New flavanol O-glycosides in grape and wine

Wine Phenolic Compounds: Chemistry, Functionality and Health Benefits

Wine phenolic compounds, often known as polyphenols, are a diverse group of secondary bioactive compounds derived from grapes. They play a crucial role in defining the sensory characteristics, functionality, and health benefits of wine. This review explores the complex chemistry of these compounds, focusing on key classes such as flavonoids, which include flavanones, flavonols, anthocyanins, and flavan-3-ols, and non-flavonoids, such as hydroxycinnamic acids, hydroxybenzoic acids, and stilbenes. The health benefits of wine phenolics, particularly their antioxidant and anti-inflammatory properties, are also discussed in relation to preventing and reducing the risk of non-communicable diseases (NCDs) such as cardiovascular diseases, cancers, and neurodegenerative conditions. Furthermore, this review summarized the most current data from human population-based research that investigated the bioactivity of these red wine phytochemicals with relevant health benefits for NCDs. Finally, this review proposes some perspectives for future research to better understand the bioavailability, metabolism, and long-term health effects of these compounds.

Heterogeneity of transport and metabolism of Tormentillae rhizoma constituents across human intestinal epithelium cellular model

Tormentilla erecta (L.) Raeusch is a widespread plant in Europe and Western Asia. Its rhizomes (Tormentilae rhizoma) are the main ingredient of herbal alcoholic beverages and can be used as a natural preservative in beer production. Apart from its unique taste qualities, therapeutic properties in gastrointestinal tract ailments are attributed to the tincture obtained from Tormentillae rhizoma. The presented research aimed to determine the mutual relationship between the components of Tormentillae tincture, present in popular alcoholic beverages, and intestinal epithelium (Caco-2 cell monolayers). A comprehensive qualitative and quantitative analysis of the tincture was performed, including the determination of condensed and hydrolyzable tannins as well as triterpenoids (UHPLC-DAD-MS/MS). Incubation of the tincture with Caco-2 monolayers has shown that only triterpenes pass through the monolayer, while condensed tannins are mainly bound to the monolayer surface. Ellagic acid derivatives were the only components of the Tormentillae tinctura being metabolized by cell monolayers to the compounds not previously described in the literature, which may be crucial in the treatment of intestinal diseases with inflammatory background.

Thermal decomposition study of 4-methyloxybenzyl-glycoside by TG/DTA and on-line pyrolysis-photoionization mass spectrometry

A flavor precursor of 4-methyloxybenzyl-2, 3, 4, 6-tetra-O-acetyl-β-D-glucopyranoside (MBGL) was synthesized via a modified Koenigs-Knorr reaction. The thermal decomposition behaviour and pyrolysis intermediate products of the glycoside were studied by simultaneous thermogravimetric/differential thermal analysis (TG/DTA) and synchrotron vacuum ultraviolet (VUV) photoionization mass spectrometry (PIMS). TG/DTA results showed that the largest mass loss rate appeared at a Tp of 246.7 °C. PIMS was used to identify the pyrolysis products of MBGL at 300 °C, 500 °C and 700 °C, respectively. The experimental apparatus had some advantages in real-time analysis and fewer secondary reactions. Some important pyrolysis intermediates, such as the ions of the 4-methyloxybenzyl group at m/z 121 and the glycone moiety at m/z 347, were detected by PIMS. The results indicate that the MBGL was probably showed a different pyrolysis way compared with the other glycosides. This work reports a useful application of synchrotron VUV PIMS in a thermal decomposition study of glycoside flavor precursors.

