Role Of Tannins Research Articles

Protective role of tannin-rich fraction of Camellia sinensis in tissue arsenic burden in Sprague Dawley rats

The protective effect of green tea (Camellia sinensis) was tested against arsenic-induced toxicity. However, the possible role of tannins in green tea in alleviating hepatic and renal oxidative injury has also been studied. Administration of sodium arsenite (100 mg/kg/day) for 28 days in Sprague Dawley female rats resulted in significant reduction of biochemical parameters such as delta-aminolevulinic acid dehydratase (ALAD), reduced glutathione (GSH), glutathione peroxidase (GPx), superoxide dismutase (SOD) and elevation of thiobarbituric acid reactive substances (TBARS) and the index of nitrite/nitrate (NOx) levels. The tissue arsenic burden was increased after arsenic exposure for a period of 28 days. Green tea crude fraction (GTC) co-treated with sodium arsenite for 28 days caused significant (p < .01) elevation of ALAD, GSH, GPx, SOD, and nitrate/nitrite levels and reduction of the TBARS level and tissue burden when compared to detannified green tea fraction (GTDT)-treated groups. The protective role of tannin-rich fraction of C. sinensis when compared to the detannified fraction was also confirmed by histological examinations. The greater activity of GTC than that of detannified green tea fraction correlates with the higher content of tannins in green tea. Overall, these results indicate that the tannin-rich green tea could have improved the defense mechanism against arsenic-induced oxidative stress and reduced the tissue arsenic burden.

Mangrove-sponge associations: a possible role for tannins

A positive correlation between sponge coverage and tannin concentrations in prop roots of Rhizophora mangle L. has previously been reported. However, the ecological role of tannins within the mangrove sponge association remains speculative. This study investigated whether tannins play a role in sponge recruitment and assessed tannin and polyphenol production in R. mangle roots in response to sponge colonization. We demonstrated in a field experiment using artificial substrates with different tannin concentrations that tannins are positively involved in larval recruitment of the sponge Tedania ignis and that roots significantly enhanced tannin and polyphenolic content in response to natural and experimental sponge fouling. Differential recruitment in response to tannins may have been the result of a behavioral response in sponge larvae. It is also possible that tannins affected the structure of the fouling microbial biofilm on the artificial substrate, or tannins affected the post-settlement dynamics of sponge recruits. Elevations in concentrations of tannins and polyphenolic compounds upon coverage with sponges, combined with differential recruitment of T. ignis in response to differences in tannin concentrations, may indicate a positive feedback in recruitment. This may in part explain the typical heterogeneity in sponge coverage and community composition among roots.

Tannins: Current knowledge of food sources, intake, bioavailability and biological effects

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.

The role of tannins in conventional and membrane treatment of tannery wastewater

The role that tannins play in tannery wastewater treatment has been evaluated employing a pilot Membrane Bioreactor (MBR) plant and a full scale Conventional Activated Sludge Process (CASP) plant conducted in parallel. The proposed methodology has established the preliminary use of respirometry to examine the biodegradability of a selection of commercial products (synthetic and natural tannins); the subsequent analysis, by means of spectrophotometric reading and RP-IPC (Reverse-Phase Ion-Pair) liquid chromatography, estimates the concentrations of natural tannins and naphthalenesulfonic tanning agents in the influent and effluent samples. The results show that a consistent percentage of the Total Organic Carbon (TOC) in the effluent of the biological phase of the plants is attributable to the presence of natural and synthetic (Sulfonated Naphthalene-Formaldehyde Condensates, SNFC) tannins (17% and 14% respectively). The titrimetric tests that were aimed at evaluating the levels of inhibition on the nitrifying biomass samples did not allow a direct inhibiting effect to be associated with the concentration levels of the tannin in the effluent. Nonetheless, the reduced specific growth rates of ammonium and nitrite oxidising bacteria imply that a strong environmental pressure is present, if not necessarily due to the concentration of tannins, due to the wastewater as a whole. The differences that have emerged by comparing the two technologies (CASP and MBR), in regards to the role that tannins play in terms of biodegradability, did not appear to be significant.

