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Rationale: Grape polyphenols are antioxidant compounds, markers in vine chemotaxonomy, and involved in color stabilization of red wines. Sugar acylation usually confers higher stability on glycoside derivatives and this effect is enhanced by an aromatic substituent such as p-coumaric acid. Until now, only p-coumaroyl anthocyanins have been found in grape., Methods: A method of 'suspect screening analysis' by ultra-high-performance liquid chromatography/high-resolution mass spectrometry (UHPLC/QTOFMS) has recently been developed to study grape metabolomics. In the present study, this approach was used to identify new polyphenols in grape by accurate mass measurement, MS/MS fragmentation, and study of correlations between fragments observed and putative structures., Results: Three putative p-coumaroyl flavonoids were identified in Raboso Piave grape extract: a dihydrokaempferide-3-O-p-coumaroylhexoside-like flavanone, isorhamnetin-3-O-p-coumaroylglucoside, and a chrysoeriol-p-coumaroylhexoside-like flavone. Accurate MS provided structural characterization of functional groups, and literature data indicates their probable position in the molecule. A fragmentation scheme is proposed for each compound., Conclusions: Compounds were identified by overlapping various analytical methods according to recommendations in the MS-based metabolomics literature. Stereochemistry and the definitive position of substituents in the molecule can only be confirmed by isolation and characterization or synthesis of each compound. These findings suggest addressing research of acylated polyphenol glycosides to other grape varieties., (Copyright © 2015 John Wiley & Sons, Ltd.)

Rationale: Anthocyanins confer the color to red wines. During wine aging, new anthocyanin derivatives with peculiar chromatic characteristics are formed. A fast and selective method for screening the anthocyanin composition of wine has been developed., Methods: Direct-infusion electrospray ionization tandem mass spectrometry (ESI-MS/MS) analysis of wine extracts has been performed by operating in positive ion mode with a low spray capillary voltage (0.5 kV) to detect only the species already present in ionic form. The method has been called direct-infusion pneumatic spray (DIPS) mass spectrometry. The anthocyanin profiles of thirteen red wines at different aging stages were studied. Using malvidin-3,5-diglucoside as internal standard, the indices of wine color and of wine color evolution were estimated., Results: By decreasing the spray capillary voltage a dramatic increase in selectivity toward anthocyanins has been observed and the related peaks are the most abundant in the spectra. Several anthocyanins and anthocyanin derivatives (pyranoanthocyanins and derivatives formed by reaction with flavan-3-ols) have been identified in the wines. The younger wines showed higher total anthocyanin index. The aged wines showed color evolution index higher than 20% while it was lower in the younger samples., Conclusions: The anthocyanin fingerprint is effective for estimating the aging state of wine. The color evolution index can be correlated to barrel conditions during wine aging and used to distinguish between aged and younger wines. The study of pyranoanthocyanins and anthocyanin-flavanol derivatives can be useful to predict wine color stability., (Copyright © 2012 John Wiley & Sons, Ltd.)

2'-Aminoacetophenone (o-AAP) was identified as the main cause of the aging note called 'hybrid note' or 'foxy smell' which is typical of non-Vitis vinifera grapes. Together with methyl anthranilate (MA), this compound contributes to the typical foxy taint of wines made with non-Vitis vinifera grapes. 3-Alkyl-2-methoxypyrazines in grapes, with their herbaceous note and very low sensory thresholds, contribute to the aroma of several wines. In this study, a solid-phase microextraction gas chromatography/ion trap tandem mass spectrometry (SPME-GC/IT-MS/MS) method for simultaneous detection of o-AAP, MA and ethyl-, isopropyl-, sec-butyl- and isobutylmethoxypyrazine in grape juice was developed. The method was applied to the study of several grape juices: the time required for analysis was less than 24 min, and the method was considered to be suitable for analysis of 'foxy compounds' and methoxypyrazines in grape juice. The high levels of MA and o-AAP found in Clinton and Siebel grapes confirmed the 'hybrid' character of these varieties., (Copyright 2010 John Wiley & Sons, Ltd.)

In a previous work, direct-infusion electrospray ionization ion trap tandem mass spectrometry (ESI-IT-MS/MS) was applied to the study of anthocyanins in extracts from the skins of Clinton grapes, a non-Vitis vinifera red grape variety qualitatively and quantitatively rich in anthocyanins. A good characterization of anthocyaninins was obtained, but it was impossible to differentiate some compounds with the same nominal mass but with different elemental composition. In this work, the capabilities of quadrupole time-of-flight mass spectrometry (QTOF-MS) coupled with Chip-liquid chromatography (LC-Chip) were applied to the study of Clinton anthocyanins and this method provided the complete sample anthocyanin fingerprint in less than 5 min. Multi-stage mass spectrometry (MS(n); n >2) was not necessary to identify isobaric compounds, nor were deuterium-exchange experiments necessary to distinguish between compounds containing the same aglycone. The fast separation bypasses the problem of petunidin-3-O-(6-O-acetyl)monoglucoside and delphinidin-3,5-O-diglucoside quantification, present in the direct-infusion ESI-ITMS approach, due to overlapping with matrix interferences.

Resveratrol (3,5,4'-trihydroxystilbene) and piceatannol (3,4,3',5'-tetrahydroxy-trans-stilbene) are phytoalexins present in red grapes and wines. In vitro studies have revealed that piceatannol blocks LMP2A, a viral protein-tyrosine kinase implicated in leukemia, non-Hodgkin's lymphoma and other diseases associated with the Epstein-Barr virus, and has an antimelanoma effect on human melanoma cells. Resveratrol has several beneficial effects on human health, such as anticancer, cardioprotection, antioxidant, inhibition of platelet aggregation and anti-inflammatory activity. In this investigation, the collisional behaviour of deprotonated resveratrol and piceatannol obtained under electrospray conditions is described. The mechanisms involved in the fragmentation pattern of [M-H](-) species of the two compounds were investigated by performing MS(n) experiments, deuterium labelling and accurate mass measurements.

A new sensitive and selective analytical method for the analysis of ochratoxin A (OTA) in grape and wine was developed by coupling liquid chromatography and surface activated chemical ionization and mass spectrometry with multistage fragmentation (LC/SACI-MS(3)). A high flow gradient was used to strongly reduce the matrix effect phenomenon, and the wine sample was directly injected onto the chromatographic column without sample pre-concentration or purification steps. The amount of OTA was determined for two grape extracts and the amount of OTA, percent accuracy error and percent precision error were analyzed for 15 wine samples. An excellent limit of detection of 0.02 ng/mL was achieved, and the limit of quantification was at least 20-fold lower than the maximum legal limit for OTA (2 ppb). Due to the low limit of quantification, this novel method is a potential tool for official OTA screening purposes., (Copyright 2007 John Wiley & Sons, Ltd.)