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At least 253 records · Page 14Linked to original sources
PubMed2004

Tannins and catechin gallate mediate the vasorelaxant effect of Arbutus unedo on the rat isolated aorta.

This study examined the vascular effect of Arbutus leaves (aqueous extract) and described the isolation of several fractions responsible for their vasorelaxant activity. The aqueous extract (AE) of leaves was tested on rat aortic rings precontracted with 0.1 microm noradrenaline. At 10(-2) g/L, AE produced an endothelium dependent relaxation of 66% +/- 5%, (n = 8). The leaves of Arbutus were then extracted successively with different solvents and the methanol extract was the most active. When tannins (primarily condensed tannins) were precipitated from the methanol extract, they showed a strong vasorelaxant activity (87% +/- 4%, n = 5), whereas the elimination of tannins in the methanol extract reduced significantly its vasorelaxant activity (42% +/- 8%, n = 8, p < 0.005). The methanol extract was further separated semi-preparatively by reversed-phase HPLC. Four fractions (Fr2, Fr3, Fr4 and Fr6) were the most active and produced 88% +/- 2% (n = 5), 75% +/- 6% (n = 5), 76% +/- 3% (n = 7) and 77% +/- 3% (n = 10) relaxation, respectively. These four fractions mainly correspond to polyphenol compounds. Analysis of Fr6 indicated that this fraction contained catechin gallate. In conclusion, the vasorelaxant activity of Arbutus is likely to be due to polyphenol compounds, primarily condensed tannins and catechin gallate.

Animals↗
PubMed1992

Pharmacologically active tannins isolated from medicinal plants.

Starting with the isolation of a crystalline tannin (geraniin) of mild property from a popular herb medicine (Geranii herba), various polyphenolic compounds including those belonging to new classes of tannins (oligomeric hydrolyzable tannins, complex tannins, and other metabolites and condensates) have been isolated from various medicinal plants. Noticeable biological and pharmacological activities (inhibition of carcinogenesis, host-mediated antitumor activity, antiviral activity, and inhibition of active oxygen, such as inhibition of lipid peroxidation and lipoxygenase, xanthine oxidase, and monoamine oxidase) have been found for several of these polyphenolic compounds.

Animals↗
PubMed1992

Condensed tannins in some forage legumes: their role in the prevention of ruminant pasture bloat.

For the past 20 years, the focus in our laboratory has been on finding the causes of ruminant pasture bloat and eventually breeding a bloat-safe alfalfa (Medicago sativa L.); i.e., with bloat potential reduced to the economic threshold. In the mid-seventies, the mechanisms of bloat were explored and found to be more physical than chemical. Characteristic of all bloating legumes after ingestion was a very rapid initial rate of ingestion by rumen microbes. Through the study of bloating and non-bloating legumes, factors were elucidated in the plant that would slow this process. One of these factors was the presence of condensed tannins in the herbage. Some of the non-bloating legumes contained these secondary metabolites, but no condensed tannins were found in any of the bloating legumes. Therefore, species containing an appreciable amount of condensed tannins in their leaves and stems are considered to be non-bloating. Conventional breeding methods have not been successful in producing an alfalfa with condensed tannins in its herbage. New approaches using tissue culture techniques are being attempted, but genetic engineering has the greatest potential for success.

Animals↗
PubMed1979

Effect of peanut tannins on percent seed colonization and in vitro growth by Aspergillus parasiticus.

The relationship between tannin content of mature, intact, cured peanut seed and percent seed colonization by Aspergillus parasiticus was examined. Tannin content in 9 cultivars, 7 of which were grown in both Tifton, Georgia and Puerto Rico, was significantly correlated with percent seed colonization. For data expressed as mg tannin/g intact seed and mg tannin/g seed coat, correlation coefficients with percent colonization were 0.74 and 0.76, respectively. Seed coat tannin, methanol-extracted, water-soluble material from peanut seed coats, was tested in vitro for effects on growth of A. parasiticus. As concentrations of tannins were increased to 7.5%, inhibition of fungal growth increased linearly to 88%; a concentration of 20% produced over 96% inhibition.

Arachis↗
PubMed1994

Mass determination of the fatty acids released from tannin-stimulated rabbit alveolar macrophages.