Effect of tannic acid on Lactobacillus hilgardii analysed by a proteomic approach

A contribution towards the elucidation of the mechanisms of tannins on bacteria growth inhibition, with particular focus on the interaction between tannins and bacterial proteins. The interaction between tannic acid (TA) and Lactobacillus hilgardii, a wine spoilage bacterium, was investigated by a combination of physiologic and proteomic approaches. Growing tests were performed on medium supplemented with TA at concentrations ranging from 100 to 1000 mg l(-1) demonstrating the inhibitory effect of TA on the growth rate. Total proteins extracted from cells unexposed and exposed to TA were then analysed by 2D-electrophoresis and significant quantitative variations with a marked decrease of protein intensity upon TA exposure were observed. Most of the proteins, identified by ESI tandem Mass Spectrometry, were metabolic enzymes of different pathways, located in cytoplasm and membrane. The effects of TA on cells are deduced by the involvement of metabolic enzymes, and functional proteins on the tannin-protein interaction. These results might be related to the altered functions of the cell metabolism. The possible role of tannins in the inhibition of the bacterial survival and growth in a natural environment such as wine. A similar approach could be applied for evaluating the effects of tannins on food borne and pathogenic bacteria.

Effect of bioactive compounds from Sainfoin ( Onobrychis viciifolia Scop.) on the in vitro larval migration of Haemonchus contortus : role of tannins and flavonol glycosides

Anthelmintic bioactivity against gastrointestinal nematodes has been associated with leguminous forages supporting the hypothesis of a role of condensed tannins. However, the possibility that other compounds might also been involved has received less consideration. Using bio-guided fractionation, the current study aimed at characterizing the biochemical nature of the active compounds present in sainfoin (Onobrychis viciifolia ), previously identified as an anthelmintic leguminous forage. The effects of sainfoin extracts were evaluated on 3rd-stage larvae (L3) of Haemonchus contortus by using a larval migration inhibition (LMI) assay. Comparison of extracts obtained with several solvent systems showed that the bioactivity was associated with the 70ratio30 acetone/water extract. Further fractionation of the later allowed the separation of phenolic compounds. By use of a dialysis method, compounds were separated with a molecular weight cut-off of 2000 Da. The in vitro anthelmintic effect of the fraction with condensed tannins was confirmed. In the fraction containing molecules of MW <2000 Da, 3 flavonol glycosides were identified as rutin, nicotiflorin and narcissin. At 1200 mug/ml, each inhibited significantly the migration of larvae. Addition of polyvinyl pyrrolidone (PVPP) to both fractions before incubation restored larval migration. These results confirmed the role of both tannins and flavonol glycosides in the anthelmintic properties of sainfoin.

The effect of some tannins on trout erythrocytes exposed to oxidative stress

In order to gain more knowledge on the role of tannins as antioxidants, their ability to protect ( Salmo irideus) erythrocytes against oxidative stress was investigated. Antioxidant activity of different tannins (tannic, gallic and ellagic acid) was evaluated by chemiluminescence (CL) techniques using lucigenin and luminol as chemiluminogenic probes for the superoxide radical generated by the xanthine/xanthine oxidase system and hydrogen peroxide, respectively. The superoxide-scavenging activity of these tannins was shown for all the compounds; however, it is not clear if this is due to their ability of scavenging the superoxide radical or to their inhibitory activity on xanthine oxidase. Tannic and ellagic acid showed a marked effect on the reduction of H 2O 2-luminol chemiluminescence. The influence of these tannins on the rate of hemolysis in stressed trout erythrocytes was investigated and the results indicate that tannic acid accelerates the hemolytic event while gallic and ellagic acid have no significant effect. The possible protective action of these compounds against oxidative DNA damage was assessed using the comet assay, a rapid and sensitive single-cell gel electrophoresis technique, used to detect primary DNA damage in individual cells. The results here reported show that tannins under study are capable at low concentrations of protecting DNA breakage, while at high concentrations they can be genotoxic.

