Steryl glycosides and acylated steryl glycosides in plant foods reflect unique sterol patterns

Glycosylated plant sterols (steryl glycosides, SG and acylated steryl glycosides, ASG) are minor glycolipids found in a variety of plants at different levels and in different compositions. They have until now been far less studied than other sterol conjugates, though they possess at least the same potential health benefits as free or esterified plant sterols. Additionally, due to the more hydrophilic conjugated part, they may possess further beneficial properties in forming water-soluble structures. We studied the content and sterol profiles of glycosylated sterols in various plant foods to be able to better understand their levels in human diets, as well as to identify sources with high levels and/or unique sterol profile for possible extraction for ingredients. Glycosylated sterols contributed up to almost 60% of total sterols in e.g. potatoes, indicating that they indeed are an important group of sterols in plants. The ratio of ASG and SG varied from 0.4 to 3.6, indicating significant differences in the proportions of these two conjugates in various plants. Furthermore, extremely large differences were observed in the sterol profiles not only between but also within different plants, which indicates that the sterol profile of the glycosylated sterols does not always reflect the total sterol composition in the same plant tissue. Practical applications: Glycosylated sterols have hydrophilic properties owing to the carbohydrate moiety of the conjugate. As a consequence, they could potentially be introduced to water-based functional foods (unlike the hydrophobic free sterols and sterol esters in current applications). Various plant materials or side streams of food processes were shown to be good sources of these glycosylated plant sterols, and could be used as sources for extraction of glycosylated sterols for food ingredients. Furthermore, the detailed compositional information reported here will provide a basis to select also the desired sterol composition for the product. Finally, the data presented in this paper is invaluable for estimating the contribution of different foods as sources of glycosylated sterols in the diet. See commentary by Jimenez-Escrig [p. 615616]