Browsing by Author "Silva, S."
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- Anthocyanin extraction from plant tissues: a reviewPublication . Silva, S.; Costa, E. M.; Calhau, C.; Morais, R. M.; Pintado, M. E.Anthocyanins have gathered the attention of the scientific community mostly due to their vast range of possible applications. They have been the center point of the research in many different fields, among which is food development, where their innate coloring, antioxidant capacity, and biological potential open interesting venues to the development of new food additives and functional foodstuffs. As the range of application grows, so does the necessity to obtain these compounds, and since they are naturally occurring, the most common way to obtain anthocyanins is to extract them from different plant sources, such as fruits and flowers. Several efforts have been made to develop methods that allow for better extraction yields and higher purification rates therefore this review aims to compile the information regarding extraction and purification procedures in a comprehensive manner.
- Antimicrobial activity of an anthocyanin rich blueberry extract, purified using SPEPublication . Silva, S.; Costa, E. M.; Morais, R. M.; Pintado, M. M.There is a wide recognition of the biological potential of phenolic compounds, with their potential as antimicrobials gaining a particular interest when taking into account the emergence of microbial resistance and the need for alternative sources of antimicrobial compounds. Anthocyanins are one of the families of flavonoids that gather most of the attention for their biological potential therefore they are one of the main focus whenever blueberry extracts are concerned. As such, the present work aimed to evaluate the antimicrobial potential of a purified anthocyanin fraction (ca. 85% of total phenolics are anthocyanins) against a plethora of microorganims: multiresistant clinical isolates of Escherichia coli, Proteus mirabilis, Acinetobacter baumanii, Pseudomonas aeruginosa, a Methicillin resistant (MRSA) and a methicillin sensitive (MSSA) Staphylococcus aureus, Pseudomonas aeruginosa 10145, Escherichia coli 25922 and MSSA ATCC 25923. Firstly, the antimicrobial activity of the extract against each microorganism was screened by drawing inactivation curves. The analysis of these results showed that the most sensitive microorganisms was S. aureus, for which all strains studied were unable to grow in the presence of 500 μg/mL of powdered extract. P. mirabilis and A. baumanii suffered no inhibition. All other microorganisms, while not fully inhibited showed some signs of biological activity by the extract with delayed start of the exponential stage, lower growth rates and/or lower microbial loads after 24 and 48h (when compared to the control). As an example, the E. coli clinical isolate registered a microbial load 22 to 25% (after 24 and 48 h respectively) lower than the positive control when incubated with 500 μg/mL of powdered extract, while the collection strain registered reductions of 47 to 69% (after 24 and 48 h respectively) when under the same conditions. As for P. aeruginosa both strains portrayed longer lag stages when exposed to 500 μg/mL, with the clinical isolate exhibiting a 9 h longer lag stage than that of the control. Secondly, the extracts capacity to inhibit biofilm formation was screened. In this test, all microorganims except P. mirabilis demonstrated some sensitivity toward the extracts, with inhibition percentages ranging from 75 to 45% when exposed to 500 μg/mL, 75-23% when exposed to a 250 μg/mL concentration and in some cases, the extracts remained active when used in concentrations as low as 50 μg/mL (35-21%). In this assay, the collection strain of P. aeruginosa appeared to be the most sensitive to the extracts activity with concentrations as low as 50 μg/mL still being able to cause an inhibition of 47 ± 12 % of biomass. It is interesting to note that, while the growth of A. baumanii was not affected by the extracts its biofilm formation was with a range of inhibition percentages from 74 to 35 %. For P. mirabilis, the presence of the extracts appears to strongly promote biofilm formation. Additionally, the extracts capacity to inhibit short term adhesion, a 3h adhesion test was performed with only the clinical isolates of S. aureus and the collection strain of P. aeruginosa exhibiting inhibition of bacterial adherence in this time frame. Overall, the present work demostrated that anthocyanin rich fractions possess significant antimicrobial and antibiofilm activity against several multiresistant and culture collection microorganisms, thus showing their potential as possible active ingredients in future pharmacological solutions for the treatment of bacterial infections.
- Behavioural approaches to the strategic partner selectionPublication . Silva, S.; Silva, F.; Vlacic, B.; Meneses, R.
- Bioavailability of phenolic compounds from brewer’s spent grain extractsPublication . Bonifácio-Lopes, T.; Batista, P.; Silva, S.; Teixeira, José A.; Pintado, Manuela
- Chitosan as an effective inhibitor of multidrug resistant Acinetobacter baumanniiPublication . Costa, E. M.; Silva, S.; Vicente, S.; Veiga, M.; Tavaria, F.; Pintado, M. M.Over the last two decades worldwide levels of antibiotic resistance have risen leading to the appearance of multidrug resistant microorganisms. Acinetobacter baumannii is a known skin pathogen which has emerged as a major cause of nosocomial outbreaks due to its capacity to colonize indwelling medical devices and natural antibiotic resistance. With chitosan being an effective antimicrobial agent against antibiotic resistant microorganisms, the aim of this work was to access its potential as an alternative to traditional antimicrobials in the management of A. baumannii growth. What the results showed was that both chitosan MW’s tested were active upon A. baumannii’s planktonic and sessile growth. For planktonic growth MICs and MBCs were obtained at relatively low concentrations (0.5–2 mg/mL) while for sessile growth chitosan proved to be an effective inhibitor of A. baumannii’s adhesion and biofilm formation. Considering these results chitosan shows a high potential for control of A. baumannii infections.
