Hopeaphenol: the first resveratrol tetramer in wines from North Africa

Grapes and wines are now known to constitute a rich source of phenolics such as stilbenes and flavonoids. These compounds have been shown to have cancer chemopreventive activity and potential beneficial effects on cardiovascular diseases thanks to their antioxidant and antiplatelet properties. However, because little is known about African wines and their phenolic compositions, we investigated wine samples from North Africa. A three-step method was used for the fractionation of the Merlot variety wine: column chromatography followed by centrifugal partition chromatography and reversed-phase semipreparative high-performance liquid chromatography (HPLC). Six polyphenolic compounds of the Merlot variety (from Algeria) were isolated and identified by NMR spectroscopy, five of which are known (trans-resveratrol, trans-piceid, trans-epsilon-viniferin, pallidol, and astilbin) and one that is reported for the first time in wine, (+)-hopeaphenol, a stilbene tetramer. Furthermore, these molecules were quantified in 10 commercial wines from North Africa by means of an analytical HPLC system coupled with diode array detection. Differences in concentrations were found ranging in mg/L from 4.6 to 45 (trans-piceid), 0.66 to 3.45 (trans-resveratrol), 0.2 to 1.2 (trans-epsilon-viniferin), 0.2 to 9.2 (pallidol), 0.3 to 3.8 (hopeaphenol), and 10.8 to 24.22 (astilbin). Such a high level of pallidol and astilbin has never been recorded in wine. North African wines may contribute to a significant proportion of dietary intake of stilbene and astilbin, which may have health benefits.     

Isolation and characterization of novel benzoates, cinnamates, flavonoids, and lignans from Riesling wine and screening for antioxidant activity.

A German Riesling wine has been fractionated with the aid of countercurrent chromatography. After purification by HPLC, the structures of 101 compounds were established by mass spectrometry and NMR spectroscopy. Seventy-three of the isolated compounds exhibited a phenolic or benzylic structure. Fifty-four compounds were reported for the first time as Riesling wine constituents. New compounds identified in this work included twelve benzoic and cinnamic acid derivatives. In addition to two isomeric (E)-caffeoyl ethyl tartrates, the glucose esters of (E)-cinnamic, (E)-p-coumaric, and (E)-ferulic acid, as well as the 4-O-glucosides of (E)- and (Z)-ferulic acid, have been identified for the first time in Riesling wine. The structures of two additional phenylpropanoids were elucidated as 3-hydroxy-1-(4-hydroxy-3-methoxyphenyl)-propan-1-one and 2,3-dihydroxy-1-(4-hydroxy-3-methoxyphenyl)-propan-1-one. Moreover, two ethyl esters, i.e., ethyl protocatechuate and ethyl gallate, as well as the glucose ester of vanillic acid, were newly detected in Riesling wine. Novel representatives in the flavonoid group were dihydrokaempferol, dihydroquercetin, and four dihydroflavonol glycoconjugates, i.e., the 3-O-glucosides of dihydrokaempferol and dihydroquercetin, as well as the 3-O-xyloside and the 3'-O-glucoside of dihydroquercetin. Additionally, six novel lignans, i.e., lariciresinol 4-O-glucoside, three isolariciresinol derivatives, and two secoisolariciresinols, as well as three neolignans were isolated. Structural elucidation of the newly isolated wine constituents is reported together with the determination of their antioxidant activity.     

Levels of stilbene oligomers and astilbin in French varietal wines and in grapes during noble rot development

