Plant sterols are well known cholesterol-lowering agents, and their high dietary intake is associated with positive health effects. As various sterols and sterol conjugates have differences in their bioactivities and metabolism, it is essential to know the sterol profile found in foods, not merely their total amount. Therefore, the aim of this study was to demonstrate the shortcomings of the currently used methodologies in sterol analysis, and to show possibilities enabled by modern instrumentation and use of enzymes in sample preparation. Official and other commonly applied procedures are based on hydrolysis of sterols from their conjugates and subsequent analysis of the liberated free sterols by GC. This approach has the disadvantage of simultaneously losing the information on the compounds (fatty acids, phenolic acids or sugars) conjugated to sterols. Additionally, if acid hydrolysis is included, some less stabile sterols are isomerized or degraded. Our recent studies demonstrate that that applying modern analytical techniques, such as liquid chromatography combined with high-resolution mass spectrometry (HR-MSMS) enables identification of the true sterol profiles in foods. Alternatively, if such instrumentation is not available, correct sterol profiles can be achieved after an enzymatic pretreatment, which does not cause isomerization or degradation of sterols. Cucurbitaceae family plants, for example are particularly rich in ?7-sterols that are isomerized or degraded during acid hydrolysis. When acid hydrolysis is replaced with an enzymatic hydrolysis, even more than half the sterols are identified differently, indicating that acid hydrolysis causes significant falsifications in sterol profiles. As enzymes capable of hydrolyzing glycosylated sterols have only recently been identified, the enzymatic alternative has not earlier been available. Furthermore, sensitivity of HR-MSMS allows identification of new sterols and their conjugates that have not been detected earlier. These data demonstrate that further analytical work is needed to reveal true sterol contents and profiles in plant foods.

Sterols in plant foods: New revelations enabled by developments in analytical methods

248th National Meeting (2014)

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