Complex Tannins Research Articles

Exploring interactions between saprotrophic microbes and ectomycorrhizal fungi using a protein-tannin complex as an N source by red pine (Pinus resinosa).

• Recent studies suggest that some plants may circumvent N mineralization carried out by saprotrophs because their ectomycorrhizal fungi have the capacity to hydrolyse protein. When complexed by tannins, however, proteins may be unavailable to some ectomycorrhizal fungi. • Here we tested the hypothesis that when protein-tannin complex is the N source, Pisolithus tinctorius will promote N uptake into red pine (Pinus resinosa) only in the presence of saprotrophs. • The model protein-tannin complex was stable at field pH. P.tinctorius could not obtain N from it, but saprotrophs could. Pre-treatment of the complex by saprotrophs did make its N available to ectomycorrhizal fungi. However, when the protein-tannin complex was the major N source, P.tinctorius increased shoot P but not N content, even in the presence of saprotrophs. • Interactions between saprotrophs and ectomycorrhizal fungi may be different for N and P because of immobilization of N by ectomycorrhizal fungi, or by the more rapid diffusion of ammonium than phosphate, rendering the absorptive surface area of ectomycorrhizal fungi superfluous for uptake of N but not for P.

Dietary fibre in cocoa shell: characterisation of component polysaccharides

Polysaccharides were isolated from cocoa shells and characterised by compositional and linkage analysis. The polysaccharide types were diverse and included pectic polysaccharides (∼45%) which were made up of a heterogeneous mixture of rhamnogalacturonans with variable degrees of branching. Hemicelluloses (∼20%) consisted of a mixture of a fucosylated xyloglucan, galactoglucomannans, and glucuronoarabinoxylan. Cellulose accounted for ∼35% of the cell wall polysaccharides. The total dietary fibre content was approximately 40%, not as high as previous reports. This was attributed to the fact that previous studies have included a “Klason Lignin” fraction in estimates of fibre. A solid state NMR study of the cocoa shell “Klason Lignin” fraction provided evidence that it contained little if any lignin and presumably consisted principally of protein–Maillard–tannin complexes.

Interactions Between Wine Lees and Polyphenols: Influence on Oxygen Consumption Capacity During Simulation of Wine Aging

ABSTRACT: During wine aging on lees, some membrane lipids of yeast lees, in contact with dissolved oxygen at low concentration, may undergo mild oxidation explaining the capacity of yeast lees to consume oxygen. We studied the cross‐reactivity of complex polyphenols and tannins from wine and yeast lees towards oxygen during simulation of wine aging. We observed a total decrease of oxygen consumption capacity of mixed yeast lees and wine polyphenol by comparison with the reactivity of each component studied alone. A strong loss of reactivity of yeast lees towards oxygen was observed when separated from soluble polyphenols, although only a fraction of the total polyphenols remained adsorbed on lees.

Electron spin resonance study on the vanadium adsorption by persimmon tannin gel

The persimmon tannin gel can adsorb vanadium highly effectively from aqueous solutions containing VOCl 2 and NH 4VO 3, respectively. The adsorption of vanadium from the VOCl 2 solution had a broad maximum at around pH 5–6, while that from the NH 4VO 3 solution, a sharp maximum at around pH 3.75 and a broad one at around pH 5–6. The adsorption of vanadium by the gel from both VOCl 2 and NH 4VO 3 solutions was rapid, and was obeyed the Langmuir adsorption isotherm. The ESR spectrum of VO 2+ in the persimmon tannin gel showed a typical powder pattern with g-anisotropy and anisotropic hyperfine structure ( I=7/2), with g //=1.937, g ⊥=2.005, ∣ A //∣=552 MHz, and ∣ A ⊥∣=168 MHz, suggesting a square pyramidal coordination structure of VO 2+-persimmon tannin complex. The ESR analysis of vanadium adsorption from the NH 4VO 3 solution (pH 6) indicated the reduction of VO 3 − to VO 2+. The high vanadium-adsorption ability of the persimmon tannin gel from the VOCl 2 solution was attributed to the stable complex formation of VO 2+ with catechol and pyrogallol groups in the gel, while the vanadium adsorption from the NH 4VO 3 solution can be explained as the combination of H 3VO 4 and VO 2+ adsorptions.