Previous studies with macrophages that had been prelabeled with [14C]arachidonic acid (20:4) have shown that condensed tannin is a potent agonist for the release of arachidonic acid. However, it has not been demonstrated that the percentage release of [14C]20:4 accurately reflects the metabolic activity of the endogenous 20:4 pool. In order to measure the 20:4 mass release relative to the total cellular 20:4 pool, the free fatty acids of freshly isolated alveolar macrophages were derivatized with a fluorescent reagent, and then separated and quantified by high-performance liquid chromatography. The amounts of esterified fatty acids were measured by gas chromatography of the methyl esters. Free fatty acid levels were compared to those of the total esterified plus unesterified fatty acids to determine the actual percentage release of each fatty acid. Tannin-stimulated release of 20:4 mass reflected that previously reported for the release of [14C]20:4 label but at a slower rate and at a much lower percentage indicating that [14C]20:4 had been incorporated into part of a more reactive pool. The specificity of the fatty acid release induced by tannin and beta-1,3-glucan, a known agonist for 20:4 release, was also examined. Both agonists promoted an increase in the levels of free 20:4 and of other fatty acids. A comparison of the absolute increases of each of the fatty acids indicated that tannin caused a preferential increase in the mass of free 20:4, whereas beta-1,3-glucan evoked a selective increase in the mass of 16:0.

Animals↗
PubMed2004

Determination of flavonoids, tannins and ellagic acid in leaves from Rubus L. species.

This paper describes the quantitative determination of flavonoids, tannins and ellagic acid in the leaves from wild and cultivated variations of Rubus L. species (Rosaceae): raspberry (2 wild and 13 cultivars) and blackberry (3 wild and 3 cultivars). The content of flavonoids was analyzed using spectrophotometric (the Christ-Mullers method) and HPLC analysis after acid hydrolysis. The content of tannins was determined by the weight method, with hide powder, described by German Pharmacopoeia 10 (DAB 10). Ellagic acid content was examined using the HPLC method after acid hydrolysis. Flavonoid content, determined using the Christ-Muller's method was higher for the blackberry leaves than for the raspberry leaves and varied between 0.46% and 1.05%. Quercetin and kaempferol were predominant in all samples analyzed using the HPLC method. The highest flavonoid content was found in the leaves of R. nessensis (1.06%); with results in all of the examined samples varying between 0.27% and 1.06%. The concentration of ellagic acid in all species was determined after acid hydrolysis and ranged from 2.06% to 6.89%. The leaves of raspberries are characterized by greater amounts of tannins (varying between 2.62% and 6.87%) than the leaves of other species. The results from this study indicate that the analyzed species are a rich source of flavonoids, ellagic acid and tannins, which may be used for the quality assessment of Rubus L. species leaves.

Chromatography, High Pressure Liquid↗
PubMed1998

Byssinosis: role of polymer length on the effect of tannin on the airway beta-adrenergic receptor.

Tannin, isolated from cotton bracts and implicated in the pathogenesis of byssinosis, inhibits isoproterenol and forskolin-stimulated cAMP release from airway cells in part by decreasing cell surface beta-adrenergic receptor number and uncoupling the beta-adrenergic receptor from its stimulatory G-protein (Gs) and in part by inhibiting adenylyl cyclase activity. We have hypothesized that cotton tannin, because of its long polymer length, interacts with the hydrophobic binding pocket of the beta-adrenergic receptor and alters beta-adrenergic receptor binding and Gs coupling. In these studies, tannins of three different polymer lengths and molecular masses were isolated from cotton bracts using sequential Amicon ultrafiltration [molecular mass > 10, 000 (YM10 retentate), 1,000-10,000 (YM10 filtrate), and 1,000-5,000 Da (YM2 retentate)]. The YM10 retentate (25 microg/ml) decreased chloride secretion (Jnet = 1.11 +/- 0.28 (control) to 0.59 +/- 0.18 microEq/cm2.h, p < 0.05, n = 6), decreased cell surface beta-adrenergic receptor number (18.0 +/- 1.8 (control) to 10.6 +/- 0.9 fmol/mg protein, p < 0.02, n = 4), and inhibited forskolin-stimulated cAMP release (5,254 +/- 1,290 (control) to 2, 968 +/- 620 pmol/mg protein, p < 0.01, n = 8). In contrast, neither the YM10 filtrate nor the YM2 retentate had any effect on net chloride secretion, beta-adrenergic cell surface receptor number, or forskolin-stimulated cAMP release. We conclude that polymer length is essential for the effect of tannin on the beta-adrenergic receptor and on adenylyl cyclase.