Valorisation of Three Underutilised Native Australian Plants: Phenolic and Organic Acid Profiles and In Vitro Antimicrobial Activity

Tasmannia lanceolata, Diploglottis bracteata and Syzygium aqueum are understudied native Australian plants. This study aimed to characterise the non-anthocyanin phenolic and organic acid profiles of the aqueous extracts obtained from the leaves of T. lanceolata and fruits of D. bracteata and S. aqueum by UHPLC-Q-Orbitrap-MS/MS and UHPLC-TQ-MS/MS. A total of 39, 22, and 27 non-anthocyanin polyphenols were tentatively identified in T. lanceolata, D. bracteata, and S. aqueum extracts, respectively. Furthermore, sugars and ascorbic acid contents as well as in vitro antioxidant and antimicrobial activities of the extracts were determined. Response surface methodology was applied to achieve an extract blend with a strong inhibitory effect against Pseudomonas viridiflava, the main cause of soft rot in vegetables, Bacillus subtilis, Rhodotorula diobovata and Alternaria alternata. The identified compounds including organic acids (e.g., quinic, citric and malic acids) and polyphenols (e.g., catechin, procyanidins, and ellagitannins) might contribute to the observed antimicrobial activity. Furthermore, this study provides the most comprehensive phenolic profiles of these three underutilised native Australian plants to date.

Chemical Diversity of Flavan-3-Ols in Grape Seeds: Modulating Factors and Quality Requirements

Grape seeds are a rich source of flavan-3-ol monomers, oligomers, and polymers. The diverse profile of compounds includes mainly B-type procyanidins (especially C4→C8 linked molecules) and the key monomers, catechin, and epicatechin that are positively implicated in the 'French Paradox'. Today grape seed nutraceuticals have become a multi-million-dollar industry. This has created incentives to elucidate the variations in chemistry across cultivars, to identify signs of adulteration, and to understand the intrinsic and extrinsic factors controlling the expression of metabolites in the seeds' metabolome. This review provides a critical overview of the existing literature on grape seed chemistry. Although the biosynthetic pathways for polymeric procyanidins in seeds have not yet been explained, abiotic factors have been shown to modulate associated genes. Research of extrinsic factors has demonstrated that the control of procyanidin expression is strongly influenced, in order of importance, by genotype (species first, then variety) and environment, as claimed anecdotally. Unfortunately, research outcomes on the effects of abiotic factors have low certainty, because effects can be specific to genotype or variety, and there is limited control over physical metrics in the field. Thus, to gain a fuller understanding of the effects of abiotic factors and biosynthetic pathways, and realise potential for optimisation, a more fundamental research approach is needed. Nevertheless, the current synthesis offers insight into the selection of species or varieties according to the profile of polyphenols, as well as for optimisation of horticultural practices, with a view to produce products that contain the compounds that support health claims.

Recent advances in NMR-based metabolomics of alcoholic beverages

Alcoholic beverages have a complex chemistry that can be influenced by their alcoholic content, origin, fermentation process, additives, and contaminants. The complex composition of these beverages leave them susceptible to fraud, potentially compromising their authenticity, quality, and market value, thus increasing risks to consumers' health. In recent years, intensive studies have been carried out on alcoholic beverages using different analytical techniques to evaluate the authenticity, variety, age, and fermentation processes that were used. Among these techniques, NMR-based metabolomics holds promise in profiling the chemistry of alcoholic beverages, especially in Asia where metabolomics studies on alcoholic beverages remain limited.

Focus on the role of seed tannins and pectolytic enzymes in the color development of Pinot noir wine

Maceration techniques which promote the extraction of color pigments and tannin from grapes are often sought in Pinot noir winemaking to optimise color stability; alternatively, exogenous grape tannins may be included during fermentation. To examine the effect of seed-derived tannins and the use of pectolytic enzymes on color development in wines, conventional must preparations of Vitis vinifera L. cv Pinot noir grapes were compared with wines made using a supplementary addition of either a commercial seed tannin product or previously fermented seeds, while in a complementary experiment, seeds were sequentially removed during fermentation. After 6 months bottle aging, wines supplemented with either a commercial seed tannin solution (0.4 ​g/L), or fermented seeds (20% w/w seeds) had from 60% to 95% higher tannin concentration than the untreated wine, and up to 60% more monomeric anthocyanins. Conversely, when a third of the seeds were removed from the fermenting wine, the concentration of both tannin and non-bleachable pigments was 20-30% lower than in untreated wines and the wine hue had more red-purple tones. Exploration of the use of pectolytic enzymes in conjunction with seed removal was also found to have a significant impact on wine color parameters. Further insights on the timing of egress of tannin precursors from seeds was obtained from histochemical examination of the seeds that had been removed during alcoholic fermentation.

