RESUMO
Colombia is a producer of fine cocoa, according to the International Cocoa Organization; however, most of its exports are in the ordinary cocoa category. To remedy this situation, several national organizations are working to create technological platforms for small producers to certify the quality of their beans. The objective of this study was to identify differential chemical markers in 36 cocoa bean samples from five Colombian departments and associate them with cocoa quality properties. For this purpose, a non-targeted metabolomics approach was performed using UHPLC-HRMS, along with sensory and physicochemical analyses. The 36 samples did not differ in sensory quality, polyphenol content, and theobromine/caffeine ratio. However, the multivariate statistical analysis allowed us to differentiate the samples into four clusters. In addition, a similar grouping of the samples was also observed in the physical analyses. The metabolites responsible for such clustering were investigated with univariate statistical analysis and presumptively identified by comparison of experimental mass spectra with those reported in databases. Alkaloids, flavonoids, terpenoids, peptides, quinolines, and sulfur compounds were identified as discriminants between sample groups. Here, it was presented the metabolic profiles as an important chemical feature for further studies in quality control and more specific characterization of fine cocoa.
Assuntos
Cacau , Colômbia , Cacau/química , Polifenóis/análise , Flavonoides/metabolismo , MetabolômicaRESUMO
Abstract This paper presents a study of the fluorescence quenching of 1-hydroxypyrene-3,6,8-trisulfonic acid (HPTS) in the presence of single-walled carbon nanotubes (SWCNT) using a fluorescence method. To investigate the quenching mechanism (dynamic or static) of HPTS, Stern-Volmer plots of single walled carbon nanotubes at different temperatures were used. The positive deviation from linearity in Stern-Volmer plots suggests that single walled carbon nanotubes follow a static quenching mechanism evidenced by the formation of a stable ground state complex. The results presented here help us to clarify the quenching mechanism in the interaction of a pyrene derived dye and carbon nanotubes. This study will open new possibilities in the use of the conjugate formed by SWCNTs and HPTS in the fabrication of a biosensor based on intracellular fluorescent probes.
Resumen Este artículo presenta el estudio de la desactivación de florescencia del ácido 1-hidroxipyreno-3,6,8-trisulfónico (HPTS) en presencia de nanotubos de carbono de pared única (SWCNT). Para investigar el mecanismo de desactivación (dinámico o estático) del HPTS se evaluaron nanotubos de carbono de pared única a diferentes temperaturas y se analizaron por medio de gráficas Stern-Volmer. La desviación positiva de la linealidad en las gráficas Stern-Volmer sugiere que los nanotubos de carbono de pared única actúan por medio de un mecanismo de desactivación estático, que se evidencia también por la formación de un complejo estable en estado fundamental. Los resultados presentados aquí nos ayudan a aclarar el mecanismo de desactivación de fluorescencia cuando tiene lugar la interacción entre un colorante derivado del pireno y nanotubos de carbono. Este estudio abre nuevas posibilidades para el uso de conjugados formados por SWCNT y HPTS en la fabricación de un biosensor basado en sondas fluorescentes intracelulares.
Resumo Este artigo apresentao estudo da diminuicao da fluorescência do ácido 1-hidroxipireno-3,6,8-trisulfônico (HPTS) em presença de nanotubos de carbono de parede simples (SWCNT). Para investigar o mecanismo da desativação (dinâmico ou estático) do HPTS se avaliaram nanotubos de parede simples em diferentes temperaturas e se analisaram por meio de gráficos Stern-Volmer. O desvio positivo de linearidade nos gráficos Stern-Volmer sugere que os nanotubos de carbono de parede simples atuam por meio de um mecanismo de desativação estática, que também se evidencia pela formação de um complexo estável fundamental. Os resultados apresentados aqui nos ajudam a aclarar o mecanismo de desativação de fluorescência quando ocorre a interação entre um corante derivado do pireno e nanotubos de carbono. Este estudo abre novas possibilidades para o uso de conjugados formados por SWCNT e HPTS na fabricação de um biosensor baseado em sondas fluorescentes intracelulares.
Assuntos
Nanotubos de Carbono/estatística & dados numéricos , FluorescênciaRESUMO
The mechanisms and energetics governing the gas-phase reactions of a series of substituted singlet carbenes with water were studied using highly correlated ab initio molecular orbital calculations. Monosubstituted singlet carbenes ((1)[X-C-H]) were allowed to react with one and two water molecules in the gas phase (X = H, Me, CN, Cl, F for reactions with one water molecule and X = CN, Cl, F for reactions with two water molecules). Our results indicate the presence of stable ylide-like intermediates in all cases studied, with overall and intrinsic barriers depending on the nature of the group bonded to the central carbon atom. For the reactions with one water molecule, it is found that, whereas all reaction profiles exhibit positive or near zero intrinsic barriers (intermediate --> TS), carbenes substituted with strong electron withdrawing groups (X = Cl, F) have positive overall barriers but carbenes bearing other substituents react in an overall barrierless fashion to produce the respective alcohols. For reactions with two water molecules, only the fluorine-substituted carbene exhibits an overall barrier. Classical transition-state theory with Eckart tunneling corrections (TST/Eckart) predicts the intermediate --> TS step to be about 3 to 6 orders of magnitude faster for the (1)[X-C-H] + 2H(2)O reactions than for the corresponding 1 water molecule cases. The competitive mechanisms and the effects of substituent and level of theory on the reaction paths are discussed in detail.