RESUMO
The photophysical, photoinduced pro-oxidant and antibacterial properties in vitro of the natural occurring parietin (PTN; 1,8-dihydroxy-3-methoxy-6-methyl-9,10-anthraquinone) were evaluated. PTN was extracted from the lichen identified as Teloschistes flavicans (Sw.) Norm. (Telochistaceae). Results indicate that in chloroform solution, PTN presents spectroscopic features corresponding to an excited-state intramolecular proton-transfer (ESIPT) state with partial keto-enol tautomerization. In argon-saturated solutions, the singlet excited state is poorly fluorescent (ΦF = 0.03), decaying by efficient intersystem crossing to an excited triplet state 3PTN*, as detected by laser-flash photolysis experiments. In the presence of triplet molecular oxygen, the 3PTN* was fully quenched producing singlet molecular oxygen (1O2) with a quantum yield of 0.69. In addition, in buffer solutions, PTN has the ability to also generate a superoxide radical anion (O2Ë-) in a human leukocyte model and its production was enhanced under UVA-Vis irradiation. Finally, the in vitro antibacterial capability of PTN in the dark and under UVA-Vis illumination was compared in microbial cultures of both Gram positive and negative bacteria. As a result, PTN showed promising photo-induced antibacterial activity through the efficient photosensitized generation of both 1O2 and O2Ë- species. Thus, we have demonstrated that PTN, an efficient photo-screening pigment in lichens, is also a good photosensitizer in solution with promising applications in antibacterial photodynamic therapy.
Assuntos
Emodina/análogos & derivados , Fármacos Fotossensibilizantes/química , Fármacos Fotossensibilizantes/farmacologia , Animais , Antibacterianos/química , Antibacterianos/farmacologia , Sobrevivência Celular/efeitos dos fármacos , Chlorocebus aethiops , Emodina/química , Emodina/isolamento & purificação , Emodina/farmacologia , Bactérias Gram-Negativas/efeitos dos fármacos , Bactérias Gram-Negativas/efeitos da radiação , Bactérias Gram-Positivas/efeitos dos fármacos , Bactérias Gram-Positivas/efeitos da radiação , Humanos , Leucócitos/efeitos dos fármacos , Leucócitos/metabolismo , Leucócitos/efeitos da radiação , Líquens/química , Líquens/metabolismo , Luz , Testes de Sensibilidade Microbiana , Fármacos Fotossensibilizantes/isolamento & purificação , Oxigênio Singlete/química , Oxigênio Singlete/metabolismo , Espectrofotometria Ultravioleta , Superóxidos/química , Superóxidos/metabolismo , Raios Ultravioleta , Células VeroRESUMO
A simple, environmentally friendly and cost-effective method was used to synthesize silver nanoparticles using tryptophan and light. To prepare the nanoparticles, the following components were used: deionized water, silver nitrate, light and tryptophan. The effects of the tryptophan concentration and light exposure time on the formation of tryptophan silver nanoparticles (Tnnps) were studied. The synthesized Tnnps were characterized using transmission electron microscopy (TEM), absorption and fluorescence spectroscopy and zeta potential measurements. The synthesized Tnnps were nearly spherical, with sizes of approximately 17 nm. In addition, the antibacterial activity of Tnnps was determined by monitoring the growth curves of strains of Escherichia coli, Pseudomonas aeruginosa, Staphylococcus epidermidis, Serratia marcescens, and Enterococcus faecalis using the microdilution test. The Minimum Inhibitory Concentration (MIC) for 4 of 5 tested bacteria was determined to be between 20.0 and 17.5 µg/mL for 48 h and between 22.5 and 20.0 µg/mL for 72 h.
