Tannin Fractions Research Articles

Antibacterial Substances in Green Tea Extract

Antibacterial substances in hot-water extract (110°C, 15min) of a green tea product was investigated. The experimental results obtained were as follows.1. Antibacterial effects of the green tea extract appeared to be conspicuous on Vibrio metschnikovii and Alcaligenes faecalis. These bacteria were found to be about ten-times as sensitive as Staphylococcus aureus to the extract.2. The green tea extract was adsorbed to casein and the tannin fraction, which showed antibacterial effects, was eluted from the adsorbent with 90% aq. acetone. Five catechins were separated from the tannin fraction by paper chromatography and their contents were quantitatively determined. The minimum inhibitory concentrations (mcg/ml) of these catechins on V. metschnikovii were: epigallocatechin 20, epigallocatechin gallate 45, epicatechin gallate 45, gallocatechin 50, and epicatechin 75.3. Addition of caffeine at a concentration of approx. 1mg/ml showed a marked synergetic effect to increase the antibacterial titre of catechins (ca. 4mg/ml). However, caffeine itself (2mg/ml) had no antibacterial action.4. An aqueous solution containing the above five catechins and caffeine at the same concentrations as in the green tea extract showed a similar antibacterial titre to that of the extract.

Urinary phenolic metabolites of rats fed carobs ( Ceratonia siliqua) and carob fractions

1. 1. The two major urinary metabolites of rats ingesting carobs ( Ceratonia siliqua) and carob fractions were chromatographically identified as gallic acid and 4- O-methylgallic acid. 2. 2. These metabolites probably originate from free gallic acid in green carob pods, or from the ester-linked gallates in the tannin fraction. 3. 3. The catechin moiety of condensed carob tannins does not undergo metabolism in the rat.

Seasonal Changes in an Enzyme Inhibitor and Tannin Content in Sericea Lespedeza1

We sampled 10 high‐ and two low‐tannin plants of sericea (Lespedeza cuneata (Dumont) G. Don) at 2‐week intervals from May 17 to October 18 by taking two or three stems from the numerous original spring crown shoots. Aqueous leaf extracts of all samples were tested for concentration of an enzyme‐inhibitor substance (a fraction of the total tannin) by measuring its inhibition of one pectinase and two cellulases. Most of the samples were also tested for concentrations of two other tannin fractions, astringent tannin and leucoanthocyanidin. In the common high‐tannin sericea plants all tannin fractions rose from low initial levels to high levels in July, with a gradual return to low levels in October. The low‐tannin plants were quite low for all tannin fractions throughout the season. Although the inhibitor concentration followed the other tannins in a general way during the season, it was not closely correlated with the astringent tannin or the leucoanthocyanidin, neither for sampling date nor over the high‐tannin plants. The inhibitor concentration for a given date or genotype appears to be relatively independent of the accumulation of other tannins. The implications of tannin concentration in the utilization of sericea forage were discussed briefly.

Relationship Between Tannin Levels and Nutritive Value of Sericea1

One low‐tannin sericea synthetic strain (Lespedeza cuneata (Dumont) G. Don) was compared with high‐tannin strains over different years, harvests, and test locations for in vitro dry matter disappearance (IVDMD). Concentrations of fiber and lignin were determined for representative samples of both low‐tannin and high‐tannin strains. Increments of a water‐soluble purified tannin fraction, “sericin,” were added to samples of one lowtannin and one high‐tannin strain for IVDMD analysis. The low‐tannin strain was consistently about 25% higher in IVDMD than high‐tannin sericea over years, harvests, and locations where mean values varied widely. There were only small differences among high‐tannin strains for IVDMD. The low‐tannin strain was quite similar to two high‐tannin strains in fiber and lignin concentrations. The results strongly support the conclusion that tannin was the cause of IVDMD difference between lowand high‐tannin genotypes. IVDMD of both low‐ and high‐tannin sericea decreased progressively with added increments of sericin. Both tannin and sericin were effective in limiting the IVDMD of sericea forage.