Degradation and metabolism of 14C‐labelled proanthocyanidins from carob (Ceratonia siliqua) pods in the gastrointestinal tract of the rat

AbstractThe aim of the work was to study the binding, degradation and metabolism of dietary condensed tannins in the gastrointestinal tract of an omnivore. Young pods of carob (Ceratonia siliqua L) were radiolabelled by in vivo feeding of 14CO2, trans‐[U‐14C]cinnamate or L‐[U‐14C]phenylalanine. [14C]Proanthocyanidins (condensed tannins) were extracted with acetone/water (3:1 v/v), isolated on Sephadex LH‐20 and fed to rats by gavage. After 4 and 18 h, 90–94% of the gavaged 14C was in the gut contents and/or faeces. Much of the gavaged 14C (57%), predominantly that originally in tannins of high degree of polymerisation (DP), became insolubilised, mainly in the form of protein–tannin complexes. Some of the [14C]tannins that remained soluble decreased in DP, especially in the small intestine and caecum. A further fraction (12% of the 14C gavaged) underwent chemical modifications in the gut to form soluble, non‐tannin compounds. Small proportions of the 14C were found in the liver (1.0–1.5%), urine (1–2%) and 14CO2 (1–2%). We conclude that proanthocyanidins are not inert within the gut but undergo various modifications which may affect the nutrition of the animal.© 2001 Society of Chemical Industry

Calf-Thymus DNA Interaction with Cr(III)-Gallate and Cr(III)-Ethyl Gallate Studied by FTIR Spectroscopy and Capillary Electrophoresis

Abstract Cr(VI) salts are well known to be carcinogen, and are reduced by various cellular components to form cross-linked Cr(III) products. Organic compounds, such as gallic acid (GA) and ethyl gallate (EGA), reduce Cr(VI) to Cr(III) to form Cr(III)-gallate [Cr(III)-GA] and Cr(III)-ethyl gallate [Cr(III)-EGA] as final products. These Cr(III)-tannin complexes are DNA binders. The interaction of calf-thymus DNA with Cr(III)-GA and Cr(III)-EGA in aqueous solutions at physiological pH were studied at Cr(III)/DNA (phosphate) molar ratios (r) of 1 : 160, 1 : 80, 1 : 40, 1 : 20, 1 : 10, 1 : 4, and 1 : 2 using FTIR spectroscopy and capillary electrophoresis. An analysis by FTIR showed that at low concentrations (r = 1/80 and 1/40), Cr(III)-GA and Cr(III)–EGA mainly bind to the guanine N-7 atom of the G–C base pairs with minor perturbations of the A–T base pairs. At r > 1/20, a partial helix opening occurred with major perturbations of the G–C and A–T base pairs. At r > 1/10, aggregation of the Cr(III)-tannin–DNA complexes occurred. However, no DNA conformational changes were observed, and the DNA maintained the B-family structure. The binding constants of the Cr(III)-GA–DNA and Cr(III)-EGA–DNA were estimated to be 3.8 × 104 M−1 and 6.2 × 104 M−1, respectively, by Scatchard plots following capillary electrophoresis. These results suggest that the Cr(III)-tannin complexes are external DNA binders, and do not form a chelate with the DNA.

Roles of peritrophic membranes in protecting herbivorous insects from ingested plant allelochemicals.

