Evaluation of urban pollution in a tropical lacustrine ecosystem by using n-alkanes and sterols as biomarkers.

The Jacarepaguá Lagoon System (JLS) receives industrial and domestic waste in an urban area with high population density and intense economic activity. The hydrography of the lagoons favours the sedimentation of particulate material transferred from the drainage basin. Water engineering, such as channel dredging and subsea outfall, did not satisfactorily mitigate pollution effects. Therefore, the environment is highly eutrophic, presents frequent blooms of algae and generates high emissions of greenhouse gases. There is no record in the literature on the analysis of organic compounds in the water compartment. The present work applies sterols as biomarkers to quantify the degree of pollution caused by biogenic compounds in riverine and lacustrine water of the JLS. n-Alkanes were applied to estimate the fractions of petrogenic contaminants. The sums of n-alkanes and sterols analysed had average concentrations of 21 ± 20 µg L-1 and 10 ± 8 µg L-1, respectively, in the river samples and 235 ± 156 µg L-1 and 30 ± 28 µg L-1, respectively, in the lagoon samples. The work also showed that the organic compounds inside the lagoons are evenly distributed, and approximately 7% of them are transferred to the marine ecosystem. Biogenic biomarkers and the absolute concentrations of sterols showed that sewage contaminants transferred by the rivers are partially decomposed in the lagoons. The correlations between indices and physicochemical parameters indicated that the degradation of organic compounds in the lagoons occurs mainly in the sediment compartment under anoxic conditions. The indices for sewage indicate that the ecosystem has exceeded its carrying capacity. The indices based on n-alkanes reported strong contamination at all sampling stations and inferred that 75-100% of these compounds were derived from petrogenic sources. These indices did not show any difference between rivers and the lagoon, which demonstrates the resilience of these compounds in the ecosystem.

The cleavage kinetics of hydrazide derivatives of isoniazid by HPLC-UV/DAD and its impact on activity against Mycobacterium tuberculosis.

Isoniazid is a first-line drug for the treatment of tuberculosis, a bacterial disease caused by Mycobacterium tuberculosis. Its terminal amino group is highly reactive, leading to significant metabolic deactivation, drug interactions and hepatotoxicity. It is speculated that the activity of isoniazid derivatives is, in part, related to the cleavage of the protecting group. Therefore, this study aimed to evaluate the cleavage characteristics of previously developed isoniazid derivatives through kinetic studies by high-performance liquid chromatography with ultraviolet-diode array detectio to establish a comparison between the rates of the process and the respective activities against M. tuberculosis. Chromatographic separations were performed on an XDB C18 column coupled to an XDB C18 precolumn. The mobile phase consisted of ultrapure water and acetonitrile in gradient mode. The flow rate was 1.0 mL/min, the injection volume was 20 µL, and the detection wavelengths were 230 nm (derivatives and isatins) and 270 nm (isoniazid). Incubation of derivatives was carried out for 5 days in 10 mmol/L phosphate buffer solution (pH 3.0, 7.4, 8.0) or in fetal bovine serum at 37 °C. The incubation reduced the concentration of the derivatives and led to the formation of isoniazid in a first-order kinetic reaction. Isoniazid formation was logarithmically correlated with the minimum inhibitory concentration of the derivatives. The results showed that higher cleavage rates are associated with greater activities against M. tuberculosis, providing important information for the development of future generations of isoniazid derivatives and for screening drug candidates for the treatment of tuberculosis.

Ochratoxin a levels in fermented specialty coffees from Caparaó, Brazil: Is it a cause of concern for coffee drinkers?

Although postharvest coffee fruit fermentation can improve coffee flavour and quality, the mycotoxin ochratoxin A (OTA) can also be a result of microbiological activity, albeit in the later drying step of coffee processing. To evaluate the possible occurrence of OTA contamination in postharvest fruit fermentation, fourteen coffees that entailed two different postharvest fruit fermentation times were evaluated. These coffees originated in the surroundings of the village of Pedra Menina in the qualified Denomination of Origin and coffee producer region of Caparaó on the border between Minas Gerais and Espírito Santo states in Brazil. All coffees were classified according to the Specialty Coffee Association (SCA) protocol and 12 achieved specialty level. OTA was determined in all 14 coffees using immunoaffinity for sample clean-up and high-performance liquid chromatography with fluorescence detection for quantification. One sample presented an OTA concentration of 0.75 µg kg-1 and two samples showed OTA concentrations of 0.87 µg kg-1. The other samples had concentrations of OTA below the limit of quantification obtained in this work (0.64 µg kg-1). Thus, all samples showed OTA concentrations far below the most stringent maximum residue limit (MRL) of 5 µg kg-1 established for roasted coffees by European legislation. These low levels were similar to most of the previous results for Brazilian coffees listed and tabled in this work. This comparison showed that OTA contamination due to this kind of postharvest process - fruit fermentation - should not be a concern for producers and consumers of these fermented coffees.

Development and validation of a multipurpose and multicomponent method for the simultaneous determination of six synthetic dyes in different foodstuffs by HPLC-UV-DAD.

A simple and low-cost multipurpose analytical method using HPLC-UV-DAD was developed and validated, following international guidelines, for the determination of six synthetic food dyes: Tartrazine, Sunset Yellow, Amaranth, Allura Red, Indigotine, and Brilliant Blue. The method required a simple sample preparation step that consisted of dissolution or dilution of the samples in water, followed by pH adjustment and filtering through PVDF filters. No significant matrix effect was verified. Linear working ranges varied from 0.25 to 6.0 mg L-1. Appropriate limits of quantification (0.10 to 0.15 mg L-1), mean recoveries (90.2 to 106.6%), and repeatability and intermediate precision (<4.5%) were obtained. Sixty-one samples of different types of foodstuffs were analyzed: jelly and juice powder, jelly candy, jujube candy, hard candy, ice cream syrup, sports drinks, soft drinks, energy drinks, artificially colored ready-to-drink fruit juices and flavored alcoholic beverages. All studied samples showed dye levels in conformity with Brazilian regulations.

Direct determination of amino acids in brewery worts produced by different processes by capillary zone electrophoresis.

The direct and simultaneous determination of cysteine, histidine, phenylalanine, lysine, tryptophan and arginine in brewery worts by capillary zone electrophoresis (CZE) was applied to evaluate the effects of temperature control and protease supplementation during mashing on the changes of these amino acids (AAs) wort composition. A cation exchange resin was used for AAs extraction from wort samples prior to CZE determination. The separation was achieved using a 50 mmol/L phosphate buffer at pH 12.5, containing 0.4 mmol/L cetyltrimethylammonium bromide (CTAB), as background electrolyte (BGE) solution; -20 kV; 20°C and hydrodynamic injection time of 15 s, at 50 mbar. Recovery evaluation using worts led to values between 83.1 and 96.2%, demonstrating the method feasibility, which was successfully applied in the quantification of AAs in wort samples. This study showed that temperature control and addition of exogenous proteases in the mashing may increase the AAs concentration in wort, improving the final product quality (beer). The present method is a good alternative for monitoring specific AAs in worts and their determination can allow the brewing process optimization.