Native Catechins Research Articles

The impact of catechins included in high fat diet on AMP-dependent protein kinase in apoE knock-out mice

Due to their health-promoting effects green tea catechins have gained a keen interest in recent years in the context of bodyweight reduction treatments and alleviation of inflammatory diseases. This study was designed to evaluate the impact of native and thermally modified catechins (TMC) on the body weight gain, fatty acid profile in subcutaneous adipose tissue and the activity of the enzymes involved in lipid metabolism regulation: AMP-dependent protein kinase (AMPK) and acetyl-CoA carboxylase (ACC) in apoE-deficient mice maintained on a high-fat diet. We observed that TMC decreased bodyweight gain as compared to the control group. Furthermore, TMC increased AMPK activity and reduced ACC activity in the metabolically important tissues: intestine, liver and subcutaneous adipose tissue and affected adipose tissue fatty acid composition. Native catechins produced less pronounced effects. These results suggest that TMC down-regulate endogenous fatty acid synthesis, which should be taken into account in dietary applications of catechins.

Anti-atherosclerotic activity of catechins depends on their stereoisomerism

In terms of stereochemistry, catechins are divided into two groups: (−) epi forms (2R, 3R) and (−) forms (2S, 3R). Most of the catechins present in green tea are (−) epi forms (2R, 3R). Under the influence of high temperatures, in anaerobic conditions, as a result of epimerization the proportion of the (−) form (2S, 3R) increases. The data indicate that the presence of thermally modified catechins in the diet more efficiently reduces the development of atherosclerosis in apoE knockout mice than the presence of native catechins. The addition of the thermally modified formulations to the high-fat diet resulted in a reduction of the area of atherosclerotic lesions by about 28% (en face method) and 45% (cross-section method) compared to the group fed the high-fat diet without catechins. Furthermore, the body weight gain and plasma TBARS concentration in mice fed a diet with the addition of catechins depends on the degree of epimerization of catechins and decreases with increasing content of catechins belonging to the (−) form (2S, 3R). Moreover, plasma HDL cholesterol concentration in mice depends on catechins' stereoisomerism and increases along with the increasing content of catechins belonging to the (−) form (2S, 3R).

Simulated gastrointestinal digestion, intestinal permeation and plasma protein interaction of white, green, and black tea polyphenols

The gastrointestinal digestion, intestinal permeation, and plasma protein interaction of polyphenols from a single tea cultivar at different stages of processing (white, green, and black teas) were simulated. The salivary phase contained 74.8–99.5% of native polyphenols, suggesting potential bioavailability of significant amounts of antioxidants through the oral mucosal epithelium that might be gastric sensitive and/or poorly absorbed in the intestine. White tea had the highest content and provided the best intestinal bioaccessibility and bioavailability for catechins. Since most of native catechins were not absorbed, they were expected to accumulate in the intestinal lumen where a potential inhibition capacity of cellular glucose and cholesterol uptake was assumed. The permeated catechins (approximately, 2–15% of intestinal levels) significantly bound (about 37%) to plasma HDLs, suggesting a major role in cholesterol metabolism. White tea and its potential nutraceuticals could be effective in the regulation of plasma glucose and cholesterol levels.

Simultaneous UPLC–MS/MS analysis of native catechins and procyanidins and their microbial metabolites in intestinal contents and tissues of male Wistar Furth inbred rats

Procyanidins have been extensively investigated for their potential health protective activities. However, the potential bioactivities of procyanidins are limited by their poor bioavailability. The majority of the ingested dose remains unabsorbed and reaches the colon where extensive microbial metabolism occurs. Most existing analytical methods measure either native compounds (catechins and procyanidins), or their microbial metabolites. The objectives of this study were to develop a high-throughput extraction and UPLC-MS/MS method for simultaneous measurement of both native procyanidins and their metabolites, facilitating high-throughput analysis of native and metabolite profiles in various regions of the colon. The present UPLC-MS/MS method facilitates simultaneous resolution and detection of authentic standards of 14 native catechin monomers and procyanidins, as well as 24 microbial metabolites. Detection and resolution of an additional 3 procyanidin dimers and 10 metabolites for which standards were not available was achieved. Elution and adequate resolution of both native compounds and metabolites were achieved within 10min. The intraday repeatability for native compounds was between 1.1 and 16.5%, and the interday repeatability for native compounds was between 2.2 and 25%. Intraday and interday repeatability for metabolites was between 0.6 and 24.1% and 1 and 23.9%, respectively. Observed lower limits of quantification for native compounds were ∼9-350fmol on-column, and for the microbial metabolites were ∼0.8-12,000fmol on-column. Observed lower limits of detection for native compounds were ∼4.5-190fmol on-column, and for metabolites were 0.304-6020fmol on-column. For native monomers and procyanidins, extraction recoveries ranged from 38 to 102%. Extraction recoveries for the 9 microbial metabolites tested ranged from 41 to 95%. Data from tissue analysis of rats gavaged with grape seed extract indicate fairly high accumulation of native compounds, primarily monomers and dimers, in the cecum and colon. Metabolite data indicate the progressive nature of microbial metabolism as the digesta moves through the lower GI tract. This method facilitates the high-throughput, sensitive, and simultaneous analysis of both native compounds and their microbial metabolites in biological samples and provides a more efficient means of extraction and analysis than previous methods.