Four mechanisms by which peritrophic membranes (PMs) potentially protect herbivorous insects from ingested allelochemicals are reviewed: adsorption, ultrafiltration, polyanion exclusion, and the capacity of PMs to act as antioxidants. Most of the research on the protective roles of PMs against ingested allelochemicals has focused on their impermeability to tannins. Adsorption of tannins by the PMs in grasshoppers may limit their permeability, but ultrafiltration of tannin complexes in the caeca is an alternative explanation. Polyanion exclusion does not explain the impermeability of caterpillar PMs to tannins (polyphenolate anions). Ultrafiltration remains the most likely mechanism by which tannins, and other tested allelochemicals, are retained in the endoperitrophic space. Although the pores in PMs are too large to impede the passage of most free allelochemicals, large allelochemical complexes are retained. Such complexes form in the gut fluid of caterpillars between tannic acid, proteins, lipids, and polyvalent metal cations, and also in the gut fluid of grasshoppers (Melanoplus sanguinipes) between some amphiphilic allelochemicals (digitoxin) and surfactant micelles. Further work is needed to examine the role of PMs as antioxidants in vivo, such as their potential to bind catalytically-active metal ions.

Antioxidant and radical scavenging properties in vitro of polyphenolic extracts from red wine.

Red wine polyphenols inhibit chemically-induced oxidative DNA damage in vivo in experimental animals through a mechanism which is still unclear. On this basis, we tried to clarify the mechanisms of inhibition of DNA oxidation in vitro by wine extracts containing monomeric and polymeric phenols (WE) and monomer-free complex polyphenols and tannins (WCPT) from red wine. Oxidative DNA damage was induced by incubating DNA with GSH/Fe3+ or cumene hydroperoxide (CumOOH) in vitro and using 8-OH-2-deoxyguanosine (8-OHdG) levels as a measure of DNA oxidation. Levels of 8-OHdG were determined by HPLC coupled with electrochemical detector (ESA). WCPT and WE, at microM concentrations, reduced concentration-dependently oxidative DNA damage induced by GSH/Fe3+. WCPT and WE also reduced DNA oxidation by CumOOH. In conclusion, complex polyphenols and tannin extracts from red wine, with or without small molecular phenols, prevent oxidative DNA damage through a dual mechanism, iron binding and direct free radical scavenging.

Effect of complex polyphenols and tannins from red wine on DNA oxidative damage of rat colon mucosa in vivo.

Dietary polyphenols have been reported to have a variety of biological actions, including anti-carcinogenic, antioxidant and anti-inflammatory activities. In the present study we have evaluated the effect of an oral treatment with complex polyphenols and tannins from red wine and tea on DNA oxidative damage in the rat colon mucosa. Isolated colonocytes were prepared from the colon mucosa of rats treated for ten days with either wine complex polyphenols (57.2 mg/kg/d) or thearubigin (40 mg/kg/d) by oral gavage. Colonocyte oxidative DNA damage was analysed at the single cell level using a modification of the comet assay technique. The results show that wine complex polyphenols and tannins induce a significant decrease (-62% for pyrimidine and -57% for purine oxidation) in basal DNA oxidative damage in colon mucosal cells without affecting the basal level of single-strand breaks. On the other hand, tea polyphenols, namely a crude extract of thearubigin, did not affect either strand breaks or pyrimidine oxidation in colon mucosal cells. Our experiments are the first demonstration that dietary polyphenols can modulate in vivo oxidative damage in the gastrointestinal tract of rodents. These data support the hypothesis that dietary polyphenols might have both a protective and a therapeutic potential in oxidative damage-related pathologies.

Extraction of natural complex phenols and tannins from grape seeds by using supercritical mixtures of carbon dioxide and alcohol.

Proanthocyanidins are supposed to have some therapeutical properties as antioxidants and antineoplasics. Most of the proanthocyanidins, however, are not commercialized since their separation from natural sources is either very expensive or not well-known. In this work, the feasibility of application of mixtures of carbon dioxide and alcohol under supercritical conditions for selective extraction of some phenolic compounds from grape seeds has been studied, among them some low polymerized proanthocyanidins, their main monomer units, (+)-catechin and (-)-epicatechin, and some low molecular weight phenolic compounds, like gallic acid. An analytical-scale supercritical fluid extractor, whose operation was previously optimized, was used to carry out the experiments. A commercial concentrate of complex phenols and tannins from grape seeds was subjected to supercritical extraction in order to find the best operation conditions before directly extracting defatted milled grape seeds. The solvent capacity was found to increase with pressure and with the amount of alcohol used as cosolvent as expected. Such variation in solvent capacity could be used for design of a selective separation process where individual phenolic compounds or groups of them could be obtained. HPLC coupled with two types of detectors, diode array and mass spectrometry, was used for tentative identification and quantification of complex phenols and tannins in the extracts and in the raw materials used for extraction.