Phenolics from grapes and wines can play a role against oxidation and development of atherosclerosis. Stilbenes have been shown to have cancer chemopreventive activity and to protect lipoproteins from oxidative damage. A method for the direct determination of stilbene oligomers (viniferin and pallidol) as well as astilbin in different types of wine using high-performance liquid chromatography with UV detection is described. In a survey of 21 commercial wines from the south of France, levels of pallidol and viniferin are reported for the first time in different types of wines. Viniferin was found to be present only in red and botrytized sweet white wines with levels between 0.1 and 1.63 mg/L; pallidol was not found in dry and sweet white wines but only in wines made by maceration with stems, with levels between 0.38 and 2.22 mg/L. Highest levels of astilbin were found in Egiodola (15.13 mg/L), Merlot (11.61 mg/L), and Cabernet Sauvignon (8.24 mg/L) for red wines and in Sauvignon (5.04 mg/L) for white varietal wines. Astilbin levels are highest for recent vintages, but pallidol is not found in older vintages. During noble rot development in Sauvignon or Sémillon grapes from the Sauternes area, levels of trans-astringin, trans-resveratrol, trans-piceid, and pallidol are quite low (<0.5 mg/kg of grapes). Viniferin and astilbin levels become optimum at 2 and 30 mg/kg, respectively, during spot grape and speckle grape stages.     

Positive correlation between high levels of ochratoxin A and resveratrol-related compounds in red wines

The natural occurrence of ochratoxin A in red wines has been widely reported by several authors, as well as a that of group of stilbenes including cis- and trans-resveratrols and related glucosylated forms. In the present study 112 samples of retail red wines were collected from northern (17), central (46), and southern (49) Italy and were analyzed for both ochratoxin A and resveratrol-related stilbenes. The mean levels of total resveratrols and total piceids were 3.14 and 5.80 mg/L, respectively, whereas the ochratoxin A mean level was 0.64 microg/L. The Merlot wines showed the highest mean value of total stilbenes, followed by Negroamaro and Negroamaro blend, Aglianico, and Syrah, all with mean levels of >10 mg/L. Ochratoxin A was detected in 70, 59, and 100% of wine samples from northern, central, and southern Italy, with mean levels of 0.12, 0.07, and 1.36 microg/L, respectively. The highest values of ochratoxin A were recorded in Negroamaro- and Primitivo-based wine samples from southern Italy, showing also the highest content of stilbenes. In wine samples from southern Italy, a positive correlation was obtained between levels of ochratoxin A and total stilbenes (r = 0.74) as well as between ochratoxin A and total resveratrols (r = 0.50) and between ochratoxin A and total piceids (r = 0.74). These results suggest that toxic levels of ochratoxin A in red wine may be, at some extent, counterbalanced by the beneficial effects of resveratrol derivatives. Further investigation should be warranted in this regard.     

Sensory threshold of 1,1,6-trimethyl-1,2-dihydronaphthalene (TDN) and concentrations in young Riesling and non-Riesling wines

1,1,6-Trimethyl-1,2-dihydronaphthalene (TDN) is well-known to contribute "petrol" aromas to aged Riesling wines, but its prevalence and contribution to young Riesling or non-Riesling wines is not well understood. TDN concentrations were measured in 1-3-year-old varietal wines produced from Cabernet franc (n = 14 wines), Chardonnay (17), Cabernet Sauvignon (4), Gewurztraminer (4), Merlot (9), Pinot gris (6), Pinot noir (9), Riesling (28), or Sauvignon blanc (6). TDN concentrations in the Riesling wines, 6.4 ± 3.8 μg/L, were significantly higher than in all other varietals, 1.3 ± 0.8 μg/L. The odor detection thresholds for TDN were then determined in both model wine and a neutral white wine. Group sensory thresholds were found to be the same in both matrices, 2 μg/L, indicating little masking of TDN due to the odorants in the neutral white. The TDN sensory threshold was a factor of 10 below the previously reported odor threshold. On the basis of this revised threshold, 27 of 28 Riesling wines had suprathreshold TDN, whereas only 7 of 69 non-Riesling wines had suprathreshold TDN. The monoterpenes linalool and geraniol were also measured in the Riesling wines, and odor activity values (OAVs) were calculated for the monoterpenes and TDN. The OAV for TDN was higher than for the monoterpenes in 25 of 28 Riesling wines.     

