Reactivity of Cork Extracts with (+)-Catechin and Malvidin-3-O-glucoside in Wine Model Solutions: Identification of a New Family of Ellagitannin-Derived Compounds (Corklins)

Identification and structural characterization of a novel (+)-catechin-caffeic acid adduct present in wines

A new compound with a molecular ion mass of m/z 467 in the negative ion mode was found to occur in a white wine aged 30 months in bottle. In this latter, fragment ions compatible with the loss of a carboxylic acid (-44 a.m.u.), a caffeic acid unit (-178 a.m.u.), and a Retro-Diels Alder (-152 a.m.u.) were observed. The present work reports the synthesis of a (+)-catechin-caffeic acid adduct resulting from the condensation reaction between caffeic acid and (+)-catechin. The structural characterization by NMR showed that this adduct is formed by the linkage between carbon 8 at ring A from (+)-catechin and carbon 9 from caffeic acid. In addition, the similarity in the HPLC retention time and UV-Visible spectra of the synthesized compound with the one detected in white wine and the bottling experiments, confirms the presence of this novel (+)-catechin-derived compound in those matrices.

Molecular networking-assisted systematical profiling and the in vivo neuroprotective effect of ellagitannins from the Melastoma dodecandrum Lour

BACKGROUND

Ellagitannins (ETs) are a major classification of natural tannins, with relatively large and complex structures. ETs from medicinal plants are focused increasingly due to urolithins, a kind of intestinal metabolite of ETs, which showed promising anti-Alzheimer's disease (AD) effects. Melastoma dodecandrum (MD), a widely used traditional Chinese medicine is rich in ETs, but their chemistry and potential neuroprotective effects have not been investigated.

PURPOSE

This study aimed to identify the chemical composition of ETs in the crude extract of MD and to investigate their neuroprotective effects in vivo.

METHODS

UPLC-QTOF-MS-based molecular networking (MN) and structural characterization were applied to targeted profiling of the MD-ETs. Animal behavior experiments, including the novel object recognition test (NOR), open field test (OFT), and Morris water maze test (MWM), were conducted to assess the memory improvement effects of MD-ETs in AD model mice.

RESULTS

A total of 70 ETs, ranging from monomers to tetramers, were tracked and characterized in the MD extract using MN-guided targeted profiling, with 59 of them reported for the first time in this species. MD-ETs significantly improved memory impairment in AD mice, as indicated by decreased escape latency, increased number of crossings and target quadrant distance in MWM, increased rearing number in OFT, and increased preference index in NOR.

CONCLUSION

This study systematically characterized the composition and structural features of ETs in MD using targeted LC-MS profiling, expanding the chemical information of ETs in MD. Furthermore, the results demonstrate that MD-ETs have significant effects on improving impaired memory in AD mice, suggesting their potential as alternative natural medicines for the treatment of neurodegenerative diseases.

The Impact of Storage Conditions and Bottle Orientation on the Evolution of Phenolic and Volatile Compounds of Vintage Port Wine

This work evaluates the influence of the cellar conditions and bottle orientation, on the phenolic and volatile composition of a Vintage Port wine, sealed with natural cork stoppers, for 44 months post-bottling. The storage was performed in two different cellars, namely a cellar A with controlled temperature and humidity, and a cellar B, representing a traditional cellar, with uncontrolled temperature and humidity. The impact of bottle orientation was studied in cellar A, where the bottles were stored in horizontal and vertical positions. The phenolic and volatile composition of the bottled Vintage Port wine were analyzed after 6, 15 and 44 months. The results unveiled that the cellar conditions and bottle orientation had an impact in Port wine composition which was higher at 44 months post-bottling. The samples stored in the traditional cellar unveiled significantly higher yellow tones, lower tannin specific activity, and higher levels of furfural and 5-methylfurfural. Furthermore, the samples stored in the horizontal position revealed significant higher levels of total proanthocyanidins and higher tannin specific activity than the samples stored in the vertical position. Interestingly, for the first time to our knowledge, an ellagitannin-derived compound (Corklin) was detected in Vintage Port wines stored in the horizontal position, which results from the reaction of cork constituents with phenolic compounds present in wines.

Cork, a Natural Choice to Wine?

This review presents the most recent data on the state-of-the-art of the main compounds present in cork, their interaction with wine, and the impact that natural stoppers may have on wines’ physical-chemical and sensory properties. According to the recent scientific literature, the chemical composition of cork and the scientific relevance of the compounds extract from cork to wine over time are reviewed. Furthermore, the effect of cork compounds transfer into wines during post-bottling is also discussed, as well as their impact on the organoleptic (colour and taste) of wines. This knowledge is essential for the decision-making process undertaken by wine producers to select the stopper most suitable for their wines. In addition, sustainability is also a topic addressed since it is a natural product that generates some waste as well as the way in which this industry is adapting to the closure of the waste cycle.

