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Why are some cyano-based ionic liquids better glucose solvents than water?

Publication . Batista, Marta; Passos, Helena; Henriques, Bruno J.M.; Maginn, Edward J.; Pinho, Simão; Freire, Mara G.; Gomes, J.R.B.; Coutinho, João A.P.

Among different classes of ionic liquids (ILs), those with cyano-based anions have been of special interest due to their low viscosity and enhanced solvation ability for a large variety of compounds. Experimental results from this work reveal that the solubility of glucose in some of these ionic liquids may be higher than in water – a well-known solvent with enhanced capacity to dissolve mono- and disaccharides. This raises questions on the ability of cyano groups to establish strong hydrogen bonds with carbohydrates and on the optimal number of cyano groups at the IL anion that maximizes the solubility of glucose. In addition to experimental solubility data, these questions are addressed in this study using a combination of density functional theory (DFT) and molecular dynamics (MD) simulations. Through the calculation of the number of hydrogen bonds, coordination numbers, energies of interaction and radial and spatial distribution functions, it was possible to explain the experimental results and to show that the ability to favorably interact with glucose is driven by the polarity of each IL anion, with the optimal anion being dicyanamide.

2016Journal article

Restricted access

A novel approach for honey pollen profile assessment using an electronic tongue and chemometric tools

Publication . Dias, L.G.; Veloso, Ana C.A.; Sousa, Mara E.B.C.; Estevinho, Leticia M.; Machado, Adélio A.M.; Peres, António M.

Nowadays the main honey producing countries require accurate labeling of honey before commercialization, including floral classification. Traditionally, this classification is made by melissopalynology analysis, an accurate but time-consuming task requiring laborious sample pre-treatment and high-skilled technicians. In this work the potential use of a potentiometric electronic tongue for pollinic assessment is evaluated, using monofloral and polyfloral honeys. The results showed that after splitting honeys according to color (white, amber and dark), the novel methodology enabled quantifying the relative percentage of the main pollens (Castanea sp., Echium sp., Erica sp., Eucaliptus sp., Lavandula sp., Prunus sp., Rubus sp. and Trifolium sp.). Multiple linear regression models were established for each type of pollen, based on the best sensors' sub-sets selected using the simulated annealing algorithm. To minimize the overfitting risk, a repeated K-fold cross-validation procedure was implemented, ensuring that at least 10-20% of the honeys were used for internal validation. With this approach, a minimum average determination coefficient of 0.91 ± 0.15 was obtained. Also, the proposed technique enabled the correct classification of 92% and 100% of monofloral and polyfloral honeys, respectively. The quite satisfactory performance of the novel procedure for quantifying the relative pollen frequency may envisage its applicability for honey labeling and geographical origin identification. Nevertheless, this approach is not a full alternative to the traditional melissopalynologic analysis; it may be seen as a practical complementary tool for preliminary honey floral classification, leaving only problematic cases for pollinic evaluation.

2015Journal article

Restricted access

Strategies for multicomponent separation of Nadolol stereoisomers by simulated moving bed and jo processes

Publication . Ribeiro, António E.; Graça, Nuno S.; Arafah, Rami; Rodrigues, Alírio; Pais, Luís S.

The Simulated Moving Bed (SMB) chromatography is an interesting alternative technique for the production of fine chemicals and pharmaceuticals. The pioneer classical SMB concept was designed for the separation of binary mixtures or to the recovery of one single component from a multicomponent mixture. In recent years, this technology has undergone through several important technical developments, allowing the exploitation of better preparative separation performances. The introduction of a wide range of new and more powerful preparative stationary phases allied to the development of new and more versatile strategies and modes of SMB operation are now a reality. Several configurations have been proposed in order to extend the SMB technology to the separation of multicomponent mixtures by using a cascade of SMBs in series or other complex SMB related techniques like multi-zone SMB, intermittent SMB and JO processes [1-3]. Nadolol is a pharmaceutical drug marketed as a mixture of its four stereoisomers and its prescription is related with some severe risks such as heart failure. This four component mixture will be used as a case study for the development of chromatographic strategies for multicomponent separation. Recently, our research group reported the pseudo-binary separation of nadolol stereoisomers by SMB chromatography [4]. A SMB pilot unit with Chiralpak AD chiral stationary phase was used to obtained the more retained stereoisomer 100% pure. A different strategy was also recently published based on a three column intermittent SMB unit [5]. A new methodology for the design, optimization and experimental implementation of the multicomponent separation will be introduced, including the use of different chiral and achiral adsorbents, the screening and choice of the best adsorbent-solvent combinations, and the use of different SMB operating modes and strategies.

