Oxysterols (oxidized derivatives of cholesterol an phytosterols) can be generated in the human organism through different oxidation processes, some requiring enzymes.Furthermore, oxysterols are also present in food due to lipid oxidation reactions caused by heating treatments, contact with oxygen, exposure to sunlight, etc., and they could be absorbed from the diet, at different rates depending on their side chain lenght.In the organism, oxysterols can follow different routes: secreted into the intestinal lumen, esterified and distributed by lipoproteins to different tissues or degraded, maily in the liver. Cholesterol oxidation products (COPs) have shown citotoxicity, apoptotic and pro-inflammatory effects and they have also been linked with chronic diseases including atherosclerotic and neurodegenerative processess. In the case of phytosterols oxidation products (POPs), the evidences for toxic effects need more research. Nevertheless, current knowledge suggest their relation to cytotoxic and proapoptotic effects, although at higher concentrations than COPs.Recently, new beneficial biological activities of oxysterols are being under research. Whereas COPs are associated with cholesterol homeostasis mediated by different mechanisms, the implication of POPs is not clear yet.Available literature on sources of oxysterols in the organism, metabolism, toxicity and potential benefitial effects of these compounds are reviewed in this paper.2

Cholesterol and phytosterols can suffer oxidation under heating conditions to give Sterol Oxidation Products (SOPs), known by their toxic effects. This paper studied the degradation of cholesterol and three plant sterols during a 360 min heating treatment (180ºC). The formation and further degradation of SOPs was also analyzed by GC-MS.Results revealed a sterol susceptibility to degradation according to the following decreasing order: campesterol ≈ β-sitosterol ≥ stigmasterol > cholesterol. Their degradation curve fit (R 2 = 0.907 -0.979) a logarithmic model. Sterol Oxidation Products increased their concentration during the first 5-10 min and thereafter, their degradation rate was higher than their formation rate, resulting in a decrease over time. Irrespective of the sterol from which they had derived, 7-keto derivatives presented the highest levels throughout the entire process, and also SOPs with the same type of oxidation followed a similar degradation pattern (R = 0.90-0.99).