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At least 19 recordsLinked to original sources
PubMed2003

Heat-epimerized tea catechins rich in gallocatechin gallate and catechin gallate are more effective to inhibit cholesterol absorption than tea catechins rich in epigallocatechin gallate and epicatechin gallate.

It has been known that tea catechins, (-)-epicatechin (1), (-)-epigallocatechin (2), (-)-epicatechin gallate (3), and (-)-epigallocatechin gallate (4) are epimerized to(-)-catechin (5), (-)-gallocatechin (6), (-)-catechin gallate (7), and (-)-gallocatechin gallate (8), respectively, during retort pasteurization. We previously reported that tea catechins, mainly composed of 3 and 4, effectively inhibit cholesterol absorption in rats. In this study, the effect of heat-epimerized catechins on cholesterol absorption was compared with tea catechins. Both tea catechins and heat-epimerized catechins lowered lymphatic recovery of cholesterol in rats cannulated in the thoracic duct and epimerized catechins were more effective than tea catechins. The effect of purified catechins on micellar solubility of cholesterol was examined in an in vitro study. The addition of gallate esters of catechins reduced micellar solubility of cholesterol by precipitating cholesterol from bile salt micelles. Compounds 7 and 8 were more effective to precipitate cholesterol than 3 and 4, respectively. These observations strongly suggest that heat-epimerized catechins may be more hypocholesterolemic than tea catechins.

Animals↗
PubMed2006

(+)-Catechin is more bioavailable than (-)-catechin: relevance to the bioavailability of catechin from cocoa.

Catechin is a flavonoid present in fruits, wine and cocoa products. Most foods contain the (+)-enantiomer of catechin but chocolate mainly contains ( - )-catechin, in addition to its major flavanol, ( - )-epicatechin. Previous studies have shown poor bioavailability of catechin when consumed in chocolate. We compared the absorption of ( - ) and (+)-catechin after in situ perfusion of 10, 30 or 50 micromol/l of each catechin enantiomer in the jejunum and ileum in the rat. We also assayed 23 samples of chocolate for (+) and ( - )-catechin. Samples were analyzed using HPLC with a Cyclobond I-2000 RSP chiral column. At all concentrations studied, the intestinal absorption of ( - )-catechin was lower than the intestinal absorption of (+)-catechin (p < 0.01). Plasma concentrations of ( - )-catechin were significantly reduced compared to (+)-catechin (p < 0.05). The mean concentration of ( - )-catechin in chocolate was 218 +/- 126 mg/kg compared to 25 +/- 15 mg/kg (+)-catechin. Our findings provide an explanation for the poor bioavailability of catechin when consumed in chocolate or other cocoa containing products.

Animals↗
PubMed1985

Influence of palmitoyl-3-catechin and heptyl-3-catechin on the leucocyte migration inhibition test carried out in the presence of PPD and hepatitis B surface antigen (HBsAg).

It has been shown that (+)-cyanidanol-3 [+)-catechin) is able to stimulate in vitro the cell-mediated immune response specific for hepatitis B surface antigen (HBsAg), and might contribute to the elimination of hepatitis B virus (HBV) during HBV infection. In the present study, the possible action of two of its derivatives, palmitoyl-3-catechin and heptyl-3-catechin, on this type of immunity was investigated by adding the substances to leucocyte migration inhibition tests performed in presence of PPD and HBsAg, with leucocytes from individuals sensitized to these antigens. In normal individuals sensitized to PPD, the addition of palmitoyl-3-catechin and heptyl-3-catechin amplified the inhibition of migration by resp. 7.2% (p less than 0.05) and 13.5% (p less than 0.001). In patients previously infected by HBV and sensitized to HBsAg, the maximum amplification was resp. 12.7% (p less than 0.001) and 7.6% (p less than 0.05). This effect was dose-dependent. These substances did not modify the leucocyte migration measured in the absence of antigen. Palmitoyl-3-catechin and heptyl-3-catechin therefore seem capable of amplifying the cell-mediated immune response. The effect of the two derivatives, which were selected because of their liposolubility, was more pronounced than the effect of (+)-cyanidanol-3. It is thus possible that the two new catechin-derivatives, not yet in therapeutical use, will also stimulate cell-mediated immunity to HBsAg, and that a more marked clinical effect might be expected.

Adjuvants, Immunologic↗
PubMed2005

Reduction of catechin astringency by the complexation of gallate-type catechins with pectin.

