Extraction of Polyphenols from Vine Shoots of Vitis vinifera by Superheated Ethanol−Water Mixtures

• Published in: Journal of agricultural and food chemistry Vol. 54; no. 23; pp. 8775 - 8781
• Main Authors: Luque-Rodríguez, José M, Pérez-Juan, Pedro, Luque de Castro, María D
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 15.11.2006
• Subjects: agricultural wastes; aqueous solutions; Biological and medical sciences; Chromatography, High Pressure Liquid; Chromatography, Supercritical Fluid - methods; crop residues; ethanol; Ethanol - chemistry; extraction; Flavonoids - analysis; Flavonoids - isolation & purification; Food engineering; Food industries; Fundamental and applied biological sciences. Psychology; General aspects; grapes; heat treatment; Kinetics; Phenols - analysis; Phenols - isolation & purification; Plant Shoots - chemistry; Polyphenols; shoots; superheating; Temperature; Vitis - chemistry; Vitis vinifera; water; Water - chemistry; winemaking; Wood; Ethanol; Extract; Phenolic compounds; Superheated water; Vitis vinifera; Mixture; vine shoots; Liquid; Polyphenol; Vitidaceae; Dicotyledones; Angiospermae; Phenols; agricultural byproducts; Spermatophyta; Extraction; superheated liquid extraction; wood extracts; Shoot
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf061855j

A study of the nonvolatile fraction of extracts from vine shoots obtained by superheated ethanol−water mixtures is presented. The influence of the temperature, extraction time, and percentage of ethanol on extraction was investigated by a multivariate experimental design to maximize the yield of total phenolic compounds, measured by using the Folin−Ciocalteu method. The best values found for these variables were 80% (v/v) ethanol, 240 °C, and 60 min. Under these conditions, the effect of pH was also investigated, and a strong improvement of yield was observed by decreasing the pH. The extracts were subject to liquid−liquid extraction with n-hexane. The remaining polar phase was dried in a rotary evaporator and then reconstituted in 10 mL of water. The insoluble residue was dissolved in 10 mL of methanol. Both fractions (aqueous and methanolic) were analyzed by HPLC, and the differences in composition according to the extraction conditions were studied. Compounds usually present in commercial wood extracts were identified (mainly benzoic and hydroxycinnamic acids and aldehydes); the most abundant were quantified, and the stability of the identified phenolic families under different extraction conditions was also investigated. Finally, the superiority of the superheated liquid extraction over conventional solid−liquid extraction was demonstrated. Keywords: Phenolic compounds; vine shoots; superheated liquid extraction; wood extracts; agricultural byproducts