Hydrolyzable Tannin

About: Hydrolyzable Tannin is a research topic. Over the lifetime, 476 publications have been published within this topic receiving 20093 citations.

High Molecular Weight Plant Polyphenolics (Tannins) as Biological Antioxidants.

Abstract: Representative condensed and hydrolyzable tannins and related simple phenolics were evaluated as biological antioxidants using cyclic voltammetry, the metmyoglobin assay, and the deoxyribose assay. The redox potentials of the tannins were similar to those of structurally related simple phenolics. However, the tannins were 15-30 times more effective at quenching peroxyl radicals than simple phenolics or Trolox. One of the tannins, polygalloyl glucose, reacted an order of magnitude more quickly with hydroxyl radical than mannitol. These results suggest that tannins, which are found in many plant-based foods and beverages, are potentially very important biological antioxidants.

Nutritional toxicology of tannins and related polyphenols in forage legumes

Abstract: Proanthocyanidins (PA) (condensed tannins) and hydrolyzable tannins (HT) are the two major classes of tannins. Proanthocyanidins are flavonoid polymers. Hydrolyzable tannins are polymers of gallic or ellagic acid esterified to a core molecule, commonly glucose or a polyphenol such as catechin. Proanthocyanidins are the most common type of tannin found in forage legumes. Problems in the analysis of tannins are that sample processing and drying decrease extraction and reactivity, suitable standards are unavailable, and quantitative analytical methods are poorly correlated with enzyme inhibition, protein precipitation, and nutritional effects. Hydrolyzable tannins are potentially toxic to ruminants. Pyrogallol, a hepatotoxin and nephrotoxin, is a product of HT degradation by ruminal microbes. Proanthocyanidins are considered to be non-toxic because they are not absorbed, but they are associated with lesions of the gut mucosa. Research on tannins in forage legumes has determined their effects on protein digestion and metabolism but more research on tannin structure in relation to digestion of specific proteins is needed. The widely accepted explanation for positive effects of PA on protein digestion and metabolism is that PA-protein complexes escape ruminal degradation and the protein is available in the lower tract. This proposed mechanism may be incorrect because PA also complex carbohydrates, endogenous proteins, and microbial products and the degradability of PA-protein complexes by ruminal microbes has not been adequately studied. Several alternative hypotheses (to escape protein) that explain the effect of PA on protein digestion and metabolism in ruminants are also consistent with experimental results on forage legumes. These include increased microbial protein synthesis, increased use of endogenous nitrogen in the rumen, and increased secretion of salivary glycoproteins. Research on manipulating the content and type of PA in forage legumes is justified because they are associated with non-bloating legumes, lower soluble non-protein nitrogen in silage, and improved efficiency of protein utilization. Research on the biosynthesis, molecular genetics, and cell biology of PA in forage legumes needs to be integrated with research on toxicology and nutrition.

Effects of the Interaction of Tannins with Co-existing Substances. VI. : Effects of Tannins and Related Polyphenols on Superoxide Anion Radical, and on 1, 1-Diphenyl-2-picrylhydrazyl Radical

Abstract: The scavenging effects of twenty-five tannins including low-molecular polyphenols on the superoxide anion radical (O2-) generated in the hypoxanthine-xanthine oxidase system were estimated by electron spin resonance (ESR) measurements of the adducts formed by 5, 5-dimethyl-1-pyrroline-N-oxide (DMPO) and the radical. The scavenging effects of tannins and related polyphenols having ortho-trihydroxyl (pyrogallol) structure [galloyl, hexahydroxydiphenoyl (HHDP) groups in hydrolyzable tannins, galloyl group in acylated proanthocyanidins, and the B-ring of some flavan-3-ols] were stronger than the effects of unacylated proanthocyanidins. The effects of tannins and related polyphenols on the superoxide anion radical were also compared with those on the 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical. Each tannin in an ethanol solution of DPPH radical reduced the intensity of the signal of the DPPH radical, and gave a weak signal assignable to a radical derived from that tannin, in a similar way to the appearance of the signal of dl-α-tocopherol radical, accompanied with reduction of the signal of DPPH radical, in a mixture of dl-α-tocopherol and the DPPH radical. In contrast to the case of the superoxide anion radical, the effects of unacylated proanthocyanidins on DPPH radical were comparable with those of the other types of tannins. The scavenging effects of all of the tannins and related polyphenols tested in the experiments on DPPH radical were stronger than that of dl-α-tocopherol.

Role of tannins in defending plants against ruminants: reduction in dry matter digestion?

Abstract: 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

Herbivores and Plant Tannins

Abstract: Publisher Summary This chapter traces the historical background of plant tannins. It describes distribution, chemistry, potential modes of action, and the quantitative evaluation of tannins. Biological activity of tannins on herbivores is presented. Botanical works considered tannins as excretory products, but sometimes because of their widespread occurrence in bark, as protective agents against invading microorganisms. With respect to herbivores, Haberlandt and Nierenstein suggested that tannins could be protective. Tannins may be present in any or all plant parts but are often at higher concentrations in woody, lignified tissues. In leaves they may decrease or increase with age of the leaf. Chemically, tannins are polyphenolic compounds with a molecular weight between 300 and 3000 Daltons. Compounds that act as tannins in forming complexes with proteins and other macromolecules can be divided into four groups, i.e., according to chemical structure, molecular weight, water solubility, and tannin action. The two major structural groups of tannins include the condensed tannins and the hydrolyzable tannins. Condensed tannins are the most widely distributed tannins in vascular plants. Hydrolyzable tannins are restricted to the dicotyledons. Depending on the acids obtained from the hydrolysis, hydrolysable tannins are conventionally divided into gallotannins or ellagitannins. The chapter concludes with an overview and summary of potential roles of tannins in plants other than defensive activity against herbivores, and suggestions for research needs.