Resolution and analysis of total phenolic constituents of grape pigment

AbstractA procedure for the analysis of plant phenolics is described which allows the quantitative isolation of the high‐molecular‐weight tannin fraction, the separation of acylated anthocyanins from other anthocyanins, and the further partial separation of the monomeric polyphenols by adsorptive partition within each zone. The system used is a column of Sephadex G‐25 gel prepared in an aqueous acetone medium at low pH and eluted with the same solvent.By this means, an extract of the pigment from a single berry of Vitis vinifera cv. Shiraz has been separated into three distinct pigment fractions, the first of which, a red tannin pigment, was excluded from the gel. The second and third bands contained acylated anthocyanin 3‐glucosides and anthocyanin 3‐glucosides respectively, the components of each band being eluted in order of their decreasing RF in normal paper chromatography. Other phenolics of corresponding RF were found in each of these latter fractions.Pigment composition, expressed in terms of the three fractions, was calculated by use of mean extinction values. The red tannin pigment is the major fraction of total extractable pigment in the grape, although it is only a minor contributor to total colour of extracts.

On the polyphenolic substances in the chestnut trees and the relation of the contents of them to the resistance to chestnut gall wasps

The determination of polyphenolic substances in the Japanese and Chinese chestnut barks of current year shoots were made quantitatively and qualitatively by paper chromatography, colorimetry and other methods to elucidate the phenolic pattern among the species and varieties. Furthermore, the authors investigated the relation of the polypheno lic contents to the resistance to chestnut gall wasps which gave much trouble in chestnut culture.1. The phenolics detected in chestnut barks are as follows; gallic acid, leucocyanidins, flavonol, ellagic acid, gallocatechin, catechol tannin, pyrogallol tannins and coumarin derivatives.2. The Japanese chestnuts contain more catechol tannins (about 10-20mg/g. on the basis of dry weight) than Chinese ones (5mg/g. or so). High content of pyrogallol tannins was found in both the bark of them. Furthermore, of Chinese chestnuts, the southern varieties contain more of less water soluble fractions of pyrogallol tannins than the nor-thern ones.3. In the resistant varieties to chestnut gall wasps, catechol tannins are high but pyrogallol tannins are relatively low in content. The correlation coefficients between the tolerance for chestnut gall wasps and catechol tannin contents and pyrogallol tannin contents are +0.782 and -0.476, respectively. The catechol tannin contents of resistant and susceptible varieties in one gram dry matter are 10.3 to 22.4mg and 2.7 to 16.2mg., respectively. Pyrogallol tannin content of resistant varieties varies 70 to 110mg., and of susceptible ones, 90-120mg.

Flavor Effects and Adsorptive Properties of Purified Fractions of Grape-Seed Phenols

Grape seed phenolics were extracted and separated into three distinct groups of compounds. The separated fractions were evaluated in turn for their sensory effects in water and in wine with respect to their thresholds for astringency, bitterness, and effect on taste interaction with acidity. If was found that the three fractions have considerably different flavor effects, both qualitatively and quantitatively. The catechin fraction was bitter but not astringent at levels likely to occur in wine. The leucoanthocyanin fraction and the condensed tannin fraction were both bitter and astringent. All three affected the judges9 reaction to acidity by moderating the apparent sour taste when added at levels near threshold. All three fractions appear capable of important effects on these quality factors at levels which may occur in white wines and certainly do occur in rosé and red wines. The condensed tannin fraction contributed the most intense flavor effects on a weight basis, and the evident flavor effects of the phenolic substances in wine were found to be 10 to 100 times as intense as previously noted. The levels present in a red wine are about 10 to 100 times the level barely detectable in a white wine. A comparison was made of the adsorptive properties of casein, gelatin, isinglass, nylon, and insoluble polyvinylpyrrolidone with respect to these phenolic fractions. Large differences were found in relative affinity for the different phenolic fractions. The PVP had a greater capacity in phenol per unit weight than did nylon, and the proteins were greater yet. The synthetic resins had a greater affinity for the smaller molecules than for the condensed tannins, and the proteins were the reverse, under the conditions tested. The resins had considerable affinity for all the fractions in column tests, but, as fining agents the proteins showed no affinity for the catechin fraction under our conditions.

