Document Detail

Properties of food folates determined by stability and susceptibility to intestinal pteroylpolyglutamate hydrolase action.
MedLine Citation:
PMID:  9808649     Owner:  NLM     Status:  MEDLINE    
The intestinal absorption of folate occurs at the monoglutamyl level, and an important measure of food folate bioavailability is how much folate from the food reaches the intestinal sites in forms that can readily be absorbed. In the absence of protecting agents, e.g., vitamin C and reduced thiols, many labile folates may be lost during cooking and during residence in the acid-peptic milieu of the stomach. On the other hand, the presence of polyglutamyl folate necessitates the action of intestinal hydrolases, which could be affected by food constituents. In this study, we developed an in vitro assay for the determination of an index of food folate availability. The index of folate availability in this study was defined as that proportion of folate that has been identified as monoglutamyl derivatives after tests for stability and susceptibility to an enzymatic hydrolysis. The index of folate availability varied widely among foods. The highest index was for egg yolk (72.2%), followed by cow's livers (55.7%), orange juice (21. 3%), cabbage (6.0%), lima beans (4.5%) and lettuce (2.9%). Yeast folate had the lowest index (0.3%). The availability indices generated by this study correlate with the indices of the bioavailability of the corresponding food folate observed in earlier studies, R2 = 0.529 (P = 0.068). Additional information is required on the bioavailability of other food products to test the usefulness of this in vitro approach for assessing food folate availability.
E Seyoum; J Selhub
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  The Journal of nutrition     Volume:  128     ISSN:  0022-3166     ISO Abbreviation:  J. Nutr.     Publication Date:  1998 Nov 
Date Detail:
Created Date:  1998-12-07     Completed Date:  1998-12-07     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  0404243     Medline TA:  J Nutr     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1956-60     Citation Subset:  IM    
Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, Boston, MA 02111, USA.
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MeSH Terms
Ascorbic Acid / pharmacology
Biological Availability
Drug Stability
Egg Yolk
Folic Acid / analysis,  chemistry*,  metabolism*
Food Analysis
Hot Temperature
Hydrogen-Ion Concentration
Intestinal Absorption
Intestines / enzymology*
Liver / chemistry
Sulfhydryl Compounds / pharmacology
gamma-Glutamyl Hydrolase / metabolism*
Reg. No./Substance:
0/Sulfhydryl Compounds; 50-81-7/Ascorbic Acid; 59-30-3/Folic Acid; EC Hydrolase

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