Spectroscopy analysis of phenolic and sugar patterns in a food grade chestnut tannin

Ellagitannins from Castanea sativa Mill. Leaf Extracts Impair H. pylori Viability and Infection-Induced Inflammation in Human Gastric Epithelial Cells

Helicobacter pylori (H. pylori) is an etiologic factor of peptic ulcer disease and gastric cancer. Virulent strains of H. pylori are correlated with the severity of gastritis, due to NF-κB activation and IL-8 expression at the epithelial level. Ellagitannins have been documented for antibacterial and anti-inflammatory activities, thus suggesting their potential use in gastritis. Recently, several authors, including our group, demonstrated that tannin-rich extracts from chestnut byproducts, at present considered agricultural waste, display promising biological activities. In this work, we detected high levels of polyphenols in hydroalcoholic extracts from chestnut leaves (Castanea sativa L.). Among polyphenols, the ellagitannin isomers castalagin and vescalagin (about 1% w/w of dry extract) were identified as potential bioactive compounds. In GES-1 cells infected by H. pylori, leaf extract and pure ellagitannins inhibited IL-8 release (IC₅₀ ≈ 28 µg/mL and 11 µM, respectively). Mechanistically, the anti-inflammatory activity was partly due to attenuation of NF-κB signaling. Moreover, the extract and pure ellagitannins reduced bacterial growth and cell adhesion. A simulation of the gastric digestion suggested that the bioactivity might be maintained after oral administration. At the transcriptional level, castalagin downregulated genes involved in inflammatory pathways (NF-κB and AP-1) and cell migration (Rho GTPase). To the best of our knowledge, this is the first investigation in which ellagitannins from plant extracts have demonstrated a potential role in the interaction among H. pylori and human gastric epithelium.

Chestnut-Tannin-Crosslinked, Antibacterial, Antifreezing, Conductive Organohydrogel as a Strain Sensor for Motion Monitoring, Flexible Keyboards, and Velocity Monitoring

Flexible sensing devices (FSDs) fabricated using conductive hydrogels have attracted researchers' extensive enthusiasm in recent years due to their versatility. Considering the complexity of their application environments, the integration of various functional characteristics (e.g., excellent mechanical, antibacterial, and antifreezing properties) is an important guarantee for FSDs to stably perform their applications in different environments. Herein, we developed a multifunctional conductive polyvinyl alcohol (PVA) organohydrogel PVA-CT-Ag-Al-Gly (PCAAG) by using a green, natural, and cheap biomass, chestnut tannin (CT), as a crosslinking agent, nano-silver particles (AgNPs) as an antimicrobial agent, aluminum trichloride (AlCl₃) as a conducting medium, and the mixed water-glycerol as the solvent system. In this organohydrogel system, CT acted not only as the reducing and stabilizing agent for the preparation of antibacterial AgNPs but also as the crosslinking agent owing to its strong multiple hydrogen bonding interactions with PVA, realizing its multifunctional application. The PCAAG organohydrogel possessed outstanding physical and mechanical properties (350.54% of the maximum fracture strain and 1.55 MPa of the maximum tensile strength), considerable bacteriostatic effects against both Escherichia coli and Staphylococcus aureus, and excellent freeze resistance (it could function normally at -20 °C). The motion-monitoring sensor based on the PCAAG organohydrogel exhibited excellent specificity recognition for both large-amplitude (e.g., elbow bending, wrist bending, finger bending, running and walking, etc.) and small-amplitude (frowning and swallowing) human movements. The flexible keyboard constructed by using the PCAAG organohydrogel could easily achieve the transformation between digital signals and electrical signals, and the signal output had both specificity and stability. The velocity-monitoring sensor fabricated by using the PCAAG organohydrogel could accurately measure the speed of the object movement (less than 3% of relative error). In short, the present PCAAG organohydrogel solves the problems of the single application environment and a few application scenarios of traditional conductive hydrogels and possesses remarkable application potential as a multifunctional FSD in many fields such as artificial intelligence, sport management, soft robots, and human-computer interface.

