Catechin Solutions Research Articles

Time–intensity studies of astringent taste

The intensity of astringent taste was studied in wine, vermouth and other beverages during ingestion and for up to 100 s after swallowing, and the reproducibilities determined. Better reproducibility was observed of the same assessor on different days than between different assessors on the same day. Preprinted forms and mouse operated or touch-sensitive computer recording gave similar results. The residence time in the mouth influenced the maximum intensity and the rate of its decrease, which followed exponential relation. Solutions of tannic acid and catechin tasted more astringent in water than in wine or orange juice. Natural astringent substances in red wine or in tea infusion gave similar time dependence as model solutions. Sugar decreased the astringency in red wine, but quinine hydrochloride or additional ethanol had no pronounced effect.

Investigation of alumina/(+)-catechin system properties. Part I: a study of the system by FTIR-UV–Vis spectroscopy

Catechin belongs to a group of flavonoids, which are present in many fruits and plants. Catechin is often employed in model investigations on antioxidant behavior of flavonoids. Recently also some anti-disease properties of flavonoids were reported. In this paper investigations were carried out on alumina/(+)-catechin solution system. FTIR spectra were taken for the catechin samples retaken from its aqueous solutions at pH 3, 5.5 (natural) and 10.5. In other series, the solutions were contacted with an alumina powder during 20 days. Also UV–Vis spectra were taken for similar solutions incubated for 1, 7, 20, 50 and 70 days with and without contact with alumina. It appeared that the alumina essentially accelerated the autooxidation processes occurring in the solutions. The results show that the processes have completed between day 20 and 50, because the UV–Vis spectra for day 50 and 70 overlapped. Moreover, it looks that this is a specific property of alumina, which behaves as a catalyst. Similar experiments with silica showed that during 50 days, this oxide affected the processes only slightly.

Phenolic compounds and browning in sherry wines subjected to oxidative and biological aging.

The composition in hydroxybenzoic and hydroxycinnamic acids, hydroxycinnamic esters, tyrosol, syringaldehyde, and flavan-3-ol derivatives of three different types of sherry wine obtained by aging of the same starting wine under different conditions was studied. So-called "fino" wine was obtained by biological aging under flor yeasts, "oloroso" wine by oxidative aging, and "amontillado" wine by a first stage of biological aging followed by a second oxidative step. On the basis of the results, the wines subjected to oxidative aging exhibited higher phenol contents, in addition to scarcely polar compounds absorbing at 420 nm that were absent in the wines obtained by biological aging. Taking into account that flavan-3-ol derivatives play an important role in wine browning, a model catechin solution was inoculated with flor yeast which, contrary to the findings of other authors in the absence of yeasts, formed no colored compounds. This different behavior may account for the resistance to browning of pale sherry wines in the presence of flor yeasts.

Oral administration of (-)catechin protects against ischemia-reperfusion-induced neuronal death in the gerbil

The effect of ad libitum oral-administration of (-)catechin solution on ischemia-reperfusion-induced cell death of hippocampal CA1 in the gerbil was histologically examined. When (-)catechin solution instead of drinking water was orally administered ad libitum for 2 weeks, dose-dependent protection against neuronal death following by transient ischemia and reperfusion was observed. To evaluate the involvement of reduction of reactive-oxygen-species (ROIs) by the antioxidant activity of (-)catechin in this protection, the superoxide scavenging activity of the brain in catechin-treated gerbils was measured by ESR and spin-trapping using 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). The superoxide scavenging activities of the brains obtained from catechin-treated gerbils were significantly higher than those of catechin-untreated animals. From these results, it was suggested that orally administered (-)catechin was absorbed, passed through the blood-brain barrier and that delayed neuronal death of hippocampal CA1 after ischemia-reperfusion was prevented due to its antioxidant activities.

