Percorrer por autor "Tavaria, Freni K."
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- AgNP-Polyphenol synergy on cotton fabrics: antimicrobial and free-radical-scavenging activity for dermal applicationsPublication . Fernandes, Andreia; Negut, Irina; Melo, Adma; Pintado, Manuela; Tavaria, Freni K.; Oliveira, Cláudia S.The development of antimicrobial textiles has gained increasing attention due to rising concerns regarding infection control and material safety, Conventional antimicrobial textiles often depend on synthetic agents or metal-based compounds, which may promote environmental and biocompatibility concerns. Hybrid strategies combining nanotechnology with bioactive compounds (BCs) derived from agri-food by-products have emerged as promising alternatives. In this study, silver nanoparticles (AgNPs) were first applied to cotton fabrics to create a stable antimicrobial platform. The combination of AgNPs and BCs is expected to yield synergistic bioactivity, promoting both microbial inhibition and oxidative stress modulation [1]. This study evaluated the biological performance of extracts from acorn shell (AS) functionalized with AgNPs-cotton, focusing on antimicrobial efficacy against pathogenic microorganisms (S. aureus, E. coli, C. albicans, C. tropicalis), and antioxidant activity (ABTS and DPPH radical scavenging assays). The biocompatibility with human skin cells will be further assessed through in vitro assays using HaCaT keratinocytes, aiming to evaluate potential cytotoxic effects and ensure the safety of the fabrics. Antimicrobial activity was evaluated through CFU counts, expressed as log?? reductions. Fabrics functionalized with extracts showed a greater reduction (p? 0.001) in microbial load, particularly against Candida albicans and Candida tropicalis, when compared to AgNP-only treated samples. The functionalized fabrics showed significant radical scavenging activity in both assays. In the ABTS and DPPH assay, samples treated with AS extracts exhibited higher activity compared to AgNP-only treated fabrics with inhibition values of 36 (±4.4)% and 43 (±4.1)%, respectively. In contrast, AgNPs alone showed no measurable antioxidant activity. These compounds likely act synergistically with AgNPs, contributing not only to oxidative stability but also enhancing antimicrobial performance. Interestingly, fabrics with AgNPs alone exhibited minimal antioxidant activity and may have induced pro-oxidant effects, consistent with the known ROSgenerating mechanisms. The upcoming biocompatibility will provide further insights into their safety for skin-contact use.
- Alginate edible films containing essential oils: characterization and bioactive potentialPublication . Lopes, Ana I.; Melo, Adma; Afonso, Tiago B.; Silva, Sara; Barros, Lillian; Tavaria, Freni K.; Pintado, ManuelaEssential oils (EOs) are natural substances rich in phenolic compounds with notable antimicrobial and antioxidant properties. However, they present some limitations, such as low stability and bioavailability. Incorporating EOs into polymeric films offers a novel approach to overcome these challenges while enhancing their efficacy. In this study, we produced and thoroughly characterized alginate-based edible films incorporated with five different EOs—rosemary, eucalyptus, oregano, sage, and thyme. This is the first comprehensive investigation to include this diverse range of EOs in alginate films. Their antimicrobial and antioxidant activities were also evaluated. The results demonstrated that alginate films containing EOs exhibited significant bioactive properties. Notably, the film incorporated with oregano EO completely inhibited the growth of all tested bacteria and fungi and showed the highest antioxidant activity. Based on these findings, alginate films containing EOs present promising bioactive potential and could serve as biodegradable alternatives to conventional packaging materials, reducing environmental impact. However, further studies are necessary to assess their safety profile and confirm their viability as replacements for traditional food packaging. Future research should focus on evaluating cytotoxicity, genotoxicity, and the practical application of these films in food matrices.