Identification of Native Catechin Fatty Acid Esters in Green Tea (Camellia sinensis)

Catechins are potent antioxidants and make up the primary class of polyphenols present in tea (Camellia sinensis). They are especially abundant in the less-fermented green teas that have been employed in various foods to enhance shelf life stability (Senanayake, N. J. Funct. Foods 2013, in press. Gramza, A.; Korczak, J. Trends Food Sci. 2005, 16, 351-358). The antioxidative activity of native (polar) catechins has proven to be useful in foods of relatively high polarity, while mixed results have been achieved in high-fat foods. However, the polarity of catechins can be attenuated by esterification with fatty acids, producing adducts that effectively partition into lipids and protect against rancidity even in high-fat foods (Cutler, S.; Fuller, E.; Rotberg, I.; Wray, C.; Troung, M.; Poss, M. International Patent WO 2013/036934 A1, March 14, 2013. Zhong, Y.; Shahidi, F. J. Agric. Food Chem. 2011, 59, 6526-6533). In this work, a search for the presence of naturally occurring lipid-conjugated catechins was undertaken in various green tea varieties. Rather than the traditional aqueous infusion, dried tea leaves were extracted with organic solvents followed by analysis for catechin adducts with both lower polarities and increased molecular weights as monitored by liquid chromatography and tandem mass spectrometry. Native catechin palmitates were identified and indirectly confirmed by synthesis and nuclear magnetic resonance as natural components of several Chinese green teas. Evidence of other fatty catechin esters was also observed.

Green tea and cancer

Despite being one of the most widely consumed beverages in the world, green tea is often seen by the media as a so-called superfood, attributed with various health benefits including protective effects against cancer. This reputation rests primarily on the fact that green tea is a rich source of polyphenols, which provide much of the colour and aroma of tea. Both green and black varieties are aqueous infusions of the plant Camellia sinensis, but whereas the constituent polyphenols of black tea are allowed to become oxidised to theaflavins during processing, green tea leaves are heat-treated to inactivate their polyphenol oxidase activity, enabling the native catechins to remain intact.

Improvement of (+)-catechin inhibitory activity on human PMN respiratory burst by (+)-3-O-propionyl and (-)-3-O-valeryl substitution.

Catechins and their derivatives are abundant flavanols in the plant kingdom. Usually, catechin activity correlates with chemical structure. We hypothesized that by adding hydrophobic groups to the native catechin, we could ameliorate penetration of the cell and make the derivatives more active than native molecule in inhibiting polymorphonuclear leucocyte (PMN) oxidative burst. This study was designed to compare the antioxidant activity of native catechin with that of (+)-3-propionylcatechin and (-)-3-Ovalerylcatechin esters by two cell-free colorimetric methods and by their effects on whole blood leucocytes as well as on isolated PMN chemiluminescence activity. The results showed that the colorimetric methods did not detect differences between catechins. On the contrary, cellular chemiluminescence studies showed that light emission by resting, as well as by phorbol myristate acetate (PMA)-stimulated PMNs and whole blood leucocytes was inhibited by catechin esters more intensively than native catechin. The compartmental chemiluminescence evaluation showed that the extracellular activity was similar with all catechins, while the intracellular activity was higher with esters. PMN pre-incubation, with catechins at various times before stimulation with PMA, enhanced the inhibitory activity of all compounds. Since the esterification with propionic or valeric acid increased the lipophilicity of (+)-catechin, we hypothesized that native and esterified catechins have different intracellular availability and therefore differ in effectiveness. An ancillary result obtained is that a single approach, chemical or cellular, is not sufficient to evaluate overall antioxidant activity in biological sytems. The results indicate that modified catechins may be very intriguing as possible future leucocyte modulating drugs, with possible applications in vascular and inflammatory diseases.