2016Conference object

Open access

A comparative study between natural and synthetic antioxidants: Evaluation of their performance after incorporation into biscuits

Publication . Caleja, Cristina; Barros, Lillian; Antonio, Amilcar L.; Oliveira, Beatriz; Ferreira, Isabel C.F.R.

Currently, the food industry is focused in replacing the use of synthetic by natural antioxidants. The present study focused on the use of fennel and chamomile extracts, rich in phenolic compounds, as natural antioxidants in biscuits and compared their performance with a synthetic antioxidant widely used, the butylated hydroxyl anisole (BHA). The complete nutritional profile, free sugars, fatty acids and antioxidant activity were determined immediately after baking and also after 15, 30, 45 and 60 days of storage. The results showed that the incorporation of natural and synthetic additives did not cause significant changes in colour or in nutritional value of biscuits when compared with control samples. Both natural and synthetic additives conferred similar antioxidant activity to the biscuits. Therefore, natural additives are a more convenient solution for consumers who prefer foods “free” from synthetic additives. Additionally, natural additives were obtained by aqueous extraction, an environment friendly and safe process.

2017Journal article

Open access

Antiangiogenic potential of yogurts added with extracts rich in apigenin derivatives

Publication . Ribeiro, Andreia; Oliveira, Franciely dos Santos de; Calhelha, Ricardo C.; Demczuk Junior, Bogdan; Barreiro, M.F.; Ferreira, Isabel C.F.R.

Angiogenesis is a biological process through which there is the formation of new blood vessels from preexisting ones [I]. However, in pathological cases, the abnormal growth of new blood vessels promotes the development of various diseases including cancer [2) through the production of atypically large amounts of angiogenesis factors, e.g. the vascular endothelial growth factor (VEGF) [3]. The plant secondary metabolites have been the subject of several studies to evaluate their benefits to human health. In particular, the phenolic compounds have high potential for use in the food industry, including the development of functional foods. Among these, apigenin has been associated with chemopreventive effects related to cancer [4]. In fact, chemoprevention is a present-day concept and contemplates the use of medicines, biological compounds or nutrients as an intervention strategy of cancer prevention. In this work, an Arenaria montana L hydroethanolic extract was prepared and after characterization by HPLC-DAD-ESI/MS showed to be rich in apigenin derivatives. Furthermore, it exhibited ability to inhibit the phosphorylation of VEGFR-2 (vascular endothelium growth factor receptor) through an enzymatic assay. However, for the major protection of bioactive compounds, the extract was microencapsulated by an atomization/coagulation technique with alginate as the matrix material. Posteriorly, the hydroethanolic extract, in free and microencapsulated forms, was incorporated in yogurts in order to develop a novel chemopreventer food in relation to the angiogenesis process. The functionalized yogurts with A. montana extracts (free and microencapsulated) showed a nutritional value similar to the used control (yogurt without extract); however, the samples enriched with extracts revealed added-value regarding the VEGFR-2 phosphorylation inhibition ability. This effect was more effectively preserved over time in the samples functionalized with the protected extract. Overall, this work contributes to the valorization of plants rich in flavonoids, exploring its antiangiogenic potential with VEGFR-2 as target. Moreover, the atomization/coagulation technique allowed the production of viable microspheres enriched with the plant extract. The microspheres were effectively incorporated into yogurts, protecting the extract thus envisaging the development of novel functional foods with chemopreventive effects.

2016Conference object

Open access