Quercus suber: A Promising Sustainable Raw Material for Cosmetic Application

There is a drive within the cosmetic industry towards the development of more sustainable products, supported by consumer awareness of the environmental footprint. The cosmetic industry is rising to meet consumer demand by following practices, such as the use of by-products from agro-industrial waste. Quercus suber is a tree prevalent in the Mediterranean basin. The extraction of cork is considered sustainable, as this process does not harm the tree, and the amount of cork produced increases with the number of extractions. Beyond this, the cork industry produces by-products that are used to sustain the industry itself, such as cork powder, which is reused for generating energy. Additionally, cork and cork by-products contain bioactive compounds mainly with antioxidant activity that can be of use to the cosmetic industry, such as for antiaging, anti-acne, anti-inflammatory, and depigmenting cosmetic products. We provide the reader with an overview of the putative cosmetic applications of cork and its by-products as well as of their bioactive compounds. It is noteworthy that only a few cork-based cosmetic products have reached the market, namely antiaging and exfoliant products. Clearly, the use of cork upcycled cosmetic ingredients will evolve in the future considering the wide array of biological activities already reported.

The Antidiabetic Effect of Grape Pomace Polysaccharide-Polyphenol Complexes

Type 2 diabetes mellitus (T2DM) is one of the most prevalent chronic metabolic diseases of the 21st century. Nevertheless, its prevalence might be attenuated by taking advantage of bioactive compounds commonly found in fruits and vegetables. This work is focused on the recovery of polyphenols and polysaccharide–polyphenol conjugates from grape pomace for T2DM management and prevention. Bioactives were extracted by solid–liquid extraction and by pressurized hot water extraction (PHWE). Polyphenolic fraction recovered by PHWE showed the highest value for total phenolic content (427 μg GAE.mg⁻¹), mainly anthocyanins and proanthocyanidins, and higher antioxidant activity compared to the fraction recovered by solid–liquid extraction. Polysaccharide–polyphenol conjugates comprehended pectic polysaccharides to which approximately 108 μg GAE of phenolic compounds (per mg fraction) were estimated to be bound. Polyphenols and polysaccharide–polyphenol conjugates exhibited distinct antidiabetic effects, depending on the extraction methodologies employed. Extracts were particularly relevant in the inhibition of a-glucosidase activity, with free polyphenols showing an IC₅₀ of 0.47 μg.mL⁻¹ while conjugates showed an IC₅₀ of 2.7, 4.0 and 5.2 μg.mL⁻¹ (solid–liquid extraction, PHWE at 95 and 120 °C, respectively). Antiglycation effect was more pronounced for free polyphenols recovered by PHWE, while the attenuation of glucose uptake by Caco-2 monolayers was more efficient for conjugates obtained by PHWE. The antidiabetic effect of grape pomace bioactives opens new opportunities for the exploitation of these agri-food wastes in food nutrition, the next step towards reaching a circular economy in grape products.

Interaction between salivary proteins and cork phenolic compounds able to migrate to wine model solutions

This work reports the study of the interaction of human salivary proteins (SP) with phenolic compounds that migrate from cork stoppers to wine. This study yields valuable data to understand the influence that these compounds may have on the sensory perception of wine from an astringency perspective. For that, three cork fractions containing the phenolic compounds that migrate in greater amounts from cork to model wine solutions were selected. Fraction M1 contains gallic acid, protocatechuic acid, vanillin and protocatechuic aldehyde; fraction M2 comprises essentially gallic acid and ellagic acid, as well as castalagin and dehydrocastalagin; and fraction M3 contains the two isomeric ellagitannins castalagin and vescalagin. The reactivity of each fraction towards SP was M3 > M2 > M1. Within M3 fraction, castalagin showed a higher ability to precipitate SP (mainly aPRPs, statherin and P-B peptide) comparatively to vescalagin. In M1 fraction, caffeic and sinapic acids were the compounds with the highest interaction with SP, mainly cystatins. In addition, there also seems to be a matrix effect (presence of other compounds) that could be affecting these interactions.

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.

Variation in the Phenolic Composition of Cork Stoppers from Different Geographical Origins

Cork stopper granulates from five geographical origins from Portugal and six from Spain were analyzed regarding polyphenol composition by HPLC-DAD/ESI-MS and geographical discrimination studied by near-infrared spectroscopy (NIRS). The phenolic composition of the eleven origins ranged from 30 to 52 mg/g cork granulates, with vescavaloninic acid, castalagin, sanguisorbic acid dilactone, vescalagin, castavaloninic acid, dehydrated tergallic-C-Glc, and ellagic acid being the major compounds. NIRS revealed to be a powerful tool to discriminate origins and predict the concentration of polyphenols. However, polyphenols do not fully explain the discrimination of geographical origins. Variability in the polyphenol composition of cork stoppers is not significantly influenced by geographical location but probably may be more related to the plant genetics, tree age, and phytosanitary and edaphoclimatic conditions.

Polyphenolic Characterization of Nebbiolo Red Wines and Their Interaction with Salivary Proteins

The present study correlates the polyphenolic composition of two different Nebbiolo red wines from the 2015 vintage (M and P), with the salivary proteins’ precipitation process. The work centered on the polyphenolic characterization of Nebbiolo wines and their interaction with different families of salivary proteins. Overall, both wines were found to be very reactive with human saliva which was supposed to contribute to their astringent character. The comparison of both wines showed that the M wine presented higher values of total phenolics, total proanthocyanidins, and tannin specific activity. Moreover, this wine showed a higher interaction with salivary proteins. Altogether, the chemical characterization and reactivity toward human saliva could contribute to the wine astringency.