Free sterols and steryl glycosides in sunflower seeds with high phytosterol contents

Abstract

In this paper, the distribution of sterol compounds has been analyzed in 10 samples of new sunflower seeds with high contents of phytosterols. The sunflower seeds were first extracted with hexane and the residual oil was then extracted with a mixture of chloroform: methanol (2:1). Also, the lipids from the defatted seeds and from the total seeds were analyzed after acid hydrolysis and subsequent extraction. The evaluation of the sterol compounds was performed by high temperature GC directly in the sylanized unsaponifiable matter using ¿-cholestanol as internal standard. This procedure allows for the quantification of free sterols and steryl glycosides in the oils extracted by hexane and chloroform: methanol (2:1) while in defatted meal and total seeds, they are determined as free sterols. The main characteristics of the fractions extracted by hexane were a variable oil content (19.8 - 38.7%) with medium unsaponifiable matter (1.4 - 4.8%), The major sterol compounds in the oil extracted by hexane were free sterols (4034 - 8507 mg/kg) while steryl glycosides were in low concentrations (80 -280 mg/kg). On the contrary, the fraction extracted by chloroform: methanol had low lipid content (2.2 -6-7 %) with a high unsaponifiable matter (12.6 ¿ 28.2%). The major sterol compounds in this fraction were steryl glycosides (9711 ¿ 22514 mg/kg). Finally, a third of the total sterols remained in the meal after the extraction of edible oil by hexane.