The reductive effect of pectin on tea catechin astringency was investigated by using a taste sensor system and (1)H-NMR spectroscopy. The sensor analysis revealed that the astringency of gallate-type catechins (EGCg and ECg) was reduced by the addition of pectin, whereas that of non-gallate-type catechins (EGC and EC) hardly changed. Changes in the (1)H-NMR chemical shifts of the catechins and pectin in mixed solutions showed that the gallate-type catechins formed complexes with pectin more closely than the non-gallate-type catechins. These results demonstrate that complexation between the gallate-type catechins and pectin is a factor for reducing catechin astringency.

Biosensing Techniques↗
PubMed1999

Human salivary tea catechin levels and catechin esterase activities: implication in human cancer prevention studies.

Because of the possible application of tea in the prevention of oral and esophageal cancers, the salivary levels of tea catechins were determined in six human volunteers after drinking tea. Saliva samples were collected after thoroughly rinsing the mouth with water. After drinking green tea preparations equivalent to two to three cups of tea, peak saliva levels of (-)-epigallocatechin (EGC; 11.7-43.9 microg/ml), EGC-3-gallate (EGCG; 4.8-22 microg/ml), and (-)-epicatechin (EC; 1.8-7.5 microg/ml) were observed after a few minutes. These levels were 2 orders of magnitude higher than those in the plasma. The elimination half-life (t(1/2)) of the salivary catechins was 10-20 min, much shorter than that of the plasma. Holding a tea solution in the mouth for a few minutes without swallowing produced even higher salivary catechin levels, but taking tea solids in capsules resulted in no detectable salivary catechin level. Holding an EGCG solution in the mouth resulted in EGCG and EGC in the saliva and, subsequently, EGC in the urine. The results suggest that EGCG was converted to EGC in the oral cavity, and both catechins were absorbed through the oral mucosa. A catechin esterase activity that converts EGCG to EGC was found in the saliva. The enzyme was likely of human origin, but the activity was not inhibited by common human esterase inhibitor. The present results suggest that slowly drinking tea is a very effective way of delivering rather high concentrations of catechins to the oral cavity and then the esophagus.

Absorption↗
PubMed2004

Determination of catechins and catechin gallates in tissues by liquid chromatography with coulometric array detection and selective solid phase extraction.

Catechins levels in organ tissues, particularly liver, determined by published methods are unexpectedly low, probably due to the release of oxidative enzymes, metal ions and reactive metabolites from tissue cells during homogenization and to the pro-oxidant effects of ascorbic acid during sample processing in the presence of metal ions. We describe a new method for simultaneous analysis of eight catechins in tissue: (+)-catechin (C), (-)-epicatechin (EC), (-)-gallocatechin (GC), (-)-epigallocatechin (EGC), (-)-catechin gallate (CG), (-)-epicatechin gallate (ECG), (-)-gallocatechin gallate (GCG) and (-)-epigallocatechin gallate (EGCG) (Fig. 1). The new extraction procedure utilized a methanol/ethylacetate/dithionite (2:1:3) mixture during homogenization for simultaneous enzyme precipitation and antioxidant protection. Selective solid phase extraction was used to remove most interfering bio-matrices. Reversed phase HPLC with CoulArray detection was used to determine the eight catechins simultaneously within 25 min. Good linearity (>0.9922) was obtained in the range 20-4000 ng/g. The coefficients of variance (CV) were less than 5%. Absolute recovery ranged from 62 to 96%, accuracy 92.5 +/- 4.5 to 104.9 +/- 6%. The detection limit was 5 ng/g. This method is capable for determining catechins in rat tissues of liver, brain, spleen, and kidney. The method is robust, reproducible, with high recovery, and has been validated for both in vitro and in vivo sample analysis.

Animals↗
PubMed2005

Heat-epimerized tea catechins have the same cholesterol-lowering activity as green tea catechins in cholesterol-fed rats.

Tea catechins are known to be epimerized by heat treatment. The effect of heat-epimerized tea catechins on serum cholesterol concentration was compared with that of green tea catechins. Our observations strongly suggest that both tea catechins and heat-epimerized tea catechins lower serum cholesterol concentration by inhibiting cholesterol absorption in the intestine. There was no differential effect between the two catechin preparations.

Animals↗
PubMed2005

A theoretical study of the different radical-scavenging activities of catechin, quercetin, and a rationally designed planar catechin.

To improve the radical-scavenging activity of catechin, a planar catechin analogue was designed and synthesized by Fukuhara [J. Am. Chem. Soc. 124 (2002) 5952]. Although the planar catechin is less active than quercetin, it is much more active than catechin in its ability to scavenge galvinoxyl radical, suggesting that the rational design was successful. However, an interesting question remains: what is the basis for the enhanced radical-scavenging activity of the planar catechin? By DFT calculations, we determined that the galvinoxyl radical is scavenged through an electron-transfer mechanism rather than a hydrogen-atom-transfer mechanism. Moreover, the antioxidant anion, derived from proton dissociation, plays a key role in the radical-scavenging process. Hence, the different radical-scavenging activities of the three antioxidants may result from the different ionization potentials of their anions.