Antioxidant and Antibacterial Activity of Four Tannins Isolated from Different Sources and Their Effect on the Shelf-Life Extension of Vacuum-Packed Minced Meat

Four tannin samples extracted from chestnut wood (tannin oenologique, TO), grape (tannin VR grape, TVG), oak gall (tannin galalcool, TG), and oak tree (tannin VR supra elegance, TE) were evaluated for antioxidant and antibacterial activity. The highest total phenolic content (TPC) values were observed in the order of TVG > TG > TE > TO (p < 0.05). The antioxidant activities of all samples were determined in terms of DPPH radical scavenging activity, reducing power, metal-chelating activity, and linoleic acid peroxidation assay. The antioxidant activities of all samples vary and no correlation was observed with the respective TPC values of each sample. Antibacterial activities indicate that all samples showed more or less inhibitory effects against selected Gram-positive and Gram-negative bacteria. Based on antioxidant and antibacterial activity, TO and TVG were selected for the beef mince quality preservation study during refrigerated storage. Both TO and TVG at two different concentrations, 0.25 and 0.5%, could cease the chemical and microbial changes as compared to the control sample. Although total viable count (TVC) did not show a significant difference, the H2S-producing bacteria count was lower in all samples treated with TO and TVG compared to sodium metabisulfite (SMS) and the control sample (p < 0.05). Therefore, TO and TVG could be promising natural food preservatives during refrigerated storage.

Quali-Quantitative Study on Phenol Compounds as Early Predictive Markers of Graft Incompatibility: A Case Study on Chestnut (Castanea spp.)

In recent years, research has focused on phenolic compounds and their putative role as markers of graft incompatibility. Thus far, no studies have been conducted on the role of phenolic compounds in chestnut (Castanea spp.). The present study investigated the content of phenolic compounds in different combinations of Castanea spp. cultivars and rootstocks. Analyses were performed on the inner and outer tissues of chestnut grafts at two phenological sampling stages. The separation, identification and quantification of the phenolic markers via HPLC were preceded by an ultrasonic green extraction. Two chromatographic methods were tested for a total of 15 phenol compounds. Flavonol compounds were not detected, while cinnamic acids were found in low concentrations. The amount of gallic acid turned out to be higher at the graft union of the incompatible combination (20.11 ± 1.47 mg/100 gFW vs. 8.94 ± 1.08 mg/100 gFW). The same pattern was observed for catechin (15.79 ± 1.83 mg/100 gFW vs. 9.63 ± 1.98 mg/100 gFW). Differences in tannin concentrations seemed to be species-specific, and were apparently not related to graft incompatibility. The present work underlines the potential application of certain phenol compounds for the early prediction of graft incompatibility in Castanea spp.

ANALYSIS OF CARBOHYDRATES AND GLYCOCONJUGATES BY MATRIX-ASSISTED LASER DESORPTION/IONIZATION MASS SPECTROMETRY: AN UPDATE FOR 2015-2016

This review is the ninth update of the original article published in 1999 on the application of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2016. Also included are papers that describe methods appropriate to analysis by MALDI, such as sample preparation techniques, even though the ionization method is not MALDI. Topics covered in the first part of the review include general aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, fragmentation and arrays. The second part of the review is devoted to applications to various structural types such as oligo- and poly-saccharides, glycoproteins, glycolipids, glycosides and biopharmaceuticals. Much of this material is presented in tabular form. The third part of the review covers medical and industrial applications of the technique, studies of enzyme reactions and applications to chemical synthesis. The reported work shows increasing use of combined new techniques such as ion mobility and the enormous impact that MALDI imaging is having. MALDI, although invented over 30 years ago is still an ideal technique for carbohydrate analysis and advancements in the technique and range of applications show no sign of deminishing. © 2020 Wiley Periodicals, Inc.

