Analysis of steryl glucosides in rice bran-based fermented food by LC/ESI-MS/MS

Abstract

Steryl glucosides (SGs) and acylated steryl glucosides (ASGs) are phytochemicals found in plant-based foods and are known as bioactive compounds with potential health benefits. These include anti-inflammatory properties, anti-diabetic effects, and modulation of immunoregulatory functions as well as having cholesterol lowering effects. In this study, three major SGs, i.e., glucosides of β-sitosterol, stigmasterol, and campesterol, were synthesized and used as standards for measurement of their contents in rice bran (RB)-based fermented food (FBRA) utilizing Aspergillus oryzae and raw material (RM). The compounds were quantified using liquid chromatography/electrospray ionization-tandem mass spectrometry. It was found that β-sitosteryl glucoside was most abundant among the analyzed glucosides in both samples, and the contents of each SG in FBRA decreased about 35% from those of RM. In contrast to SGs, the contents of ASGs in FBRA increased 1.5-fold during the fermentation process as evidenced by an alkaline hydrolysis. The present results suggest that the FBRA might have greater beneficial effects than the RM, since ASGs have shown to have more potent cholesterol lowering effects and stronger anti-diabetic properties than SGs.

Keywords: Acylated steryl glucoside; Aspergillus oryzae; Fermentation; LC/ESI-MS/MS; Rice bran; Steryl glucoside.