Soy Isoflavones Discussed The Preliminary Metabolism And Pharmacokinetics In The Human Body

The soybeans are our Chinese traditional food, rich in nutrition and wide in agriculture. There are plenty of records on soya diet, from cooked, raw to fermented, handed down from verbal in folk to read in literatures with hundreds of years. However, one of ingredients in soybeans----soy isoflavones, has concentrated interests in research all around the world as typical phtoestrogen, and also other bioactivities invovled. There have been 12 kind of soy isolfavones found and extracted so far, such as 3 aglycones (Daidzein, Genistein and Glycitein) and 9 corresponding glucose-conjugated forms (malonyl-, acetyl- andβ-glucoside configurations), and the latter forms are dominant (98% in total), most of reports informed that glucose-conjugated forms may be deconjugated in vivo. What has happened in the body actually is rather complicated, and the accurate absorptive mechanisms and pathway of metabolism in human body is still under the research. Now, seldom reports on the characters of metabolism of 6 kind of soy isoflavones and one of active metabolites-equol in mainland Chinese are available, comparing various data on other race (Caucasians, Japanese, Thais and Taiwanese) records. For this reason, the purpose of the study was to explore the metabolism characters in Chinese mainland inhabitants. The study was composed of two part as follows,PartⅠ:Establishment and validation of determinative analytical method for the measurement of 6 kind of soy isoflavones and metabolite equol in human plasma and urine by LC-MS/MS.The lower limits of quantitation of 6 SIFs (Daidzin, Daidziein, Genistin, Genistein, Glycitin and Glycitein) were 0.481 pmol·mL^-1, 0.787 pmol·mL^-1, 0.463 pmol·mL^-1, 0.741 pmol·mL^-1, 0.448 pmol·mL^-1 and 0.704 pmol·mL^-1 in plasma, respectively; 4.81 pmol·mL^-1, 7.87 pmol·mL^-1, 4.63 pmol·mL^-1, 7.41 pmol·mL^-1, 4.48 pmol·mL^-1, 7.04 pmol·mL^-1 and Equol 0.826 pmol·mL^-1 in urine, respectively.The calibration curves of 6 kind of soy isoflavones (Daidzin, Daidziein, Genistin, Genistein, Glycitin and Glycitein) were 0.481-1202 pmol·mL^-1,0.787-1969 pmol·mL^-1,0.463-1157 pmol·mL^-1, 0.741-1852 pmol·mL^-1, 0.448-1121 pmol·mL^-1, 0.704-1761 pmol·mL^-1in plasma, respletivily; 4.81-1202 pmol·mL^-1, 7.87-1969 pmol·mL^-1, 4.63-1157 pmol·mL^-1, 7.41-1852 pmol·mL^-1, 4.48-1121 pmol·mL^-1, 7.04-1761 pmol·mL^-1 and equol 2.07- 2066 pmol·mL^-1 in urine, respectively.The methods had been validated rigidly in specificity, linearity, sensitivity, accuracy, precision, recovery and stability. The results reflected all the analytes precisions were within 15% and accuracy were within 85-115% in within- and between batch. There were good linearity for all the calibration curves of each analytes, and the correlation coefficients (r) were all >0.995. The signal to noise ratios were all above 3 in the LLOQ of 7 analytes. The mean extraction recovery for 6 analytes (Daidzin, Daidziein, Genistin, Genistein, Glycitin and Glycitein) was 74.2, 67.4, 71.8, 85.8, 62.7 and 67.7 in plasma, respectively; for 7 analytes (Daidzin, Daidziein, Genistin, Genistein, Glycitin, Glycitein and equol) was 66.8, 68.2, 67.6, 59.3, 53.3, 66.2 and 79.3 in urine, respectively. Plasma and urine samples were stable at room temperature (25℃) for 20h and extracts samples were also stable at auto-sampler (10℃) for 12h.With specificity, sensitivity, rapidity, accuracy and convenience, the determinative quantitation could meet the requirements of the study as reliable and robust analytical method.PartⅡ:A single-dose, opened and randomized design study to evaluate the pharmacokinetics of 6 kind of soy isoflavones in healthy adult Chinese volunteers.13 healthy volunteers (9 female and 4 male) inhabitant in China mainland were recruited, ranging from 25-52 years, resident in Beijing. According to the recommended intake, total soy isoflavones 162.9 mg administrated and the formula was soy isoflavones' glucosides (main contents) and aglucone (micro contents). Plasma and urine collected before (0h) and after oral ingestion in the defined time interval for 6 kind of soy isoflavones and equol determination. Pharmacokinetic parameters were calculated with non-compartment analysis. The results showed that after oral single-dose in Chinese volunteers, the calculated PK parameters included Cmax, Tmax, AUC_0-t and MRT_0-t for 6 kind of soy isoflavones, the glucoside forms had more rapid in absorption and clearance than corresponding aglycone forms, but the exposures were low significantly; both glucoside forms and aglycone forms were eliminated almost totally within 24h. Urinary accumulation excretion almost completed within 48h. Equol producer identification discovered equol non-producers were 23% in total, and demonstrated no significant difference between former analytes (daidzein and Daidzin) and equol. All the urinary accumulation excretions have no correlation with gender, age and BMI for the anaytes. The results inferred that the soy isoflavones as phtosetroge diets supplyment may cause different outcome in individuals with the same amount of soybeans and soya derived foods. The bioactivities of soy isoflvones maybe only bring out in part of people in the way of diets intake and additional supplements. Once or twice a day for administration was satisfied with the PK characters of Chinese people.