Plant Tannins Inhibit the Induction of Aberrant Crypt Foci and Colonic Tumors by 1,2-Dimethylhydrazine in Mice

We have shown that naturally occurring tannins possess antitumor promotion activity in mouse skin. In the present investigation, we studied the ability of a hydrolyzable tannin, gallotannin (GT), and a condensed tannin extracted from red alder (RA) bark to inhibit 1,2-dimethylhydrazine (DMH)-induced colonic aberrant crypt foci (ACF) and tumors in Balb/c mice. In addition, we determined the ability of GT to inhibit the proliferation and to induce apoptosis in a human colon cancer cell line (T-84). Mice were given tannins by intraperitoneal injections, by gavage, or in drinking water before treatment with DMH for 24 weeks. Alternatively, mice were given tannins by intraperitoneal injection or gavage for only 2 weeks before DMH administration, then tannin administration was discontinued and mice were treated with DMH for 24 weeks. The multiplicity, size, and distribution of ACF and tumors were significantly inhibited by GT and RA in the above treatment regimens. The most effective treatments included GT by gavage, RA bark extract by intraperitoneal injection, and either tannin dissolved in drinking water. Extent of inhibition of ACF and tumors was gender independent. In cell culture experiments, GT treatment for three days inhibited the growth of T-84 cells, with a concentration resulting in half-maximal inhibition estimated to be 20 μg/ml. The treatment was not cytotoxic to cells at 1-40 μg/ml. Interestingly, at 10 μg/ml, GT induced apoptosis in T-84 cells as determined by the Hoechst DNA staining technique. Collectively, these findings support a potential role for tannins as chemopreventive agents against colon cancer.

Plant-toxin interactions in transgenic Bt cotton and their effect on mortality of Helicoverpa armigera (Lepidoptera: Noctuidae).

In Australia, transgenic cotton plants expressing the cry1Ac gene from Bacillus thuringiensis Berliner variety kurstaki are less toxic to first-instar Helicoverpa armigera (Hübner) after the plant is producing fruit. We developed two bioassay methods (leaf mush, leaf disk) to test if the physiological state of the plants explained changes in toxicity and a third method (diet incorporation) was developed to quantify the toxicity of Bt leaves when mixed in chickpea diet. Cry1Ac protein was less toxic to H. armigera larvae when the protein was mixed with leaves from fruiting versus presquare conventional cotton. Differences in LC50 varied from 2.4- to 726-fold, depending on the source of toxin and conventional plant material. These results suggest that plant-toxin interactions in fruiting cotton are reducing the toxicity of the Cry1Ac protein. The possible role of tannins in these changes is discussed.

Research on Trace Minerals in the Common Bean

The common bean (Phaseolus vulgaris L.) is the most important grain legume for direct human consumption, being especially important in eastern Africa and in Latin America. The objective of the Centro Internacional de Agricultura Tropical (CIAT) in participating in the Consultative Group on International Agricultural Research (CGIAR) Micronutrients Project has been to assess the feasibility of improving common beans for micronutrient content, especially iron and zinc. In the evaluation of more than a thousand accessions in the cultivated core collection, a mean iron concentration of 55 mg/kg was found, with a range of 34 to 89 mg/kg. Zinc concentrations ranged between 21 and 54 mg/kg, with an average value of 35 mg/kg. These initial data suggest that sufficient genetic variability exists to improve iron content by about 80% and zinc content by about 50%. An essential question for the improvement of any trait through plant-breeding is the degree to which the trait is stable across environments. Genetic differences have been expressed over environments and seasons, offering good prospects that genotypes selected in one environment for high iron or zinc will express superior levels of minerals in other environments as well. Correlations among mineral concentrations suggest that the improvement of one mineral may simultaneously improve the contents of other minerals, thus multiplying the impact of the effort. The fact that the bioavailability of iron was higher in white beans in rat studies suggests that a lower tannin content could be beneficial, but the role of tannin is still not well elucidated. The genetics of iron and zinc content appears to be complex, involving between 7 and 11 loci.