Evaluation of methods for measuring polyphenols in conifer foliage

There is a resurgence of interest in the quantification of polyphenols in plant tissues because of their presumed ecological importance in plant–litter–soil and plant–animal interactions. The influence of sample preparation, extracting solvent, foliage quality, and assay method was investigated for the quantification of total phenols and condensed tannins in conifer foliage. Our results suggest that it is not possible to recommend a single optimal protocol for quantification of total phenol and condensed tannin fractions from plant materials. In general, the use of aqueous acetone (50–70% v/v) with freeze-dried materials gave the highest recovery. The Folin-Ciocalteau method for total phenols and the butanol–HCl hydrolysis method for condensed tannins appear superior to other common assays tested. There were large differences (1.4–2.2 times) in the reactivity of purified condensed tannins among species, indicating the importance of an appropriate standard for polyphenol quantification. A solid-state 13C NMR method with an improved "interrupted decoupling" pulse sequence yielded the highest concentrations for condensed tannins. Assuming that 13C NMR provides an accurate measure of total condensed tannin, the other extraction/assay methods used in this study recovered 50–86% of the condensed tannin fraction. The recovery rate is correlated with the nitrogen content of the foliage, which suggests that the formation of protein–tannin complexes may limit the extractability of condensed tannins. While 13C NMR condensed tannin values may give the best value for total condensed tannin concentrations, the water-soluble fraction may have the greatest physiological and/or ecological significance.

Effect of complex polyphenols and tannins from red wine (WCPT) on chemically induced oxidative DNA damage in the rat.

Flavonoids are polyphenolic antioxidants occurring in vegetables and fruits as well as beverages such as tea and wine which have been thought to influence oxidative damage. We wanted to verify whether a complex mixture of wine tannins (wine complex polyphenols and tannins, WCPT) prevent chemically-induced oxidative DNA damage in vivo. Oxidative DNA damage was evaluated by measuring the ratio of 8-hydroxy-2'-deoxyguanosine (80HdG)/ 2-deoxyguanosine (2dG) x 10(-6) in hydrolyzed DNA using HPLC coupled with electrochemical and UV detectors. We treated rats with WCPT (57 mg/kg p.o.) for 14 d, a dose 10-fold higher than what a moderate wine drinker would be exposed to. WCPT administration significantly reduced the ratio of 80HdG/2dG x 10(-6) in liver DNA obtained from rats treated with 2-nitropropane (2NP) relative to controls administered 2NP only (33. 3 +/- 2.5 vs. 44.9 +/- 3.2 x 10(-6) 2dG; micro +/- SE; p<0.05). On the contrary, pretreatment with WCPT for 10 d did not protect the colon mucosa from oxidative DNA damage induced by 1, 2-dimethylhydrazine (DMH). 2NP and DMH are hepatic and colon carcinogens, respectively, capable of inducing oxidative DNA damage. WCPT have protective action against some types of chemically-induced oxidative DNA damage in vivo.

Effect of complex polyphenols on colon carcinogenesis.

Complex polyphenols and tannins from wine (WCPT) are being considered increasingly as potential cancer chemopreventive agents, since epidemiological studies suggest that populations consuming a high amount of polyphenols in the diet may have a lower incidence of some types of cancer. We studied the effect of WCPT on a series of parameters related to colon carcinogenesis in rats. WCPT were administered to F344 rats at a dose of 14 or 57 mg/kg/d, mixed with the diet. The higher dose is about ten times the exposure to polyphenols of a moderate drinker of red wine. In rats treated with WCPT, we measured fecal bile acids and long chain fatty acids, colon mucosa cell proliferation, apoptosis and, after administration of colon carcinogens, the number and size of aberrant crypt foci (ACF) and nuclear aberrations. Colon mucosa proliferation was not varied by chronic administration (90 d) of WCPT (14 or 57 mg/kg/d). The highest dose of WCPT decreased the number of cells in the colon crypts, but did not increase apoptosis. WCPT (57 mg/kg) administered before or after the administration of azoxymethane (AOM) did not vary the number or multiplicity of ACF in the colon. The number of nuclear aberrations (NA) in colon mucosa was studied after administration of 1,2-dimethylhydrazine (DMH) and 2-amino-3-methylimidazo (4,5-f)quinoline (IQ), colon-specific carcinogens which require metabolic activation. The effect of DMH and IQ was not varied by pre-feeding WCPT (57 mg/kg) for 10 d. Similarly, the levels of total, secondary bile acids and long chain fatty acids did not varied significantly in animals fed WCPT for 90 d. WCPT administration does not influence parameters related to colon carcinogenesis in the rat.

