Tannins are a unique group of phenolic metabolites with molecular weights between 500 and 30 000 Da, which are widely distributed in almost all plant foods and beverages. Proanthocyanidins and ...hydrolysable tannins are the two major groups of these bioactive compounds, but complex tannins containing structural elements of both groups and specific tannins in marine brown algae have also been described. Most literature data on food tannins refer only to oligomeric compounds that are extracted with aqueous-organic solvents, but a significant number of non-extractable tannins are usually not mentioned in the literature. The biological effects of tannins usually depend on their grade of polymerisation and solubility. Highly polymerised tannins exhibit low bioaccessibility in the small intestine and low fermentability by colonic microflora. This review summarises a new approach to analysis of extractable and non-extractable tannins, major food sources, and effects of storage and processing on tannin content and bioavailability. Biological properties such as antioxidant, antimicrobial and antiviral effects are also described. In addition, the role of tannins in diabetes mellitus has been discussed.
Tannins are a heterogeneous group of high MW, water‐soluble, polyphenolic compounds, naturally present in cereals, leguminous seeds and, predominantly, in many fruits and vegetables, where they ...provide protection against a wide range of biotic and abiotic stressors. Tannins exert several pharmacological effects, including antioxidant and free radical scavenging activity as well as antimicrobial, anti‐cancer, anti‐nutritional and cardio‐protective properties. They also seem to exert beneficial effects on metabolic disorders and prevent the onset of several oxidative stress‐related diseases. Although the bioavailability and pharmacokinetic data for these phytochemicals are still sparse, gut absorption of these compounds seems to be inversely correlated with the degree of polymerization. Further studies are mandatory to better clarify how these molecules and their metabolites are able to cross the intestinal barrier in order to exert their biological properties. This review summarizes the current literature on tannins, focusing on the main, recently proposed mechanisms of action that underlie their pharmacological and disease‐prevention properties, as well as their bioavailability, safety and toxicology.
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This article is part of a themed section on Principles of Pharmacological Research of Nutraceuticals. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.11/issuetoc
Tannic acid is a chief gallo-tannin belonging to the hydrolysable tannins extracted from gall nuts and other plant sources. A myriad of pharmaceutical and biological applications in the medical field ...has been well recognized to tannic acid. Among these effects, potential anticancer activities against several solid malignancies such as liver, breast, lung, pancreatic, colorectal and ovarian cancers have been reported. Tannic acid was found to play a maestro-role in tuning several oncological signaling pathways including JAK/STAT, RAS/RAF/mTOR, TGF-β1/TGF-β1R axis, VEGF/VEGFR and CXCL12/CXCR4 axes. The combinational beneficial effects of tannic acid with other conventional chemotherapeutic drugs have been clearly demonstrated in literature such as a synergistic anticancer effect and enhancement of the chemo-sensitivity in several resistant cases. Yet, clinical applications of tannic acid have been limited owing to its poor lipid solubility, low bioavailability, off-taste, and short half-life. To overcome such obstacles, novel drug delivery systems have been employed to deliver tannic acid with the aim of improving its applications and/or efficacy against cancer cells. Among these drug delivery systems are several types of organic and metallic nanoparticles. In this review, the authors focus on the molecular mechanisms of tannic acid in tuning several neoplastic diseases as well as novel drug delivery systems that can be used for its clinical applications with an attempt to provide a systemic reference to promote the development of tannic acid as a cheap drug and/or drug delivery system in cancer management.
The wound healing process of the diabetic wound is often hindered by excessive oxygen free radicals and infection. An ideal wound dressing should possess great reactive oxygen species (ROS) ...scavenging property and considerable antibacterial ability. In this study, we facilely constructed a novel hydrogel dressing with excellent ROS scavenging property and outstanding antibacterial performance by introducing tannic acid (TA) into quaternized chitosan (QCS) matrix. Attributing to the suitable physical crosslinking between TA and QCS, this QCS/TA hydrogel was endowed with injectable and self-healing properties, which could avoid the various external squeezing on the irregular shape by wound dressing. The results showed that it could promote coagulation, suppress inflammation and expedite collagen deposition in the skin defect model of diabetic rats. This study provides a facile and convenient method for constructing injectable hydrogel dressing, which has application potentials in the clinical management of diabetic wounds.
•An injectable hydrogel (QT) composed of quaternized chitosan and tannic acid was designed.•One-step fabrication of QT hydrogel was achieved via alkali neutralization strategy.•QT hydrogel possessed robust antibacterial and ROS scavenging capabilities.•QT hydrogel significantly accelerated skin tissue regeneration in diabetic wounds.
•Acorn flour has lower in vitro digestibility comparing to that of rice.•Starch hydrolase inhibitors are responsible for the low digestibility of acorn flour.•Ellagitannins are active compounds for ...retarding starch digestion of acorn flour.•Acorn is promising for making staple foods with low glycemic index.