Antioxidants↗
PubMed1983

Identification of the major urinary metabolites of (+)-catechin and 3-O-methyl-(+)-catechin in man.

Following oral administration of (+)-catechin and 3-O-methyl-(+)-catechin to human volunteers the major urinary metabolites were shown to be the glucuronides of 3'-O-methyl-(+)-catechin respectively. Isolations from urine and from synthetic products have been carried out by semi-preparative high performance liquid chromatography; definitive elucidations of structures have been carried out by gas chromatography-mass spectrometry and nuclear magnetic resonance spectroscopy.

Benzopyrans↗
PubMed2002

Chemical studies on antioxidant mechanism of tea catechins: analysis of radical reaction products of catechin and epicatechin with 2,2-diphenyl-1-picrylhydrazyl.

Tea catechins, an important class of polyphenols, have been shown to have wide spectrum of antitumor activity believed to be due mainly to their antioxidative effect. In this study, the radical scavenging behavior of catechins on 2,2-diphenyl-1-picrylhydrazyl (DPPH) was studied. Two reaction products of (+)-catechin, and two reaction products of (-)-epicatechin were purified and identified. Their structures were determined on the basis of detailed high-field 1-D and 2-D NMR spectral analysis. Structure elucidation of these products can provide insights into specific mechanisms of antioxidant reactions. A possible mechanism of the formation of reaction products is suggested.

Antioxidants↗
PubMedDate not supplied

Superoxide anion scavenging and xanthine oxidase inhibition of (+)-catechin-aldehyde polycondensates. Amplification of the antioxidant property of (+)-catechin by polycondensation with aldehydes.

In this study, the antioxidant property of (+)-catechin-aldehyde polycondensates has been examined. Superoxide anions are one of the most typical reactive oxygen species (ROS) and generated by xanthine oxidase (XO). The measurements of the superoxide anion scavenging and XO inhibition activity showed that catechin had pro-oxidant properties in lower concentrations and little XO inhibition. On the other hand, the polycondensates exhibited much higher effects compared to the catechin monomer, and their physiological activities were greatly affected by the structure of polycondensates. Steady-state analysis of the inhibition against XO showed that the inhibition type of the polycondensate was uncompetitive. Furthermore, the results of the circular dichroism and UV-visible measurements of a mixture of the polycondensate and XO were in good agreement with that of the steady-state analysis; the spectral changes due to the chelation of the polycondensate onto the Fe/S and/or the FAD center of XO were observed. These data strongly suggest that the polycondensates possess a great potential as antioxidant for various applications.

Aldehydes↗
PubMed2004

A planar catechin analogue having a more negative oxidation potential than (+)-catechin as an electron transfer antioxidant against a peroxyl radical.

The hydrogen transfer reaction of antioxidative polyphenol with reactive oxygen species has proved to be the main mechanism for radical scavenging. The planar catechin (P1H(2)), in which the catechol and chroman structure in (+)-catechin (1H(2)) are constrained to be planar, undergoes efficient hydrogen atom transfer toward galvinoxyol radical, showing an enhanced protective effect against the oxidative DNA damage induced by the Fenton reaction. The present studies were undertaken to further characterize the radical scavenging ability of P1H(2) in the reaction with cumylperoxyl radical, which is a model radical of lipid peroxyl radical for lipid peroxidation. The kinetics of hydrogen transfer from catechins to cumylperoxyl radical has been examined in propionitrile at low temperature with use of ESR, showing that the rate of hydrogen transfer from P1H(2) is significantly faster than that from 1H(2). The rate was also accelerated by the presence of Sc(OSO(2)CF(3))(3). Such an acceleration effect of metal ion indicates that the hydrogen transfer reaction proceeds via metal ion-promoted electron transfer from P1H(2) to oxyl radical followed by proton transfer rather than via a one-step hydrogen atom transfer. The electrochemical ease of P1H(2) for the one-electron oxidation investigated by second-harmonic alternating current voltammetry strongly supports the two step mechanism for hydrogen transfer, resulting in the enhanced radical scavenging ability.

Antioxidants↗
PubMed1987

Effects of antibiotic pretreatments on the metabolism and excretion of [U14C](+)-catechin [( U14C](+)-cyanidanol-3) and its metabolite, 3'-0-methyl-(+)-catechin.

