Nuevos métodos de extracción y fraccionamiento de carbohidratos bioactivos

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Química Física Aplicada. Fecha de lectura: 27-11-2015The extraction of bioactive carbohydrates, such as inositols and prebiotics, from natural sources is of great interest for their use as food ingredients due to the benefits they represent to consumers' health. These compounds are involved in several biological processes related with metabolic disorders or inducing changes in gut microbiota. The potential use of these bioactive ingredients from the food and / or pharmaceutical industry makes that the search for new extraction alternatives, more effective and advantageous than the available ones, gains an increasing importance. Therefore, the main objective of this PhD dissertation is the development of new methods for the extraction and selective fractionation of bioactive carbohydrates (inositol and prebiotics). To achieve this goal, two main research lines have been addressed: (i) the evaluation of the use of new solvents (ionic liquids, ILs) for the selective fractionation of carbohydrates based on their chemical structure, and (ii) the development of new methods of extraction and enrichment of bioactive carbohydrates from natural matrices. First of all, it was necessary to develop a derivatization method that allows the analysis of low molecular weight carbohydrates (LMWC) dissolved in ILs by gas chromatography (GC). The optimized and validated method proved to be effective for this purpose, being this the first time that carbohydrates dissolved in ILs are analyzed by this technique. Subsequently, and due to the scarce data published so far in the literature on the solubility of LMWC in ILs, solubility studies of different monosaccharides, polyols, disaccharides and trisaccharides in methyl-imidazolium based-ILs were carried out, and these values were related to their chemical structure. ILs were found to be promising solvents for the selective fractionation of aldoses and bioactive ketoses, such as lactose and lactulose, as well as several polyols and other LMWC. Prior to the development of extraction methods, significant advances in qualitative and quantitative determination of the LMWC (particularly inositol and prebiotics) present in different food matrices (pine nuts, vegetables, legumes) were carried out by GC-MS after derivatization to their corresponding trimethylsylil oximes (TMSO). Different carbohydrates were identified for the first time in these matrices. In this thesis, pressurized liquid extraction (PLE) and microwave assisted extraction (MAE) were selected to evaluate their efficiency in the extraction of bioactive carbohydrates, as well as their respective advantages and disadvantages. The developed PLE and MAE methods allowed to obtain greater yields of inositols than those achieved by the conventional solid-liquid extraction method, using shorter extraction times and with a lower solvent consumption. Moreover, the developed methods allowed, for the first time, the simultaneous extraction of inositol and inulin from food industry by-products. Finally, a biotechnological process based on the use of Saccharomyces cerevisiae which allowed the removal of coexisting sugars in the extracts that might interfere with the bioactivity of the carbohydrates of interest has been optimized. The results described in this thesis represent a remarkable contribution to the study of carbohydrates, as well as to the development of new ingredients and bioactive supplements, which is a subject of great interest and scientific and economic impac