Sara Silva

Evaluation and insights into chitosan antimicrobial activity against anaerobic oral pathogens

The objective of this study was to assess the antimicrobial capability of non-chemically altered chitosan as an alternative to traditional antimicrobials used in the treatment of oral infections. The action mechanism of chitosan was also ascertained. High and low molecular weight chitosan showed antimicrobial activity at low concentrations for all tested bacteria with the MICs varying between 1 and 7 mg/ml with a drop of efficacy relatively to the action of LMW chitosan. In addition chitosan showed also to be an effective bactericidal presenting bactericidal effect within 8 h at the latest. Additionally the evaluation of chitosans action mechanism showed that both MWs acted upon the bacterial cell wall and were not capable of interacting with the intracellular substances, as showed by the inefficacy obtained in the flocculation assay.

Bauhinia forficata Link authenticity using flavonoids profile: Relation with their biological properties

HPLC-DAD-ESI/MS(n) was used to ascertain the authenticity of two certified and two commercial Bauhinia forficata Link samples. Different flavonoids profiles were obtained, involving 39 compounds. Just kaempferol-3-O-(2-rhamnosyl)rutinoside was found in all analysed samples. Five compounds were common to the certified samples of B. forficata Link and B. forficata Link subsp. pruinosa (Vogel) Fortunato & Wunderlin, being kaempferol derivatives the most representative ones. The phenolic composition of B. forficata Link subsp. pruinosa (Vogel) Fortunato & Wunderlin is described herein for the first time, accounting for eight compounds, while 10 new compounds were identified in B. forficata Link. Commercial B. forficata Link showed higher contents of quercetin derivatives, in addition to the presence of myricetin derivatives and flavonoids-(galloyl)glycosides, for which the MS fragmentation pattern is reported for the first time. B. forficata Link and the two commercial samples were able to inhibit α-glucosidase, with EC(50) values lower than that found for acarbose. Mild effects on cholinesterases were observed with the certified samples, while commercial ones were more effective. The same behaviour was observed concerning the scavenging of DPPH, nitric oxide and superoxide radicals. The presence of high contents of quercetin derivatives in commercial samples seems to directly influence their biological properties. The differences between phenolic profiles and their relation with the authenticity of commercial samples are discussed.

Antimicrobial and Antibiofilm Activity of Chitosan on the Oral Pathogen Candida albicans

Oral candidiasis is particularly evident, not only in cancer patients receiving chemotherapy, but also in elderly people with xerostomy. In general, Candida is an opportunistic pathogen, causing infections in immunocompromised people and, in some cases, when the natural microbiota is altered. Chitosan, a natural derivative of chitin, is a polysaccharide that has been proven to possess a broad spectrum of antimicrobial activity that encompasses action against fungi, yeast and bacteria. While recent studies have revealed a significant antibiofilm activity upon several microorganisms, including C. albicans, little is known regarding the impact of chitosan upon the adhesive process or mature biofilms. With that in mind, the purpose of this work was to evaluate, in vitro, the capability of chitosan to inhibit C. albicans growth and biofilm formation. The results obtained showed that chitosan is capable of inhibiting C. albicans planktonic growth (HMW, 1 mg/mL; LMW, 3 mg/mL). Regarding biofilm growth, chitosan inhibited C. albicans adhesion (ca. 95%), biofilm formation (percentages above 90%) and reduced mature biofilms by ca. 65% and dual species biofilms (C. albicans and S. mutans) by ca. 70%. These results display the potential of this molecule to be used as an effective anti-Candida agent capable of acting upon C. albicans infections.

Insights into chitosan antibiofilm activity against methicillin-resistant Staphylococcus aureus

Chitosan is a natural compound that has been validated as a viable antimicrobial agent against Staphylococcus aureus. With this work we sought to evaluate the planktonic and sessile sensitivity of methicillin‐resistant S. aureus to chitosans activity and evaluate if methicillin‐resistant S. aureus (MRSA) would be more or less sensitive to chitosans activity than methicillin‐sensitive S. aureus (MSSA).

Antimicrobial, antiadhesive and antibiofilm activity of an ethanolic, anthocyanin-rich blueberry extract purified by solid phase extraction.

The present work aimed to characterize the impact of an anthocyanin‐rich blueberry extract upon the growth, adhesion and biofilm formation of several pathogens including some multiresistant bacteria.