A novel method to evaluate the relative tannin-binding capacities of salivary proteins

Many herbivore species have a diet containing high proportions of polyphenolics, principally lignins and tannins; the latter reduce the conversion of ingested nutrients into biomass and exert systemic toxicity at high levels of intake. It has been proposed that tannin-binding proteins in the saliva might be responsible for minimizing these tannin-related effects by forming soluble protein–tannin complexes. We have developed a method that permits evaluation of the relative tannin-binding properties of salivary proteins at a pH of 8.0–8.5. It is aimed at facilitating both the identification of tannin-binding proteins and the investigation of their relative tannin binding. The principle of the assay is the inhibition of trypsin by tannins and the subsequent reversal of that inhibition when other tannin-binding proteins are added (indirect assay). The method is rapid; large sample numbers may be processed by virtue of its microtiterplate format.

Modeling the conformation of polyphenols and their complexation with polypeptides: self-association of catechin and its complexation with L-proline glycine oligomers.

Over the past 10 years, several scientific thrusts have come together in the study of flavanoids that make it possible to move forward into the study of complexation between polyphenols and polypeptides. Enhanced understanding of the conformational properties of flavanoid monomers and polyflavanoids through molecular modeling, combined with the detailed NMR experimental data now in the literature, provide the foundation.1–13 Recent work using conformational searching techniques with the GMMX6–8 protocol has shown additional detail about the distribution of pseudo equatorial and pseudo low-energy axial conformers in the ensemble, as shown in figure 1. This leads to information about the relationship between the conformer ensemble and the Boltzmann averaged NMR proton coupling constants that one would expect to observe in a solution. Figure 1 also illustrates the pseudo equatorial to axial transformation that takes place in all catechin or (+)-catechin-(4α→8)-(+)-catechin (B3) dimer complexes during the conformer searches and which would also be expected to occur in solution. Interest continues to further understand the details about this conformer distribution as well as in the prediction of complexation of tannins with metal ions and proteins. Although the GMMX software has given many interesting results, it is limited in handling cases that require systematic conformational searching of molecules combined in a complex. In addition, there are no solvent model options.KeywordsLower Energy StructureAmber Force FieldPyran RingMMFF Force FieldAxial ConformerThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Development of a Competition Assay for the Evaluation of the Binding of Human Parotid Salivary Proteins to Dietary Complex Phenols and Tannins Using a Peroxidase-Labeled Tannin

Proline-rich proteins (PRP) are secreted by herbivores, including humans, in their parotid saliva into the oral cavity. These PRP have a high affinity for dietary complex phenols and tannins (CPT). The stable complexes formed may then pass through the digestive tract and are excreted. It is postulated that such complexes may modulate both the antinutritional effects and beneficial properties of CPTs. A novel competitive tannin−salivary protein binding assay is described that allows the detailed investigation of binding of tannins to salivary proteins. The assay is based on the competition between an enzyme-labeled tannin [(−)-epigallocatechin conjugated to horseradish peroxidase via a linker molecule] and a test tannin to bind to parotid salivary protein immobilized in the wells of a polystyrene microtiter plate. The binding affinities of a series of flavan-3-ol monomers from tea and a commercial tannic acid preparation were determined. Major differences in the binding affinities of the compounds tested t...