- Alternative cheesemaking methods with raw ewes’ milk – microbiological, chemical, textural and sensory characteristicsPublication . Reis, Patrícia J. M.; Tavaria, Freni K.; Malcata, F. XavierSerra da Estrela cheese was manufactured using a novel, customised apparatus – designed to meet the specialty cheese’s specifications, and the resulting product was compared with that obtained via traditional manufacture in the same dairy. Semiindustrial cheesemaking led to a significantly (p<0.05) higher fat content in the final cheeses, with favourable consequences in terms of flavour and consumer acceptability – and significantly (p<0.05) lower viable numbers of (unwanted) enterococci in the matured cheese. Textural characteristics were broadly similar. Proteolysis was significantly (p<0.05) faster, but it was more variable in artisanal than in semi-industrial cheeses. The latter received significantly (p<0.05) better scores for texture, but lower scores for flavour. However, both products were within the specifications set forth by national regulations pertaining to Serra da Estrela PDO cheeses, so the novel apparatus is rather promising towards improved small-scale cheesemaking.
- Amino acid and soluble nitrogen evolution throughout ripening of Serra da Estrela cheesePublication . Tavaria, Freni K.; Franco, Inmaculada; Carballo, F. Javier; Malcata, F. XavierFour batches of Serra da Estrela cheese originating from as many dairy farms were sampled throughout the ripening period, and assayed for the evolution of free amino acid (FAA) content, total nitrogen content (TN), water-soluble nitrogen content (WSN), trichloroacetic acid-soluble nitrogen content (TCASN) and phosphotungstic acid-soluble nitrogen content (PTASN). The WSN content increased from 1% (on the day of manufacture) up to 43% of TN by 180 d of ripening, thus reflecting the intense proteolytic activity of the enzymes contributed by the plant coagulant utilized. The TCASN was also found to be high in this cheese by the end of ripening (16–20%), which suggests a high extent of FAA release throughout maturation. The major FAA by 180 d of ripening were Glu, Val, Leu and Lys, representing 56–70% of the total in all four dairies sampled. Cheeses produced from refrigerated milk possessed higher amounts of g-amino-n-butyric acid (Gaba) and lower amounts of Glu when compared with those manufactured withnon-refrigerated milk.
- An overview on mushroom polysaccharides: health-promoting properties, prebiotic and gut microbiota modulation effects and structure-function correlationPublication . Araújo-Rodrigues, Helena; Sousa, Ana Sofia; Relvas, João Bettencourt; Tavaria, Freni K.; Pintado, ManuelaMushroom polysaccharides are recognized as “biological response modifiers”. Besides several bioactivities, a growing interest in their prebiotic potential has been raised due to the gut microbiota modulation potential. This review comprehensively summarizes mushroom polysaccharides' biological properties, structure-function relationship, and underlying mechanisms. It provides a recent overview of the key findings in the field (2018–2024). Key findings and limitations on structure-function correlation are discussed. Although most studies focus on β-glucans or extracts, α-glucans and chitin have gained interest. Prebiotic capacity has been associated with α-glucans and chitin, while antimicrobial and wound healing potential is attributed to chitin. However, further research is of utmost importance. Human fecal fermentation is the most reported approach to assess prebiotic potential, indicating impacts on intestinal biological, mechanical, chemical and immunological barriers. Gut microbiota dysbiosis has been directly connected with intestinal, cardiovascular, metabolic, and neurological diseases. Concerning gut microbiota modulation, animal experiments have suggested proinflammatory cytokines reduction and redox balance re-establishment. Most literature focused on the anticancer and immunomodulatory potential. However, anti-inflammatory, antimicrobial, antiviral, antidiabetic, hypocholesterolemic, antilipidemic, antioxidant, and neuroprotective properties are discussed. A significant overview of the gaps and research directions in synergistic effects, underlying mechanisms, structure-function correlation, clinical trials and scientific data is also given.