Latent Anti-nutrients and Unintentional Breeding Consequences in Australian Sorghum bicolor Varieties

Modern feed quality sorghum grain has been bred to reduce anti-nutrients, most conspicuously condensed tannins, but its inclusion in the diets of monogastric animals can still result in variable performance that is only partially understood. Sorghum grain contains several negative intrinsic factors, including non-tannin phenolics and polyphenols, phytate, and kafirin protein, which may be responsible for these muted feed performances. To better understand the non-tannin phenolic and polyphenolic metabolites that may have negative effects on nutritional parameters, the chemical composition of sorghum grain polyphenol extracts from three commercial varieties (MR-Buster, Cracka, and Liberty) was determined through the use of an under-studied, alternative analytical approach involving Fourier-transform infrared (FT-IR) spectroscopy and direct ionization mass spectrometry. Supervised analyses and interrogation of the data contributing to variation resulted in the identification of a variety of metabolites, including established polyphenols, lignin-like anti-nutrients, and complex sugars, as well as high levels of fatty acids which could contribute to nutritional variation and underperformance in monogastrics. FT-IR and mass spectrometry could both discriminate among the different sorghum varieties indicating that FT-IR, rather than more sophisticated chromatographic and mass spectrometric methods, could be incorporated into quality control applications.

Natural Tannin Wood Extracts as a Potential Food Ingredient in the Food Industry

Wood extracts are one of the most important natural sources of industrially obtained tannins. Their use in the food industry could be one of the biggest (most important) recent innovations in food science as a result of their multiple (many) possible applications. The use of tannin wood extracts (TWEs) as additives directly added in foods or in their packaging meets an ever-increasing consumer demand for innovative approaches to sustainability. The latest research is focusing on new ways to include them directly in food, to take advantage of their specific actions to prevent individual pathological conditions. The present review begins with the biology of TWEs and then explores their chemistry, specific sensorial properties, and current application in food production. Moreover, this review is intended to cover recent studies dealing with the potential use of TWEs as a starting point for novel food ingredients.

The condensed tannins of Okoume (Aucoumea klaineana Pierre): A molecular structure and thermal stability study

In order to promote convenient strategies for the valorization of Aucoumea klaineana Pierre (Okoume) plywood and sawmill wastes industry in the fields of adhesives and composites, the total phenolic content of Okoume bark, sapwood and heartwood was measured. The molecular structure of tannins extracted from the bark was determined by Matrix Assisted Laser Desorption/Ionization Time-Of-Flight (Maldi-ToF) mass spectrometry and Fourier transform infrared spectroscopy (FTIR). The total phenolic content displayed significant difference (p = 0.001) between the bark, sapwood and heartwood which decreased as follows: 6 ± 0.4, 2 ± 0.8 and 0.7 ± 0.1% respectively. The pro-anthocyanidins content was also significantly different (p = 0.01) among the three wood wastes, and the bark was the richest in condensed tannins (4.2 ± 0.4%) compared to the sapwood (0.5 ± 0.1%) and heartwood (0.2 ± 0.2%). Liquid chromatography coupled mass spectroscopy (LC-MS) and Maldi-ToF analysis of the bark showed for the first time that Okoume condensed tannins are fisetinidin, gallocatechin and trihydroxyflavan based monomers and complex polymers obtained with glycosylated units. No free catechin or robitinidin units were detected, whereas distinctive dihydroxy or trihydroxyflavan-3-benzoate dimers were observed in the investigated condensed tannin extracts. FTIR analysis showed the occurrence of glucan- and mannan-like sugars in the condensed tannins, and Maldi-ToF highlighted that these sugars should account for ten glycosylated units chemically bonded with two fisetinidins and one gallocatechin trimer. The condensation of these polyphenols with formaldehyde led to Stiasny numbers of 83.3, 73.3 and 53.3% for the bark, sapwood and heartwood, respectively.

Comprehensive analysis of chestnut tannins by reversed phase and hydrophilic interaction chromatography coupled to ion mobility and high resolution mass spectrometry

In this study, we report a methodology based on reversed phase LC (RP-LC) and hydrophilic interaction chromatography (HILIC) separations coupled to ion mobility (IM) and high resolution mass spectrometry (HR-MS) for the detailed analysis of hydrolysable tannins. The application of this approach to the analysis of an industrial chestnut (Castanea sativa, wood chips) tannin extract is demonstrated. A total of 38 molecular species, including a large number or isomers, were identified in this sample based on HR-MS^(E) and UV absorption spectral information as well as retention behaviour in both separation modes. In total, 128 and 90 isomeric species were resolved by RP- and HILIC-LC-IM-TOF-MS, respectively. The combination of low- and high collision energy mass spectral data with complementary chromatographic separations allowed tentative and putative identification of twenty molecular species, comprising 78 isomers, in chestnut for the first time. Ion mobility resolved six new dimeric and trimeric vescalagin conformers with unique arrival (drift) times, including new conformers of roburin A-D which were not separated using either RP-LC or HILIC. HILIC was found to be the preferred separation mode for the analysis of vescalagin derivatives, while RP-LC is preferred for the analysis of ellagitannins with a cyclic glucose core. For the complete separation of the galloyl glucose species, comprehensive HILIC × RP-LC separation would be required.

