Dissertação mest., Engenharia Biológica, Universidade do Algarve, 2009 In this work it was determined the antioxidant, neuroprotective and anti-hyperglycemic activity of methanol (MeOH), hexane and water extracts made from two species of Mediterranean oaks, Quercus suber L. (cork oak) and Quercus ilex L. (holm oak), and Ceratonia siliqua L. (carob tree). Additionally, a phytochemical evaluation was made. The extracts were made from different organs or products namely leaves, fruits, pulps, germ flour, gum and stem bark from carob tree and leaves and acorns from Quercus species. Samples were collected from mature trees growing in the Algarve. Acorns from cork oak were also sampled in Alentejo, to check for the influence of geographic origin on the biological activities of the extracts. Moreover, a thermal treatment (‘dry roasting’) at 200 ºC was applied to a part of the acorn samples, and compared to the results obtained in samples dried at 50 ºC. The chemical profile varied in all the parameters, the MeOH extracts were richer in phenolic compounds, which were present in higher amounts in leaves (Quercus species), and in leaves and stem bark (carob tree). Acorns had a considerable amount of phenolics and lipids. There was a great variation in the major compound between samples. Methanol extracts from leaves, acorns and stem bark exhibited an interesting antioxidant activity. The leaf extracts from the two species had a high inhibitory activity against acetylcholinesterase and butyrylcholinesterase. The extracts had no relevant activity against α-amylase, but a potent inhibitory activity on α-glucosidase from baker’s yeast. Altogether, these results indicate that leaves and stem bark from carob tree, and acorns from cork oak and holm oak have bioactive compounds useful in the prevention/treatment of the above mentioned disorders. Further research is needed in order to identify the bioactive compounds, trough a bio-guided fractioning of the extracts.