Phytosterols as Functional Compounds and Their Oxidized Derivatives

Plant sterols, also called phytosterols, are plant-derived compounds that structurally and functionally resemble cholesterol in mammals. These compounds are known to lower the total and low-density lipoprotein (LDL-C) fractions of cholesterol in humans. For a number of decades, various food products have been enriched with phytosterols and phytostanols as free compounds, or as their esters with fatty acids. The quality of the raw material, as well as the conditions of food processing and storage, affects the degradation of phytosterols and the formation of the various derivatives. The speed at which they degrade in model systems, as well as in raw materials and food products, is associated with autoxidation and photooxidation reactions. Phytosterol oxidation products (POPs) are derivatives formed during thermo-oxidation of sterols; they then undergo decomposition to volatile compounds and oligomers. The toxic properties of POPs in humans have been demonstrated, and their biological properties are based on literature data. The chemical structure of phytosterols, their biological properties, and their content in food products are presented in this work.