Determination of stilbenes (delta-viniferin, trans-astringin, trans-piceid, cis- and trans-resveratrol, epsilon-viniferin) in Brazilian wines

Phenolics from grapes and wines can play a role against oxidation and development of atherosclerosis. Stilbenes have been shown to protect lipoproteins from oxidative damage and to have cancer chemopreventive activity. We describe a method for the direct determination of stilbenes in several red wines using high-performance liquid chromatography with UV detection. In a survey of 12 commercial wines from the south of Brazil (Rio Grande del Sul), levels of delta-viniferin are reported for the first time in different varieties of red wines. Brazilian red wine contains trans-astringin, trans-piceid, trans-resveratrol, cis-resveratrol (in high quantity: 5 times more than the trans form), epsilon-viniferin, and a compound isolated for the first time in wine, trans-delta-viniferin. Isolation and identification of delta-viniferin was achieved by NMR after extraction and fractionation of red wine phenolics. delta-Viniferin contributes, as well as cis-resveratrol and trans-piceid, to a significant proportion of stilbenes in wine dietary intake, particularly with Merlot varieties containing an average level of 10 mg/L for delta-viniferin, 15 mg/L for cis-resveratrol, and 13 mg/L for trans-piceid. The total stilbene intake from wine origin was estimated for the Brazilian population as 5.3 mg/day per person (on the basis of a regular wine consumption of 160 mL/day). delta-Viniferin can contribute to around 20% of total stilbenes in wine (average of 6.4 mg/L in red Brazilian wines). It would be important in the future to investigate the origins of the differences in wine stilbene levels in relation to the vine varieties, and the bioavailability of the newly extracted stilbene delta-viniferin in plasma after consumption of different types of wines.     

Stilbene levels in grape cane of different cultivars in southern Chile: determination by HPLC-DAD-MS/MS method

Health benefits of trans-resveratrol and other stilbenes in grapes, must, and wine have been pointed out by numerous authors. Less attention has been paid to the presence of stilbene derivatives in viticultural residues, such as grape canes. The present work reports the first results of a systematic study of stilbene levels in different grape varieties and cultivation areas in Chile, to evaluate their potential as an alternative source of bioactive stilbenes. In all cane samples, the predominant stilbene is trans-resveratrol, followed by ε-viniferin and piceatannol. In canes of Pinot noir up to 5590 ± 172 mg kg(-1) of trans-resveratrol and up to 6915 ± 175 mg kg(-1) of total stilbenes were detected. The observed concentrations of stilbenes in canes of Pinot noir from southern Chile until now are higher than those reported previously for this red variety. However, the highest concentration of total stilbenes observed in the analyzed samples was in the canes of white variety Gewürztraminer with 7857 ± 498 mg kg(-1). Preliminary results indicate that these levels can evolve if canes are left for some months on the vineyard after pruning, observing an increase during the first 2 months and a decrease after this period.     

Postharvest UV-C-irradiated grapes as a potential source for producing stilbene-enriched red wines

The use of postharvest controlled irradiation by UV pulses is proposed as a potential method to produce stilbene-enriched red wine. "Monastrell" grapes were UV-C-irradiated to increase stilbene content. The main inducible stilbenes were resveratrol and piceatannol, which are molecules with reported health-beneficial activities. The evolution of both compounds was followed in the different steps of an "analytical" traditional maceration wine-making process. The final wine made from UV-C-irradiated grapes was enriched about 2- and 1.5-fold in resveratrol and piceatannol, respectively, when compared to the control wine. In addition, no difference was detected regarding the standard enological parameters (color, acidity, etc.). It is strongly suggested that, with the use of more susceptible wine grapes to induce bioactive stilbenes upon UV-C irradiation, the stilbene-enrichment of wine can be much higher.     