Animals↗
PubMed1995

Inhibition of signal-regulated protein kinases by plant-derived hydrolysable tannins.

A variety of hydrolysable tannins purified from Phyllanthus amarus are potent inhibitors of rat liver cyclic AMP-dependent protein kinase catalytic subunit (cAK) with IC50 values (concentrations for 50% inhibition) in the range 0.2-1.7 microM. The three most effective compounds of this series of hydrolysable tannins have five phenolic substituents. These three compounds are also the most effective inhibitors of wheat embryo Ca(2+)-dependent protein kinase (CDPK), rat brain Ca(2+)- and phospholipid-dependent protein kinase C (PKC) and Ca(2+)-calmodulin-dependent myosin light chain kinase (MLCK). The order of sensitivity for protein kinase inhibition by the hydrolysable tannins studied is cAK > CDPK > PKC > MLCK. Thus the IC50 values for protein kinase inhibition by the most potent compound are 0.2 microM (for cAK), 1.8 microM (for CDPK), 26 microM (for PKC) and 56 microM (for MLCK) when protein kinase affinity is measured using synthetic peptide substrates. These hydrolysable tannin inhibitors found are the most specific and potent plant-derived inhibitors of cAK yet found.

Amino Acid Sequence↗
PubMed1987

Tannins occurring in the toxic Brazilian plant Thiloa glaucocarpa.

Four tannins were isolated from dried leaves of Thiloa glaucocarpa, which is one of the plants causing poisoning of cattle in Brazil. These four tannins were determined from spectrometric and chemical evidence to be the ellagic C-glucosyl tannins vescalagin, castalagin, stachyurin and casuarinin. The main components, vescalagin and castalagin, are also known as constituents of oak (Quercus spp.), the toxicity of which for cattle is supposed to be due to tannins. Suggestions concerning the resemblance of the symptoms of poisoning by Thiloa glaucocarpa and by oak are supported by the presence of the constituents in both plants.

Acetylation↗
PubMed1988

Tannins, salivary proline-rich proteins and oesophageal cancer.

No single dietary factor or ingested substance has been implicated in the aetiology of oesophageal carcinoma especially in high-risk areas of the world. Although not well defined, there is heavy consumption of tannin-rich foods, particularly sorghum, by populations at high risk for carcinoma. The carcinogenic properties of tannins and extracts of tannin-rich plants have been demonstrated experimentally. It is proposed herein that salivary proline-rich proteins (PRPs) by binding ingested tannins protect the oesophagus from the carcinogenic effects of the latter. It is also possible that genetic variants of PRPs may influence the incidence of oesophageal cancer in different populations.

Esophageal Neoplasms↗
PubMed1985

Antihepatotoxic actions of tannins.

The antihepatotoxic effects of tannin analogues were examined utilizing carbon tetrachloride- and galactosamine-induced cytotoxicity in primary cultured rat hepatocytes. Most tannins showed significant antihepatotoxic effects in these two assay systems. Hydrolyzable tannins generally exhibited an intense enzyme inhibitory action on glutamic-pyruvic transaminase while condensed tannins exerted a much less inhibitory action, although variations were observed depending on structure. Structure-activity relationships are discussed.

Alanine Transaminase↗
PubMed2004

Tannins elevate the level of poly(ADP-ribose) in HeLa cell extracts.

Phenolic phytochemicals such as tannins, which are natural constituents of green tea, red wine, and other plant products, are considered to have cancer-preventive properties. An important endogenous mediator of tumorigenesis is the nuclear enzyme poly(ADP-ribose) polymerase 1 (PARP-1). PARP-1 synthesizes polymers of ADP-ribose (PAR), which, in turn, are degraded by the catabolic enzyme poly(ADP-ribose) glycohydrolase (PARG). In the present study, we investigated the effects of tannins on the level of PAR in HeLa nuclear extracts. The addition of tannins to nuclear extracts led to a 40-fold elevation of PAR-levels. The observed increased PAR-levels resulted from inhibition of the catalytic activity of PARG. Additionally, the human PARG cDNA was cloned and the recombinant enzyme was overexpressed and isolated. Recombinant PARG was immobilized using an affinity column composed of tannins covalently linked to Sepharose beads. Finally, an interaction between immobilized PARG and endogenous PARP-1 from HeLa cell extracts is demonstrated.