- Antimicrobial effect of chitosan against periodontal pathogens biofilmsPublication . Costa, Eduardo M.; Silva, Sara; Pina, Cristina; Tavaria, Freni K.; Pintado, ManuelaOver the years authors have established that chitosan possesses significant antimicrobial activity against planktonic bacteria however, little is known about the effect of chitosan upon sessile microbial communities. The aim of this work was to assess the effect of chitosan against 5 periodontal pathogens, Porphyromonasgingivalis, Prevotellaintermedia, Prevotellabuccae, Tanerellaforsythensis and Aggregatibacter actinomycetemcomitans biofilm formation. The results obtained show that both high molecular weight and low molecular weight chitosan were capable of inhibiting biofilm formation and biofilm associated phenomena. Sub-MIC concentrations of chitosan inhibited single species biofilm formation up to 90% and dual species biofilms formation up to 80%. Furthermore analysis of the effect of chitosan upon quorum sensing showed inhibition values that reached 70% after 24h exposure to chitosan. The results obtained open new possibilities in the fight against biofilm formation in the oral cavity and the prevention of undesirable microbiological colonization following dental treatments.
- Antimicrobial effects of chitosans and chitooligosaccharides, upon Staphylococcus aureus and Escherichia coli, in food model systemsPublication . Fernandes, João C.; Tavaria, Freni K.; Soares, José C.; Ramos, Óscar S.; Monteiro, M. João; Pintado, Manuela E.; Malcata, F. XavierThe objective of this study was to elucidate the controversial relationship between the molecular weight (MW) of chitosans and their antibacterial activity (upon different inoculum levels, at several concentrations). The influence of food components on the activity was also ascertained, as well as acceptance by a sensory panel. All the compounds tested exhibited antibacterial activity against Staphylococcus aureus and Escherichia coli. This activity was shown to be closely dependent on the inoculum level, MW and concentration used. Within 4 h at 10³ cells/mL, all five compounds, at every concentration (0.5%, 0.25% and 0.1%, w/v), proved to be bactericidal; for higher inocula, 0.1% (w/v) was only bacteriostatic; at 107 or 105 cells/mL, and independently of the inoculum level, 0.25% (w/v) of any chitooligosaccharide (COS) mixture was sufficient to reduce the E. coli initial population by at least 3 log cycles; COS never exhibited bactericidal action over S. aureus, unlike high and medium MW chitosans—which, at 0.5% (w/v), presented a bactericidal effect even against 107 cells/mL. When incorporated in liquid food matrices, medium and high MW chitosans maintained their activity, for both matrices and bacteria, although a slower activity was noticeable in milk; however, COS lost their activity upon both bacteria in milk after 4–8 h. Furthermore, addition of chitosans to apple juice led to several unpleasant off-flavors, such as astringency and after taste—which increased in magnitude with MW.
- Antimicrobial impact of essential oils on human skin colonizers and pathogens: targeting Staphylococcus speciesPublication . Lopes, Ana I.; Oliveira, Cláudia S.; Pintado, Manuela E.; Tavaria, Freni K.Background: Staphylococcus spp., one of the most abundant bacterial genera of the human skin microbiome, comprises commensal microorganisms – Staphylococcus epidermidis (S. epidermidis) – and opportunistic pathogens – Staphylococcus aureus (S. aureus). Staphylococcus-caused diseases are typically treated with antibiotics, but the antimicrobial resistance underscores the need for alternative treatments. Essential oils (EOs) are natural compounds made of terpenes and terpenoid molecules. Their antimicrobial activity results from the effect upon several cell targets, making the appearance of resistances unlikely. Objective: To study the antimicrobial activity of three EOs (eucalyptus, lavender, and thyme) on two Staphylococcus species (S. epidermidis and S. aureus). Methods: To assess the antimicrobial potential of EOs against the selected bacteria, the following assays were performed: i) determination of the minimum inhibitory (MIC) and minimum bactericidal (MBC) concentrations; ii) inhibition curves for each oil defined for the MIC, to understand how the bacteria respond to the oils; iii) antibiofilm formation assays using MIC, ½ MIC and ¼ MIC dilutions for each oil; and iv) evaluation of the membrane damage through flow cytometry, by staining the bacterial cells exposed to the oils, with propidium iodide (PI) and thiazole orange (TO). Results: The MIC and MBC values for the selected EOs ranged from 0.078% and 2.5% (v/v). Thyme presented the lower MIC for both bacteria. The inhibition curves corroborated the MIC results for all EOs. However, thyme was the one with a bactericidal effect on both bacteria. Thyme also presented higher antibiofilm activity compared to eucalyptus and lavender. The flow cytometry assay showed that all oils were able to damage the cell membrane of both bacteria (positive PI staining), but S. epidermidis showed less cell damage than S. aureus. Conclusion: The selected EOs presented antibacterial activity against S. epidermidis and S. aureus. Thyme EO was the one with the best antibacterial activity. S. epidermidis is more resistant to the oils than S. aureus.
