Complex Tannins Research Articles

13C Nuclear magnetic resonance spectra of hydrolyzable tannins. III. Tannins having 1C4 glucose and C-glucosidic linkage.

Two-dimensional (2D) nuclear magnetic resonance (NMR) spectroscopy was utilized for the assignments of the glucose carbon signals in the 13C-NMR spectra of hydrolyzable tannins in which the glucopyranose core takes a 1C4 or related boat conformation, and of tannins possessing a Cglucosidic linkage. Remarkable changes in the sequences of glucose carbons were observed with change in the conformation of the glucose core, and with the formation of a C-glucosidic linkage. The chemical shifts of the C-2 signals of the glucose cores adopting the open-chain form in Cglucosidic tannins and in complex tannins can be utilized for the discrimination of the configurations at C-1 in these tannins.

The inhibition of digestive enzymes by polyphenolic compounds.

The ability of polyphenolic compounds to form insoluble complexes with other macro-molecules such as proteins has long been associated with the observed reduction in nutritive value resulting from their inclusion in animal diets. Naturally occurring polyphenols, and in particular condensed tannins isolated from various plant sources, have been shown to inhibit in vitro a number of digestive enzymes including trypsin, alpha-amylase and lipase. In addition, the results of various feeding trials suggest that similar reductions in intestinal digestive enzyme activity may result from the feeding of high polyphenolic diets. The evidence for this is summarised and discussed in relation to the possible effect of enzyme inhibition on reduced nutritive value and it is concluded that the observed reduction in protein availability found in vivo on consuming high tannin diets cannot simply be explained by the formation of dietary protein tannin complexes and that the ability of polyphenolic compounds to inhibit digestive enzymes may be of greater significance than realised previously.

A hydrolyzable tannin substance from the fruit ofRosa platyacantha

A new hydrolyzable tannin substance has been isolated from an anqueous hydrolysate of an aqueous-acetone extract of the fruit ofRosa platyacantha — 1-dehydrotrigalloyl-α-D-glucose — and it has been named platyacanthin. The substance is a minor component of the tannin complex.

Proteingewinnung unter Einsatz von komplexbildenden Stoffen

Taking vegetable albumins for models, the authors report of the possibilities of isolating proteins (which cannot be precipitated isoelectrically) by using their property of forming complexes with tannin or poly-anions. The precipitation of proteins with dextran sulphate or polyphosphates, which is due to electrostatic interaction, depends on the pH value and the electrolyte content of the solution. Under appropriate experimental conditions, protein yields of 100% are achieved. By means of tannin, the proteins are completely precipitated in a wide range of pH. The protein component of the poly-anion-containing complexes is isolated by precipitation with salt or by thermal coagulation after dissolving of the complexes. The isolation of protein from the tannin complexes is preferably realized by reaction with coffeine.

Effect of Tannin on In Vitro Dry Matter and Protein Disappearance in Sorghum Grain1

The purpose of this investigation was to determine the effect of tannin and added urea on in vitro dry matter disappearance (IVDMD) and in vitro protein disappearance (IVPD) in sorghum (Sorghum bicolor (L.) Moench) grain. IVDMD of low and high tannin genotypes after 48 hours of fermentation was 72.5 and 46.4% respectively. The addition of urea increased IVDMD to 93.4 and 79.2% for the low and high tannin genotypes. IVPD of low and high tannin genotypes was not affected by urea and averaged 88.2 and 69.6%, respectively. After 96 hours of fermentation the IVDMD of low and high tannin genotypes was 93.8 and 85.8%, respectively, indicating a true difference in digestibiltiy of about 8 percentage units.The major factor limiting the utilization of high tannin sorghum is apparently the availability of protein. Undigestible protein and tannin complex may account for more than half of the difference in IVDMD between low and high tannin genotypes.

Hydrolysable tannins of Eucalyptus delegatensis wood

Five ellagitannins have been isolated from the wood of Eucalyptus delegatensis by fractionation with Sephadex and characterized by hydrolysis reactions and NMR spectra. They include 2,3- and 4,6-(hexahydroxydiphenoyl)-glucose, a di-(hexahydroxydiphenoyl)-glucose known as pedunculagin, and two more complex tannins of incompletely determined structure. Two new chromatographic sprays for distinguishing between ellagitannins have been developed.

Phytochemical Investigation of Abies Concolor

Extracts of the bark of Abies concolor have shown antitumor activity against the adenocarcinoma of the duodenum test system of the Cancer Chemotherapy National Service Center. One of the active materials appears to be a complex tannin. The isolation of the active fractions has been reported utilizing solvent extraction, column, paper, and thin-layer chromatography.

HISTOLOGICAL AND HISTOCHEMICAL CHANGES IN DEVELOPING AND RIPENING PEACHES. I. THE CATECHOL TANNINS

Reeve, R. M. (U.S.D.A., Albany, California.) Histological and histochemical changes in developing and ripening peaches. I. The catechol tannins. Amer. Jour. Bot. 46(3) : 210‐217. Illus. 1959.—Selective histochemical tests for catechol derivatives revealed marked changes in tannin contents during the development and ripening of peaches. The principal test used was a nitroso reaction found to be colorimetrically selective for catechol and derivatives such as chlorogenic acid. Intensities of color produced by this test were photometrically measured. Increases in catechol derivatives, so indicated in situ, were associated with early maturation and lignification of the endocarp sclereids and particularly with cessation of cell divisions and early cell enlargement of the mesocarp parenchyma. Characteristic progressive localizations of tannins in patches of enlarging mesocarp parenchyma cells, as revealed by staining with iron salts as well as by the nitroso reaction, were observed in green fruits approaching maturity. The insoluble tannin color complexes produced by these tests remained coarsely granular and intense in green fruit. Upon ripening of the fruit color intensity produced by the nitroso reaction decreased and the insoluble tannin complexes were more finely divided. The association of phenols with cellular differentiation, lignification and suberization are briefly discussed.

Black Wattle Catechin

CONDENSED tannins present in black wattle or commercial ‘mimosa’ extracts from the bark of Acacia mollissima show absorption behaviour (λmax. = 203 and 280 mµ) in the ultra-violet spectrum1, which is typical of the natural catechins and flavan-3.4-diols2 and also of their constituent phenols. Furthermore, the degradation products resulting from the fusion of the tannins with alkali under anhydrous conditions (mainly resorcinol and gallic acid, but also phloroglucinol and protocatechuic acid), and from alkaline permanganate oxidation of the methylated tannins, resemble those degradation products usually obtained by similar methods from flavans3. On such evidence and by analogy with Freudenberg and Maitland's4 earlier concept of ‘quebracho catechin’, one of us previously5 regarded the catechin structure, 3.7.3′.4′.5′-pentahydroxyflavan (I), as a possible prototype of many of the complex tannins present in black wattle extract.

Tannin as a reagent in qualitative analysis

The tannin complexes of Bismuth and Cerium are described for the first time and the use of the reagent advocated as a routine test in the qualitative analysis of single substances. The specificity of the test is claimed for several elements. The usual qualitative group separation of tin is criticised and an alternative method offered.

III. Influence of Brucine, Antipyrine, Aminopyrine and Urotropin upon the pH of Formation of Tannin Complex. Separation of Tantalum from Niobium with Tannin and Brucine

III. Influence of Brucine, Antipyrine, Aminopyrine and Urotropin upon the pH of Formation of Tannin Complex. Separation of Tantalum from Niobium with Tannin and Brucine