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Title: HYDROLYSIS OF NATURAL PHYTOSTEROL CONJUGATES BY MAMMALIAN DIGESTIVE ENZYMES

Author
item Moreau, Robert
item Powell, Michael
item Hicks, Kevin

Submitted to: Meeting Abstract
Publication Type: Other
Publication Acceptance Date: 4/2/2004
Publication Date: 4/4/2004
Citation: Moreau, R.A., Powell, M.J., Hicks, K.B. 2004. Hydrolysis of natural phytosterol conjugates by mammalian digestive enzymes. Meeting Abstract. 95th AOCS Annual Meeting and Expo, Cincinnati, OH, May 9-12, 2004, Session Bio-P, Poster 4.

Interpretive Summary:

Technical Abstract: All fruits, vegetables and grains contain phytosterols. Numerous clinical studies have documented that phytosterols have a significant positive effect for reducing LDL-cholesterol levels and thereby reducing the risk of cardiovascular disease. Dietary phytosterols include fifteen common types of sterol molecules that occur either in the 'free' (unesterified) form or as conjugates. Most experts believe that the cholesterol-lowering mechanism of phytosterols requires that they be in their 'free' form. The four common phytosteryl conjugates are: a) fatty acyl esters, b) hydroxycinnamate esters, c) steryl glucosides, and d) fatty acylated steryl glucosides. This study was undertaken to investigate the ability of mammalian digestive enzymes (cholesterol esterase and pancreatin, a mixture of pancreatic enzymes) and KOH to hydrolyze the four common phytosterol conjugates. Phytosteryl fatty acyl esters were hydrolyzed at a moderate rate by both enzymes. Hydroxycinnamate esters (sitostanyl ferulate and oryzanol) were hydrolyzed at a moderate rate by cholesterol esterase and at a low rate by pancreatin. Cholesterol esterase had no effect on either of the glucosides. Pancreatin had no effect on steryl glucoside but it did hydrolyze the fatty acyl moiety of fatty acylated steryl glucoside, converting it to steryl glucoside. The rates of hydrolysis of phytosteryl esters by base (saponification) were also studied and it was found that conditions commonly used for the saponification of acyl lipids (1.5 N methanolic KOH, 30 min at 70º C), resulted in a nearly 100% hydrolysis of triacylglycerols but only about 35-45% hydrolysis of the phytosteryl fatty acyl esters or phytosteryl hydroxycinnamate esters.