Preparation of Epimers of Tea Catechins by Heat Treatment

Products from tea catechins ((+)-catechin, (−)-epicatechin, (−)-epigallocatechin, (−)-epicatechin gallate, and (−)-epigallocatechin gallate) after heat treatment were individually isolated by preparative HPLC and subsequent crystallization. FAB-MS, elemental, 1H- and 13C-NMR, and optical rotation analyses indicated these products to be the C-2 epimers of the original catechins. The effects of temperature, time, pH, and concentration on this conversion of tea catechins to their epimers were examined. It was determined that the epimerization reaction should be conducted with 1% each of the tea catechin solution (pH5) at l20°C for 30 min.

Interaction of catechin with poly(L-proline)

Catechin binds strongly to both poly(vinylpyrrolidone) and poly(L-proline) in dilute aqueous solution, inducing a collapse of the more flexible poly(vinylpyrrolidone) chains, but forming a microgel with the more extended poly(L-proline) chains. Low concentrations of poly(L-proline) inhibit the discoloration of aqueous solutions of catechin, thereby implicating the ortho hydroxyyl groups in the catechol moiety in the binding process. Modeling shows that the likely binding sites on poly(L-proline) arise from two minor local conformations. These minor conformations are less frequent in poly(γ-hydroxy-L-proline) than in poly(L-proline), which may explain why catechin interacts more strongly with poly(L-proline) than with poly(γ-hydroxy-L-proline).

Inhibition of β-Glucosidase (Amygdalae dulces) by (+)-Catechin Oxidation Products and Procyanidin Dimers.

The sensitivity and specificity of the inhibition of β-glucosidase (Amygdalae dulces) by (+ )-catechin, an oxidized (+)-catechin solution, three dimeric procyanidins, and five (+)-catechin dimers obtained by enzymatic oxidation were evaluated by using a chromatographic method. All the polyphenols tested presented a significant inhibitory effect. Non-competitive inhibition was observed for the oxidized (+)-catechin solution. Some oxidation products were at least as powerful inhibitors as procyanidins which are known for their tanning effect. Yellow oxidation products were among the strongest inhibitors. No marked role of the number of hydroxyl and o-diphenol groups nor of the nature or position of the interflavanic linkage in the inhibitory effect was apparent.

Iron-Catalyzed Oxidation of (+)-Catechin in Model Systems

Autoxidation of (+)-catechin in wine-like model solutions containing 0−20 mg L-1 of ferrous iron was monitored by HPLC with diode array detection. The rate of catechin oxidation and the extent of browning increased with the iron level. Some of the oxidation products were formed in larger amounts at higher iron concentrations. These included colorless compounds and yellow pigments with absorbance maxima between 440 and 460 nm. The iron-catalyzed reactions leading to these compounds competed with iron-independent reactions generating different products which are presumably identical to those formed in enzymically oxidized catechin solutions. Keywords: (+)-Catechin; autoxidation; ferrous ions; CLHP; browning

The effects of green tea catechins (Polyphenon) on DL-ethionine-induced acute pancreatitis.

The effects of green tea catechins (Polyphenon) on DL-ethionine-induced acute pancreatitis in rats were examined. The acute pancreatitis induced in this study was characterized by moderate inter- and intrastitial edema and patchy acinar cell necrosis. In rats induced with acute pancreatitis by an intraperitoneal injection of DL-ethionine, the wet weight of the pancreas (0.47 +/- 0.059 g/100 g body weight; p < 0.05), the serum amylase (10,432 +/- 996 IU/L; p < 0.001), and the tissue concentration of lipid peroxides (19.5 +/- 1.78 nmol/mg tissue DNA; p < 0.001) were significantly increased compared with values obtained in control rats (0.39 +/- 0.037 g/100 g body weight, 5,639 +/- 1,568 IU/L, and 10.7 +/- 1.04 nmol/mg tissue DNA, respectively) injected with isotonic saline. In contrast, in rats injected with DL-ethionine and supplied with a green tea catechin solution as a beverage instead of water during the experimental period, the tissue of pancreas was almost-correct, and the wet weight of the pancreas (0.39 +/- 0.054 g/100 g body weight; p < 0.05), the serum amylase (5,716 +/- 708 IU/L; p < 0.001), and the concentration of lipid peroxides in tissue (11.5 +/- 2.15 nmol/mg tissue DNA; p < 0.001) were significantly decreased compared with values obtained in rats injected with DL-ethionine and supplied with water as a beverage. These data suggest that green tea catechins may have a protective effect on the pathogenesis of experimental acute pancreatitis.