Feasibility study on the use of visible and near-infrared spectroscopy together with chemometrics to discriminate between commercial white wines of different varietal origins

The use of visible (vis) and near-infrared spectroscopy (NIR) was explored as a tool to discriminate between samples of Australian commercial white wines of different varietal origins (Chardonnay and Riesling). Discriminant models were developed using principal component analysis (PCA), principal component regression (PCR), and discriminant partial least-squares (DPLS) regression. The samples were randomly split into two sets, one used as a calibration set (n = 136) and the remaining samples as a validation set (n = 133). When used to predict the variety of the validation set samples, the DPLS models correctly classified 100% of Riesling and up to 96% of Chardonnay wines. These results showed that vis-NIR might be a suitable and alternative technology that can be easily implemented by the wine industry to discriminate Riesling and Chardonnay commercial wine varieties. However, the relatively limited number of samples and varieties involved in the present work suggests caution in extending the potential of such a technique to other wine varieties.     

Determination of stilbenes (trans-astringin, cis- and trans-piceid, and cis- and trans-resveratrol) in Portuguese wines.

Stilbenes have been shown to have cancer chemopreventive activity and to protect lipoproteins from oxidative damage. A method is described for their direct determination in different types of wine using high-performance liquid chromatography with ultraviolet detection. In a survey of 120 commercial wines from Portugal and France, the highest concentrations of stilbenes were found in red wines. The glucosides of resveratrol were present in higher concentrations than the free isomers. Isolation from wine and characterization of trans-astringin in a large quantity are described for the first time.     

Odor potency of aroma compounds in Riesling and Vidal blanc table wines and icewines by gas chromatography-olfactometry-mass spectrometry

This study aimed to elucidate the odor potency of aroma compounds in Riesling and Vidal blanc (syn. Vidal) table wines and icewines from the Niagara Peninsula using stir bar sorptive extraction-gas chromatography-olfactometry-mass spectrometry. Dilution analysis determined the most odor-potent compounds in Vidal and Riesling icewines (n = 2) and table wines (n = 2) from a commercial producer. The top 15 odor-potent compounds in each wine were identified and quantified, resulting in 23 and 24 compounds for Riesling and Vidal, respectively. The most odor-potent compounds were β-damascenone, decanal, 1-hexanol, 1-octen-3-ol, 4-vinylguaiacol, ethyl hexanoate, and ethyl 3-methylbutyrate. In general, icewines had higher concentrations of most aroma compounds compared to table wines. Through computation of odor activity values, the compounds with the highest odor activity for the icewines were β-damascenone, 1-octen-3-ol, ethyl octanoate, cis-rose oxide, and ethyl hexanoate. In table wines the highest odor activity values were found for ethyl octanoate, β-damascenone, ethyl hexanoate, cis-rose oxide, ethyl 3-methylbutyrate, and 4-vinylguaiacol. These findings provide a foundation to determine impact odorants in icewines and the effects of viticultural and enological practices on wine aroma volatile composition.     

不同浸渍工艺对贵人香干白葡萄酒香气品质的影响

为提升贵人香干白葡萄酒的香气品质,以澄清汁发酵工艺(CQ)为对照,利用顶空固相微萃取结合气相色谱质谱联用技术(HS-SPME/GC-MS)检测浸渍工艺(JZ)和浸渍澄清工艺(JC)处理发酵酒样中的挥发性香气化合物。结果表明,浸渍处理可以明显增加葡萄酒中香气物质的含量。与CQ相比,JZ和JC对发酵酒样中品种香气物质的含量影响显著(P<0.05),萜烯类化合物含量分别增加1.86、1.01倍,且JC酒样中醇类、酯类香气物质含量最高,分别为4 799.38 μg·L^-1和5 013.28 μg·L^-1。主成分分析结合感官评价结果表明,JZ和JC酒样的花香特征相似,且JC酒样的热带水果香气以及醇香特征更为明显;与CQ相比,JC发酵酒样香气优雅、纯正,口感平衡。综合分析,浸渍澄清工艺(JC)可有效提升甘肃河西产区贵人香干白葡萄酒的香气品质。本研究结果可为干白葡萄酒增香酿造提供技术支持。     

Optimization, in-house validation, and application of a liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based method for the quantification of selected polyphenolic compounds in leaves of grapevine (Vitis vinifera L.)