Dose-Response Relationship, Drug↗
PubMed2006

Effect of salivary proteins on the transport of tannin and quercetin across intestinal epithelial cells in culture.

Polyphenols including tannins and flavonoids are common in plant foods. While tannins may be deleterious to animals, flavonoids can have beneficial effects on the cardio-vascular system. Since salivary proteins can form complexes with polyphenols and thereby interfere with their intestinal absorption, the effect of salivary proteins on transport of tannins and flavonoids across intestinal epithelial cells (Caco-2 cells) was investigated. In presence of the salivary protein Histatin5 (Hst5) the rate of transport (dC/dt) of pentagalloyl glucose (5GG), a tannic acid, across Caco-2 cells in culture was reduced maximally 3.6-fold to 5x10(-7)microM/s in apical to basolateral direction. Replacing the basolateral salt solution with serum caused a 13-fold increase in dC/dt of 5GG in the absence of Hst5, but addition of Hst5 decreased dC/dt l4-fold. Transport of 5GG in basolateral to apical direction was decreased in half in the presence of Hst5. Decreases in dC/dt were closely paralleled by formation of insoluble 5GG-Hst5 complexes. In contrast, Hst5 and 1B4, a salivary proline-rich protein, had little if any effect on the transepithelial transport of the flavonoid quercetin in apical to basolateral as well as basolateral to apical direction. Taken together with previous studies [Cai K, Hagerman AE, Minto RE, Bennick A. Decreased polyphenol transport across cultured intestinal cells by a salivary proline-rich protein. Biochem Pharmacol 2006;71:1570-80] it appears that although Hst5 and 1B4 are synthesized in salivary glands they have an important biological function in the intestines as scavenger molecules preventing uptake of tannin but without notably affecting absorption of flavonoids.

Biological Transport↗
PubMed2005

Inhibition of Caco-2 colon, MCF-7 and Hs578T breast, and DU 145 prostatic cancer cell proliferation by water-soluble black bean condensed tannins.

The potential anti-angiogenic activities of water-soluble condensed tannins isolated from black beans were evaluated using HEL 299 normal human fibroblast lung cells, Caco-2 colon, MCF-7 and Hs578T breast, and DU 145 human prostatic cancer cells. Condensed tannins at 0.24-24 microM did not affect the growth of normal cells, but dose-dependently induced cancer cell death by apoptosis as shown by a concentration-dependent decrease in ATP and cell gross morphology. After 24h exposure to Caco-2, MCF-7, Hs578T, and DU 145 cancer cells, water-soluble black bean condensed tannins at 24 microM suppressed fetal bovine serum stimulated cell migration, the secretion of matrix metalloproteinase-2 (MMP-2 or gelatinase A), matrix metalloproteinase-9 (MMP-9 or gelatinase B), and vascular endothelial growth factor VEGF(165) receptor expression by the cancer cells in the conditioned media. The potential health enhancing properties of condensed tannins from black beans as inhibitors of angiogenesis is discussed.

Adenosine Triphosphate↗
PubMed2006

Vegetable and synthetic tannins induce hormesis/toxicity in sea urchin early development and in algal growth.

Mimosa tannin and phenol-based synthetic tannin (syntan) were tested for toxicity to sea urchin (Paracentrotus lividus and Sphaerechinus granularis) early development and to marine algal growth (Dunaliella tertiolecta). Sea urchin embryogenesis was affected by vegetable tannin and syntan water extracts (VTWE and STWE) at levels >or=1mg/L. Developmental defects were significantly decreased at VTWE and STWE levels of 0.1 and 0.3mg/L when control cultures displayed suboptimal quality, i.e. <70% "viable" (normal or retarded) larvae. Fertilization success of sea urchin sperm was increased up to 0.3 mg/L STWE or VTWE, then was inhibited by increasing tannin levels (1-30 mg/L). Offspring abnormalities, following sperm exposure to VTWE or STWE, showed the same shift from hormesis to toxicity. Cell growth bioassays in D. tertiolecta exposed to VTWE or STWE (0.1-30 mg/L) showed non-linear concentration-related toxicity. Novel criteria are suggested in defining control quality that should reveal hormetic effects.

Animals↗
PubMed2006

Effects of condensed tannin from Acacia mearnsii on sheep infected naturally with gastrointestinal helminthes.