Hydrogen Peroxide Formation during Catechin Oxidation Is Inhibited by Superoxide Dismutase.

We established a simple method to quantify hydrogen peroxide (H2O2) generated during the aerobic heating process of (+)-catechin solution. Using this method, we found that non-enzymatic H2O2 formation from catechin depended on pH, temperature, incubation time, and the presence of O2 in the solution. The formation of oxidized products of (+)-catechin, which was estimated by measuring the absorbance of the solution at 430 nm, also depended on these factors. The H2O2 formation was inhibited by various kinds of superoxide dismutase (SOD) with almost the same dose dependency. Although the oxidation of (+)-catechin was enhanced by superoxide (O2−), neither catalase nor H2O2 had any effects on the oxidation. These results suggest that O2−, rather than H2O2, participated in the autoxidation of (+)-catechin, which was coupled with the H2O2 formation.

Immobilised laccase for phenolic removal in must and wine

The possibility of the use of immobilised Laccase (EC 1.10.3.1.) for the enzymatic removal of phenolic compounds from must and wine has been attempted on laboratory scale. The immobilised enzyme was packed in column and model solutions of catechin or white grape must were eluted through. Oxygen saturation, flow-rate and immobilised enzyme amount were the main parameters used to study phenolic oxidation.

Responses of a compatible lucerne variety to attack by spotted alfalfa aphid: changes in the redox balance in affected tissues

AbstractThe spotted alfalfa aphid, Therioaphis trifolii maculata (Buckton), caused local browning of cells surrounding feeding sites on lucerne plants (cv. Hunter River). Aqueous extracts of infested leaves underwent a marked browning process that did not occur in extracts of healthy leaves. The process was accelerated by addition of tyrosinase and peroxidase and reversed by reducing agents such as ascorbate and glutathione. In the presence of added reducing agents, the extracts produced brown precipitates, probably conjugates of phenolics with leaf proteins similar to those involved in the sealing of damaged tissues in vivo.Partially autoxidised catechin (PAC) solutions showed an absorbance peak at 438 nm that was increased by polyphenol oxidase and decreased by ascorbate and glutathione. When extraction of tissues into PAC was used to assess redox activities, healthy tissues showed a rapid, short lived oxidising activity combined with a much more persistent reducing activity, whereas infested leaves had even greater oxidising activity and no detectable reducing activity.Soluble phenolics increased in infested leaves and stems. Total protein decreased, but the specific activity of peroxidase, catechol oxidase and superoxide dismutase relative to protein content increased. The ability of extracts to reduce cytochrome c increased, indicating an overall increase in superoxide radicals in attacked tissues.These results are consistent with a general disturbance of redox balance induced in tissues by aphid feeding, including accumulation of oxidases and phenolic substrates and loss of reducing activity and protein.

Use of the fluorescence quantum yield for the determination of the number-average molecular weight of polymers of epicatechin with 4β→8 interflavan bonds

Excitation at 280 nm produces a structureless emission band with a maximum at 321–324 nm for dilute solutions of catechin, epicatechin, and their oligomers in 1,4-dioxane or water. The fluorescence quantum yield, Q, has been measured in these two solvents for five dimers, a trimer, a tetramer, a pentamer, a hexamer, and a polymer in which the monomer units are catechin and/or epicatechin. In a homologous series of monodisperse oligomers in which epicatechin units are connected by interflavan bonds with 4β→8 stereochemistry, Q is found to be inversely proportional to the degree of polymerization. Measurement of Q for a polydisperse sample of this polymer yields the number-average degree of polymerization.

