The influence of the processing conditions during the spray drying of mixtures of blueberry juice (BJ) and maltodextrin (MX) was determined quantitatively by the analysis of variance (ANOVA), and ...qualitatively by the surface response plots (SRP). The effect of two independent variables (inlet temperature, and MX concentration), and one categorical variable (type of MX), was determined on the yield (Y), content (Q), and retention (R) of the antioxidant quercetin 3-d-galactoside. From the ANOVA results, the concentration was the main variable affecting Y and Q, while temperature had a negligible effect, and the low molecular weight MXs exhibited a better response. The physicochemical characterization showed that the powder appearance and microstructure remained unaffected, but size and morphology of the particles varied with the processing conditions. This study established the optimal processing conditions for the spray drying of BJ-MX, and the application limits of the MXs based on the molecular weight distribution.
Rationale
Capsaicinoids are prevalent secondary metabolites in many natural and synthetic pharmacological compounds. To date, several soft ionization studies related to capsaicinoids have been ...reported; they all proposed a common fragmentation pattern based on a rearrangement of the aromatic double bonds and the fragmentation of the various positional acyl chains. However, the mechanism has never been validated by high‐resolution analyses. Consequently, in this work, a validated fragmentation mechanism of the main capsaicinoids, capsaicin (1) and dihydrocapsaicin (2), is offered.
Methods
In order to propose and validate a common electron ionization (EI) fragmentation mechanism for the target analytes, the following mass spectrometric methods were employed: collision‐induced dissociation (CID) by means of linked scans (LS), reinforcing the methodology by high‐resolution mass spectrometry (HRMS), in addition to appropriate deuterium‐labeled experiments performed using gas chromatography/mass spectrometry (GC/MS) and direct analysis in real time (DART).
Results
In a first stage, a common EI fragmentation pattern comprising two pathways was proposed for compounds 1 and 2; then, the suggested mechanism was validated by CID‐LS together with HRMS complemented by DART‐deuterium‐labeling studies. The obtained results are indicative that the corresponding molecular ions were conveniently observed, m/z 305 and m/z 307; it is worth noting that the common base peak is in correspondence with a tropylium ion derivative (m/z 137), as a consequence of a McLafferty rearrangement. In addition to these highlighted fragments, other common ions, m/z 122 and m/z 94, and their corresponding trajectory, were confirmed using the same approach. Finally, the proposed mechanism was complementarily validated by deuterium‐labeling studies, taking into account the two exchangeable hydrogens present in the phenolic and the amidic moieties.
Conclusions
A common validated EI fragmentation pattern for both capsaicin and dihydrocapsaicin was established using appropriated mass spectrometric methods together with convenient hydrogen/deuterium labeling. This study provides a new alternative to validate mechanisms of fragmentation of important natural products.
In recent years, phylogenetic analysis of HIV sequence data has been used in research studies to investigate transmission patterns between individuals and groups, including analysis of data from HIV ...prevention clinical trials, in molecular epidemiology, and in public health surveillance programs. Phylogenetic analysis can provide valuable information to inform HIV prevention efforts, but it also has risks, including stigma and marginalization of groups, or potential identification of HIV transmission between individuals. In response to these concerns, an interdisciplinary working group was assembled to address ethical challenges in US-based HIV phylogenetic research. The working group developed recommendations regarding (1) study design; (2) data security, access, and sharing; (3) legal issues; (4) community engagement; and (5) communication and dissemination. The working group also identified areas for future research and scholarship to promote ethical conduct of HIV phylogenetic research.
A green approach for the synthesis of a set of ten 4-aryl substituted-5-alcoxy carbonyl-6-methyl-3,4-dihydro-2(1H)-pyridones using Meldrum's acid has been devised, the absence of solvent and the ...activation with infrared irradiation in addition to a multicomponent protocol are the main reaction conditions. The transformations proceeded with moderated yields (50-75%) with a reasonable reaction rate (3 h). It is worth noting that two novel molecules of the new class of the bis-3,4-dihydropyridones were also obtained. In addition, a comparison without the use of infrared irradiation was performed.
La colangiopancreatografía retrógrada endoscópica (CPRE) es uno de los procedimientos endoscópicos más complejos y ampliamente utilizados. El equipo encargado de realizar una CPRE debe ofrecer la ...máxima eficiencia y seguridad durante el procedimiento. Para lograr calidad en la realización de CPRE deben establecerse indicadores de calidad. El presente manuscrito es el consenso desarrollado por la AMEG sobre indicadores de calidad en atención de la salud al efectuar una CPRE. Dichos indicadores se establecen dentro de un marco conceptual que toma en cuenta la evidencia científica disponible en la actualidad y la disponibilidad de recursos en nuestro país.
A new magnetically assisted transferred plasma torch (MA-TPT) was specially developed for the treatment of ceramic clay and harmful substances. The electrical plasma source consists mainly of a power ...buck converter and an alternating magnetic field, which allow sustaining a highly efficient plasma discharge at different arc lengths. The interaction of the electric arc with the magnetic field produces a broadening arc effect on the anode, enhancing the heat fluxes to the ceramic clay. Electrical and thermal characterization of the plasma torch showed that high thermal efficiency is easily reached with the current plasma configuration. In turn, the characterization tests of the vitrified clay revealed that the final vitrified product presents good chemical stability.
Qué tan verde es un experimento? Morales Galicia, Marina L.; Martínez, Joel O.; Reyes-Sánchez, Laura Bertha ...
Educación química,
July 2011, Letnik:
22, Številka:
3
Journal Article
Recenzirano
Odprti dostop
There are many publications pretending to belong to the green chemistry protocol; however, only few papers ask questions and make suggestions in order to obtain an appropriate evaluation about the ...green approach of a particular experiment. Thus, in this paper a contribution for an educative change is offered, searching for sustainability; the goal is to establish a model, in a critical way and under the green chemistry protocol: how green is a chemical experiment?
En muchos trabajos de investigación publicados se manifiesta que son verdes; sin embargo, hasta ahora pocos son en los que se cuestiona qué tanta es su incidencia en los planteamientos de la Química Verde, o en los cuales se proponga cómo evaluar ésta. Por ello, con la finalidad de contribuir a un cambio educativo que acerque a la química a la búsqueda cotidiana de la sostenibilidad, en este documento se presenta una propuesta para analizar de forma crítica y bajo el protocolo de la química verde, desarrollos experimentales, tanto de publicaciones en revistas indizadas, como de prácticas, ejercicios o proyectos educativos, con objeto de establecer criterios para determinar qué tan verde es un experimento o proceso.
El protocolo de la Química Verde no estipula un número mínimo de principios que deben satisfacerse para que un proceso, un producto químico o una reacción sean considerados como verdes, por lo que en este trabajo se presenta una propuesta innovadora de índices para evaluar el acercamiento verde de un desarrollo experimental. Para ejemplificar dicha sugerencia metodológica se presenta el análisis de tres trabajos diferentes.
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