Assuntos
Antibacterianos/química , Bactérias Gram-Negativas/efeitos dos fármacos , Bactérias Gram-Positivas/efeitos dos fármacos , Nanopartículas Metálicas/química , Prata/química , Triptofano/química , Antibacterianos/síntese química , Antibacterianos/farmacologia , Bactérias Gram-Negativas/efeitos da radiação , Bactérias Gram-Positivas/efeitos da radiação , Química Verde , Luz , Nanopartículas Metálicas/toxicidade , Testes de Sensibilidade Microbiana , Microscopia Eletrônica de Transmissão , Tamanho da Partícula , Espectrometria de FluorescênciaRESUMO
The aim of this paper was to investigate a collection of plant extracts from Argentina as a source of new natural photosensitizers (PS) to be used in Photodynamic Inactivation (PDI) of bacteria. A collection of plants were screened for phototoxicity upon the Gram-positive species Staphylococcus epidermidis. Three extracts turned out to be photoactive: Solanum verbascifolium flower, Tecoma stans flower and Cissus verticillata root. Upon exposure to a light dose of 55J/cm(2), they induced 4, 2 and 3logs decrease in bacterial survival, respectively. Photochemical characterisation of S. verbascifolium extract was carried out. PDI reaction was dependent mainly on singlet oxygen and to a lesser extent, on hydroxyl radicals, through type II and I reactions. Photodegradation experiments revealed that the active principle of the extract was not particularly photolabile. It is noticeable that S. verbascifolium -PDI was more efficient under sunlight as compared to artificial light (total eradication vs. 4 logs decrease upon 120min of sunlight). The balance between oxidant and antioxidant compounds is likely to be masking or unmasking potential PS of plant extracts, but employing the crude extract, the level of photoactivity of S. verbascifolium is similar to some artificial PS upon exposure to sunlight, demonstrating that natural resources can be employed in PDI of bacteria.
Assuntos
Bactérias Gram-Positivas/efeitos dos fármacos , Fármacos Fotossensibilizantes/farmacologia , Extratos Vegetais/farmacologia , Bignoniaceae/química , Bignoniaceae/metabolismo , Cissus/química , Cissus/metabolismo , Testes de Sensibilidade a Antimicrobianos por Disco-Difusão , Flores/química , Flores/metabolismo , Bactérias Gram-Negativas/efeitos dos fármacos , Bactérias Gram-Negativas/efeitos da radiação , Bactérias Gram-Positivas/efeitos da radiação , Fotodegradação , Fármacos Fotossensibilizantes/química , Extratos Vegetais/química , Raízes de Plantas/química , Raízes de Plantas/metabolismo , Oxigênio Singlete/metabolismo , Solanum/química , Solanum/metabolismoRESUMO
UNLABELLED: The objective of this work was to select a Ultraviolet-C (UV-C) treatment for fresh-cut mature green bell pepper, and to evaluate the effect of its combination with refrigeration on quality maintenance. Bell pepper sticks were treated with 0, 3, 10, or 20 kJ/m² UV-C in the outer (O), inner (I), or both sides of the pericarp (I/O) and stored for 8 d at 10 °C. During the first 5 d of storage, all UV-C treatments reduced deterioration as compared to the control. The treatment with 20 kJ/m² I/O was the most effective to reduce deterioration, and was used for further evaluations. In a second group of experiments, mature green bell pepper sticks were treated with 20 kJ/m² I/O, stored at 5 °C for 7 or 12 d and assessed for physical and chemical analysis, and microbiological quality. UV-C-treated fruit showed lower exudates and shriveling than the control. UV exposure also reduced decay, tissue damage, and electrolyte leakage. After 12 d at 5 °C, UV-C irradiated peppers remained firmer and had higher resistance to deformation than the control. The UV-C treatments also reduced weight loss and pectin solubilization. UV-C exposure decreased the counts of mesophile bacteria and molds, and did not affect acidity or sugars. UV-C-treated fruit stored for 0 or 7 d at 5 °C did not show major differences in antioxidants from the control as measured against DPPH(â¢) or ABTS(â¢)⺠radicals. Results suggest that UV-C exposure is useful to maintain quality of refrigerated fresh-cut green pepper. PRACTICAL APPLICATION: Exposure to UV-C radiation before packing and refrigeration could be a useful nonchemical alternative to maintain quality and reduce postharvest losses in the fresh-cut industry.
