Determinação de ácidos graxos em amostras alimentícias e biológicas utilizando eletroforese capilar de zona

Abstract

An alternative method for the simultaneous analysis majority of cis/trans fatty acids (FA): stearic (C18:0), elaidic (C18:1 9t), oleic (C18:1 9c), palmitic (C16:0), linoleic (C18: 2 9c 12c) and linolenic (C18: 3 9c 12c 15c ) by Capillary Zone Electrophoresis (CZE) with indirect detection was proposed. The methodology was optimized through central composite rotational design 23 (CCD - 23) and after studies, along with the Principal Component Analysis (PCA) , the electrolyte with optimum conditions, consisted of 15.0 mmol L- 1 NaH2PO4/Na2HPO4 buffer at pH ≈ 6.86, 4.0 mmol L -1 SDBS , 8.3 mmol L -1 Brij 35, 45 % v/v acetonitrile and 2.1 % 1-octanol . The FA quantification in real samples was performed by calculating the response factor (Rf) with the subsequent linearity of the proposed mathematical models verification. The CZE method was successfully applied and no significant difference was found within the range of 95 % when compared with the official method by gas chromatography (GC) for food samples such as: olive oil, soybean oil, hydrogenated vegetable fat, butter, margarine, spreadable cheese and filled cookie. In addition to the use of the methodology for analysis of food samples was also applied to FA determination in the Wistar liver rat three groups and fed diets whose lipid fraction was composed of soybean oil used for different stages of time for deep frying processes. After 45 days consuming these diets, the rats were euthanized and the content of FA in liver was monitored by CZE. The results were compared with the official method by GC and no significant differences were observed in the range of 95 % and/or 99 % of confidence interval. The results of the rat liver electropherograms were evaluated by PCA, it was possible to obtain a recognition pattern and to discriminate the final group of the intermediate and control groups, indicating that total exposure time subjected to oil deep frying processes may be relevant for evaluating the quality of the oil. After detecting differences in the content of FA in the liver of animal groups, we required to verify potential biomarkers for cellular metabolism and, whereas some elements act as cofactors for enzyme activity, certain minerals were evaluated in samples of Wistar liver and femur rat involved in the study mentioned above, using the technique of Inductively Coupled Plasma Optic Emission Spectroscopy (ICP OES). It is known that all animals involved in this study received the same amount of selenium from the same origin (Mineral Mix). However, the animals belonging to the late group showed a significant decrease in

selenium content in comparison with to the control and intermediate groups. Therefore, it is possible observe that the selenium interaction with other dietary components (FA) has been changed, since the animals in this study were distinctly affected by diet, with a broad dispersion in the values of selenium in the final group . The decrease in final group selenium content may be related to the decrease of antioxidant function , since oxidation processes also generate highly reactive compounds which excessive increase the oxidative stress of cell structures .