Long-term pharmacokinetics of an extract of isoflavones from red clover (Trifolium pratense).
OBJECTIVE
To study the pharmacokinetics of isoflavones from red clover (Trifolium pratense) after long-term administration as a once-daily dietary supplementary.


METHODS
Fourteen (14) subjects who had been consuming a low-isoflavone diet for 2 weeks were given an oral dose of two isoflavone tablets (approximately 80 mg of total isoflavones) daily for 2 weeks and appeared for a study day at 9:00 AM after an overnight fast on the day that they were to receive the last dose. Plasma samples were collected for a 48-hour period after the last dose. Plasma isoflavones were assayed by high-performance liquid chromatography (HPLC).


RESULTS
Trough plasma levels were significantly higher for daidzein and genistein after long-term dosing than levels taken prior to the commencement of the study and plasma levels of isoflavones after long-term dosing were in the range previously reported in populations that consume an isoflavone-rich diet. The plasma half-lives observed after long-term administration were, in most cases, consistent with once-daily administration.


CONCLUSIONS
Isoflavones have pharmacokinetic characteristics that suggest that once-daily administration is adequate when they are administered long-term as dietary supplements.
Howes
Jan
J
Department of Obstetrics and Gynaecology, St George Hospital/UNSW, Kogarah, New South Wales, Australia.
Waring
Mark
M
Huang
Li
L
Howes
Laurence G
LG
D000328:Adult; D002851:Chromatography, High Pressure Liquid; D019587:Dietary Supplements; D004305:Dose-Response Relationship, Drug; D005260:Female; D019833:Genistein / Q000493:pharmacokinetics; D006801:Humans; D007529:Isoflavones / Q000097:blood / Q000493:pharmacokinetics* / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D010936:Plant Extracts / Q000097:blood / Q000493:pharmacokinetics* / Q000627:therapeutic use; D013997:Time Factors; D029921:Trifolium
D007529:Isoflavones; D010936:Plant Extracts; C007768:formononetin; C004742:daidzein; D019833:Genistein; C004541:biochanin A