Polyphenols in foods: Classification, methods of identification, and nutritional aspects in human health

Polyphenols widely exists in various foods, including main crops, fruits, beverages and some wines. Famous representatives of polyphenols, such as resveratrol in red wine, (-)-epigallocatechin gallate in green tea, chlorogenic acid in coffee, anthocyanins in colored fruits, procyanidins in grape seed have become hot research topics in food science and nutrition. There have been thousands of papers on the biochemistry, chemistry, nutritional values and population-based investigations of dietary polyphenols. In this chapter, we reviewed the published articles and database of dietary polyphenols to draw a profile for the classification, structural identification, and biological activities mainly based on enzymes, cell bioassay and animal models, as well as the population-based investigation results. The typical compound and its health benefits for each category of polyphenols was also introduced. The identification of dietary polyphenols could be solved by combined spectroscopy methods, of which the liquid chromatography tandem mass spectrometry is highlighted to greatly increase the efficiency on structural identification. Although the population-based investigation showed some controversial results for health benefits, the multi-functions of dietary polyphenols on preventing metabolic syndromes, various cancers and neurodegenerative disease have attracted much attention.

NMR spectroscopy in wine authentication: An official control perspective

Wine authentication is vital in identifying malpractice and fraud, and various physical and chemical analytical techniques have been employed for this purpose. Besides wet chemistry, these include chromatography, isotopic ratio mass spectrometry, optical spectroscopy, and nuclear magnetic resonance (NMR) spectroscopy, which have been applied in recent years in combination with chemometric approaches. For many years, ² H NMR spectroscopy was the method of choice and achieved official recognition in the detection of sugar addition to grape products. Recently, ¹ H NMR spectroscopy, a simpler and faster method (in terms of sample preparation), has gathered more and more attention in wine analysis, even if it still lacks official recognition. This technique makes targeted quantitative determination of wine ingredients and nontargeted detection of the metabolomic fingerprint of a wine sample possible. This review summarizes the possibilities and limitations of ¹ H NMR spectroscopy in analytical wine authentication, by reviewing its applications as reported in the literature. Examples of commercial and open-source solutions combining NMR spectroscopy and chemometrics are also examined herein, together with its opportunities of becoming an official method.

Bloodwood: the composition and secreting-site of the characteristic red exudate that gives the name to the Swartzia species (Fabaceae)

The Swartzia species are commonly known as bloodwood due to the red exudate released from the stem after injury. This exudate has aroused great interest, and an integrative study is essential to describe it in detail. Thus, this work aimed to identify the red exudate's secreting-site in S. flaemingii and S. langsdorffii, and determine if it is a latex or a resin. Samples of the stem bark and the secondary xylem were prepared for histological analysis. Fresh exudates were dissolved in deuterated methanol and analyzed by ¹H-NMR; other samples were resuspended in MeOH:H₂O (9:1), partitioned with organic solvents and analyzed by direct infusion mass spectrometry. Total phenolic and total flavonoid contents were determined spectrophotometrically, and antioxidant capacity was determined using ferric reducing antioxidant power assay. The results showed that the exudate is a red latex produced by articulated laticifers located among the phloem cells. The latex is composed of sucrose, catechin glucosides, chlorophyll derivatives, and hederagenin-type saponins. Both samples of S. flaemingii and S. langsdorffii presented high amounts of phenolics and flavonoids, as well as a strong antioxidant capacity. The anatomical study showed that the secreting-site of the Swartzia red exudates were laticifers. This finding allows us to exclude other substances such as resin or oleoresin, generally produced by secretory cavities or ducts. Furthermore, since laticifers are rare in Fabaceae, this finding is significant, and represents an essential taxonomic feature. The showy red color is due to the large amounts of flavonoids. This latex probably has a protective role against microorganisms and photodamage. The bioactive potential of this exudate inspires further studies, which may boost the economic importance of Swartzia.

