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- Valorisation of Sargassum muticum through the extraction of phenolic compounds using eutectic solvents and intensification techniquesPublication . Jesus, Bárbara C.; Sáenz de Miera, Blanca; Santiago, Rubén; Martins, Alice; Pedrosa, Rui; Gonzalez-Miquel, Maria; Marrucho, Isabel M.Seaweeds are naturally abundant and spread all over the globe. They have several biologically active secondary metabolites of great interest. In this work, Sargassum muticum was the algae employed as biomass and the aim was to extract phenolic compounds (PCs) using eutectic solvents (ESs). Several betaine-based, proline-based, and choline-based ESs were tested for the extraction of PCs. All extracts were evaluated according to the total phenolic content (TPC), total flavonoid content (TFC) and antioxidant activity (DPPH). Afterwards, the extracts were characterized using HPLC in terms of 9 target PCs (gallic acid, 3,4-dihydroxybenzoic acid, caffeic acid, syringic acid, p-coumaric acid, ferulic acid, salicylic acid, catechin and quercetin). Proline combined with propylene glycol (Pro[thin space (1/6-em)]:[thin space (1/6-em)]PPG) exhibited a higher yield according to HPLC results, followed by proline[thin space (1/6-em)]:[thin space (1/6-em)]1,2-butanediol (Pro[thin space (1/6-em)]:[thin space (1/6-em)]1,2-But) and choline[thin space (1/6-em)]:[thin space (1/6-em)]citric acid (ChCl[thin space (1/6-em)]:[thin space (1/6-em)]CA). Pro[thin space (1/6-em)]:[thin space (1/6-em)]PPG also presented high selectivity towards salicylic acid, while ChCl[thin space (1/6-em)]:[thin space (1/6-em)]CA towards gallic acid. Optimization studies of water content and temperature were performed for the three best ESs, the optimum conditions being 30% (v/v) water and 60 °C extraction temperature. Ultrasound-assisted extraction (UAE) and microwave-assisted extraction (MAE) were two intensification methods evaluated to enhance the extraction process, proving their ability to reduce the extraction time when compared with the conventional solid–liquid extraction (SLE) process. In particular, Pro[thin space (1/6-em)]:[thin space (1/6-em)]PPG-based MAE provided a significantly higher extraction yield in comparison with conventional extraction and with the other extraction solvents. In summary, the combination of ESs with intensification techniques was shown to be a valuable valorization strategy of a marine macroalgae waste, in particular Sargassum muticum.
- Lanthanide-based organic salts: Synthesis, characterization, and cytotoxicity studiesPublication . Forte, Andreia; Gago, Sandra; Alves, Celso; Silva, Joana; Pedrosa, Rui; Laia, César A.T.; Marrucho, Isabel M.; Branco, Luis C.The formulation of magnetic ionic liquids (MILs) or organic salts based on lanthanides as anions has been explored. In this work, a set of choline-family-based salts, and two other, different cation families, were combined with Gadolinium(III) and Terbium(III) anions. Synthetic methodologies were previously optimized, and all organic salts were obtained as solids with melting temperatures higher than 100 °C. The magnetic moments obtained for the Gd(III) salts were, as expected, smaller than those obtained for the Tb(III)-based compounds. The values for Gd(III) and Tb(III) magnetic salts are in the range of 6.55–7.30 MB and 8.22–9.34 MB, respectively. It is important to note a correlation between the magnetic moments obtained for lanthanides, and the structural features of the cation. The cytotoxicity of lanthanide-based salts was also evaluated using 3T3, 293T, Caco2, and HepG2 cells, and it was revealed that most of the prepared compounds are not toxic.
- Mesoporous silica nanoparticles with manganese and lanthanide salts: synthesis, characterization and cytotoxicity studiesPublication . Forte, Andreia; Gago, Sandra; Carrott, Manuela Ribeiro; Carrott, Peter; Alves, Celso; Teodoro, Fernando; Pedrosa, Rui; Marrucho, Isabel M.; Branco, Luis CSeveral organic salts based on the combination of two different choline derivative cations and MnCl3−, GdCl4− and TbCl4− as anions were immobilized in mesoporous silica nanoparticles (MSNs) by a two-step synthetic method. Firstly, MSNs were functionalized with choline derivative cations with chloride anions and then the metals were incorporated by the reaction of the chloride with the respective metal chloride salts. These nanomaterials were fully characterized by different characterization techniques such as 1H-NMR, FT-IR, elemental analysis, TEM, TGA, N2 adsorption, XRD and DLS. These characterization data were important to confirm the successful functionalization of the nanomaterials and to access their textural properties and colloidal stability. The final materials were also characterized by ICP-MS that indicated the metal contents. The cytotoxicity profile was evaluated in four different cell lines (3T3, 293T, HepG2 and Caco-2), which shows some relevant differences between the metal organic salts and their immobilized analogues.