In vitro immunomodulatory activity ofFilipendula ulmaria

Extracts of the roots, herb and flowers of Filipendula ulmaria (L.) Maxim. were investigated for in vitro immunomodulatory properties. Strong inhibitory activity was found towards the classical pathway of complement in the ethyl acetate extracts of roots and flowers, in all methanol extracts and in the aqueous root extract. Except for the light-petroleum extracts, all fractions tested inhibited the production of reactive oxygen species by human polymorphonuclear leukocytes. The diethyl ether root extract was found to be most potent in inhibiting lymphocyte proliferation. The role of tannins and other constituents in these processes are discussed. © 1997 John Wiley & Sons, Ltd.

Development and ultrastructure of the endodermis in the primary root of cork oak (Quercus suber)

The endodermis maturation process was studied in the primary root of the cork oak (Quercus suber L.) with emphasis on the chemical nature of the cell wall and on the possible role of tannins. Tannins were found in endodermal and adjacent cortical cells in all maturation stages. We discuss our findings in relation to the previous literature in other woody and herbaceous species. The results of the histochemical tests showed differences in the aliphatic compounds of the suberin between the Casparian strip suberin and the suberin layer deposited in state II cells. Plasmodesmata were present in radial and tangential walls during the entire maturation process. The significance of plasmodesmata and of the suberin deposition pattern is discussed in relation to apoplastic and symplastic transport in roots. Key words: Casparian strip, endodermis, primary root, suberin, Quercus suber L.

Inhibitory Effects of Dietary Tannins on the Infectivity of a Nuclear Polyhedrosis Virus to Helicoverpa zea (Noctuidae: Lepidoptera)

The role of tannins in Helicoverpa zea (Boddie) larval mortality in H. zea nuclear polyhedrosis virus (HzNPV)-exposed third instars was examined in bioassays on semisynthetic diet. Mortality was observed in H. zea larvae not exposed to HzNPV when reared on diet that contained tannic acid at 0.025, 0.05, and 0.1% (w/v) but not on diets that contained Quebracho (condensed tannin) or catechin. The percentage of mortality (45.8%) of third instars fed HzNPV diet was significantly less when Quebracho tannin but not catechin was added to the diet (P ≤ 0.05). At the 0.025% rate of tannic acid, the percentage of mortality in larvae fed HzNPV was significantly less than that expected from the tannic acid-HzNPV mixture. The HzNPV-exposed larvae fed on Quebracho tannin diets also had significantly lower (corrected) mortalities than did HzNPV-exposed larvae fed on tannic acid and catechin diets. Larval mortality was delayed in all tannic acid treatments. When larvae were exposed to an aqueous suspension of HzNPV that was 0.025, 0.05, and 0.1% (w/v) tannic acid or Quebacho tannin prior to being placed on diets without a source of tannin, mortality was significantly reduced on the tannic acid diets but not on Quebracho tannin diets. Larval mortality was not altered significantly when larvae were exposed to HzNPV in tannin-free aqueous suspensions prior to being placed on the tannic acid or Quebracho tannin.

Alcoholic beverage choice and risk of coronary artery disease mortality: Do red wine drinkers fare best?

Several population studies have described a lower coronary artery disease (CAD) mortality risk in alcohol drinkers (vs abstainers). 1–3 Those studies showed no consensus that any specific beverage type (wine, liquor or beer) is likely to be more protective than are the others. 3 The importance of allowing for other traits and habits related to wine, liquor or beer use when studying beverage choice is now clear. 4 Recent media attention (e.g., “60 Minutes,” CBS Television Network, 7:00 p.m., November 17, 1991) concerning the “French paradox” (lower CAD incidence in France than in the United States) has focused on the possible benefits of red wine in particular. Isolated reports suggest a possible role of tannins 5 or phenolic compounds 6 in red wine. In this report, we present data from a large prospective population study that are pertinent to the possible role of preference for wine, liquor or beer in CAD mortality risk.