Grapevine as a Rich Source of Polyphenolic Compounds

Grapes are rich in primary and secondary metabolites. Among the secondary metabolites, polyphenolic compounds are the most abundant in grape berries. Besides their important impacts on grape and wine quality, this class of compounds has beneficial effects on human health. Due to their antioxidant activity, polyphenols and phenolic acids can act as anti-inflammatory and anticancerogenic agents, and can modulate the immune system. In grape berries, polyphenols and phenolic acids can be located in the pericarp and seeds, but distribution differs considerably among these tissues. Although some classes of polyphenols and phenolic acids are under strict genetic control, the final content is highly influenced by environmental factors, such as climate, soil, vineyard, and management. This review aims to present the main classes of polyphenolic compounds and phenolic acids in different berry tissues and grape varieties and special emphasis on their beneficial effect on human health.

Gentianose: Purification and structural determination of an unknown oligosaccharide in grape seeds

Grape seeds are among the main constituents of grape pomace, ranging between 20% and 30% of the wet matrix; however, their oligosaccharide composition has not been studied. This paper describes the purification and the identification of low molecular weight oligosaccharides contained in an EtOH/water extract of grape seeds. A sequential two-step purification by size exclusion chromatography was carried out to fractionate compounds according to molecular weights. Chemical characterization of the combined fractions was performed by Magnetic Resonance Spectroscopy and Gas Chromatography-Mass Spectrometry analyses. The separation process gave two fractions abundant in sucrose and glucose. A third fraction containing trisaccharides was acetylated allowing the purification of the main trisaccharide. The structure elucidation of the acetylated product made it possible to identify gentianose, a predominant carbohydrate reserve found in the storage roots of perennial Gentiana lutea. Grape seeds are wine industry by-products and the obtained results suggest the importance of their recovery.

Valorization of European Cranberry Bush (Viburnum opulus L.) Berry Pomace Extracts Isolated with Pressurized Ethanol and Water by Assessing Their Phytochemical Composition, Antioxidant, and Antiproliferative Activities

Defatted by supercritical CO₂, Viburnum opulus berry pomace (VOP) was subjected to consecutive extraction with pressurized ethanol (E) and water (W) and yielded 23% of VOP-E and 8% of VOP-W, respectively. The major phytochemical groups covering 42 identified and quantified constituents in VOP extracts were organic and phenolic acids, iridoids, quercetin and (epi)catechin derivatives, flavalignans, procyanidins, and anthocyanins. The on-line HPLC-DPPH^•-scavenging assay revealed the presence of numerous antioxidants. VOP-E had a higher total phenolic content, was a stronger antioxidant (equivalent to 0.77, 0.42, and 0.17 g trolox/g in oxygen radical absorbance capacity (ORAC), ABTS, and DPPH assays, respectively), and recovered the major part of phenolics from the pomace; however, both extracts demonstrated similar antioxidant activity in the cellular assay. VOP-E inhibited HT29 cancer cells at non-cytotoxic concentrations. The results of this study revealed that VOP contains valuable phytochemicals possessing antioxidant and antiproliferative activities. Consequently, extracts from VOP substances may be of interest in developing functional ingredients for healthy foods, nutraceuticals, and cosmeceuticals.

Voltammetric Behavior, Flavanol and Anthocyanin Contents, and Antioxidant Capacity of Grape Skins and Seeds during Ripening (Vitis vinifera var. Merlot, Tannat, and Syrah)

Skin and seed grape extracts of three red varieties (Merlot, Tannat, and Syrah) at different stages of ripening were studied for their total phenolic content (TPC) by using the Folin-Ciocalteu assay and for their total antioxidant capacity (TAC) by using spectrophotometric and electrochemical assays. Flavanol and anthocyanin compositions were also investigated using Ultra Performance Liquid Chromatography coupled with Mass Spectrometry (UPLC-MS). Results showed that seeds had the highest phenolic content and the highest antioxidant potential compared to skins at all stages of ripening. The highest TPC and TAC values were measured in seeds at close to veraison and veraison ripening stages. In skins, the highest values were found at the green stage, it was in accordance with the flavanols content. The voltammetric measurements were carried out using disposable single walled carbon nanotubes modified screen-printed carbon electrodes (SWCNT-SPCE). Three peaks on voltammograms were obtained at different oxidation potentials. The first anodic peak that oxidized at a low potential describes the oxidation of ortho-dihydroxy phenols and gallate groups, the second peak corresponds to the malvidin anthocyanins oxidation and the second oxidation of flavonoids. The third voltammetric peak could be due to phenolic acids such as p-coumaric acid and ferulic acid or the second oxidation of malvidin anthocyanins. The high linear correlation was observed between antioxidant tests and flavanols in skins (0.86 ≤ r ≤ 0.94), while in seeds, 'r' was higher between electrochemical parameters and flavanols (0.64 ≤ r ≤ 0.8).