Polyphenols in grapevine can be constitutive or induced, depending upon cultivar, plant organ, and environmental influences. The aim of the presented work was to develop and optimize a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to study the pattern and amount of selected polyphenols in leaves of Vitis vinifera L. The method is simple and does not require any sample cleanup. It covers representative metabolites of the structure classes cinnamic acids, flavonoids, and stilbenes and enables the simultaneous separation and quantification of 13 polyphenols within 9 min at concentration levels between 0.1 and 3 μg/g. We present the method performance characteristics and its application to the quantification of polyphenols in grapevine leaves of the cultivars Riesling and Pinot noir. A total of 7 of 13 target polyphenols were detected at concentrations above the limits of quantification. Interestingly, instead of the expected trans-resveratrol, the investigated leaf samples of both cultivars contained cis-resveratrol-3-O-glucoside. The measurements also showed that Riesling leaves tended to contain higher concentrations of the selected polyphenols than Pinot noir. In view of its intended future use, the developed method has been shown to be a powerful and fast tool to study polyphenols in grapevine leaves subjected to environmental stress conditions.     

Quantitative analysis, occurrence, and stability of (E)-1-(2,3,6-Trimethylphenyl)buta-1,3-diene in wine

A stable isotope dilution assay has been developed for quantification of (E)-1-(2,3,6-trimethylphenyl)buta-1,3-diene (4) in wine using a [(2)H(6)]-analogue. Using this method, 4 was found in 96 out of 97 white wines, but in none of 12 red wines analyzed. 4 was found to be most prevalent in Semillon wines, followed by Chardonnay, with Riesling showing the least amount of 4 among these three varieties. 4, like 1,1,6-trimethyldihydronaphthalene (TDN, 3), appears to be formed during the aging process. 4 was found to be unstable in model wine, and in both white and red wine, with the order of stability being model > white > red. In a PVPP-stripped red wine, the rate of degradation of 4 was substantially lessened, with the final concentrations very close to those observed in model wine. When treated with either grape or wine tannin extracts in model wine, the concentration of 4 was found to decrease to levels very close to those observed with an untreated red wine. When white wine was heated at 45 degrees C, 4 was formed, indicating the presence of precursor forms. The amounts formed were much higher than those found in a commercial white wine. 4 was also observed in red wine heated to 45 degrees C, but the concentration produced was much less than that with white wine.     

Polyphenols newly extracted in red wine from southwestern France by centrifugal partition chromatography.

Polyphenols from the ethyl acetate extracts of red wine were successfully fractionated using a four-step process (solvent extraction, ion-exchange column chromatography, centrifugal partition chromatography, and semipreparative HPLC), which resulted in the isolation of 22 compounds belonging to different classes of polyphenols (stilbenes, cinnamic acids, flavonoids). Five of them are red wine constituents reported for the first time. The newly isolated compounds include resveratrol dimers, dihydroflavonols, and a cinnamic derivative.     

A versatile targeted metabolomics method for the rapid quantification of multiple classes of phenolics in fruits and beverages

Compelling evidence of the health benefits of phenolic compounds and their impact on food quality have stimulated the development of analytical methods for the identification and quantification of these compounds in different matrices in recent years. A targeted metabolomics method has been developed for the quantification of 135 phenolics, such as benzoates, phenylpropanoids, coumarins, stilbenes, dihydrochalcones, and flavonoids, in fruit and tea extracts and wine using UPLC/QqQ-MS/MS. Chromatography was optimized to achieve separation of the compounds over a period of 15 min, and MRM transitions were selected for accurate quantification. The method was validated by studying the detection and quantification limits, the linearity ranges, and the intraday and interday repeatability of the analysis. The validated method was applied to the analysis of apples, berries, green tea, and red wine, providing a valuable tool for food quality evaluation and breeding studies.     