Assuntos
Capsicum/efeitos da radiação , Fast Foods/efeitos da radiação , Irradiação de Alimentos/métodos , Embalagem de Alimentos , Armazenamento de Alimentos , Frutas/efeitos da radiação , Raios Ultravioleta , Antioxidantes/análise , Capsicum/crescimento & desenvolvimento , Capsicum/microbiologia , Fenômenos Químicos , Carboidratos da Dieta/análise , Relação Dose-Resposta à Radiação , Eletrólitos/análise , Fast Foods/análise , Fast Foods/microbiologia , Frutas/crescimento & desenvolvimento , Frutas/microbiologia , Fungos/crescimento & desenvolvimento , Fungos/efeitos da radiação , Bactérias Gram-Negativas/crescimento & desenvolvimento , Bactérias Gram-Negativas/efeitos da radiação , Bactérias Gram-Positivas/crescimento & desenvolvimento , Bactérias Gram-Positivas/efeitos da radiação , Concentração de Íons de Hidrogênio , Fenômenos Mecânicos , Pectinas/análise , Pectinas/química , Controle de Qualidade , SolubilidadeRESUMO
Batch solar disinfection (SODIS) inactivation kinetics are reported for suspensions in water of Campylobacter jejuni, Yersinia enterocolitica, enteropathogenic Escherichia coli, Staphylococcus epidermidis, and endospores of Bacillus subtilis, exposed to strong natural sunlight in Spain and Bolivia. The exposure time required for complete inactivation (at least 4-log-unit reduction and below the limit of detection, 17 CFU/ml) under conditions of strong natural sunlight (maximum global irradiance, approximately 1,050 W m(-2) +/- 10 W m(-2)) was as follows: C. jejuni, 20 min; S. epidermidis, 45 min; enteropathogenic E. coli, 90 min; Y. enterocolitica, 150 min. Following incomplete inactivation of B. subtilis endospores after the first day, reexposure of these samples on the following day found that 4% (standard error, 3%) of the endospores remained viable after a cumulative exposure time of 16 h of strong natural sunlight. SODIS is shown to be effective against the vegetative cells of a number of emerging waterborne pathogens; however, bacterial species which are spore forming may survive this intervention process.
Assuntos
Desinfecção/métodos , Bactérias Gram-Negativas/efeitos da radiação , Bactérias Gram-Positivas/efeitos da radiação , Luz Solar , Microbiologia da Água , Bolívia , Contagem de Colônia Microbiana , Viabilidade Microbiana , Espanha , Esporos Bacterianos/efeitos da radiação , Fatores de TempoRESUMO
Isolation of most ultraviolet B (UV-B)-resistant culturable bacteria that occur in the habitat of Laguna Azul, a high-altitude wetland [4554 m above sea level (asl)] from the Northwestern Argentinean Andes, was carried out by culture-based methods. Water from this environment was exposed to UV-B radiation under laboratory conditions during 36 h, at an irradiance of 4.94 W/m2. It was found that the total number of bacteria in water samples decreased; however, most of the community survived long-term irradiation (312 nm) (53.3 kJ/m2). The percentage of bacteria belonging to dominant species did not vary significantly, depending on the number of UV irradiation doses. The most resistant microbes in the culturable community were Gram-positive pigmented species (Bacillus megaterium [endospores and/or vegetative cells], Staphylococcus saprophyticus, and Nocardia sp.). Only one Gram-negative bacterium could be cultivated (Acinetobacter johnsonii). Nocardia sp. that survived doses of 3201 kJ/m2 were the most resistant bacteria to UV-B treatment. This study is the first report on UV-B resistance of a microbial community isolated from high-altitude extreme environments, and proposes a method for direct isolation of UV-B-resistant bacteria from extreme irradiated environments.