Polyphenols: Natural Antioxidants to Be Used as a Quality Tool in Wine Authenticity

Polyphenols are a diverse group of compounds possessing various health-promoting properties that are of utmost importance for many wine sensory attributes. Apart from genetic and environmental parameters, the implementation of specific oenological practices as well as the subsequent storage conditions deeply affect the content and nature of the polyphenols present in wine. However, polyphenols are effectively employed in authenticity studies. Provision of authentic wines to the market has always been a prerequisite meaning that the declarations on the wine label should mirror the composition and provenance of this intriguing product. Nonetheless, multiple cases of intentional or unintentional wine mislabeling have been recorded alarming wine consumers who demand for strict controls safeguarding wine authenticity. The emergence of novel platforms employing instrumentation of exceptional selectivity and sensitivity along with the use of advanced chemometrics such as NMR (nuclear magnetic resonance)- and MS (mass spectrometry)-based metabolomics is considered as a powerful asset towards wine authentication.

α-Glucosidase Inhibitory Activity of Tannat Grape Phenolic Extracts in Relation to Their Ripening Stages

The present study aimed to screen grape extracts as novel α-glucosidase inhibitors to prevent type-2 diabetes and hyperglycemia. The total polyphenol content (TPC) was measured by Folin-Ciocalteu assay and the stilbene, anthocyanin and flavan-3-ol compounds were measured by Ultra High-Performance Liquid Chromatography coupled to Mass Spectrometry (UHPLC-MS). The α-glucosidase inhibitory of seed and skin Tannat grape extracts at four ripening stages were investigated. The highest TPC values were measured in seeds at the “veraison stage” (65.29 ± 5.33 g of Gallic Acid Equivalent (GAE) per kilogram of Fresh Weight (FW)). This was in accordance with the high flavan-3-ol contents measured for these two extracts (43.22 ± 2.59 and 45.45 ± 6.48 g/kg of seeds FW, respectively). The skin and seed extracts at the first stage of ripening exerted strong α-glucosidase inhibition, exceeding 95% (p < 0.05). A high linear correlation (R = 0.723, p ≤ 0.05) was observed between flavan-3-ol contents and the α-glucosidase inhibitory activity. The stilbene contents and this activity were moderately to strongly anti-correlated (R = –0.828, p ≤ 0.05 for trans-resveratrol). The enzyme kinetic studies revealed a mixed type of inhibition. This study brings promising results for the therapeutic potential of seed and skin Tannat grape extracts as a functional food product with anti-diabetic activity.

Grape skins as supplements for color development in Pinot noir wine

A particular challenge to making wine from Pinot noir grapes is the delicate flavor, light color and poor ageing potential of the wine. Conventional Pinot noir must preparations were compared with those made using a skin-based supplement to assess the impact on non-bleachable (sulfur resistant) pigments in the wine. When supplemented with either fresh grape pomace of Pinot noir, Pinot gris or Chardonnay grapes; Pinot noir grape marc or a commercial liquid grape skin extract, the additional seeds and pulp from the supplements were shown to compromise the development of stable pigments in the wine. To compare the relative merits of tannin derived from grape skins and seeds, the supplements used in a parallel experiment were the skins alone of the same three grape varieties and at six months bottle age, the stable pigment concentration was found to exceed the amount attributable to the supplement. A third experiment used fermented grape skins as the supplement, with 85% of the supplementary anthocyanin recovered as stable pigment complexes in the wine. Notably, this series of experiments showed that supplements containing grape seeds appeared to compromise non-bleachable pigment formation in the wine while skin only supplements stimulated their development.

