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Journal of Lipid Research, Vol. 49, 2188-2196, October 2008
Copyright © 2008 by American Society for Biochemistry and Molecular Biology

Structural analysis of novel bioactive acylated steryl glucosides in pre-germinated brown rice bran¹

Seigo Usuki^*, Toshio Ariga^*, Somsankar Dasgupta^*, Takeshi Kasama, Keiko Morikawa, Shota Nonaka, Yasuhide Okuhara, Mitsuo Kise and Robert K. Yu^2,*

^* Institute of Molecular Medicine and Genetics, Medical College of Georgia, Augusta, GA 30912
Instrumental Analysis Research Center for Life Science, Tokyo Medical and Dental University, Tokyo, Japan 113-8510
FANCL Research Institute, FANCL Corporation, Yokohama, Japan 244-0806

¹ Glycosphingolipid nomenclature is based on that recommended by the IUPAC-IUB Commission on Biochemical Nomenclature.

This work was supported by a project grant from FANCL.

Published, JLR Papers in Press, June 27, 2008.

² To whom correspondence should be addressed. e-mail: 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. 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 NMR, GC-MS, and tandem mass spectrometry. We demonstrated that the bioactive component consists of a mixture of acylated steryl β-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 were not active. This activity may be quite peculiar to PR-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.

Supplementary key words diabetes • steryl glucoside • homocysteine • glycolipids • ATPase

Abbreviations: ASG, acylated steryl glucoside; BR, brown rice; GABA, -aminobutyric acid; HPTLC, high-performance thin-layer chromatography; HT, homocysteine-thiolactone; HTase, homocysteine-thiolactonase; LC-MS, liquid chromatography-mass spectrometry; MS/MS, tandem mass spectrometry; PR, pre-germinated brown rice; PVDF, polyvinylidene difluoride; SG, steryl glucoside; SIMS, secondary-ion mass spectrometry; S-AGS, soybean-derived acylated steryl glucoside; STZ, streptozotocin; TL_B, total lipid fraction from brown rice bran; TL_P, total lipid fraction from pre-germinated brown rice bran

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