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Title: Natural antioxidants extraction and their incorporation into model pharmaceutical systems
Author: Marques, Luís Miguel Costa
Advisor: Lopes, António
Keywords: Coffee polyphenols
Cold and drought stresses
Antioxidants in microemulsions
Defense Date: 2011
Publisher: Faculdade de Ciências e Tecnologia
Abstract: This work is divided in two parts comprising two distinct areas of science that are bonded with a functional purpose: study of the polyphenolic composition in leaves of three coffee genotypes and their responses to cold and drought stresses; and analysis of the effect of incorporation of some polyphenolic compounds in a microemulsion model system. Three genotypes of coffee, Icatu Obatã and Apoatã, were subjected to temperature and water content stress conditions and their sensitivity or resistance to the treatments imposed was investigated. Responses were analyzed from phenolic fraction point of view in the leaves of coffee plants. It was found that polyphenols are actually involved in the response to these abiotic stresses and that the 4.5-diCQA seems to have an essential role in the recovery from cold in Obatã. Various phenolic compounds were identified and quantified, being the majority: 5-CQA, epicatechin, procyanidin, 3,4-diCQA, 3.5-diCQA, 4.5-diCQA, 5-FQA and mangiferin that was discovery as a new polyphenol in C. arabica and also works as a biomarker to differentiate between C. arabica and C. canephora. It was confirmed that Apoatã (Coffea canephora) possesses a greater amount of polyphenols than Obatã and Icatu (Coffea arabica). It was ascertained that Icatu and Obatã seem to be more resistant to cold stress than Apoatã, but more sensitive to drought than Apoatã. The model microemulsions is build up from a nonionic surfactant, C12E5, decane and water, a system already well characterized. Two antioxidants, 5-CQA and α-tocopherol, and a drug, lidocaine, were incorporated in microemulsions, being the effect of its addition studied through phase diagrams and DLS. A general model was proposed, arguing that the addition of a hydrophilic molecule increases the temperature of the microemulsion phase (micelles), while a hydrophobic decreases, which is of most importance for pharmaceutical applications. The antioxidant activity is not significantly affected within and outside the microemulsion and was determined the existence of synergistic effect when mixing 5-CQA and α-tocopherol in this system.
Description: Dissertation to obtain a Master Degree in Biotechnology
Appears in Collections:FCT: DQ - Dissertações de Mestrado

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