Analysis of steryl glucosides in foods and dietary supplements by solid-phase extraction and gas chromatography

A method to quantify beta-sitosterol (BSS) and beta-sitosteryl glucoside (BSSG) in dietary supplements containing added BSS and BSSG was developed and also validated for the analysis of naturally occurring free and esterified sterols and steryl glucosides in foods. Steryl glucosides were extracted with hexane-diethyl ether (1 : 1, v/v) after the alkaline saponification of a powdered supplement or of total lipid extracts of whole wheat flour, granola bars, soybeans, flaxseed, dried figs, peanut butter, lyophilized mixed vegetables, almonds, pine nuts and a diet homogenate. An oil-based supplement was analyzed directly. Steryl glucosides were isolated by solid-phase extraction, derivatized and quantified as trimethylsilyl ethers using capillary gas chromatography (GC) with a 5% diphenyl-95% dimethylpolysiloxane column. Recovery studies using a commercially available mixed steryl glucoside standard and gas chromatography-mass spectrometry (GC-MS) analyses validated the method. Approximately 2-36 mg/100 g (9-37%) of total sitosterol, campesterol and stigmasterol in the foods was contributed by the glucosides.