title: Ultrasound extracted flavonoids from four varieties of Portuguese red grape skins determined by reverse-phase high-performance liquid chromatography with electrochemical detection.
abstract: Several flavonoids present in red grape skins from four varieties of Portuguese grapes were determined by reverse-phase high-performance liquid chromatography (RP-HPLC) with electrochemical detection (ECD). Extraction of flavonoids from red grape skins was performed by ultrasonication, and hydrochloric acid in methanol was used as extraction solvent. The developed RP-HPLC method used combined isocratic and gradient elution with amperometric detection with a glassy carbon-working electrode. Good peak resolution was obtained following direct injection of a sample of red grape extract in a pH 2.20 mobile phase. Eleven different flavonoids: cyanidin-3-O-glucoside (kuromanin), delphinidin-3-O-glucoside (myrtillin), petunidin-3-O-glucoside, peonidin-3-O-glucoside, malvidin-3-O-glucoside (oenin), (+)-catechin, rutin, fisetin, myricetin, morin and quercetin, can be separated in a single run by direct injection of sample solution. The limit of detection obtained for these compounds by ECD was 20-90 pg/L, 1000 times lower when compared with photodiode array (PDA) limit of detection of 12-55 ng/L. RP-HPLC-ECD was characterized by an excellent sensitivity and selectivity, and appropriate for the simultaneous determination of these electroactive phenolic compounds present in red grape skins.
authors.affiliation: Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade de Coimbra, Coimbra, Portugal.
authors.forename: Ivana
authors.initials: I
authors.lastname: Novak
authors.forename: Patricia
authors.initials: P
authors.lastname: Janeiro
authors.forename: Marijan
authors.initials: M
authors.lastname: Seruga
authors.forename: Ana Maria
authors.initials: AM
authors.lastname: Oliveira-Brett
mesh_terms: D000872:Anthocyanins / Q000032:analysis / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid / Q000295:instrumentation / Q000379:methods*; D004563:Electrochemistry / Q000295:instrumentation / Q000379:methods; D005419:Flavonoids / Q000032:analysis* / Q000737:chemistry; D010936:Plant Extracts / Q000737:chemistry; D011174:Portugal; D012680:Sensitivity and Specificity; D014465:Ultrasonics; D027843:Vitis / Q000737:chemistry*
chemical_list: D000872:Anthocyanins; D005419:Flavonoids; D010936:Plant Extracts