title: Supercritical fluid extraction and HPLC determination of relevant polyphenolic compounds in grape skin.
abstract: The polyphenols determined are: (+)-catechin, (-)-epicatechin, rutin, quercetin and trans-resveratrol. Suitable conditions of supercritical fluid extraction were established using ethanol as a modifier of the polarity solvent (supercritical carbon dioxide). Final extraction conditions were: 20% v/v ethanol, 60degreesC, 250 bars and flow rate 2 mL/min. Static step time and dynamic step time were established using a selected grape skin sample. The extract was collected in water; the more polar polyphenols ((+)-catechin and (-)-epicatechin) remain in solution but rutin, quercetin and trans-resveratrol precipitate in this medium, thereby the solution of the extracted polyphenols was filtered. (+)-Catechin and (-)-epicatechin were determined in the liquid fraction, while the solid fraction, containing rutin, quercetin and trans-resveratrol, was solved with ethanol/H20 (40:60). HPLC determination was carried out at C18 stationary phase, with ethanol/water/acetic acid as mobile phases and UV-visible diode array detection. Due to the significant differences between the polarity of the polyphenols, two different mobile phases were used. An ethanol/water/acetic acid (5:93:2) mobile phase was used to determine (+)-catechin (280 nm) and (-)-epicatechin (280 nm). On the other hand, rutin (254 nm), quercetin (254 nm) and trans-resveratrol (306 nm) were resolved using ethanol/water/acetic acid (40:58:2) as mobile phase. Instrumental parameters were optimised and analytical parameters obtained. The analytical method was validated and applied to five different varieties of Vitis vinifera from the geographical area of Valencia.
authors.affiliation: Departamento de Ingeniería Química, Universitat de Valencia, Burjassot, Valencia, Spain.
authors.forename: Amparo
authors.initials: A
authors.lastname: Chafer
authors.forename: M Carmen
authors.initials: MC
authors.lastname: Pascual-Martí
authors.forename: Amparo
authors.initials: A
authors.lastname: Salvador
authors.forename: Angel
authors.initials: A
authors.lastname: Berna
mesh_terms: D002851:Chromatography, High Pressure Liquid; D025924:Chromatography, Supercritical Fluid; D000431:Ethanol; D005419:Flavonoids / Q000032:analysis* / Q000737:chemistry / Q000302:isolation & purification; D005638:Fruit / Q000737:chemistry; D010636:Phenols / Q000032:analysis* / Q000737:chemistry / Q000302:isolation & purification; D059808:Polyphenols; D027843:Vitis / Q000737:chemistry*
chemical_list: D005419:Flavonoids; D010636:Phenols; D059808:Polyphenols; D000431:Ethanol