Food selection by the silver leaf monkey,Trachypithecus auratus sondaicus, in relation to plant chemistry.

Samples of leaves and fruits exploited as food items byTrachypithecus auratus sondaicus were analysed for nitrogen content, acid detergent fibre (ADF), pepsin cellulase digestibility (CDIG), condensed tannins (CT), total phenolics (TP) and protein precipitation capacity (PP) and compared with fruits and leaves not eaten. Differences in chemical measures for items eaten and not eaten were not statistically significant but trends indicate that leaves may have been selected for their lower fibre content and greater digestibility. Fruits eaten also had a higher mean level of CDIG and lower mean level of ADF than fruits not eaten but these measures are not considered to be of major importance in fruit selection as CDIG was lower and ADF higher in fruits eaten than in leaves eaten. Levels of CT, TP and PP capacity were higher in fruits eaten than in fruits not eaten but lower in leaves eaten than in leaves not eaten. The role of tannins and phenolics in food selection is discussed. Leaves (and fruits) were not strongly selected on the basis of protein content. Approximately half the dietary intake ofT. auratus sondaicus was leaves, a protein-rich food source. Possibly, protein levels in foliage at Pangandaran were sufficient that selection for this nutrient was not required. A nutrient other than protein (for example, soluble carbohydrates) may have been maximised through food selection. The protein/ADF ratio may provide an indicator of the acceptability of foliage in a habitat as potential food for a colobine. However, this ratio did not govern food selection byT. auratus sondaicus at Pangandaran.

Tannins in mangrove tree roots and their role in the root environment

Mangrove trees grow under reductive and sometimes acidic conditions, both of which are injurious to the root growth. In this report, the role of tannins in mangrove tree roots was studied in order to alleviate their detrimental effect on the soil environment. The mangrove tree roots contain a large amount of tannins and it combines with ferric ion in the soil solution resulting in the blackening of the roots due to the formation of a tannin-ferric iron complex. The black complex is decolorized by the reduction treatment with sodium hydrosulfite. Hydrogen sulfide is also able to decolorize the black complex. The decolorized roots can become reversibly black with the addition of ferric iron. Based on these phenomena, it is considered that the tannins in mangrove tree roots combine with iron in the soil solution, to alleviate the iron excess damage. The tannin-ferric iron comlex thus formed counteracts the hydrogen sulfide toxicity to roots by oxidation. Both of these harmful substances are usually present i...

Grazing behavior and diet selection of goats

Goats possess characteristics including versatility in harvesting forage and ability to survive under adverse foraging conditions which set them apart from other species of livestock. Classification of goats as grazers or browsers is equivocal especially when grazing patterns are examined over a variety of environmental conditions. It is perhaps more appropriate to term goats as mixed-feeding ‘opportunists’ because they adapt much faster than cattle or sheep to seasonal and geographic variation. Goats preferentially select plant parts that are higher in digestibility when stocking density is low. Tolerance of goats toward bitterness may play an important role in maximizing grazing capacity and in biological control of weeds. Allelochemical-type reactions may contribute to the detoxification of secondary plant compounds in goats' diets. The role of tannins and saponins deserves further studies. The pattern of rumination in goats is not different from cattle and sheep although a faster rate of eating and more frequent feeding may be observed in goats. Estimating energy expenditures for grazing may be critical for the estimation of energy requirements of goats under different management systems. Precise estimations of intake and digestibility remain to be established for grazing goats.

In vitro availability of iron and zinc in white and coloured ragi (Eleusine coracana): role of tannin and phytate.

