Untitled

Funder

Organizational Unit

Publications

Synthesis, photochemical and in vitro cytotoxic evaluation of new iodinated aminosquaraines as potential sensitizers for photodynamic therapy

Publication . Mandim, Filipa; Graça, Vânia C.; Calhelha, Ricardo C.; Machado, Isabel Ferreira; Ferreira, Luis F.V.; Ferreira, Isabel C.F.R.; Santos, Paulo F.

In this work, several benzothiazole-based aminosquaraine dyes, displaying strong absorption within the so-called phototherapeutic window (650–800 nm), were synthesized. The ability, of all the new dyes, to generate singlet oxygen was assessed by determining the correspondent phosphorescence emission and through the comparison with a standard. The quantum yields of singlet oxygen generation were determined and exhibited to be strongly dependent on the nature of the amino substituents introduced in the squaric ring. The photodynamic activity of the synthesized dyes was tested against four human tumor cell lines: breast (MCF-7), lung (NCI-H460), cervical (HeLa) and hepatocellular (HepG2) carcinomas; and a non-tumor porcine liver primary cell culture (PLP2). All the compounds synthesized were found to be able to inhibit tumor cells growth upon irradiation more than in the dark, in most of the cases, very significantly. Considering the photodynamic activity exhibited and the low toxicity displayed for the non-tumor cells, some of the synthetized dyes can be regarded as potential candidates as photosensitizers for PDT.

2019Journal article

Open access

Tunisian olive oils geographical origin discrimination using the potentiometric fingerprints recorded by an electronic tongue

Publication . Veloso, Ana C.A.; Souayah, Fatma; Rodrigues, Nuno; Dias, L.G.; Oueslati, Souheib; Pereira, J.A.; Peres, António M.

The development of fast and cost-effective analytical techniques for EVOO authentication is a challenging task. Moreover, if a specific meteorological or geographical factor affects different geographical regions similarly, olive oils geographical discrimination may be a hard task using conventional analytical techniques [1]. E-noses and/or voltammetric E-tongues have already been applied to assess olive oils' geographical origin, mainly to discriminate different countries or quite different regions of the same country [2]. In this work, we used an electronic tongue (E-tongue ), with 40 lipid membrane sensors, to extract representative potentiometric fingerprints of Tunisian monovarietal olive oils that, in combination with linear discriminant analysis (LOA), could be used to classify olive oils according to the geographical origin. Aqueous ethanolic (80:20, v/v) extracts of different single-cultivar Tunisian olive oils were electrochemically analysed. According to the literature [3-6], these olive oil' extracts are rich in polar compounds that deliver different overall potentiometric responses, which can then be used to evaluate the E-tongue performance for olive oils geographical origin discrimination. The proposed E-tongue-LDA approach, based on the signal profiles of different sub-sets of sensors (seleted with the simulated annealing meta-heuristic algorithm) allowed the correct geographical origin classification of Tunisian olive oils produced from autochthonous Chemleli or Sahli cultivars (i.e., Kairouan, Sidi Bouzid and Sfax; or, Mahdia, Sousse and Kairouan; respectively). Indeed, predictive correct classifications of 92±7% and 97±8% (for repeated K-fold cross-validation) could be obtained for Chemleli or Sahli olive oils, pointing out the potential use of the E-tongue device for geographical origin identification of olive oils.

2017Conference object

Open access

The effects of starter culture on the biogenic amine accumulation in traditional Portuguese dry-sausages

Publication . Panov, Dimitriy; Dias, L.G.; Pereira, Ana Paula; Lopes-da-Silva, M.F.; Peres, António M.; Estevinho, Leticia M.; Dias, Teresa