Flavanol Glycoside Content of Grape Seeds and Skins of Vitis vinifera Varieties Grown in Castilla-La Mancha, Spain

Glycosylated flavanols (monoglycosides and diglycosides) in skin and seed extracts of Vitis vinifera grapes grown in Castilla-La Mancha (Spain) were investigated using ultra-high-performance liquid chromatography—tandem mass spectrometry (UHPLC-ESI-QQQ-MS/MS). Six grape varieties (Airén, Tempranillo, the recently identified Albillo Dorado, Montonera del Casar, Moribel, and Tinto Fragoso) were studied over two consecutive years (2016 and 2017). A total of twenty monomeric flavanol monoglycosides, four diglycosylated monomers, and three dimeric flavanol monoglycosides were detected in all grape samples. The diversity observed in the composition of glycosylated flavanol in the grape berries suggests a strong influence of variety and grape tissue (skin or seed). Monomeric flavanol glycosides were more abundant in grape seed extracts, in contrast with monoglycosylated dimeric forms. In addition, the glycosylated flavanol content was related to berry color in grape skins, with higher concentrations measured in black grape varieties.

From Flavanols Biosynthesis to Wine Tannins: What Place for Grape Seeds?

Phenolic compounds are among the most important quality factors of wines. They contribute to the organoleptic characteristics of wine such as color, astringency, and bitterness. Although tannins found in wine can come from microbial and oak sources, the main sources of polyphenols are grape skins and seeds. Since the 1960s, this subject has been widely studied by a large number of researchers covering different types of wine, climate conditions, growing practices, and grape varieties. As these works have been conducted under different conditions, the data collected can be conflicting. Moreover, even though the biosynthesis of the major proanthocyanidins units (+)-catechin and (-)-epicatechin is well-known, the mechanism of their polymerization remains unexplained. This is why the question remains: what factors influence the biosynthesis, the quantity, and the distribution of tannins in grape seeds and how can winemaking processes impact the extractability of seed tannins in wine?

Evolution of Flavanol Glycosides during Red Grape Fermentation

Monomeric and dimeric flavanol glycosides were quantified by UHPLC-MRM in Syrah (SYR) and Grenache (GRE) grapes and in their corresponding wines for the first time. Quantities were extremely variable depending on grape tissue (seeds or skins) and during fermentation. Overall, 22 monomeric and dimeric mono- and diglycosides were determined with concentrations ranging from 0.7 nanograms to 0.700 micrograms per gram of grape tissue, and 0 to 60 micrograms per liter for wines. The evolution of the glycosides' composition during winemaking suggests that almost all these compounds originate in the grapes themselves and display different extraction kinetics during winemaking. One isomer of the monomeric (epi) flavanol monoglycosides seemed to be biosynthesized by yeasts during wine fermentation. The sharp decrease in concentration of some isomers at the late stages of fermentation or after pressing suggests that some grape glycosidase activities convert these compounds into non-glycosylated flavanols.

Identification and Quantification of Flavanol Glycosides in Vitis vinifera Grape Seeds and Skins during Ripening

Monomeric and dimeric flavanol glycosides were analyzed in Vitis vinifera grapes and seeds during ripening. An analytical method using ultra-high performance liquid chromatography coupled with a triple quadrupole mass spectrometry (UHPLC-ESI-QQQ-MS/MS) in multiple reaction monitoring (MRM) mode was employed. Three grape varieties (Merlot, Syrah and Tannat) were chosen and grape berries were sampled at different stages of development. Ten monoglycosylated and six diglycosylated flavanol monomers were detected. Twelve monoglycosylated and three diglycosylated flavanol dimers were also detected for all three grape varieties. All diglycosides were detected for the first time in Vitis vinifera grapes, though some of these compounds were only detected in skins or seeds. Furthermore, the evolution of all these compounds was studied, and a decrease in monomeric (epi) catechin monoglycosides was observed during ripening for Tannat, Merlot and Syrah grape skins. The dimers would appear to accumulate in skin tissues up to mid-summer (after veraison) and decrease when grape berries reached maturity.