An Improved Synthesis of Procyanidin Dimers: Regio‐ and Stereocontrol of the Interflavan Bond

AbstractA direct and general synthesis of procyanidin dimers B1, B2, B3 and B4 (10a–d) is presented. The approach is based on the stoichiometric coupling of two protected monomeric units (the nucleophilic 2a–b and electrophilic 4a–b partners) and deals with the regio‐ and stereocontrol of the C4–C8 interflavan bond as well as the control of the degree of oligomerization. The synthesis involves a five‐step pathway starting from the native catechin (1a) or epicatechin (1b) to the fully deprotected dimers 10a–d. Furthermore, the process appears to be iterative as the coupling intermediates 9a–d themselves can be readily used in further selective syntheses of trimers or higher oligomers. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

A planar catechin analogue as a promising antioxidant with reduced prooxidant activity.

A planar catechin analogue (1H2), in which catechol and chroman moieties in (+)-catechin are constrained to be coplanar, is an efficient radical scavenger compared to the native catechin, and are nearly as effective as quercetin, a strong radical scavenger. The dianion (1(2-)) of 1H2 produced by the reaction of 1H2 with 2 equiv of tetramethylammonium methoxide reduced molecular oxygen (O2) to generate superoxide anion (O2*-). The resulting radical anion (1*-) from 1H2 underwent intramolecular proton transfer to give an o-semiquinone radical anion form of 1*-, which shows a characteristic ESR spectrum with g value of 2.0048. Although the same mechanism has also been shown for (+)-catechin, the rate constant of electron transfer (ket) from 1(2-) to O2 is about a half of that reported for (+)-catechin, indicating that the electron transfer from 1(2-) to O2 is slower than that from (+)-catechin dianion to O2. Together with efficient protection against DNA strand breakage induced by the Fenton reaction, the small ket value for 1H2 implies that, in physiologically relevant systems, there is less of a possibility of generating oxygen radicals responsible for prooxidant activity with 1H2 than that with (+)-catechin. The strong radical scavenging ability and less-efficient generation of O2*- suggest that the planar catechin analogue may be useful for the prevention and/or treatment of free-radical-associated diseases.

Catechin Is Metabolized by Both the Small Intestine and Liver of Rats

Flavan-3-ols are the most abundant flavonoids in the human diet, but little is known about their absorption and metabolism. In this study, the absorption and metabolism of the monomeric flavan-3-ol, catechin, was investigated after the in situ perfusion of the jejunum + ileum in rats. Five concentrations of catechin were studied, ranging from 1 to 100 micromol/L. The absorption of catechin was directly proportional to the concentration, and 35 +/- 2% of the perfused catechin was absorbed during the 30-min period. Effluent samples contained only native catechin, indicating that intestinal excretion of metabolites is not a mechanism of catechin elimination. Catechin was absorbed into intestinal cells and metabolized extensively because no native catechin could be detected in plasma from the mesenteric vein. Mesenteric plasma contained glucuronide conjugates of catechin and 3'-O-methyl catechin (3'OMC), indicating the intestinal origin of these conjugates. Additional methylation and sulfation occurred in the liver, and glucuronide + sulfate conjugates of 3'OMC were excreted extensively in bile. Circulating forms were mainly glucuronide conjugates of catechin and 3'OMC. The data further demonstrate the role of the rat small intestine in the glucuronidation and methylation of flavonoids as well as the role of the liver in sulfation, methylation and biliary excretion.

茶葉中のカテキン及び色素の研究(其の1) 茶葉カテキンの分別測定法

On studying the paper chromatography of the extract from tea leaves, we found 6 spots on one-dimensional chromatogram and 9 spots on two-dimensional chromatogram and comparing with the reports of BRADFIELD and ROBERT, we identified these substances as shown in Table 2 from the color of spots and RF values. (Figs. 1 and 2 and Table 1.) We have considered that the principal native catechins in tea leaves consist of 4 kinds of catechins (spots No. 2, 4, 7, and 9.) and other 3 kinds (spots No. 3, 6, and 8.) are isomers formed in the preparation, so we have studied to estimate these catechins by one-dimensional paper chromatographic method. There is a linear relation between the area of spots and the content of catechins in. limited range as shown in Tables 3 and 4 and Figs. 4 and 5. Each curve for catechins has different inclination, but if S×RF values are plotted, all curves agreed with one curve A-B in Fig. 4. So this relation is indicated as log.mg, /1000cc.catechin=S×RF×0.004+1.2. By this method, we have been able to estimate each catechin individually in some species of tea leaves as shown in Table 5 and Fig. 6.