Model studies on the photosensitized isomerization of bixin

dc.creatorMontenegro, MA
dc.creatorRios, AD
dc.creatorMercadante, AZ
dc.creatorNazareno, MA
dc.creatorBorsarelli, CD
dc.date2004
dc.date46753
dc.date2014-11-18T09:37:59Z
dc.date2015-11-26T16:53:34Z
dc.date2014-11-18T09:37:59Z
dc.date2015-11-26T16:53:34Z
dc.date.accessioned2018-03-28T23:40:42Z
dc.date.available2018-03-28T23:40:42Z
dc.identifierJournal Of Agricultural And Food Chemistry. Amer Chemical Soc, v. 52, n. 2, n. 367, n. 373, 2004.
dc.identifier0021-8561
dc.identifierWOS:000188366300036
dc.identifier10.1021/jf0349026
dc.identifierhttp://www.repositorio.unicamp.br/jspui/handle/REPOSIP/82462
dc.identifierhttp://www.repositorio.unicamp.br/handle/REPOSIP/82462
dc.identifierhttp://repositorio.unicamp.br/jspui/handle/REPOSIP/82462
dc.identifier.urihttp://repositorioslatinoamericanos.uchile.cl/handle/2250/1276621
dc.descriptionThe photosensitized isomerization reaction of the natural cis carotenoid bixin (methyl hydrogen 9'-cis-6, 6'-diapocarotene-6, 6'-dioate) with rose bengal or methylene blue as the sensitizer in acetonitrile/methanol (1:1) solution was studied using UV-vis spectroscopy, high-performance liquid chromatography (HPLC), and time-resolved spectroscopic techniques, such as laser-flash photolysis and singlet oxygen phosphorescence detection. In both N-2- and air-saturated solutions, the main product formed was all-trans-bixin. The observed isomerization rate constants, k(obs), decreased in the presence of air or with increase in the bixin concentration, suggesting the participation of the excited triplet state of bixin, (3)Bix*, as precursor of the cis--> trans process. On the other hand, bixin solutions in the absence of sensitizer and/or light did not degrade, indicating that the ground state of bixin is stable to thermal isomerization at room temperature. Time-resolved spectroscopic experiments confirmed the formation of the excited triplet state of bixin and its deactivation by ground state bixin and molecular oxygen quenching processes. The primary isomerization products only degraded, in the presence of air and under prolonged illumination conditions, probably due to the formation of oxidation products by reaction with singlet molecular oxygen. An energy-transfer mechanism was used to explain the observed results for the bixin transformations, and the consequences for food color are discussed.
dc.description52
dc.description2
dc.description367
dc.description373
dc.languageen
dc.publisherAmer Chemical Soc
dc.publisherWashington
dc.publisherEUA
dc.relationJournal Of Agricultural And Food Chemistry
dc.relationJ. Agric. Food Chem.
dc.rightsfechado
dc.sourceWeb of Science
dc.subjectbixin
dc.subjectphotoisomerization
dc.subjectphotosensitization
dc.subjectsinglet oxygen and triplet states
dc.subjectThermal-degradation Products
dc.subjectFood Coloring Formulations
dc.subjectSinglet Oxygen
dc.subjectMolecular-oxygen
dc.subjectBeta-carotene
dc.subjectRate Constants
dc.subjectMinor Carotenoids
dc.subjectAqueous-solution
dc.subjectOrellana Seeds
dc.subjectTriplet-state
dc.titleModel studies on the photosensitized isomerization of bixin
dc.typeArtículos de revistas


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