EFFECT OF CAROB POD EXTRACT ON CELLULOLYSIS, PROTEOLYSIS, DEAMINATION, AND PROTEIN BIOSYNTHESIS IN AN ARTIFICIAL RUMEN.

Carob pod extract and its tannin and sugar fractions were compared with gallotannic acid and sucrose for their effect on the cellulolytic, proteolytic, protein biosynthetic, and deaminative activities of rumen microorganisms. The inhibitory effects of carob pod extract upon the cellulolysis and deamination were correlated mainly with its sugar, rather than its tannin components. On the other hand, proteolytic activity and protein biosynthesis were more significantly affected by the tannin fraction. In contrast to the tannin fraction of carob pod extract, gallotannic acid inhibited cellulolytic activity. The harmful effect of a low concentration of tannins on protein biosynthesis could be prevented by the addition of carbohydrates to the reaction mixture. At high tannin concentration (40 mug/ml), however, the addition of carbohydrates did not prevent the inhibition.

The inhibition of enzymes by tannins

A study has been made of the inhibition of β-glucosidase and other enzymes by tannic acid and a condensed tannin fraction from wattle. Tannic acid forms a 0·46:1 complex by weight with the glucosidase and complex formation can be reversed by a number of reagents, the best being non-ionic polymers or non-ionic and cationic detergents.

Effect of Carob Pod Extract on Cellulolysis, Proteolysis, Deamination, and Protein Biosynthesis in an Artificial Rumen1

Carob pod extract and its tannin and sugar fractions were compared with gallotannic acid and sucrose for their effect on the cellulolytic, proteolytic, protein biosynthetic, and deaminative activities of rumen microorganisms. The inhibitory effects of carob pod extract upon the cellulolysis and deamination were correlated mainly with its sugar, rather than its tannin components. On the other hand, proteolytic activity and protein biosynthesis were more significantly affected by the tannin fraction. In contrast to the tannin fraction of carob pod extract, gallotannic acid inhibited cellulolytic activity. The harmful effect of a low concentration of tannins on protein biosynthesis could be prevented by the addition of carbohydrates to the reaction mixture. At high tannin concentration (40 mug/ml), however, the addition of carbohydrates did not prevent the inhibition.

EFFECT OF WATER EXTRACTS OF CAROB PODS, TANNIC ACID, AND THEIR DERIVATIVES ON THE MORPHOLOGY AND GROWTH OF MICROORGANISMS.

The effect of aqueous extracts of carob (Ceratonia siliqua) pods, gallotannic acid, gallic acid, and catechol on several microorganisms was studied. Carob pod extract and tannic acid showed a strong antimicrobial activity toward some cellulolytic bacteria. On the basis of tannin content, to which antimicrobial effect was related, carob pod extracts inhibited Cellvibrio fulvus and Clostridium cellulosolvens at 15 mug/ml, Sporocytophaga myxococcoides at 45 mug/ml, and Bacillus subtilis at 75 mug/ml. The inhibiting concentrations for tannic acid were found to be 12, 10, 45, and 30 mug/ml, respectively. Gallic acid and catechol were much less effective. Tannic acid and the tannin fraction of carob extract exerted both bacteriostatic and bactericidal effects on C. fulvus. Respiration of C. fulvus in the presence of bactericidal concentrations of tannic acid or tannin fraction of carob extract was inhibited less than 30%. A partial formation of "protoplasts" by C. fulvus was obtained after 2 hr of incubation in a growth medium to which 20% sucrose, 0.15% MgSO(4).7H(2)O, and 10 to 50 mug/ml of tannic acid or 500mug/ml of penicillin, or both, had been added. Tannic acid and the tannin fraction of carob extract protected C. fulvus from metabolic lysis in sucrose solution. Although the growth of other microorganisms tested was only slightly affected, the morphology of some of them was drastically changed in the presence of subinhibitory concentrations of carob pod extracts of tannic acid. It is suggested that the site of action of tannins on sensitive microorganisms is primarily the cell envelope.