The effect of tannins on endoparasite control in hair sheep was investigated using 20 entire lambs of the Santa Inês breed. At the beginning of the experiment these animals were 6-months old and weighed 22.5kg+/-4.7. The treatments used were (10 animals each): GT (animals receiving 18g of Acácia negra containing 18% of condensed tannin/animal/week) and GC (animals not receiving tannin). The experiment lasted 84 days, with animals kept on an Andropogon gayanus pasture. Faeces were collected weekly, with weighing and blood collection carried out fortnightly. At slaughter, the adult worms were harvested for identification and counting. Although the GT animals weighed more than the GC lambs at slaughter, these differences were not significant (P>0.05). In general, the values for haemoglobin, hematocrit, total protein, urea, phosphorus and calcium in the serum were within normal levels and no significant differences between groups were observed. For faecal egg count (FEC), lower values were observed throughout the experiment in the group receiving tannin, but these differences were only significant in the eighth week. There was a lower output of eggs by regression for GT compared with GC (P<0.05). The species identified, in decreasing order of worm count, were: Trichostrongylus colubriformis, Haemonchus contortus, Oesophagostomum columbianum, Cooperia sp., Strongyloides papillosus, Trichuris globulosa and Moniezia expansa. The total worm count and number of each species of worm were lower for GT compared with GC for T. colubriformis and Cooperia sp. (P<0.05). Condensed tannin (CT) from A. negra had an antiparasitic effect, thereby representing an alternative for worm control in sheep.

Acacia↗
PubMed2006

Direct and indirect anthelmintic effects of condensed tannins in sheep.

Anthelmintic activity of condensed tannins (CT) was evaluated both in vitro and in vivo. In vitro tests included egg hatch test and paralysis/mortality assay on adult Haemonchus contortus. In vivo anthelmintic effect was determined by faecal egg count reduction test in lambs. To this end, 18 lambs were divided into three groups (low tannin, high tannin and control). The lambs of low and high tannin groups were fed diets containing 2 and 3% CT while the control group was fed on diets without CT. In vitro trials showed a dose-dependent inhibition of nematode egg hatching; whereas, there was no effect of CT on adult H. contortus. In vivo trials indicated reduction in faecal egg counts in lambs fed diets containing CT. Feed intake and nutrient digestibility of CT-fed sheep was lower and nitrogen balance was higher as compared to control. Maximum weight gain was observed in animals fed diets containing 3% CT. The direct anthelmintic effect of CT, therefore, was evidenced by inhibited egg hatching; whereas, faecal egg counts reduction in sheep was through improved nutrient utilization.

Animal Feed↗
PubMed2003

Intoxication of sheep with quebracho tannin extract.

This experiment was carried out to study the toxicity of quebracho tannin extract (containing 760 g of condensed tannins [CTs] per kg), with the aim of validating its use as a feed additive for improving the digestive utilization of protein-rich feeds. Four groups (Q(0), Q(1), Q(2) and Q(3)) of four sheep were dosed intra-ruminally once daily, for up to 21 days with, respectively, 0, 0.5, 1.5 or 3.0 g quebracho tannin extract/kg live-weight (LW). Feed intake, live-weight changes, plasma biochemistry, indicators of hepatic detoxification function, gross lesions and histopathology were examined. Animals in groups Q(0), Q(1) and Q(2) consumed all the offered feed. In contrast, feed intake was practically nil after 6 days of quebracho dosing in group Q(3), this being associated with a loss of 4.7+/-1.30 kg LW in 10 days (P<0.05). Sheep from groups Q(0), Q(1) and Q(2) remained healthy throughout the experiment. Ewes from group Q(3) became weak and depressed on day 5 and after 8 days of dosing remained recumbent. They were humanely killed after 10 days to avoid suffering. In general, neither gross lesions nor microscopical changes were observed in animals from groups Q(0), Q(1) and Q(2). However, Q(3) sheep showed striking lesions in the digestive tract (well-demarcated ulcers filled with necrotic material in the mucosa of the rumen and reticulum, distension of abomasum and small intestine, and dense mucous material in the caecum), and changes in plasma biochemistry. Cytochrome P-450 and glutathione concentrations were significantly reduced in Q(3) sheep (P<0.05). It is concluded that quebracho tannin extract is not toxic for ruminants, except in concentrations too high to be encountered under practical conditions.

Abomasum↗