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ARS Home » Southeast Area » Little Rock, Arkansas » Microbiome and Metabolism Research Unit » Research » Publications at this Location » Publication #151418
Title: THE USE OF ENZYMATIC HYDROLYSIS OF SOY ISOFLAVONE CONJUGATES MAY UNDERESTIMATE TISSUE CONCENTRATIONS

Author
item LALY, MYRIAM - UAMS
item CHANG, HEBRON - ACNC
item HARRISON, MEDODY - ACNC
item FANG, NIANBAI - UAMS
item Prior, Ronald
item RONIS, MARTIN - UAMS
item BADGER, THOMAS - 6251-10-00

Submitted to: Journal of Federation of American Societies for Experimental Biology
Publication Type: Abstract Only
Publication Acceptance Date: 1/10/2003
Publication Date: 3/17/2003
Citation: LALY, M., CHANG, H., HARRISON, M., FANG, N., PRIOR, R.L., RONIS, M.J., BADGER, T.M. THE USE OF ENZYMATIC HYDROLYSIS OF SOY ISOFLAVONE CONJUGATES MAY UNDERESTIMATE TISSUE CONCENTRATIONS. JOURNAL OF FEDERATION OF AMERICAN SOCIETIES FOR EXPERIMENTAL BIOLOGY. 2003. v. 17(5). p. A333. Abstract No. 203.6.

Interpretive Summary: Diet contains factors (other than nutrients such as vitamins, minerals, etc) that influence health. Most of these factors are in the plant foods we consume and these are called phytochemicals. Knowing the identity and concentrations of these phytochemicals in organs is essential to understanding which foods and the level of dietary intake required to promote good health. It is, therefore, necessary to have techniques that allow for accurate measurement of phytochemicals in tissues. Isoflavones are present in soybeans in high concentrations and belong to a class of phytochemicals that are known to promote health. Isoflavones are present in the blood and urine in a complex molecular. Current techniques require breaking-up these complex molecules to release the individual isolfavones, called aglycones, in order to measure their concentrations in blood and urine. This study compared two procedures (enzymatic hydrolysis and acid hydrolysis) to release aglycones for measure in tissues. In the liver, acid hydrolysis released significantly more aglycone than enzymatic digestion. Although the absolute concentrations depended on many factors (consumption, post-absorption time, etc), the total of the individual isoflavones, genistein, daidzein and their metabolites were in the low micromolar concentrations and were routinely 20% to 60% lower in samples treated with enzymes than in acid hydrolyzed samples. These data indicate that factors in tissues may reduce the effectiveness of the specific enzymes commonly used to hydrolyze isoflavone conjugates, even after conditions are optimized. This would underestimate the tissue concentrations by as much as 60% in some cases. Future studies will employ acid hydrolysis to assess the tissue concentrations of isoflavones after consuming soy foods.

Technical Abstract: Knowing the identity and concentrations of phytochemicals thought to modulate cellular functions in target tissues that affect health outcomes is essential. Bioavailability of isoflavones has been routinely studied by assessing the aglycones released upon enzymatic hydrolysis of glucuronide and sulfate conjugates in the serum and urine. We compared enzymatic hydrolysis (using Helix pomatia [HP], beta-glucuronidases, sulfatases and specific inhibitors) with acid hydrolysis in several tissues in rats fed AIN-93G diets made with soy protein isolate using LC/MS. In the liver, acid hydolysis released significantly more aglycone than enzymatic digestion (P<0.05). Although the absolute concentrations depended on many factors (consumption, post-absorption time, etc), the total genistein, daidzein and their metabolites were in the low micromolar concentrations and were routinely 20% to 60% lower in samples treated with enzymes than in acid hydrolyzed samples. These data indicate that factors in tissues may reduce the activities of beta-glucuronidases and sulfatases commonly used to hydrolyze isoflavone conjugates, even after conditions are optimized. This would underestimate the tissue concentrations by as much as 60% in some cases.