Assuntos
Acinetobacter/efeitos da radiação , Altitude , Água Doce/microbiologia , Bactérias Gram-Positivas/efeitos da radiação , Tolerância a Radiação , Raios Ultravioleta , Acinetobacter/classificação , Acinetobacter/genética , Acinetobacter/crescimento & desenvolvimento , Meios de Cultura , Ecossistema , Bactérias Gram-Positivas/classificação , Bactérias Gram-Positivas/genética , Bactérias Gram-Positivas/crescimento & desenvolvimento , Dados de Sequência Molecular , Pigmentos Biológicos/metabolismo , Análise de Sequência de DNARESUMO
PURPOSE: To evaluate in vitro the antibacterial effect of diode laser light of wavelength 650 nm, in association with the photosensitive substance toluidine blue, on the bacteria in infected skin ulcers. METHODS: Samples were collected by means of swabs containing a medium for transporting infected material from skin ulcers. The material was inoculated into culturing medium containing azide blood agar for the growth of Gram-positive bacteria, and MacConkey agar for Gram-negative bacteria, and incubated for 48 hours. The results obtained from counting the colony-forming units were correlated and subjected to statistical analysis, adopting the significance level of p > or = 0.05. RESULTS: From analysis of variance (ANOVA), the result for the general mean was p = 0.0215. Using the t test with post-hoc test, the result for TBO vs. Control was p = 0.0186, and for TBO + Laser vs. Control it was p = 0.0039. CONCLUSION: There was a significant reduction in colony-forming units when the cultures were subjected to photodynamic therapy.
Assuntos
Bactérias Gram-Negativas/efeitos da radiação , Bactérias Gram-Positivas/efeitos da radiação , Lasers Semicondutores/uso terapêutico , Terapia com Luz de Baixa Intensidade , Fármacos Fotossensibilizantes/farmacologia , Úlcera por Pressão/radioterapia , Análise de Variância , Contagem de Colônia Microbiana , Humanos , Fotoquimioterapia , Fármacos Fotossensibilizantes/uso terapêutico , Úlcera por Pressão/tratamento farmacológico , Úlcera por Pressão/microbiologia , Cloreto de Tolônio/farmacologiaRESUMO
PURPOSE: To evaluate in vitro the antibacterial effect of diode laser light of wavelength 650 nm, in association with the photosensitive substance toluidine blue, on the bacteria in infected skin ulcers. METHODS: Samples were collected by means of swabs containing a medium for transporting infected material from skin ulcers. The material was inoculated into culturing medium containing azide blood agar for the growth of Gram-positive bacteria, and MacConkey agar for Gram-negative bacteria, and incubated for 48 hours. The results obtained from counting the colony-forming units were correlated and subjected to statistical analysis, adopting the significance level of p > or = 0.05. RESULTS: From analysis of variance (ANOVA), the result for the general mean was p = 0.0215. Using the t test with post-hoc test, the result for TBO vs. Control was p = 0.0186, and for TBO + Laser vs. Control it was p = 0.0039. CONCLUSION: There was a significant reduction in colony-forming units when the cultures were subjected to photodynamic therapy.
OBJETIVO: Avaliar in vitro o efeito antibacteriano do laser diodo com comprimento de onda de 650nn, associado a substancia fotossensível azul de toluidina sobre as bactérias de ulceras cutâneas infectadas. MÉTODOS: Foram coletadas amostras através de um swab com meio de transporte, de material infectado de úlceras cutâneas. Os materiais foram inoculadas em meios de cultura contendo ágar sangue azida para o crescimento de bactérias gram-positivas e agar Mac Conkey para as gram-negativas, e incubadas por 48 horas. Os resultados obtidos da contagem das unidades formadoras de colônias foram relacionados e submetidos a analise estatística adotando como nível de significância p > ou = 0.05. RESULTADOS: Os resultados da análise de variância ANOVA para a media geral foi p= 0,0215 e para o post hoc test teste t. TBO x Controle p=0,0186, TBO + Laser x Controle p=0,0039. CONCLUSÃO: Houve redução, significativa das unidades formadoras de colônias quando submetidas à terapia fotodinâmica.