Postharvest stilbene-enrichment of red and white table grape varieties using UV-C irradiation pulses

The red table grape varieties Flame, Red Globe, Crimson, and Napoleon, as well as the white varieties Superior, Dominga, and Moscatel Italica, were irradiated with a previously optimized UV-C postharvest irradiation protocol (510 W, 40 cm, 60 s). The induction kinetics of the stilbenes trans-resveratrol, trans-piceid, trans-piceatannol, trans-astringin, and viniferins was followed by using HPLC-DAD/MS/MS. The most inducible stilbenes were trans-resveratrol, trans-piceatannol, and viniferins. Both quantitative and qualitative differences were observed in both the stilbene induction kinetics and stilbene content in the seven table grapes analyzed here. The total resveratrol content ranged from 0.69 mg/100 g fw (Dominga) to 2.3 mg/100 g fw (Red Globe). The net resveratrol induction ranged from 3.4-fold (Flame) to 2315-fold (Red Globe). The highest viniferins content was observed in the variety Flame (0.73 mg/100 g fw), although the variety Red Globe presented the highest viniferins induction (175-fold). The highest content and induction of piceatannol (0.17 mg/100 g fw and 173-fold, respectively) was observed in the variety Flame. It should be stressed that taking into account the health-beneficial effects claimed for stilbenes, the UV-C irradiated table grapes can be considered as new functional fruits that can supply (a serving of unpeeled 200 g table grapes) the resveratrol content (depending on the variety) equivalent to more than seven glasses of red wine ( approximately 1.5 L) with high resveratrol content.     

Plant foods and herbal sources of resveratrol

Stilbenes, in particular trans-resveratrol and its glucoside, are widely reported to be beneficial to health, having been shown to possess antioxidative, anticarcinogenic, and antitumor properties. Major dietary sources include grapes, wine, peanuts, and soy; however, they can also be introduced into the diet through Itadori tea, which has long been used in Japan and China as a traditional herbal remedy for heart disease and strokes. Analysis of grapes, peanuts, and Itadori tea shows that they contain mainly trans-resveratrol glucoside. In contrast, red wines are primarily a source of the aglycones cis- and trans-resveratrol. While peanuts and grapes contain low levels of the stilbenes, Itadori tea and red wine both supply relatively high concentrations of resveratrol. For people who do not consume alcohol, Itadori tea may be a suitable substitute for red wine. However, further study on the potential biological effects of other endogenous compounds in Itadori tea is required and there is also a need for more information on the absorption and in vivo biomedical actions of free and conjugated resveratrol.     

Ultraviolet-C and induced stilbenes control ochratoxigenic Aspergillus in grapes

This study investigated the efficacy of ultraviolet-C (254 nm) and induced stilbenes to inhibit Aspergillus carbonarius and Aspergillus tubingensis and control ochratoxin A production in grapes. In addition, the stilbene synthesis as a response to UV-C treatment and to infection of ochratoxigenic Aspergillus was compared. The initial microbial inactivation by a previously optimized UV-C illumination protocol for increasing trans-resveratrol content in grapes (50 W/m (2), 40 cm, 60 s) was similar on undamaged and damaged grapes, achieving 1.2 and 1.3 log conidia/100 g reductions, respectively. After 5 days of storage at 22 degrees C, UV-C treatment and the stilbenes induced by UV-C inhibited ochratoxigenic Aspergillus growth in undamaged grapes. UV-C elicited the biosynthesis of trans-resveratrol, while microbial infection and tissue damage triggered the biosynthesis of trans-piceid. trans-Resveratrol was not synthesized as a consequence of ochratoxigenic Aspergillus contamination. However, when trans-resveratrol was synthesized by UV-C, it contributed to inhibiting the development of ochratoxin A producing aspergilli. Furthermore, UV-C treatment also contributed to decrease ochratoxin A production by ochratoxigenic aspergilli. Therefore, UV-C is a promising emerging technology either for reducing the potential ochratoxigenic risk in grapes, which is of particular interest to the wine industry, and also for increasing trans-resveratrol content of grapes, which would provide an added value to the wine.