Investigation of chitosan’s antibacterial activity against vancomycin resistant microorganisms and their biofilms

Vancomycin-resistant microorganisms are a hurdle that traditional antibiotics struggle to overcome. These difficulties have led to search for new solutions based on natural products. Chitosan has been recognized as an effective antibacterial agent against a vast array of microorganisms including antibiotic resistant ones. As such, this work aimed to evaluate chitosan as an alternative to traditional antibiotics in the management/control of two vancomycin-resistant microorganisms, VRSA and VREF, in planktonic and sessile settings. The results obtained showed that chitosan was highly effective in inhibiting VRSA and VREF planktonic growth and reduced VREF viable counts by 6 log CFU in 30min. Additionally, chitosan was active upon several phases of VRSA and VREF sessile growth inhibiting adhesion, biofilm formation and dual-species biofilms at concentrations as low as 0.0125mg/mL. In lieu of these results chitosan shows great potential as a possible alternative for the control of vancomycin-resistant microorganisms in recalcitrant wound infections.

Anthocyanin Extraction from Plant Tissues: A Review

ABSTRACT 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.

Variation of anthocyanins and other major phenolic compounds throughout the ripening of four Portuguese blueberry (Vaccinium corymbosum L) cultivars

Abstract Blueberries are widely recognised as one of the richest sources of bioactive compounds, among which are anthocyanins, though the ripeness of berries has been reported as affecting the phytochemical composition of fruits. Therefore, the present work aimed to evaluate the variation of anthocyanins, and other major phenolics, throughout five ripening stages in four blueberry cultivars. The results showed that the antioxidant capacity and anthocyanin content increased during ripening, reaching the highest values when the blueberries are collected from bunches comprised of 75% ripe blueberries. Antagonistically, the amount of phenolic acid decreases, while the quercetin-3-glucoside levels remain stable. Furthermore, Goldtraube blueberries appear to possess, systematically, higher amounts of phenolic compounds than the other cultivars studied. Thus, when seeking the highest yield of anthocyanins, the preferred harvest should occur in bunches that contain ca 75% of ripe blueberries and, considering the cultivars assayed, the Goldtraube cultivar appears to be the richest in phenolic compounds.

A novel direct contact method for the assessment of the antimicrobial activity of dental cements

Dental cements are a crucial part of the odontological treatment, however, due to the hazardous nature and reduced biological efficiency of some of the used materials, newer and safer alternatives are needed, particularly so those possessing higher antimicrobial activity than their traditional counterparts. The evaluation of the antimicrobial properties of solid and semi-solid antimicrobials, such as dental cements and gels, is challenging, particularly due to the low sensitivity of the current methods. Thus, the main aim of this study was the evaluation of the antimicrobial activity of a novel chitosan containing dental cement while simultaneous assessing/validating a new, more efficient, method for the evaluation of the antimicrobial activity of solid and gel like materials. The results obtained showed that the proposed method exhibited a higher sensitivity than the standard 96 well microtiter assay and allowed the determination of bactericidal activity. Additionally, it is interesting to note that the chitosan containing cement, which presented higher antimicrobial activity than the traditional zinc oxide/eugenol mix, was capable of inducing a viable count reduction above 5 log of CFU for all of the studied microorganisms.

Preparation and biological evaluation of ethionamide-mesoporous silicon nanoparticles against Mycobacterium tuberculosis

Ethionamide (ETH) is an important second-line antituberculosis drug used for the treatment of patients infected with multidrug-resistant Mycobacterium tuberculosis. Recently, we reported that the loading of ETH into thermally carbonized-porous silicon (TCPSi) nanoparticles enhanced the solubility and permeability of ETH at different pH-values and also increased its metabolization process. Based on these results, we synthesized carboxylic acid functionalized thermally hydrocarbonized porous silicon nanoparticles (UnTHCPSi NPs) conjugated with ETH and its antimicrobial effect was evaluated against Mycobacterium tuberculosis strain H37Rv. The activity of the conjugate was increased when compared to free-ETH, which suggests that the nature of the synergy between the NPs and ETH is likely due to the weakening of the bacterial cell wall that improves conjugate-penetration. These ETH-conjugated NPs have great potential in reducing dosing frequency of ETH in the treatment of multidrug-resistant tuberculosis (MDR-TB).