Química Nova

URI permanente para esta coleçãohttps://thoth.dti.ufv.br/handle/123456789/13323

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2014 - 20183

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Data inicial: 2010Assunto: search.filters.subject.Coffea arabica

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Agora exibindo 1 - 3 de 3
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    Efeito do solvente na extração de ácidos clorogênicos, cafeína e trigonelina em Coffea arabica
    (Sociedade Brasileira de Química, 2014) Moreira, Ivanira; Scheel, Guilherme Luiz; Hatumura, Pedro Henrique; Scarminio, Ieda Spacino
    In this research work the effects of four solvents and their mixtures on the extraction of chlorogenic acids, caffeine and trigonelline in crude extracts of four coffee cultivars, traditional red bourbon, IAPAR59, IPR101 and IPR108 cultivars, were investigated by UV spectrophotometry and UV spectra obtained from RP-HPLC-DAD. The experimental results and the principal component analysis of UV spectra showed that the effect of solvent extraction of the metabolites does not depend on cultivars, because the spectral characteristics are similar, but the concentrations are different. The UV and UV-DAD spectra for four simplex centroid design mixtures were also similar but the concentrations of caffeine, trigonelline and the chlorogenic acids are different and depend on the solvent used in the extraction.
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    Saponificação assistida por micro-ondas na extração de diterpenos em café arábica torrado
    (Sociedade Brasileira de Química, 2017) Bianchin, Mirelli; Yamashita, Fabio; Benassi, Marta de Toledo
    The extraction of kahweol and cafestol involves saponification reaction. This step is important for the efficiency of the extraction as the diterpenes are susceptible to structural changes during hydrolysis. The microwave-assisted saponification has been successfully used in different matrices, but there is no previous report of the use of this technique in the saponification of diterpenes. Therefore, the effect of microwave-assisted saponification on the extraction of kahweol and cafestol in roasted coffee was evaluated. A 32 factorial experimental design was used in order to evaluate the effect of temperature (70, 80, and 90 ºC) and reaction time (4, 8, and 12 min). The quantification of diterpenes was performed by high-performance liquid chromatography and the results were compared to with those obtained by a method, which uses thermostatic bath for saponification. Temperature and time had a significant effect (p < 0.05) on diterpenes levels. For simultaneous saponification of kahweol and cafestol, the optimal reaction conditions were 80 ºC / 12 min. The use of microwave-assisted procedure lead to lower yields of kahweol (24%) and cafestol (35%) compared to reference method. However a significant reduction of reaction time (80%) was achieved, and the procedure also has the advantage of controlled process conditions and the possibility of extended scale.
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    Ursolic acid and cis-tiliroside produced by Merremia tomentosa affect oviposition of Leucoptera coffeella on coffee plants
    (Sociedade Brasileira de Química, 2018) Santos Júnior, Helvécio M.; Lopes, Karina C.; Alves, Dejane S.; Carvalho, Geraldo A.; Oliveira, Denilson F.
    To contribute to the development of new products to control the coffee leaf miner (Leucoptera coffeella), which is a major pest for coffee plants, this work aimed to select plant species able to produce substances active against this insect and to identify the active substances in the selected plant and their protein targets in the insect. Among the extracts of nineteen plant species, only that from leaves of Merremia tomentosa (Choisy) Hall. f. (Convolvulaceae) reduced the oviposition of L. coffeella on leaves of coffee plants. This extract was submitted to successive fractionation steps to achieve the isolation and identification of two active substances, ursolic acid (UA) and cis-tiliroside (CT). An in silico study showed that UA inhibits glycogen phosphorylases (GP) by binding to their allosteric site, while CT probably inhibits xanthine dehydrogenases (XT). As both GP and XT appear to be essential enzymes for insects, these results suggest that, during evolution, L. coffeella learned to identify plants producing inhibitors of these enzymes to avoid oviposition on such plants. Thus, both UA and CT have potential to be used as lead compounds in the development of new products for the control of the coffee leaf miner.