Dominico A. Guillén

Study of the polyphenol content of red and white grape varieties by liquid chromatography-mass spectrometry and its relationship to antioxidant power

There is considerable interest in the analysis of phenolic compounds due to their involvement in the organoleptic characteristics of foods and drinks, and their contribution to protection against cardiovascular diseases and cancers through their antioxidant activity. This article describes studies of the polyphenol content, both total (by means of the Folin-Ciocalteu method) and individual (by means of HPLC, LC-MS and LC-MS-MS) and the antioxidant power, of six varieties of grape over the course of their maturation. A good correlation is found to exist between the total polyphenol content of the samples and their antioxidant power, and both seem diminish along the maturation.

Automated solid-phase extraction for sample preparation followed by high-performance liquid chromatography with diode array and mass spectrometric detection for the analysis of resveratrol derivatives in wine.

A method has been developed for the simultaneous determination of resveratrol in all its forms (free isomers and glycosylates) in wines by high-performance liquid chromatography with diode array and mass spectrometric detection. Prior to injection into the column, preconcentration of the sample by automated solid-phase extraction is carried out. In the detection by UV absorption, quantitation was carried out at 280 and 305 nm, and in detection by mass spectrometry, quantitation was performed in the selected ion monitoring mode at m/z 228 and at m/z 238. A comparative study between both detection systems was carried out.

Determination of volatile phenols in fino sherry wines

An easy, fast and reliable analytical method is proposed to determine the concentration of volatile phenols (ethyl- and vinylphenols) in fino sherry wines. The technique employed is a single stage sample treatment by solid-phase extraction (SPE) following a simple, fast procedure that enables 12 samples to be extracted simultaneously and requires a small volume sample and little time. Subsequently, the extracts are analyzed by gas chromatography (GC) with flame ionization detection. The method proposed has been applied to the study of fino sherry wines affected by microbial contamination with yeasts of the Brettanomyces genus, and the relationship of these yeasts with the concentrations of volatile phenols present in this wine.

Automated on-line-solid-phase extraction—high-performance liquid chromatography-diode array detection of phenolic compounds in sherry wine

A new analytical method has been developed for sample preconcentration and analysis of phenolic compounds in sherry wine using on-line solid-phase extraction(SPE)-HPLC-diode array detection. The samples of wine were injected and adsorbed onto polystyrene divinylbenzene cartridges; a robotic semiflexible system was used to automate the SPE stage. Chromatographic separation was carried out in a Symmetry C18 steel cartridge, with a two-step elution gradient. Peaks were identified by comparing their UV spectra with the library of spectra compiled by the authors.

Development and validation of UPLC for the determination of phenolic compounds and furanic derivatives in Brandy de Jerez.

Brandy and other aged distillates are a rich source of polyphenols. For brandies, contact with wood during ageing makes an important contribution to their polyphenols content. This paper describes the use of a previously devised ultra performance LC (UPLC) method to study the polyphenols content of Brandy de Jerez. UPLC is a new technique in LC offering several potential advantages, especially the reduction of time. Analyses of brandy performed by HPLC were repeated by UPLC. A special UPLC analytical column (Acquity UPLC BEH C18 column, 100 x 2.1 mm), with a particle size of 1.7 microm, forms part of this system. Using the UPLC system enabled the time needed for analysis to be reduced to one tenth of the time needed in the conventional HPLC system. In conclusion, the separation factor results of the UPLC were compared to those obtained using HPLC methods; this demonstrated that simple, high efficiency UPLC gradients are viable and advantageous substitutes for traditional analysis of polyphenols in brandy by HPLC. The method enabled 14 phenolic compounds to be identified and determined in 33 different commercial brandies, and this allowed them to be differentiated in function of quality.

Selection of column and gradient for the separation of polyphenols in sherry wine by high-performance liquid chromatography incorporating internal standards

Abstract A chromatographic column was selected, out of five possibilities tested, which offered sufficient efficiency to separate 21 out of 22 polyphenolic compounds, and the optimum elution gradient. Applied to samples of “fino” sherry wine, a satisfactory resolution of peaks was achieved, which allowed for the inclusion of an internal standard. The chromatographic behaviour of three polyphenolic standard substances was studied using the column and gradient selected, with a view to using them as internal standards for controlling the reliability of the analysis. It was concluded that all three can be used for this task, although 2,5-dihydroxybenzaldehyde is the most suitable in terms of ease of detection at 340 nm; however, the possibility of using the other two phenolic acids, β-resorcylic and 2,6-dimethyoxybenzoic acid, is not discarded as they could conveniently be made use of depending on the chromatographic profile of the sample to be analyzed.

Analysis of low molecular mass phenolic compounds, furfural and 5-hydroxymethylfurfural in Brandy de Jerez by high-performance liquid chromatography-diode array detection with direct injection☆

Abstract The polyphenolic composition of aged distillates originates principally from the ageing process in oak casks. It is accounted for by a narrow range of species. The relative simplicity of this wine industry product permits the analysis by HPLC with direct injection. The repeatability of the method has proved very high, in respect of both retention times and peak areas. The initial optimization of the elution gradient was completed by means of a solution comprising a mixture of standards and was definitely improved using real samples. A C18 column, 25 cm × 4 mm I.D., was used, with a particle size of 5 μm. Spectrophotometric detection, covering the UV-Vis range of 240–390 nm, was performed using a photodiode array detector.

Automation of sample preparation as a preliminary stage in the high-performance liquid chromatographic determination of polyphenolic compounds in sherry wines

Abstract The procedure for automating the method of sample preparation by solid-phase extraction prior to the HPLC analysis of polyphenolic compounds in sherry wine is described. This method consists of two stages, the first being sample preconcentration and cleaning using a C18 cartridge and the second fractionation using a SAX anion exchanger. The first direct application of the method, using a semi-flexible robot system, did not produce satisfactory results, thus requiring a series of modifications and optimization of the variables inherent in the device itself. The automated method as modified produced considerable improvements over the manual method with respect to the recovery and repeatability values obtained with the different polyphenolic species used in its optimization. Subsequent testing of the method with real samples of sherry wine proved its applicability for tracking the evolution of polyphenolic species in wine.

High-performance liquid chromatographic analysis of polyphenolic compounds predominating in sherry musts

A chromatographic procedure has been developed for the analysis of polyphenolic compounds in sherry musts. The procedure allows for the use of internal standards to control the different steps of the analysis. A C18 reversed-phase column of 25 cm length and 4 mm diameter charged with 5 μm particle size filling is used in connection with a gradient in stages consisting of a 2% acetic acid solution in methanol. The choice of the gradient has been previously worked out as applied to a mixture of 22 polyphenolic compounds. In order to ensure the stability of the must samples they are mixed with 10% dimethylformamide and 2% ascorbic acid. The internal standard is then added to the samples, which are subsequently submitted to a continuous rotary extraction process for 3 h using diethyl ether.

Evolution of the colour, antioxidant activity and polyphenols in unusually aged Sherry wines.

The present paper reports the results of a study monitoring several key analytical parameters in a set of aged samples of vintages from 1999 back to 1935. The analysed parameters were: colour, antioxidant activity, low molecular weight phenolics, index of total polyphenols and SO2 content. It can be concluded that the antioxidant activity of the old wines studied is clearly related to the ageing time and to the polyphenols extracted from the wood during this period. The wines also showed differences in their chromatic characteristics according to the duration of their ageing in years. A principal component analysis confirmed that most of the studied variables (except hydroximethylfurfural and SO2) are strictly linked to ageing, which allowed a discrimination of 100% of the wines belonging to different decades, according to the results obtained by means of the application of linear discriminant analysis.