Reduction of Potassium Chromate By Tannins

Abstract The reduction of potassium chromate has been carried out with several tannin substances, including gallic acid, pyrogallol, ethyl gallate, polygalloylglucose, and withered oak-leaf tannin. Each reaction was followed by colorimetry, EPR spectroscopy, electrochemistry, and molecular-sieve chromatography. The progress of the chromate reductions was monitored by measuring the VIS and EPR spectra as a function of time. The observed preudo-first-order reaction rate constants for Cr(III) formation were derived based on the intensities of the Cr(III) signals of the EPR spectra. Cyclic voltammograms of the simple reductants and their final Cr(III)-containing products formed from the reductions of chromate have also been measured. The formation of Cr(III)–tannin complexes was indicated by separation on a Sephadex G-25 column. The results obtained from VIS, EPR, and cyclic voltammetry were found to be mutually dependent, and showed close correlations among the data. The rate of reduction for Cr(VI) revealed the following trend: gallic acid &amp;gt; pyrogallol &amp;gt; ethyl gallate &amp;gt; polygalloylglucose &amp;gt; witheredoak-leaf tannin. The results obtained in the present study suggest that the rates of reduction for Cr(VI) in the tannins depend upon their peak oxidation potentials and stabilities for Cr(III)–tannin complexes.

Wine complex phenols and tannins (CPT) protect against liver oxidative DNA damage induced by 2-nitropropane: [formula omitted], M. Lodovici, G. Paganelli and P. Dolara. Department of Pharmacology, University of Florence, Viale Morgagni 65, 50134, Florence Italy

Wine complex phenols and tannins (CPT) protect against liver oxidative DNA damage induced by 2-nitropropane: [formula omitted], M. Lodovici, G. Paganelli and P. Dolara. Department of Pharmacology, University of Florence, Viale Morgagni 65, 50134, Florence Italy

Nano-porous solid-state photovoltaic cell sensitized with tannin

Tannin and related polyphenolic substances strongly surface chelate with sensitizing nano-porous films of to the visible spectrum. The photovoltaic cell nano-porous n--CuI generates highly stable photovoltages. The result is explained as the effectiveness of the -tannin complex on the surface of in preventing short-circuiting across the /CuI barrier.

Oven drying improves the nutritional value ofCalliandra calothyrsus andGliricidia sepium as supplements for sheep given low-quality straw

Leaves from the tree legumes Gliricidia (Gliricidia sepium) and Calliandra (Calliandra calothyrsus) were fed as supplements (200 g dry matter) to sheep (n=3) given a basal diet of barley straw ad libitum. Tree leaves were fed either freshly harvested (F=fresh) or after drying at 60°C in a forced draught oven (D=dried). Voluntary intakes, digestibility and aspects of nitrogen (N) and phenolic compound metabolism were measured in all sheep. Drying decreased the condensed tannin (CT) content of Calliandra (F 117, D 82 g CT kg−1 DM). Total phenolics (TP) were significantly decreased when Gliricidia was dried (F 39, D 21 g TP kg−1 DM), and CT content was reduced from 20 g CT kg−1 DM to zero. Sheep given Gliricidia had higher rumen ammonia concentrations (73–85 mg N litre−1) than did sheep given Calliandra (37–40 mg N litre−1). For both species, drying significantly increased the voluntary consumption of straw, increased DM digestibility, decreased faecal N excretion and increased N balance. For calliandra, drying decreased the apparent degradability of N in the rumen (DNR) from 0·40 to 0·28 g N g−1 N ingested, and increased the apparent digestibility of N (ADN) in the post-ruminal tract from 0·20 to 0·52 g N absorbed g−1 N flowing into the small intestines. For Gliricidia, DNR decreased from 0·64 to 0·51 and ADN increased from 0·41 to 0·56. There were no significant effects of drying on rates of microbial N synthesis. The above changes were discussed in relation to changes in tannin content and it was concluded that drying facilitates the formation of protein–tannin complexes which protect proteins from degradation in the rumen. These proteins are subsequently released in the small intestines, thereby promoting an increased efficiency of dietary N utilisation. ©1997 SCI