Astringency of Fruits and Fruit Products in Relation to Phenolic Content

Publisher Summary This chapter briefly discusses the nature of the constituents responsible for the sensation of astringency and the physiology of the astringency sensation and the factors influencing it. Variety, maturity, and climate are known to influence the astringency of fruit. The chapter presents extensive data on the effect of seasonal conditions on the astringency of American grape juices, and also on apple juices. Certain fruits are astringent when they are unripe. During ripening on the tree or in storage, this astringency disappears. This loss in astringency may be accompanied by a change in the tannin fraction. The actual change in tannins, determined chemically, are small and may either increase or decrease. In astringent fruits, the main phenolic compounds found are flavanols. Both the flavanols and the flavan diols occur. Other major constituents of the phenolic fraction consist of the flavanols, kaempferol, quercetin, myricetin, chlorogenic acid, and the cinnarnic acids such as caffeic acid. Apart from environmental factors such as locality, season, stage of development, and mineral nutrition, which are known to affect the level of phenolic compounds in fruits, and hence astringency, various secondary treatments can decrease the degree of astringency in fruits, for example, treatment with carbon dioxide, ethylene; precipitation of the tannin with acetic acid, formaldehyde; and oxidation with ozone. Astringency may also be reduced by air drying, particularly in persimmons. If the fruit is chilled, astringency may increase. The various theories proposed to explain loss in astringency have been classified into three groups: binding, change in molecular size of the tannins, and a change in the hydroxylatzon pattern of the Phenolic Compound.

Effect of Water Extracts of Carob Pods, Tannic Acid, and Their Derivatives on the Morphology and Growth of Microorganisms1

The effect of aqueous extracts of carob (Ceratonia siliqua) pods, gallotannic acid, gallic acid, and catechol on several microorganisms was studied. Carob pod extract and tannic acid showed a strong antimicrobial activity toward some cellulolytic bacteria. On the basis of tannin content, to which antimicrobial effect was related, carob pod extracts inhibited Cellvibrio fulvus and Clostridium cellulosolvens at 15 mug/ml, Sporocytophaga myxococcoides at 45 mug/ml, and Bacillus subtilis at 75 mug/ml. The inhibiting concentrations for tannic acid were found to be 12, 10, 45, and 30 mug/ml, respectively. Gallic acid and catechol were much less effective. Tannic acid and the tannin fraction of carob extract exerted both bacteriostatic and bactericidal effects on C. fulvus. Respiration of C. fulvus in the presence of bactericidal concentrations of tannic acid or tannin fraction of carob extract was inhibited less than 30%. A partial formation of "protoplasts" by C. fulvus was obtained after 2 hr of incubation in a growth medium to which 20% sucrose, 0.15% MgSO(4).7H(2)O, and 10 to 50 mug/ml of tannic acid or 500mug/ml of penicillin, or both, had been added. Tannic acid and the tannin fraction of carob extract protected C. fulvus from metabolic lysis in sucrose solution. Although the growth of other microorganisms tested was only slightly affected, the morphology of some of them was drastically changed in the presence of subinhibitory concentrations of carob pod extracts of tannic acid. It is suggested that the site of action of tannins on sensitive microorganisms is primarily the cell envelope.

STUDIES ON NON-BIOLOGICAL HAZES OF BEERS V. ROLE OF HOP AND MALT TANNINS

An earlier suggestion that both hop tannins and malt tannins participate in the formation of beer hazes is confirmed by the results of experimental brewings, using malt from which the husks had been removed as the basic raw material, together with additions to the wort of fractions of malt-husk tannin together with hops or isohumulone. With regard to haze development, it was shown that under certain conditions the most active tannin fraction is one derived from malt husk and containing leucoanthocyanins (anthocyanogens) related to the anthocyanidins, cyanidin and delphinidin. Under other conditions, e.g. using higher hopping rates, the corresponding compounds of hops played a greater part. Anthocyanogens were found in various hazes isolated from British beers, especially in chill hazes. Further observations, based on the results of fractionating proteintannin compounds in beer, bear out earlier indications that the effective anthocyanogens are possibly present in beer in bound form.