Evaluation of cholesterol oxidation in model systems containing fatty acids, moglobin and natural and synthetic antioxidants

Author(s)

Elisângela Serenato Madalozzo

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Engenharia de Alimentos
• Defense date: 2014-05-23

Examining board members

Neura Bragagnolo; Gislaine Chrystina Nogueira; Lilian Regina Barros Mariutti; Monica Roberta Mazalli; Sueli Regina Baggio

• Advisor: Neura Bragagnolo

Abstract

Cholesterol is one of the most important sterols in animal tissue in its free form or as esters. This compound presents an unique behavior in relation to oxidation since it has a double bond between carbons 5 and 6 of the cyclic structure, generating oxidation products, the so called cholesterol oxides (COP's), especially when exposed to high temperature, radical initiators, light, metal or a combination of these factors. Therefore, the aim of this study was to study the impact of different antioxidants (sodium erythorbate, citric acid and bixin) on thermal degradation of cholesterol in model systems in the presence of metals (myoglobin) and fatty acids with different degrees of unsaturation (oleic acid, eicosapentaenoic acid - EPA and palmitic acid) at constant O2 flow (10 ml/min). The effect of antioxidants, pro-oxidant and fatty acids was monitored by the degradation of cholesterol and the consequent formation of COP¿s, by the changes in the fatty acid composition, as well as by the degradation of the antioxidants added to model systems subjected to 130, 160 and 230°C. To evaluate the interaction between cholesterol and the different compounds present in the model systems a Plackett & Burman experimental design was carried out in each temperature. The model system containing cholesterol, bixin, oleic acid and myoglobin (sample 11) showed the highest degradation of cholesterol and concentration of COP¿s. The lowest degradation of cholesterol was observed in sample 1, containing cholesterol, sodium erythorbate, citric acid and myoglobin. At 230°C, the samples that showed the lowest degradation contained cholesterol, sodium erythorbate, citric acid and myoglobin (sample 1) and sodium erythorbate, bixin and palmitic acid (sample 2). Five COP's were identified and quantified in the model systems (7-keto, 7?-OH, 7?-OH, 5,6?-epoxide and 5,6?-epoxide). The COP present in the highest content at 130°C and 160°C was 5,6?-epoxide, and at 230°C, 7-keto. These results demonstrated that a high formation of COP¿s is directly related to a high degradation of cholesterol at the studied temperatures (AU)

• FAPESP's process: 10/12169-1 - Interaction of fatty acids, prooxidants, antioxidants in the oxidation of cholesterol in model system
• Grantee: Elisângela Serenato Madalozzo
• Support Opportunities: Scholarships in Brazil - Doctorate