in plasma and urine were measured with isotope dilution capillary gas chromatography-mass spectrometry.

RESULTS:

The systemic bioavailability (area under the curve; AUC(inf)), the maximal plasma concentration (C(max)), and the cumulative recovery of DAI in urine after administration of DG were 3-6 times greater than after the ingestion of DAI. Except for equol, which was formed by only one volunteer, all other quantified metabolites exhibited 2-12 times greater AUC(inf), C(max), and urinary recoveries after consumption of DG.

CONCLUSION:

Our results show that DG exhibits a greater bioavailability than its aglycone when ingested in an isolated form.

• Authors: Corinna E Rüfer, Achim Bub, Jutta Möseneder, Peter Winterhalter, Melanie Stürtz, Sabine E Kulling
• Journal: The American journal of clinical nutrition (Am J Clin Nutr) Vol. 87 Issue 5 Pg. 1314-23 (May 2008) ISSN: 1938-3207 [Electronic] United States
• PMID: 18469255 (Publication Type: Journal Article, Randomized Controlled Trial, Research Support, Non-U.S. Gov't)

Chemical References

• 4',7-dihydroxy-3,4-dihydroisoflavone
• Isoflavones
• Equol
• daidzein

Topics

• Administration, Oral
• Adult
• Area Under Curve
• Biological Availability
• Cross-Over Studies
• Double-Blind Method
• Equol
• Gas Chromatography-Mass Spectrometry (methods)
• Humans
• Intestinal Absorption (drug effects)
• Isoflavones (blood, chemistry, pharmacokinetics, urine)
• Male
• Soybeans (chemistry)