Isoflavone Conjugates Are Underestimated in Tissues Using Enzymatic Hydrolysis

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• 作者：Liwei Gu ; Myriam Laly ; Hebron C. Chang ; Ronald L. Prior ; Nianbai Fang ; Martin J. J. Ronis ; and Thomas M. Badger
• 刊名：Journal of Agricultural and Food Chemistry
• 出版年：2005
• 出版时间：August 24, 2005
• 年：2005
• 卷：53
• 期：17
• 页码：6858 - 6863
• 全文大小：151K
• 年卷期：v.53,no.17(August 24, 2005)
• ISSN：1520-5118

文摘

Many health effects of soy foods are attributed to isoflavones. Isoflavones upon absorption presentas free form, glucuronide, and sulfate conjugates in blood, urine, and bile. Little is known about themolecular forms and the relative concentrations of soy isoflavones in target organs. Acid hydrolysisor enzymatic hydrolysis (glucuronidases and sulfatases) was used to study isoflavone contents inthe heart, brain, epididymis, fat, lung, testis, liver, pituitary gland, prostate gland, mammary glands,uterus, and kidney from rats fed diets made with soy protein isolate. The heart had the lowestisoflavone contents (undetectable), and the kidney had the highest (1.8 ± 0.6 nmol/g total genistein;3.0 ± 1.1 nmol/g total daidzein). Acid hydrolysis released 20-60% more aglycon in tissues thanenzymatic digestion (p < 0.05), and both hydrolysis methods gave the same level of isoflavones inserum. Approximately 28-44% of the total isoflavone content within the liver was unconjugatedaglycon, and the remainder was conjugated mainly as glucuronide. The subcellular distribution oftotal isoflavones was 55-60% cytosolic and 13-16% in each of the nuclear, mitochondrial, andmicrosomal fractions. These results demonstrated that (1) soy isoflavones distribute in a wide varietyof tissues as aglycon and conjugates and (2) the concentrations of isoflavone aglycons, which arethought to be the bioactive molecules, are in the 0.2-0.25 nmol/g range, far below the concentrationsrequired for most in vitro effects of genistein or daidzein.Keywords: Isoflavones; daidzein; genistein; tissues