Varela, J.Duarte, Catarina Vizetto Guerreiro2017-02-222017-02-222016-11-242016http://hdl.handle.net/10400.1/9004Tese de doutoramento, Ciências Biológicas, Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2016Brown algae contain interesting nutritional profiles, usually with low levels of lipids but relatively high amounts of polyunsaturated fatty acids (PUFA) and minerals. Moreover, brown algae have secondary metabolites that display several biological activities. However, studies on the chemical composition, bioactive compounds and respective biological activities of brown algae are scarce. Here it is shown that Cystoseira species have potential biotechnological applications. Among the species evaluated, C. tamariscifolia and C. baccata were those that in general had the highest ash, protein and lipid contents, while the highest levels of moisture and total carbohydrates were detected in C. nodicaulis and C. compressa. Cystoseira species had also high amounts of K, Ca and Fe, and a favorable Na/K ratio. C. tamariscifolia, C. compressa and C. nodicaulis stood out for their high polyunsaturated/saturated fatty acids (PUFA/SFA) and low n-6/n- 3 PUFA ratios as well as appropriate unsaturation, atherogenicity and thrombogenicity indices, suggesting a high nutritional value. C. tamariscifolia hexane extract had the highest antioxidant and anti-proliferative activities against a panel of tumoral cells. This extract was particularly selective for hepatocarcinoma cells (HepG2) when compared to non-tumoral cells. HepG2 cells presented pro-apoptotic features and disaggregation on 3D multicellular tumor spheroids after incubation with the extract. Demethoxy cystoketal chromane was isolated and identified as an anti-proliferative compound, selective towards HepG2 cells. Furthermore, isololiolide was isolated for the first time also from C. tamariscifolia hexane extract. The latter compound exhibited significant cytotoxic activity against three human tumoral cell lines, namely HepG2 cells, whereas no cytotoxicity was found in non-malignant human fibroblasts. Isololiolide disrupted the HepG2 normal cell cycle and induced apoptosis. Moreover, it altered the expression of proteins that are important in the apoptotic cascade, increasing PARP cleavage and p53 protein expression, and decreasing procaspase-3 and Bcl-2 expression levels. Taken together, the results here presented highlight the potential of Cystoseira macroalgae as sources of products for nutra- and pharmaceutical applications.engBiological activitiesCystoseiraNatural compoundsNutritionPUFAdoctoral thesis101382880