Portuguese Nuclear Magnetic Resonance Network

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Seasonal evaluation of Pholorotannin-Enriched extracts from brown macroalgae Fucus spiralis

Publication . Almeida, Belén; Barroso, Sonia; Ferreira, Ana S. D.; Adão, Pedro; Mendes, Susana; Gil, Maria M.

Fucus spiralis that was collected in the four seasons was submitted to an extraction with ethanol:water (crude extracts Et80), followed by a liquid–liquid fractionation with organic solvents (fraction He from n-hexane; aqueous fractions AQ1, AQ2, AQ3 and AQ4; ethyl acetate fraction EA), with the aim of obtaining phlorotannin-enriched extracts. All the extracts (Et80, He, AQ1, AQ2, AQ3, AQ4 and EA) that were obtained for the F. spiralis of the four seasons were evaluated for their antioxidant capacity and total phenolic compounds. The summer extracts presented the highest contents in polyphenols (TPC), as well as the highest ferric reducing antioxidant power (FRAP), when compared to the samples from the other seasons. The reductive percentage of the DPPH (2,2-diphenyl-1-picryl-hydrazyl-hydrate) compound was similar between the seasons. For all the seasons, the EA extract showed the highest polyphenol content (TPC), and the highest antioxidant capacity (highest ferric reducing power (FRAP) and lowest concentration needed to reduce 50% of the DPPH compound), which is in agreement with a phlorotannin-enriched fraction. This study revealed that the polyphenol content and antioxidant power of the F. spiralis extracts are influenced by the time of harvest, as well as by the solvents used for their extraction.

2021Journal article

Open access

Synthesis, crystal structure, and DFT study of two new dinuclear copper(I) complexes bearing Ar-BIAN ligands functionalized with NO2 groups

Publication . Outis, Mani; Rosa, Vitor; Laia, César A.T.; Lima, João Carlos; Barroso, Sonia; Carvalho, Ana Luísa; Calhorda, Maria José; Avilés, Teresa

Two new bis(aryl-imino)-acenaphthene, Ar-BIAN (Ar = 2,4,6-trimethylphenyl = mes) ligands, bearing the NO2 group in the naphthalene moiety of the iminoacenaphthene at para- (5-NO2) and meta- (4-NO2) position, of formulations 1,2-bis(mes-imino)-5-nitroacenaphthene, 1, and 1,2-bis(mes-imino)-4-nitroacenaphthene, 2, were synthesized. Their respective dinuclear iodide bridged copper(I) complexes [Cu2(μ-I)2(mes-BIAN-5-NO2)2], 3 and [Cu2(μ-I)2(mes-BIAN-4-NO2)2], 4, were obtained in good yields by treatment with an equimolar amount of CuI. All compounds were characterized by elemental analysis, single-crystal X-ray diffraction, 1H-NMR, 13C-NMR, FTIR, UV/Vis spectroscopy. DFT calculations helped to understand the different molecular structure observed in the crystals of 3 and 4 and the determining role of packing forces. TDDFT revealed that the absorption bands in the visible were essentially MLCT (Metal to Ligand Charge Transfer), with some n→π* character (intra ligand). The shift to the red compared to the spectrum of the Cu(I) complex analogue without the NO2 group, [Cu2(μ-I)2](mes-BIAN)2], 6, could be explained by the stabilization of the ligand unoccupied π* orbitals in the presence of NO2.

2020Journal article

Open access