A sustainable approach for the extraction of cholesterol-lowering compounds from an olive by-product based on CO(2)-expanded ethyl acetate

Olive (Olea europaea) processing results in large amounts of by-products that contain valuable molecules such as phenolic compounds and phytosterols. These molecules have demonstrated to reduce blood cholesterol levels. This work proposes the development of a method to obtain simultaneously phenolic compounds and phytosterols from the olive stone using CO(2)-expanded liquid extraction. Hansen solubility parameters were employed for the theoretical prediction of the most suitable bio-based solvent to extract target compounds. The Box–Behnken experimental design was employed to select the optimal conditions of pressure (8–25 MPa), the molar fraction of CO(2) in ethyl acetate (0.15–0.55), and the temperature (40–80 °C). Extracts showing the highest and the lowest reductions of micellar cholesterol solubility capacity were analyzed by gas chromatography coupled to mass spectrometry to find out the compounds responsible for this activity. Different phenolic compounds, free fatty acids, and phytosterols were identified in the extracts. β-Sitosterol and, especially, tyrosol and hydroxytyrosol were the compounds that primarily contributed to the reduction of micellar cholesterol solubility capacity. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s00216-019-01970-4) contains supplementary material, which is available to authorized users.