Suitability of the Cyclic Voltammetry Measurements and DPPH• Spectrophotometric Assay to Determine the Antioxidant Capacity of Food-Grade Oenological Tannins

Twenty commercially available oenological tannins (including hydrolysable and condensed) were assessed for their antiradical/reducing activity, comparing two analytical approaches: The 2,2-diphenyl-1-picrylhydrazyl (DPPH•) radical scavenging spectrophotometric assay and the cyclic voltammetry (CV) electrochemical method. Electrochemical measurements were performed over a −200 mV–500 mV scan range, and integrated anodic currents to 500 mV were used to build a calibration graph with (+)-catechin as a reference standard (linear range: From 0.0078 to 1 mM, R² = 0.9887). The CV results were compared with the DPPH• assay (expressed as % of radical scavenged in time), showing high correlation due to the similarity of the chemical mechanisms underlying both methods involving polyphenolic compounds as reductants. Improved correlation was observed by increasing the incubation time with DPPH• to 24 h (R² = 0.925), demonstrating that the spectrophotometric method requires a long-term incubation to complete the scavenging reaction when high-molecular weight tannins are involved; this constraint has been overcome by using instant CV measurements. We concluded that the CV represents a valid alternative to the DPPH• colorimetric assay, taking advantage of fast analysis and control on the experimental conditions and, because of these properties, it can assist the quality control along the supply chain.

Chestnut Shell Extract Modulates Immune Parameters in the Rainbow Trout Oncorhynchus mykiss

In this study, chestnut (Castanea sativa) shell was extracted with different solvents, and immunomodulatory activity was investigated in an in vitro model system using blood and intestinal leukocytes of Oncorhynchus mykiss. Gallic acid (GA) was used as a standard. Chestnut shell extract (CSE) and GA readily entered both blood and intestinal leukocytes. Superoxide anion production and phagocytosis were decreased by low doses of CSE and increased with high doses. CSE and GA differently regulated cytokine expression in blood and intestinal leukocytes. High doses of CSE upregulated IL-1β, TNF-α, and IL-10 in intestinal leukocytes and IL-10 in blood leukocytes. Low doses of CSE upregulated IL-1β and TNF-α in blood leukocytes. GA appeared to be effective only in blood leukocytes. The effects of CSE on pro- and anti-inflammatory cytokines seemed to suggest an alert effect of the immune defense system against a possible infectious agent. The less evident effect of GA in comparison to CSE could have been attributable to the synergistic and/or additive effects of polyphenols in the latter. The immune-stimulating activity of CSE reported here could be useful for future practical applications in fish health.

A review on the application of vibrational spectroscopy to the chemistry of nuts

Nuts are highly appreciated due to their nutritional relevance and flavour, being the source of many desirable and healthy compounds as polyunsaturated fatty acids and antioxidants. Their characterization became the target of many studies in the last years through conventional analytical techniques as chromatographic ones. Due to the limitations associated to these techniques, as time, cost and environmental concerns, spectroscopic techniques have been increasingly pointed as reliable alternatives. Either applied to raw materials quality control or to more complex process, as industrial in-line monitoring, spectroscopic techniques, namely vibrational spectroscopy, are gathering strong acceptance. This paper presents a review on the application of vibrational spectroscopy, infrared and Raman, to nuts characterization. Estimates of several qualitative and quantitative parameters, origin authentication and/or adulteration in almonds, peanuts, pine nuts, hazelnuts, walnuts, Brazil nuts, cashews, chestnuts and pistachios will be covered. Advantages and limitations of these techniques and future trends will also be discussed.

