Detection of oxysterols in oxidatively modified low density lipoprotein by MALDI-TOF MS

Authors

  • Masahiro Hasegawa,

    1. Department of Analytical Chemistry, School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo, Japan
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  • Hideki Hakamata,

    Corresponding author
    1. Department of Analytical Chemistry, School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo, Japan
    • Department of Analytical Chemistry, School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, Horinouchi 1432-1, Hachioji, Tokyo 192-0392, Japan Fax: +81-42-676-4570.
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  • Io Matsunaga,

    1. Department of Analytical Chemistry, School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo, Japan
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  • Fumiyo Kusu

    1. Department of Analytical Chemistry, School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo, Japan
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  • Part of this work was presented at the 130th Annual Meeting of the Pharmaceutical Society of Japan March 28-30, 2010 in Okayama, Japan.

Abstract

A simple method for the detection of oxysterols in oxidatively modified LDL (Ox-LDL) has been developed using MALDI-TOF MS. To identify the ion peaks of oxysterols, seven major oxysterols in Ox-LDL (7α-hydroxycholesterol, 7β-hydroxycholesterol, 7-ketocholesterol, 5α,6α-epoxycholesterol, 5β,6β-epoxycholesterol, 25-hydroxychokesterol, (25R)-26-hydroxycholesterol), and cholesta-3,5-dien-7-one were analyzed by MALDI-TOF MS. Among these oxysterols, 7-ketocholesterol, a very abundant oxysterol in Ox-LDL, was found to show a characteristic peak of [M + H]+ at m/z 401. Cholesta-3,5-dien-7-one, which is known as a degradation product of 7-ketocholesterol upon saponification of Ox-LDL, gave a major peak of [M + H]+ at m/z 383. In contrast, other oxysterols showed similar peak patterns at m/z 367 and 385. These results were applied to the analysis of Ox-LDL by MALDI-TOF MS after saponification and hexane-extraction, detecting ion peaks at m/z 367, 383, 385, and 401. This MALDI-TOF MS method has a potential as a simple tool to show the presence of oxysterols in Ox-LDL without derivatization and chromatographic separation.

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