Browsing by Author "Carvalho, Marta"
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- Antimicrobial activity of in-situ bacterial nanocellulose-zinc oxide composites for food packagingPublication . Silva, Francisco A. G. Soares; Carvalho, Marta; Carvalho, Teresa Bento de; Gama, Miguel; Poças, Fátima; Teixeira, PaulaActive substances such as zinc oxide nanoparticles (ZnO) have been extensively explored due to their antimicrobial properties, low cost and scalability. Yet, their effectiveness is highly dependent on their morphology and specific surface area. Bacterial nanocellulose (BNC) is a suitable carrier due to its ability to transport and deliver active substances. In the case of nanocellulose-ZnO composites, conclusions drawn from antimicrobial studies are often based on only a few representatives of Gram-positive and Gram-negative bacteria. A more comprehensive study using different species and strains, and different methods to assess antimicrobial activity is required. Therefore, in this work, the antimicrobial activity of ZnO suspensions and BNCZnO films was assessed against a wide range of Gram-negative and Gram-positive bacteria using disc diffusion and viable cell count assays. Regarding the results of the disc diffusion assay, the increase of ZnO content (21–27% mZn/mBNCZnO) (in both ZnO suspensions and BNCZnO films), increased antimicrobial activity against all Gram-negative bacteria tested and some Gram-positive bacteria. In the viable cell count assay, BNCZnO films were effective against Escherichia coli (3 log reduction) and Listeria monocytogenes (1–3 log reduction) after 24 h. Low temperatures reduced the antimicrobial activity of BNCZnO.
- Antimicrobial properties of oregano oil (Origanum vulgare) against Listeria monocytogenes in “alheira”Publication . Carvalho, Marta; Oliveira, Márcia; Albano, Helena; Teixeira, Paula
- Antimicrobial properties of oregano oil (origanum vulgare) against salmonella enteritidis, staphylococcus aureus and listeria monocytogenes in "alheira"Publication . Carvalho, Marta; Albano, Helena; Teixeira, Paula
- Antioxidant activity, phenolic profile, cytotoxicity and genotoxicity of plant extractsPublication . Melo, Adma N. F. de; Afonso, Tiago B.; Ribeiro, Tânia; Machado, Manuela; Carvalho, Marta; Carocho, Márcio; Tavaria, Freni; Teixeira, Paula; Barros, Lillian; Pintado, ManuelaThe outbreak of COVID-19 disease caused by SARS-CoV-2 forced the scientific world to search for new alternatives to help control the virus. Plant extracts have natural compounds that might provide a starting point for the research on the use of plants as an excellent source of new antiviral agents against viruses, including COVID-19 to be included in disinfectants, fabrics or other materials. In this study, the polyphenols content (Folin-Ciocalteu), antioxidant capacity (DPPH, ABTS and ORAC) and the phenolic profile (HPLC) of different hydroethanolic (ethanol:H2O 50:50 v/v) extracts of medicinal plants cultivated under controlled conditions in Portugal (echinacea, rosemary, laurel, thyme and rock rose) were determined, as well as the cytotoxicity effect against a keratinocyte cell line using cell viability assay by PrestoBlue and genotoxicity effect using the AMES test. According to the results, total phenolic content ranged from 204.54 ± 1.78 / 274.20 ± 3.14 (mg EAG/g extract) with the rock rose extract presenting the highest content (p < 0.05). The extracts showed a good antioxidant capacity demonstrated by the high values found for ORAC, which ranged 2855.03 ± 9.75 / 5285.35 ± 60.04 µMol Trolox/mg extract. HPLC analysis revealed the presence of different compounds in the extracts such as the kaempferol-O-glucuronide, catechin, protocatechuic acid and galloyl glucoside, representing a potential source of bioactive components with antioxidant capacity. No toxicity was observed towards the keratinocyte cells and none of them showed mutagenic effects. Based on the results of safety and high polyphenols content of the extracts they demonstrate a great potential as antimicrobial agents. This will allow the design of new experiments aimed at evaluating the antiviral activity of these extracts, especially against SARS-CoV-2.
- Antioxidant activity, phenolic profile, cytotoxicity and genotoxicity of plant extractsPublication . Melo, Adma N. F. de; Afonso, Tiago B.; Ribeiro, Tânia; Machado, Manuela; Carvalho, Marta; Carocho, Márcio; Tavaria, Freni; Carvalho, Marta; Teixeira, Paula; Barros, Lillian; Pintado, Manuela
- Characterization of the toxigenic potential of bacillus cereus sensu lato isolated from raw berries and their productsPublication . Oliveira, Márcia; Carvalho, Marta; Teixeira, PaulaBacillus cereus is estimated to be responsible for 1.4–12% of all food poisoning outbreaks worldwide. The objective of this study was to investigate the toxigenic potential of 181 isolates of B. cereus previously recovered from different types of berries and berry products (strawberries, raspberries, blackberries, and blueberries) by assessing the presence of enterotoxin genes (hblA, hblC, hblD, nheA, nheB, nheC, and cytK) and an emetic toxin cereulide synthetase gene (ces). The cytotoxic activity on Caco-2 cells was also evaluated for the two isolates containing the gene cytK. Twenty-three toxigenic profiles were found. The nheABC (91.7%) and hblACD (89.0%) complexes were the most prevalent among the isolates, while the cytK and ces genes were detected in low percentages, 1.1% and 3.3%, respectively. In addition, the nheABC/hblACD complex and ces genes were detected in isolates recovered throughout the production process of blackberries and strawberries. The cytotoxic activity on Caco-2 cells was also observed to be greater than 60% for isolates containing the cytK gene.
- Chemical characterization, cytotoxic evaluation and anti-SARS-CoV2 activity of plant extracts rich in hydrolysable tanninsPublication . Melo, Adma N. F.; Afonso, Tiago B.; Carvalho, Marta; Rodrigues, Cláudia; Ribeiro, Tânia; Carocho, Márcio; Pinto, Miguel Marques; Tavaria, Freni; Teixeira, Paula; Simas, J. Pedro; Barros, Lillian; Pintado, Manuela
- Determination of minimum inhibitory concentrations of several plants extracts against different bacterial pathogensPublication . Carvalho, Marta; Melo, Adma; Afonso, Tiago; Barbosa, Joana; Ribeiro, Tânia; Tavaria, Freni; Carocho, Márcio; Barros, Lilian; Pintado, Manuela; Teixeira, PaulaIn the context of COVID 19 the use of face masks has been recommended as a preventive measure against the spread of SARS CoV 2 1 Despite their health benefits, usage of single use masks represents a threat to the environment as they are manufactured fromlong lasting plastic materials Reusable fabric masks are an alternative to reduce the risk of pollution and the amount of plastic wastage 2. The application of antimicrobial agents in the tissues used to produce masks would be an additional hurdle on the preventionof other respiratory infections and secondary bacterial infections that occur from touching contaminated masks In this context, impregnation of the fabrics with plant extracts is an attractive approach since they are potentially safe and free of adverse side effectsand powerful antimicrobials. The objective of this work was to study several plant extracts to select the most efficient against pathogenic microorganisms.
- Determination of the minimum inhibitory concentrations of the antibacterial oregano and thyme essential oils in the presence of polysorbate 80Publication . Carvalho, Marta; Barbosa, Joana; Silva, Marcelo; Albano, Helena; Teixeira, Paula
- Disinfectants efficiency against Salmonella spp. biofilms on stainless steel surfacePublication . Carvalho, Marta; Ribeiro, Deise Baggio; Moura-Alves, Márcio; Esteves, Alexandra; Teixeira, Paula
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