Opinion on the Hurdles and Potential Health Benefits in Value-Added Use of Plant Food Processing By-Products as Sources of Phenolic Compounds

Plant foods, their products and processing by-products are well recognized as important sources of phenolic compounds. Recent studies in this field have demonstrated that food processing by-products are often richer sources of bioactive compounds as compared with their original feedstock. However, their final application as a source of nutraceuticals and bioactives requires addressing certain hurdles and challenges. This review discusses recent knowledge advances in the use of plant food processing by-products as sources of phenolic compounds with special attention to the role of genetics on the distribution and biosynthesis of plant phenolics, as well as their profiling and screening, potential health benefits, and safety issues. The potentialities in health improvement from food phenolics in animal models and in humans is well substantiated, however, considering the emerging market of plant food by-products as potential sources of phenolic bioactives, more research in humans is deemed necessary.

Antioxidant and α-amylase inhibitory activities of tannic acid

Tannic acid widely exists in plants, which forms a part of human diet. The antioxidant activity of tannic acid was evaluated by the chemical and cellular antioxidant assays. And its α-amylase inhibitory activity and behavior were also investigated. It was found that hydrogen- and electron donating capacities of tannic acid were higher than those of tertiary butylhydroquinone (TBHQ) based on reducing power, ABTS and DPPH radical scavenging assays. But for its low hydrophobic property, the antioxidant activity of tannic acid in linoleic acid system was inferior to that of TBHQ. In the cellular antioxidant assay, tannic acid showed the higher activity than gallic acid in the "PBS wash" protocol, which could attribute to its high binding capacity of cell membrane. Compared with acarbose, tannic acid possessed the stronger α-amylase inhibitory capacity. And the static fluorescence quenching of α-amylase in the presence of tannic acid could be also observed, which was caused by their binding interaction.

Improved Adhesion Performance of Soy Protein-Based Adhesives with a Larch Tannin-Based Resin

This study aimed to improve the bonding strength and water resistance of soy protein-based adhesives (SPAs) by modifying with larch tannin-based resins (TRs). This is especially important because of their eco-beneficial effects. The TR was characterized by Fourier Transform Infrared (FTIR) and Thermogravimetric/Derivative Thermogravimetric (TG/DTG) in order to demonstrate the formation of the self-crosslinking structure. Rheological properties, fracture morphology, solubility, and crosslinking density were characterized in detail. Three-ply poplar plywood was fabricated and the wet shear strength was measured. The experimental data showed that the addition of TR improved the moisture uptake, residual rate, and shear strength of SPA. This improvement was attributed to the crosslink reactions of TR with the relevant active functional groups of the side chains of soy protein molecules. The crosslinking structure joined with the TR self-crosslinking structure to form an interpenetrating network, which promoted a uniform and compact cured structure. The 5 wt % TR additions in the SPA was found to yield optimum results by improving the wet shear strength of the plywood by 105.4% to 1.13 MPa, which meets the interior-use plywood requirement. Therefore, the larch tannin could be applied in the modification of soy protein adhesive.

Antioxidant activity of commercial food grade tannins exemplified in a wine model

Although commercial tannins are widely used in foods and beverages, an improved understanding of the structure and composition of vegetable tannins is needed to promote the exploitation of agri-food by-products and waste and their valorisation in more sustainable industrial applications. This study aims to characterise the phytochemical composition and antioxidant activity of 13 food grade tannins using multiple analytical approaches, including spectrophotometry and HPLC-ECD to determine the amount of targeted polyphenolic compounds. Moreover, the antioxidant activity of tannins was assessed in terms of radical scavenging activity (DPPH• assay), reducing power (FRAP assay), and redox properties (cyclic voltammetry, CV). A statistical univariate and multivariate correlation analysis was performed on 17 parameters including tannin content (range: 0.71-1.62 mM), gallic acid, (+)-catechin, syringic acid and (‒)-epicatechin. The compositional profile of tannins was related to their chemical moiety, antioxidant activity and the botanical origin of the extracts. In particular, the CV signal at 500 mV was highly correlated with DPPH• value due to the catechol ring of flavonoids and trigalloyl moieties of gallic acid-based compounds. Practical examples of tannins application in winemaking are discussed.