The effect of autoxidation on the methanogenic toxicity and anaerobic biodegradability of pyrogallol

In a previous study, catechin (a condensed tannim monomer) was polymerized by autoxidation treatments. The resulting oligomeric tannins were responsible for the methanogenic toxicity observed in the autoxidized catechin solutions (Field, J. A., Kortekaas, S. & Lettinga, G. (1989). The tannin theory of methanogenic toxicity. Biol. Wastes 29(4) 241-62). In this study the autoxidation of pyrogallol (a hydrolyzable tanning monomer) did not cause extensive polymerization. Initially, some polymerization occurred, producing toxic intermediates that were later destroyed by a destructive type of oxidation caused by prolonged autoxidation treatments. The first intermediate formed, purpurogallin (a dimer), caused a high level of toxicity to both the methanogenic activity and to the anaerobic degradation of pyrogallol. Since purpurogallin is a highly toxic autoxidation product that lacks tannic features, the changes in methanogenic toxicity induced by the autoxidation of pyrogallol cannot be estimated by changes in the oligomeric tannin concentration. Regardless of the reactions that take place during the autoxidation of tannin monomeric derivatives, the initial reactions can potentially lead to colored products of increased methanogenic toxicity. These are later detoxified by prolonged autoxidation, either by polymerization to high MW compounds (with condensed tannin model compounds), or by destruction of the initially toxic intermediates to low MW compounds (with hydrolyzable tannin model compounds).

Prevention of Sucrose Inversion during Preparation of HPLC Samples

Abstract A preparative column consisting of 1 ml each polyvinylpyrrolidone, Amberlite IRA-45 in the acetate form, and Dowex 50W in the acid form removed 98% to 99% of the cations and phenolics from leaf extracts of Euonymus japonica Thunb. and from standard solutions of magnesium acetate and catechin. Sucrose inversion occurred when 2 or 3 ml of cation exchange resin were used or when 1 ml was used at a flow rate of 0.1 ml/min. Sucrose inversion was inversely related to column flow rate.

POLYPHENOLS IN PLANT, HUMUS, AND SOIL

SummaryThe two pure polyphenols, D‐ and epi‐catechin, known to be present in the fresh green leaves of a number of tree species, have been shown to be capable of reducing ferric iron, in the form of hydrated ferric oxide, to an organic ferrous complex and solubilizing it in much the same way as do Bloomfield's leaf extracts. These polyphenols can remove iron, even when held firmly as in Triassic sand, and transport it as ferrous iron at low pH. Model soils, consisting of alumina and diatomaceous earth impregnated with ferric chloride, were treated with catechin solutions and fresh green‐leaf extracts. Both produced dark coloured bands in which substantial amounts of ferric iron had been converted to ferrous iron. Extracts of green beech leaves from a mor site were more effective than those from a mull site (June leaf collection). Extracts of humus and litter were singularly low in reducing and iron‐complex‐forming substances, corresponding to their low free polyphenol status.The illuvial horizon of a podzol formed on Barton sand has yielded organic matter on extraction with acetyl acetone. This contained much material of polyphenol origin associated with iron.The role of polyphenol activity towards iron is discussed in relation to podzolic and other soils.

茶葉中のカテキン及び色素の研究(其の2)比濁法による茶葉タンニンの定量法

On the determination of tannin (catechins and catechin gallic ester) in tea leaves, the Löwenthal method gives a small value on account of the fact that free catechins are not sufficiently precipitated by the gelatin solution (Table 4). So we have studied the nepherometric method to estimate the tannin content including free catechins in tea leaves (Fig.1. ). When the catechin solution is mixed with HCl-formalin reagent and the nepherometric ratio (r) for the standard solution is determined, r is proportional to the concentration of catechins. (Figs. 2 and 3 and Tables 1 and 2.) Its technique is as follows: the equal volume of the HCl-formalin reagent (35% HCl 100 cc., 30% formalin 200 cc., and water 50 cc.) is added to the clear extract of leaves. After 1 hour, this white turbid solution is compared to the standard catechin solution (50 mg of catechins in 100 cc. water with HCl-formalin reagent) and estimate the nepherometria ratio. From the standard curve (Fig: 4.) or the conversion table (Table 3.), we have been able to calculate the content of tannin in tea leaves (Table 4.).