title: Comprehensive evaluation of the photo-transformation routes of trans-resveratrol.
abstract: Liquid chromatography (LC) combined with accurate mass spectrometry (MS), based on the use of a hybrid quadrupole time-of-flight (TOF) MS system, is employed to systematically investigate the photo-transformation routes of trans-resveratrol. Experiments were performed in quartz tubes, containing ethanolic solutions (12% v/v) of the precursor compound, exposed to different ultraviolet (UV) sources and to solar light. Time-courses of trans-resveratrol and transformation products (TPs) were investigated by direct injection of different reaction times aliquots in the LC-QTOF-MS system. Structural elucidation of detected TPs was derived from interpretation of their accurate product ion scan spectra. Trans-resveratrol labelled with (13)C6 in the mono-hydroxylated ring was also employed to further confirm the exact positions of some substituents in the generated TPs. In addition to the well-known trans-/cis-isomerization process, three different main reactions pathways were noticed under all the investigated conditions: (1) water addition to the exocycle double bond followed by oxidation to a ketone and cleavage of the molecule, (2) intramolecular cyclization to render a trihydroxylated phenanthrene, and (3) oxidation of the phenanthrene-like derivative to generate an orto-diquinone. Both, the trihydroxylated phenanthrene and the orto-diquinone underwent further aromatic hydroxylation reactions. The above transformation routes were also noticed for cis-resveratrol and the two analogue phytoalexins piceid and piceatannol. In addition to above transformation pathways, under solar light exposure, resveratrol underwent a molecular re-arrangement rendering the so-called resveratrone, whose structure consists of two fused aromatic rings bonded to a linear chain containing a carbonyl group conjugated with a double bond.
authors.affiliation: Departamento de Química Analítica, Nutrición y Bromatología, Instituto de Investigación y Análisis Alimentario (IIAA), Universidad de Santiago de Compostela, Santiago de Compostela 15782, Spain.
authors.forename: T
authors.initials: T
authors.lastname: Rodríguez-Cabo
authors.affiliation: Departamento de Química Analítica, Nutrición y Bromatología, Instituto de Investigación y Análisis Alimentario (IIAA), Universidad de Santiago de Compostela, Santiago de Compostela 15782, Spain. Electronic address: isaac.rodriguez@usc.es.
authors.forename: I
authors.initials: I
authors.lastname: Rodríguez
authors.affiliation: Departamento de Química Analítica, Nutrición y Bromatología, Instituto de Investigación y Análisis Alimentario (IIAA), Universidad de Santiago de Compostela, Santiago de Compostela 15782, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Ramil
authors.affiliation: Departamento de Química Analítica, Nutrición y Bromatología, Instituto de Investigación y Análisis Alimentario (IIAA), Universidad de Santiago de Compostela, Santiago de Compostela 15782, Spain.
authors.forename: R
authors.initials: R
authors.lastname: Cela
mesh_terms: D002853:Chromatography, Liquid / Q000379:methods; D003500:Cyclization; D007536:Isomerism; D013058:Mass Spectrometry / Q000379:methods; D010084:Oxidation-Reduction; D055668:Photochemical Processes; D000077185:Resveratrol; D013267:Stilbenes / Q000737:chemistry / Q000528:radiation effects*; D013472:Sunlight; D013997:Time Factors; D014466:Ultraviolet Rays
chemical_list: D013267:Stilbenes; D000077185:Resveratrol
keywords: Light; Liquid chromatography quadrupole time-of-flight mass spectrometry; Resveratrol; Transformation products