Linguiça is a highly popular and appreciated traditional Portuguese dry fermented sausage. Its production involves a ripening step, which provides favorable conditions for biogenic amines formation due to microbial growth, acidification and proteolysis. The levels of biogenic amines in dry-fermented sausages are highly dependent on the type of product, producer and could even vary from batch to batch. The microbiological quality of raw materials, technological process and growth/type of microbial flora are some factors that may explain this variability. To the authors’ best knowledge, only few studies focused on the quantification of biogenic amines in Portuguese traditional sausages, reporting variable levels of accumulation, being the tyramine the most abundant followed by putrescine and cadaverine. Starter cultures have been used aiming to prevent or reduce the formation of biogenic amines during the manufacture of dry-fermented sausages. Based on the results reported in the literature, the use of starter cultures may reduce or not the biogenic amines accumulation during the fermentation of sausages. In this work, it was evaluated the influence of one commercial starter culture (Texel®ELCE Br, Danisco) on biogenic amine accumulation during manufacture process and storage. Parameters such as pH value, water activity and microbial counts were also assessed. In general the results pointed out that the starter culture inhibited the accumulation of biogenic amines (putrescine, cadaverine and tyramine) as well as the growth of S. aureus and Enterobacterias. This inhibitory effect was clear during ripening and storage periods. On the other hand the starter culture did not have a significant effect on spermidine and spermine concentrations.

2017Conference object

Open access

Electrochemical taste sensor for unmasking extra-virgin olive oils adulterated with rancid or winey-vinegary olive oils.

Publication . Veloso, Ana C.A.; Harzalli, Ussama; Rodrigues, Nuno; Dias, L.G.; Oueslati, Souheib; Pereira, J.A.; Peres, António M.

Olive oils may be commercially classified, in a decrease order of quality and economic value, as extra-virgin (EVOO), virgin (VOO) or lampante (LOO) olive oils, being quite prone to frauds. Thus legal protection regulations have been approved by the European Union Commission [1,2], being required the fulfilment of several physicochemical and sensory thresholds [3,4]. Unfortunately, the mixture of expensive olive oils with low quality oils aiming fraudulent economic revenue is still a common practice difficult to detect. In this work, a potentiometric electronic tongue (E-tongue) was used to detect adulteration of an EVOO with different added levels (2.5%, 5%, 10%, 20% and 40%; v/v) of an LOO with an intense sensory defect (rancid or wineyvinegary). Previously, similar electrochemical devices, also comprising lipid polymeric sensor membranes, showed to be able to give qualitative and/or quantitative responses towards basic taste sensations (acid, bitter, salty, sweet, and umami), positive sensory attributes (bitter, fruity, green and pungency) or defects (e.g., butyric, musty, putrid, winey-vinegary and zapateria) [5-8]. The E-tongue coupled with linear discriminant technique (based on the signal profiles of 19 or 20 E-tongue sensors, chosen using a simulated annealing meta-heuristic variable selection algorithm, for rancid and wineyvinegary adulterations, respectively) allowed to semi-quantitatively distinguish olive oils with different adulteration levels (repeated K-fold crossvalidation predictive correct classifications of 84±10% and 94±8% for rancid and winey-vinegary adulterations, respectively). The preliminary results showed the practical potential of the E-tongue as a taste device for the successful detection of EVOOs adulterated with LOO containing organoleptic defects.

2017Conference object

Open access

Echinacea purpurea (L.) moench: chemical characterization and bioactivity of its extracts and fractions

Publication . Coelho, Joana C.M.M.; Barros, Lillian; Dias, Maria Inês; Finimundy, Tiane C.; Amaral, Joana S.; Alves, Maria José; Calhelha, Ricardo C.; Santos, Paulo F.; Ferreira, Isabel C.F.R.

Echinacea purpurea (L.) Moench is widely known for its medicinal properties, being one of the most used medicinal plants for its immunostimulant properties. Nevertheless, there is still scarce information on its cytotoxic activity. Thus, this study aims at evaluating the cytotoxicity and antimicrobial activity of several aqueous and organic extracts of the aerial parts of this plant and chemically characterizing the obtained extracts. The analysis was performed by HPLC–DAD–ESI/MS. Fifteen compounds were identified; of these, seven were phenolic acids and eight were flavonoids. Non-polar compounds were evaluated by GC/MS, with a total of sixty-four compounds identified, and the most abundant groups were the sterols, fatty acids and long-chain hydrocarbons. The highest antimicrobial activity was exhibited by the dichloromethane, ethyl acetate, and acetone extracts. Dichloromethane and n-hexane extracts showed the highest cytotoxic activity. Therefore, they were fractionated, and the obtained fractions were also assessed for their cytotoxicity. Notwithstanding, the cytotoxicity of the extracts was superior to that of the obtained fractions, evidencing a possible synergistic effect of different compounds in the whole extracts.

2020Journal article

Open access