Browsing by Author "Oliveira, M. C."
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- Application of an Indenyl Molybdenum Dicarbonyl Complex in the Isomerisation of α-Pinene Oxide to Campholenic AldehydePublication . Bruno, S.; Gomes, A. C.; Gamelas ou Carla A. Gamelas, Carla; Abrantes, M.; Oliveira, M. C.; Valente, A.; Almeida-Paz, Filipe; Pillinger, M.; Romão, C.; Gonçalves, I.The complex [{(Z5-Ind)Mo(CO)2(m-Cl)}2] (1) has been tested for the industrially relevant catalytic isomerisation of a-pinene oxide (PinOx) to campholenic aldehyde (CPA) in the liquid phase. PinOx conversion and CPA selectivity are strongly influenced by the solvent employed. Complete conversion of PinOx was achieved within 1 min at 55 1C or 30 min at 35 1C using 1,2-dichloroethane as solvent, giving CPA in 68% yield. Other products included trans-carveol, iso-pinocamphone and trans-pinocarveol. The stability of 1 under the reaction conditions used was investigated by using FT-IR spectroscopy and electrospray ionisation mass spectrometry (ESI-MS) to characterise recovered solids. In the presence of air/moisture 1 undergoes oxidative decarbonylation upon dissolution to give oxomolybdenum species that are proposed to include a tetranuclear oxomolybdenum(V) complex. Conversely, ESI-MS studies of 1 dissolved in dry acetonitrile show mononuclear species of the type [IndMo(CO)2(CH3CN)n]+. The crystal structure of the ring-slipped dicarbonyl complex [(Z3-Ind)Mo(CO)2Cl(CH3CN)2] (2) (obtained after dissolution of 1 in acetonitrile) is reported.
- Supercritical Fluid Extraction vs Conventional Extraction of Myrtle Leaves and Berries: Comparison of Antioxidant Activity and Identification of Bioactive CompoundsPublication . Pereira, P.; Cebola, M. J.; Oliveira, M. C.; Bernardo-Gil, M. G.In this work, the antioxidant capacity of extracts of Portuguese myrtle (Myrtus communis L.) is being studied over a period of three years. The samples were leaves of myrtle collected at the flowering stage and berries sampled at an early ripened stage. Supercritical fluid extraction (SFE) extracts were obtained at 23 MPa, 45 °C and a CO2 flow of 0.3 kg h−1 using ethanol as co-solvent with a flow rate of 0.09 kg h−1. Hydrodistillation was carried out in a Clevenger type apparatus and the aqueous phase was extracted with diisopropylether having obtained what is hereby designated as liquid phase extract (LPE). The antioxidant capacity of all the extracts was determined by using three different methods: the Folin–Ciocalteu, the Trolox Equivalent Antioxidant Capacity (TEAC) and the Oxygen Radical Absorbance Capacity (ORAC). The results show that the SFE extracts present a significantly higher antioxidant capacity. The extracts were characterized and quantified by HPLC-DAD-MS/MS methods. The bioactive compounds identified in all the extracts were phenolic acids (only in the LPE extracts), flavonoids and anthocyanins (only in the SFE extracts). The results indicate that the higher antioxidant capacity of the SFE myrtle extracts is mainly correlated with the concentration of flavonol glycosides, the myricetin-O-glycosides.