Review article
Chromatographic Methods for the Analysis of Polyphenols in Wines
V. Rastija
; Faculty of Agriculture, Josip Juraj Strossmayer University of Osijek, Osijek, Croatia
M. Medić-Šarić
; Faculty of Pharmacy and Biochemistry, University of Zagreb, Zagreb, Croatia
Abstract
Wine is an excellent source of various classes of polyphenols, including phenolic acids, flavonoids, and trihydroxystilbene resveratrol (Fig.1). Polyphenols play a major role in wine quality since they contribute to the sensory characteristics of wine, particularly color and astringency. A recent interest in these substances has been stimulated by abundant evidence of their beneficial effects on human health, such as anticarcinogenic, antiinflamatory and antimicrobial activities. Therefore, numerous studies have been performed in the attempt to analyze polyphenols in wine. This paper reviews the current advances in the determination of polyphenols in wine by the major chromatographic techniques such as thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC).
The great complexity of the polyphenolic content of wine and the difficulty in obtaining some of the standards usually require sample preparation before analysis. Two methods for sample preparation, liquid-liquid extraction and solid-phase extraction, are most commonly applied. Hydrolysis is applied frequently, but not exclusively, to remove the sugar moieties from glycosides.
TLC on silica gel plates is useful for the rapid and low-cost separation and identification of the polyphenols present in wine (Fig. 2). Densitometric quantitative analysis of polyphenols in wine extracts is usually performed by scanning the TLC plates with UV light at wavelengths of 350–365 nm or 250–260 nm (Fig. 3). For the evaluation of the most efficient mobile phase and an optimal choice of the combination of two or more mobile phases, two methods may be applied: information theory and numerical taxonomy. HPLC currently represents the most popular technique for the analysis of polyphenols in wine. For this purpose, a reversed-phase HPLC method that uses gradient elution with binary elution system is usually employed. Routine detection is based on measurement of UV-Vis absorption with a diode array detector (DAD). Enhancing selectivity and sensitivity for the determination of certain polyphenols requires the application of different detection techniques, such as fluorimetry (Fig. 4), electrochemistry, chemiluminescence, and/or mass spectrometry coupled with ionization techniques: electrospray (ESI), matrix-assisted laser desorption/ionization (MALDI), and atmospheric pressure chemical ionization (APCI).
Gas chromatography (GC) methods developed for the analysis of polyphenols require derivatization to the volatile compounds and mass-spectrometric detection in the selective ion-monitoring mode (GC/MS-SIM).
A special technique, capillary electrophoresis (CE), is a powerful tool for the analysis of polyphenol contents of white and red wines, with an opportune sample preconcentration step. Micellar electrokinetic capillary chromatography (MECC) has extended the utility of capillary electrophoresis to the separation of neutral analytes under the influence of an electric field. Fractionation of monomeric and polymeric pigments of higher molecular mass by gel permeation chromatography (GPC) improved the analysis of these compounds by CE.
Keywords
wine; polyphenols; chromatographic methods
Hrčak ID:
32964
URI
Publication date:
5.3.2009.
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