The acorns of Quercus fabri Hance tree, or the mandarin duck fruits have been consumed by locals in the form of noodle, yet there is little scientific study. We found that they have much lower digestibility compared with that of rice flour. Solvent extraction using hexane, dichloromethane, and acetone-ethanol-water (AEW) mixture yielded three fractions but the starch hydrolase inhibitors were only found in the AEW fraction. Using assay-guided fractionation of the extracts, we were able to further separate the active compounds by using Sephadex LH-20 column and characterize the inhibitor chemical identities by LC-MS(n). The main active compounds are ellagitannins including pedunculagin, punicalagin, castalagin, and eucalbanin. Our results indicate that the acorns from Quercus fabri Hance have potential for preparation of low glycemic index foods due to the endogenous starch hydrolase inhibitors.
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Tissue adhesives play an important role in surgery to close wounds, seal tissues, and stop bleeding, but existing adhesives are costly, cytotoxic, or bond weakly to tissue. Inspired ...by the water-resistant adhesion of plant-derived tannins, we herein report a new family of bioadhesives derived from a facile, one-step Michael addition of tannic acid and gelatin under oxidizing conditions and crosslinked by silver nitrate. The oxidized polyphenol groups of tannic acid enable wet tissue adhesion through catecholamine-like chemistry, while both tannic acid and silver nanoparticles reduced from silver nitrate provide antimicrobial sources inherent within the polymeric network. These tannin-inspired gelatin bioadhesives are low-cost and readily scalable and eliminate the concerns of potential neurological effect brought by mussel-inspired strategy due to the inclusion of dopamine; variations in gelatin source (fish, bovine, or porcine) and tannic acid feeding ratios resulted in tunable gelation times (36 s–8 min), controllable degradation (up to 100% degradation within a month), considerable wet tissue adhesion strengths (up to 3.7 times to that of fibrin glue), excellent cytocompatibility, as well as antibacterial and antifungal properties. The innate properties of tannic acid as a natural phenolic crosslinker, molecular glue, and antimicrobial agent warrant a unique and significant approach to bioadhesive design.
This manuscript describes the development of a new family of tannin-inspired antimicrobial bioadhesives derived from a facile, one-step Michael addition of tannic acid and gelatin under oxidizing conditions and crosslinked by silver nitrate. Our strategy is new and can be easily extended to other polymer systems, low-cost and readily scalable, and eliminate the concerns of potential neurological effect brought by mussel-inspired strategy due to the inclusion of dopamine.
The tannin-inspired gelatin bioadhesives hold great promise for a number of applications in wound closure, tissue sealant, hemostasis, antimicrobial and cell/drug delivery, and would be interested to the readers from biomaterials, tissue engineering, and drug delivery area.
Pharmacology and toxicology of tannins Maugeri, Alessandro; Lombardo, Giovanni Enrico; Cirmi, Santa ...
Archives of toxicology,
05/2022, Volume:
96, Issue:
5
Journal Article
Peer reviewed
Tannins are an interesting class of polyphenols, characterized, in almost all cases, by a different degree of polymerization, which, inevitably, markedly influences their bioavailability, as well as ...biochemical and pharmacological activities. They have been used for the process of tanning to transform hides into leather, from which their name derives. For several time, they have not been accurately evaluated, but now researchers have started to unravel their potential, highlighting anti-inflammatory, antimicrobial, antioxidant and anticancer activities, as well as their involvement in cardiovascular, neuroprotective and in general metabolic diseases prevention. The mechanisms underlying their activity are often complex, but the main targets of their action (such as key enzymes modulation, activation of metabolic pathways and changes in the metabolic fluxes) are highlighted in this review, without losing sight of their toxicity. This aspect still needs further and better-designed study to be thoroughly understood and allow a more conscious use of tannins for human health.
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•Chestnut peels can be used to extract condensed and hydrolysable tannins.•Important antioxidant tannins were extracted from chestnut peels.•Moderate concentrations of alkali ...solutions extract more tannins.•Tannins can be used to produce adhesive formulations.•Tannins can be used in food, cosmetic or pharmaceutical industry.
The aim of the current study was to evaluate the potential of chestnut peels to produce pomaces enhanced with tannins to be used in the formulations of wood adhesives, leather tanning or as natural antioxidants in food, cosmetic and pharmaceutical industry. An analytical procedure was planned as 2 factorial design to analyze the influence of solvent (water, Na2SO3 and NaOH at different concentrations of 1, 2, 4, and 8% in water) and extraction time (30, 60, and 120, 240, 480 and 960min) on extraction yield, pH, Stiasny index, and tannins. HPLC-diode array detector equipped with an ionization mass spectrophotometer was used to assess the polyphenol composition. Our results showed that both extraction properties and phytochemicals were significantly affected (P<0.001) by all independent factors. The main tannins identified were the hydrolyzable gallic acid, vescalagin castalagin and ellagic acid, and the condensed epigallocatechin, catechin and epicatechin. The solvent 1% Na2SO3 was more effective to extract the condensed tannins whilst hydrolyzable tannins were extracted efficiently by 1% NaOH. The multivariable analysis and the Pearson’s correlation coefficients showed a direct association between Stiasny number and the average levels of condensed tannins.
In this review, a brief description of how animal skins were transformed in leathers in Europe using different vegetable tannins will be presented. Special attention will be dedicated to the ...description of the type of tannins and the characteristics of the most important type of historic leathers thus obtained. The text will also focus on the description of the techniques used in the identification of these tannins in historic objects: colorimetric tests and spectroscopic analysis.
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