White and brown ragi (Eleusine coracana) varieties were analysed for tannin, phytate phosphorus, total phosphorus, iron, ionisable iron, zinc and soluble zinc content. White ragi had no detectable tannin while in brown varieties it ranged from 351 to 2392 mg per 100 g. Germination brought about a progressive decrease in tannin and phytate phosphorus and an increase in ionisable iron and soluble zinc content of grain ragi. Both in raw and germinated grain, ionizable iron was significantly higher in white than in brown varieties. While ionisable iron was inversely correlated with the level of tannin and phytate phosphorus, soluble zinc was negatively correlated with phytate phosphorus. After extraction of tannin, ionisable iron of brown ragi rose by 85%. On the other hand, in white varieties, addition of tannin extracted from brown ragi, resulted in a 52-65% decrease in ionisable iron content. These studies indicated that poor iron availability in ragi as judged by its low ionisable iron content was due to the presence of tannin in the grain.

Role of Tannins in Defending Plants Against Ruminants: Reduction in Dry Matter Digestion?

Polyphenolic allelochemicals, such as tannins, are widely thought to reduce the digestibility of plants consumed by herbivores by binding to digestive enzymes and dietary proteins. While the apparent digestibility of protein and, therefore, cell solubles is reduced in mule deer (Odocoileus hemionus) and white-tailed deer (O. virginianus) consuming tanniferous forages, digestion of the plant cell wall is not reduced beyond that predicted from its content of lignin, cutin, and silica. The lack of a tannin effect on cell wall digestion in deer is in contrast to studies with domestic sheep and numerous in vitro studies. Herbivores adapted to consume tanniferous forages may defend against such allelochemicals by producing salivary proteins that bind tannins in a highly specific manner. These tannin-salivary protein complexes would reduce apparent digestibilities of protein and cell solubles and, if completely effective, would not reduce cell wall digestion. The occurrence of such proteins in ruminants is reported here for the first time. The saliva composition of mule deer (a mixed feeder that commonly consumes browse) and domestic cattle and sheep (predominant grazers) are compared, and the higher potential of the deer saliva to neutralize tannins is related to their feeding habits. Salivary proteins that preferentially bind tannins may minimize fecal nitrogen losses by maximizing the efficiency of tannin-binding per unit of protein and may reduce the absorption of hydrolyzable tannins and the potential for tannin toxicity.

Thermal irritation and esophageal cancer in northern Iran.

The ingestion of hot food and beverages has repeatedly been postulated as a risk factor for cancer of the esophagus. Although several studies have been performed on the correlation of the consumption of hot tea and esophageal cancer, no research has heretofore documented, by actually measuring, the temperature at which the tea is consumed. Therefore, a tea temperature measurement study was carried out in the Caspian Littoral of Iran, where the frequency of esophageal cancer is the highest in the world. The study was conducted during a population-food-habits survey in 1968 to 1969, which was performed before statistics were available regarding the incidence rate or geographic distribution of this disease in the region. Ten years later, when the results of the Caspian Cancer Registry were analyzed, the data from this nutritional study was compared with the regional distribution of esophageal cancer. A geographic correlation exists between the frequency of consumption of hot tea and the incidence of esophageal cancer. Seventy-two percent of the people in the low-risk region of esophageal cancer drank their tea at the relatively moderate temperature of below 55 degrees C, compared with only 3% in the high risk region. More importantly, 62% of the adult population in the high-risk region, as opposed to 19% in the low-risk region, drank their tea at a temperature of over 65 degrees C. In addition to the thermal irritation of hot tea, the following considerations cannot be ignored: the carcinogenicity role of tannins; the cancer-promoting effect of phenols; and the absorption facilitating role of hot tea. Alcohol and tobacco, the most important risk factors for cancer of the esophagus in many countries, play a negligible role in the cause of this disease in northern Iran. In this region, nutritional deficiencies--a special diet for pregnant women composed of sour pomegranite seeds, black pepper, and garlic; consumption of bread contaminated with silica fibre; and ingestion of opium and opium dross--combined with long-lasting and daily thermal irritation of the esophagus with very hot tea play an important role in the development of this disease. The inhabitants of the high-risk area consumed roughly 2.5 times more tea than their counterparts in the low-risk area. In addition, the mean daily consumption of tea leaves per person (average) was 5.7 g and 3.8 g, respectively.