- Antimicrobial impact of essential oils on human skin colonizers and pathogens: targeting Staphylococcus speciesPublication . Lopes, Ana I.; Oliveira, Cláudia S.; Pintado, Manuela E.; Tavaria, Freni K.Introduction: Staphylococcus spp. is one of the most abundant bacterial genera of the human skin microbiome (Joglekar et al. 2023). It comprises commensal microorganisms – Staphylococcus epidermidis (S. epidermidis) – and opportunistic pathogens – Staphylococcus aureus (S. aureus) (Imam and Luqman 2024). Staphylococci-caused diseases are typically treated with antibiotics, but the antimicrobial resistance underscores the need for alternative treatments. Essential oils (EOs) are natural compounds made of terpenes and terpenoid molecules. Their antimicrobial activity targets multiple cellular components, which reduces the likelihood of resistance development (Zuzarte et al. 2011). Objective: To study the antimicrobial activity of three EOs (eucalyptus, lavender, and thyme) on two Staphylococcus species (S. aureus and S. epidermidis). Conclusions: Eucalyptus, lavender, and thyme EOs present antibacterial activity against S. aureus and S. epidermidis. Thyme possesses the lowest MIC; the inhibition curves corroborated this result. The flow cytometry assay showed that all oils were able to damage bacterial cells; thyme oil presented the highest percentages of dead and injured cells. All EOs also showed anti-biofilm activity; thyme presented the highest anti-biofilm activity when compared to eucalyptus and lavender. S. epidermidis is more resistant to the oils than S. aureus.
- Antioxidant activity of alginate edible films containing plant extractsPublication . Lopes, Ana Isabel; Silva, Sara; Barros, Lillian; Caleja, Cristina; Pereira, Eliana; Tavaria, Freni K.; Pintado, ManuelaNowadays, food packaging has been the target of increasing attention. Traditional food packaging is usually made of plastic and accounts for 36.9% of the plastics’ demand, being considered the largest market for plastic industry. Additionally, plastics are mostly produced with polymers from non-renewable sources and so, they contribute to environmental pollution. A way to circumvent this problem is the development of edible films. Edible films can act as complements to traditional plastics because their functional properties are able to extend food’s shelf-life1.Plant extracts are obtained by plants and possess antioxidant activity because of their high concentrations of phenolic compounds. They can be effective at low concentrations, are cost-effective and easy to apply, presenting low toxicity levels and high stability during processing and may not affect the sensory characteristics of food products2.The addition of plant extracts to edible films confers them the ability to act as food preservatives because they present antimicrobial activity against a broad spectrum of food poisoning microorganisms and antioxidant properties that helps to avoid the deterioration of fats and other food constituents 3. So, the main objective of this work was to evaluate the antioxidant activity of alginate edible films containing extracts of licorice (Glycyrrhiza glabra L.), eucalyptus (Eucalyptus globulus Labill.) and sage (Salvia officinalis L.). The 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and 2,2-difenil-1-picrilhidrazil (DPPH) scavenging tests were performed on the films and the results show that the films incorporated with plant extracts present antioxidant activity when compared to the control (alginate film without plant extract).The film incorporated with sage extract was the one that presented the best antioxidant activity by both ABTS (4024,169 Trolox equivalents (M)/mg film) and DPPH (3954,813 Trolox equivalents (M)/mg film), followed by the film with eucalyptus extract (ABTS: 3706,291 Trolox equivalents (M)/mg film; DPPH: 3706,291 Trolox equivalents (M)/mg film). On the other hand, the film incorporated with licorice extract (ABTS: 942,5195 Trolox equivalents (M)/mg film; DPPH: 1040,669 Trolox equivalents (M)/mg film) was the one with least antioxidant activity.