*A quem a correspondência deve ser enviada ResumoA vitamina C é um nutriente extremamente importante para a fisiologia humana. No Brasil o consumo de vitamina C sob a forma de concentrados vitamínicos ainda é bastante restrito devido aos altos preços, restando para a maioria da população o consumo via alimentos como frutas e vegetais. A dosagem de vitamina C em alimentos tem, então, um papel crucial no que diz respeito aos estudos pós-colheita para a conservação e a minimização das perdas deste nutriente tão sensível. Neste estudo, é apresentado um método para análise de vitamina C por cromatografia líquida de alta eficiência utilizando coluna de troca iônica forma hidrogênio, que demonstrou ser mais eficiente do que os métodos usuais por coluna de fase reversa (C18) para matrizes complexas e baixos teores do analito. A reprodução dos perfis cromatográficos foi em nível de linha de base com picos de pureza espectral comprovada por detector de arranjo de diodos. Esse método também foi avaliado segundo a extração mais adequada para estabilização da vitamina C, e mostrou que a fase móvel (ácido sulfúrico suprapuro ® 0,05 M) foi uma solução extratora adequada para a estabilização da vitamina C. Palavras-chave: ácido ascórbico; ácido deidroascórbico; troca iônica; partição por fase reversa. AbstractVitamin C is an essential nutrient for human physiology. In Brazil, vitamin C supplements are expensive and most of the population obtains vitamin C through its consumption of fruits and vegetables. Therefore, the vitamin C assay in food is crucial in post-harvest studies to conserve and minimize losses of this highly sensitive nutrient. This study proposes a method for analyzing vitamin C by High Performance Liquid Chromatography using a hydrogen type ion exchange column, and demonstrates that it is more efficient than the traditional methods of reverse phase column (C18) for complex matrixes and low levels of this analyte. Chromatograms were baseline resolved and peak purity evaluation showed spectral homogeneity by photo diode array detector. This method was also tested using the best extraction solution to stabilize vitamin C, demonstrating that 0.05 M of superpure sulfuric acid (also the mobile phase) was the most efficient solution for this purpose.

Coffee is a popular drink consumed all over the world. Besides its long-recognized stimulant effect, it has important nutritional and health effects. However, the type of bean processing modifies the composition of brewed coffee and possibly its bioactivity. In this study, extracts obtained from green and roasted beans of Coffea canephora (Coffea canephora var. robusta) were submitted to spray- or freeze-drying and were tested for antiproliferative activity, using MTT assay, and their influence on the cell cycle and apoptosis by flow cytometry analysis. Moreover, colors and nutrient contents were measured to identify the changes due to the roasting process. The results obtained showed that extracts from green and light roasted beans exhibited strong bioactive capacity. Coffee extracts promoted a decrease in cell viability, modulated cell cycle and induced apoptosis in human prostate carcinoma cell line (DU-145). The level of roasting reduced this property, but the type of drying did not in all cases.

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Coffee roasting needs precise control and innovative techniques that are economically viable to monitor and improve its consistency. In this study, mass spectrometry was used as a tool to screen chemical markers that appear on the surface of coffee beans (whole bean) along the roasting process. A non-target and non-volatile approach was used with an ambient technique (EASI) coupled to a single quadrupole mass analyzer to monitor roasting chemical changes in the coffee bean. Green (raw), soft, medium, dark and very dark roasted coffee beans showed a decrease in ions in the range of m/z 500-600, whereas an increase in abundance in the m/z 800-900 range was clearly observed in the most roasted coffees. A multivariate approach through PCA separated the different roasts in 70% of the variance using PC1 and PC2. The major ions in the range of m/z 500-600 were characterized by ESI-MS and also HPLC-fluorescence as the N-alkanoyltryptamides, surface constituents of coffee wax layer which are almost fully degraded in darker roasts. The ions in the range of m/z 800-900 were characterized as di-and triacylglicerols and its increase during the roasting process was systematically observed. For these classes of chemical markers of the roasting process, ESI-MS showed also the sodium and potassium adducts with good relative abundances.