RESUMO
The antibacterial activity of nine selected essential oils (EOs) against a panel of oral pathogens was investigated in terms of their minimum inhibitory concentrations (MICs) by using the broth microdilution method. Most of the EOs displayed weak activity or were inactive against the selected oral pathogens, with MIC values ranging from 500 to 4000 µg/mL. However, the EO obtained from the leaves of Bidens sulphurea (Asteraceae) was found to display moderate activity against Streptococcus mutans (MIC = 250 µg/mL) and significant activity against Streptococcus mitis (MIC = 31.25 µg/mL). Germacrene D (38.3%), trans-caryophyllene (18.0%), ß-elemene (13.9%) and bicyclogermacrene (13.1%) were identified as the main chemical components of this oil. 2,6-Di-tert-butyl-4-methylphenol, previously described as the major constituent in the EO from the flowers of B. sulphurea, was not detected in this study.
Assuntos
Anti-Infecciosos/química , Anti-Infecciosos/farmacologia , Asteraceae/química , Bactérias/efeitos dos fármacos , Óleos Voláteis/química , Óleos Voláteis/farmacologia , Sesquiterpenos Policíclicos , Sesquiterpenos/química , Sesquiterpenos/farmacologia , Sesquiterpenos de Germacrano/química , Sesquiterpenos de Germacrano/farmacologia , Streptococcus mutans/efeitos dos fármacosRESUMO
It is known that Brazilian chrysotile is rapidly removed from the lungs, but quantitative studies about the influence of lung surfactants on chrysotile dissolution have not been investigated. In this work, the chemical behavior of chrysotile and its dissolution in the presence of dipalmitoylphosphatidylcholine (DPPC) were investigated in physiological conditions. The dissolution was investigated through quantification of magnesium and silicon released by chrysotile. At 37 degrees C, the magnesium concentration is similar to control (without DPPC), which is about 2.0x10(-4)molL(-1), meaning that the dissolution process is not affected by the presence of this surfactant. The same was observed for silicon. The silicon concentration released by chrysotile is similar in all media tested. It is known that the dissolution mechanisms of brucite and tridymite layers are different. From our results, we propose that under physiological conditions, the mechanism of brucite dissolution is based on its interaction with hydrogen ions and that the mechanism of tridymite dissolution is based on a hydrolysis process.
Assuntos
1,2-Dipalmitoilfosfatidilcolina/química , Asbestos Serpentinas/farmacocinética , Surfactantes Pulmonares/metabolismo , Asbestos Serpentinas/química , Magnésio/metabolismo , Silício/metabolismoRESUMO
The occurrence of high ozone levels in the atmosphere of urban areas has become a serious pollution problem in a number of large cities in the world. Although mathematical models have been proposed for predicting ozone concentrations as a function of a number of gas components, sometimes there are uncertainties due to lack of the combined effects of meteorological factors and the complex chemical reaction system involved. The application of neural network models, based on measured values of air pollutants and meteorological factors at different locations within the São Paulo Metropolitan Area, combine chemical and meteorological information. This has shown to be a promising tool for predicting ozone concentration. Simulations carried out with the model indicate the sensitivity of ozone in relation to different air pollution and weather conditions. Predictions using this model have shown good agreement with measured values of ozone concentrations.
Assuntos
Atmosfera/química , Ozônio/química , Algoritmos , Modelos Teóricos , Redes Neurais de ComputaçãoRESUMO
The São Paulo Metropolitan area (SPMA) is characterized as having one of the worst air pollution problems in Brazil, with frequent violations of air quality standards for particulate matter. This paper presents the results of a receptor model source apportionment study carried out to develop a quantitative database on which a control strategy could be developed. The study was conducted in four sites with distinct land uses. Fine, coarse (CP), and total suspended particles (TSP) samples were collected on Teflon and glass filters and analyzed by x-ray fluorescence (XRF), ion chromatography, and thermal evolution. The sources were characterized by similar methodology. Chemical mass balance (CMB) receptor modeling indicated that carbonaceous material plays an important role in the aerosol composition; that the three major source categories contributing to the fine particles are vehicles, secondary carbon, and sulfates; and that the main contributors to CP and TSP are road dust and vehicles. All sampling sites presented the same general pattern in terms of source contribution, although this contribution varied from site to site.