Caracterización química, propiedades antioxidantes y evaluación de los efectos neuroprotectores de bebidas fermentadas

Zusammenfassung

The strawberry is an excellent source of bioactive compounds, however, it is a very perishable fruit. The elaboration of fermented products supposes a valuable strategy to prevent the economic losses due to strawberry surplus and to increase the shelf life. On the other hand, the use of biotechnological processes that preserve the bioactive compounds is a relevant aspect to take into consideration. In this PhD Thesis, anthocyanin composition, colour and antioxidant activity of different fermented products made from strawberry purée by alcoholic, acetic and gluconic fermentations have been evaluated. Additionally, the stability of a beverage obtained from these products has been studied. Moreover, the neuroprotective effect of these products against amyloid-β (Aβ) toxicity and Reactive Oxygen Species (ROS) production has been investigated. In addition, the bioactivity of protocatechuic acid (one of the most important anthocyanin metabolite) against the aggregation and toxicity of Aβ peptide and α-synuclein (αS) protein in vitro has been demonstrated. Furthermore, it has been confirmed that other bioactive compounds (melatonin and indolic related compounds) described in strawberry and in other fermented products present an effect on the inhibition of the Aβ aggregation and the Aβ-induced toxicity. The obtained results have led to the identification of new anthocyanin compounds in alcoholic and acetic fermented products. Moreover, it has been proven that gluconic fermentation is the process, from those studied in this Thesis, that better preserves the anthocyanin profile. Thus, it was the one selected as substrate to elaborate the beverage. Furthermore, alcoholic and gluconic fermented extracts protect neuronal cells against Aβ toxicity. Protocatechuic acid possesses an inhibitory effect of the Aβ and αS fibril formation and neuroprotective properties demonstrated by several in vitro techniques. Finally, serotonin has been proved to be a potent inhibitor of the fibril formation. Melatonin and the related indolic compounds presented a preventive effect against the cell death produced by Aβ.