The extracts of valuable vegetable oils containing a number of minor components (sterols, tocopherols, carotenoids, etc.) have added value as pharmaceuticals and food additives. Beta-sitosterol (BS) as minor component of vegetable oil was extracted from ground seeds of sea buckthorn with supercritical CO(2) at pressures 15-60 MPa and temperatures 40-80 degrees C. The changes in the BS content in extract in the course of the extraction were evaluated using HPLC and described in terms of phase equilibrium. It was shown that the separation factors used in counter-current fractionation of oils apply also to the initial period of oil extraction from ground seeds. The equilibrium compositions of a model BS + trilinolein + CO(2) mixture were calculated using SRK and PSRK equations of state. The BS to triacylglycerol separation factor, ranging from 1.0 to 3.1, was correlated with CO(2) density. (C) 2010 Elsevier Ltd. All rights reserved.