- Chitosan as natural food preservative for sauces: a proof of conceptPublication . Costa, E. M.; Silva, S.; Silva, N.; Couto, J. A.; Gomes, A. M.; Pintado, M. M.Introduction: Nowadays, consumers demand more natural, nutritionally balanced, less caloric, and minimally processed foods leading to the emergence of sauces with low fat content and without chemical preservatives. This market pressure has led to the modification of a well-established and microbiologically stable matrix, triggering the search for new antimicrobial compounds of natural origin, compounds whose inhibitory efficacy must be studied [1]. Chitosan has attracted attention as a potential food preservative of natural origin due to its antimicrobial activity against a wide range of foodborne pathogens and contaminants. However, the antimicrobial capacity of chitosan, despite being extensively reported, is primarily based upon in vitro trials, where the compound, unimpeded, acts upon microorganisms. Currently, inclusion of chitosan in a food matrices is in its early steps with works reporting the application of chitosan in bread, egg, fruits, vegetables, juices, meat, milk and others, with various degrees of success [2]. In food sauces examples of chitosan application are few and scarce, as most works report on the usage of chitosan as an emulsifier or a emulsifier stabilizer and only Roller and Covill [3] described the successful usage of a chemically altered chitosan as a food preservative. As such, in this work we sought to ascertain the potential of chitosan as a viable, natural, alternative to traditional food preservatives used in food sauces, namely ketchup, mayonnaise and mustard, through assessment of the effect of chitosan containing sauces on the inhibition of lactic acid bacteria isolated therefrom and sensorial analysis of the developed prototypes.
- Chitosan effect upon biofilm formation of multiresistant Staphylococcus aureus strainsPublication . Costa, E. M.; Silva, S.; Tavaria, F. K.; Pintado, M. M.
- Chitosan mouthwash: toxicity and in vivo validationPublication . Costa, E. M.; Silva, S.; Costa, M. R.; Pereira, M.; Campos, D. A.; Odila, J.; Madureira, A. R.; Cardelle-Cobas, A.; Tavaria, F. K.; Rodrigues, A. S.; Pintado, M. M.A previous study showed that a chitosan mouthwash would be a valid alternative to current mouthwashesas it demonstrated, in vitro, significantly higher antibiofilm activity than two commercial mouthwashes.As such, the aim of this work was to verify the safety of the developed product and to validate, in vivo, thebiological activity ascertained in vitro. Chitosan mouthwash safety was evaluated through Ames, MTT andV79 chromosomal aberration assay while antimicrobial activity was evaluated through in vivo assays. Theresults showed that the chitosan mouthwash was safe, presenting lower cytotoxicity than a commercialmouthwash, and that it effectively reduced viable counts of Streptococcus spp. and Enterococcus spp. by ca.5.5 log of CFU. Furthermore, in direct comparison with a commercial mouthwash the chitosan mouthwashpossessed significantly higher antimicrobial activity. The conjunction of these results proves that thechitosan mouthwash is a safe, effective, natural alternative to the existent chemical mouthwashes.
- Chitosan nanoparticles as alternative anti-staphylococci agents: bactericidal, antibiofilm and antiadhesive effectsPublication . Costa, E. M.; Silva, S.; Vicente, S.; Neto, C.; Castro, P. M.; Veiga, M.; Madureira, R.; Tavaria, F.; Pintado, M. M.Chitosan is a biocompatible, bioactive, non-toxic polymer that due to these characteristics has been widely used as a carrier for targeted delivery of bioactive molecules. In recent years, and considering that chitosan has a strong antimicrobial potential, the scientific community's focus has shifted onto the possible antimicrobial activity of chitosan nanoparticles. With this in mind, the aim of this work was to produce low molecular weight chitosan nanoparticles, through the ionic gelation method and characterize their potential biological activity against three staphylococci (MSSA, MRSA and MRSE) in planktonic and sessile environments. The chitosan nanoparticles produced had an average size of 244 ± 12 nm, an average charge of 17.3 ± 1.4 mV and had a MIC of 1.25 mg/mL for all tested microorganisms. Bactericidal activity was only registered for MSSA and MRSA with the time-inhibition curves showing bactericidal activity within 1 h. Assays regarding chitosan nanoparticles' impact upon sessile populations showed that they were effective in preventing MRSE adhesion and highly effective in reducing MRSA and MSSA biofilm formation.
- A comparative analysis of the antibiofilm properties of crude blueberry extracts against MRSA and MSSAPublication . Silva, S.; Costa, E. M.; Costa, M. R.; Pereira, M. F.; Morais, R. M. S. C.; Pintado, M. E.
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