Submitted on May 16, 2008
Revised on June 23, 2008
Accepted on June 27, 2008
Structural analysis of novel bioactive acylated steryl glucosides (ASGs) in Pre-germinated brown rice bran
Seigo Usuki, Toshio Ariga, Somsankar Dasgupta, Takeshi Kasama, Keiko Morikawa, Shota Nonaka, Yasuhide Okuhara, Mitsuo Kise, and Robert K. Yu
Institute of Molecular Medicine and Genetics, Medical College of Georgia, Augusta, GA 30912-2697
Corresponding Author: ryu{at}mcg.edu
Previous studies from our laboratory indicated that pre-germinated brown rice (PR) contained certain unknown bioactive lipids that activated two enzymes related to diabetes: Na+/K+ATPase and homocysteine thiolactonase (HTase). In this paper, we report on the isolation and structural characterization of the activator lipids from PR bran as acylated steryl glucosides (ASGs). The activator-lipid was isolated by silica-gel column chromatography, and its chemical structure was determined by nuclear-magnetic resonance spectrometry (NMR), gas chromatography/mass spectrometry (GC/MS), and tandem mass spectrometry (MS/MS). We demonstrated that the bioactive component consists of a mixture of acylated steryl--glucosides. 8-cholesterol and 2-hydroxyl stearic acid were identified as constituents of ASGs. The steryl glucosides (SGs) subsequent to alkaline hydrolysis lost this enzyme activator activity. Soybean derived ASGs (S-ASGs) were not active This activity may be quite peculiar to PR-derived derived ASGs. Our findings suggest that the molecular species of ASG may play an important contributing role in the anti-diabetic properties of a PR diet.
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