Antibiotic pretreatment significantly altered metabolism of (+)-catechin (cyanidanol-3) in the rat, with decreases in both the urinary elimination of flavanol conjugates and of ring scission of the O-heterocyclic aglycone. The majority of the beta-glucuronidase(s) active in the degradation of flavanol conjugates is associated with the anaerobic microflora of the rat intestine. Ring scission is a minor reaction in vivo and appears to be due to anaerobic bacteria, although in vitro it is the major reaction and is promoted by both anaerobes and aerobes. The intestinal microflora are capable of demethylating the metabolite 3'-O-methyl-(+)-catechin in vivo; the major activity being associated with the aerobic microflora. Faecal elimination of unchanged (+)-catechin is of minor importance.

Animals↗
PubMed2005

Molecular classification of green tea catechin-sensitive and green tea catechin-resistant prostate cancer in the TRAMP mice model by quantitative real-time PCR gene profiling.

We previously found that human prostate cancer (CaP) progression is accompanied by differential expression of a panel of 8 informative genes, some of which are metabolically related. Gene profiling focused on this 8-gene pack by northern blot analysis in combination with standard clinical information provided reliable prognostic prediction of human CaP. For a better insight into the potential of this 8-gene signature in tumor detection/classification and therapeutic response, we determined, by qPCR, the expression of these informative genes in the TRAMP mice model of CaP progression. The 8-genes signature resulted effective in discriminating, by linear discriminant analysis (LDA), the prostate of wild type mice from transgenic TRAMP mice developing CaP (P < 0.0002). Since it is known that Green Tea Catechin (GTC) administration to TRAMP mice results in a substantial delay of CaP progression in 80% of the animals, while 20% remain unresponsive, we determined the 8-gene signature in the prostates of GTC-sensitive and GTC-resistant mice. LDA discriminated benign tissue from CaP (i.e. wild-type + chemoprevented, GTC-sensitive TRAMP mice, in which CaP progression was delayed, was discriminated from TRAMP mice + GTC-resistant TRAMP mice, in which CaP developed irrespective of GTC administration; P < 0.01). Moreover, GTC-sensitive TRAMP mice bearing CaP were discriminated from GTCs-resistant ones, (P = 0.0001). These results show that qPCR gene profiling, based on the signature of the 8-genes selected by us, could represent an appropriate means for studying the biological behavior of CaP, which may lead to identifying new tools of potential prognostic value, in that a molecular classification for the presence/absence of cancer and for discriminating GTCs-responsive from GTC-resistant CaP is provided.

Animals↗
PubMed2006

Potentiation of catechin gallate-mediated sensitization of Staphylococcus aureus to oxacillin by nongalloylated catechins.

(-)-Epicatechin gallate (ECg) and (-)-epigallocatechin gallate (EGCg) reduce oxacillin resistance in mecA-containing strains of Staphylococcus aureus. Their binding to staphylococcal cells is enhanced by the nongalloyl analogues (-)-epicatechin (EC) and (-)-epigallocatechin (EGC). EC and EGC significantly increased the capacity of ECg and EGCg to reduce levels of staphylococcal oxacillin resistance.

Catechin↗
PubMed2005

Tea catechins with a galloyl moiety suppress postprandial hypertriacylglycerolemia by delaying lymphatic transport of dietary fat in rats.

Tea catechins, (-)-epicatechin (EC), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECG), and (-)-epigallocatechin gallate (EGCG), have been shown to be epimerized to (-)-catechin (C), (-)-gallocatechin (GC), (-)-catechin gallate (CG), and (-)-gallocatechin gallate (GCG), respectively, during heat treatment. In this study, we examined the effect of tea catechins rich in ECG and EGCG and heat-treated tea catechins rich in CG and GCG on postprandial hypertriacylglycerolemia in rats. Both tea catechins and heat-treated tea catechins suppressed postprandial hypertriacylglycerolemia. Lymphatic recovery of (14)C-trioleoylglycerol in rats cannulated in the thoracic duct was delayed by the administration of tea catechins and heat-treated tea catechins. Tea catechins and heat-treated tea catechins had the same effect on all variables tested. These catechin preparations dose-dependently inhibited the activity of pancreatic lipase in vitro. When purified catechins were used, only those with a galloyl moiety inhibited the activity of pancreatic lipase. These results suggest that catechins with a galloyl moiety suppress postprandial hypertriacylglycerolemia by slowing down triacylglycerol absorption through the inhibition of pancreatic lipase. Because postprandial hypertriacylglycerolemia is a risk factor for coronary heart disease, our results suggest that catechins with a galloyl moiety may prevent this disease.

Animals↗
PubMed2003

Catechins induce oxidative damage to cellular and isolated DNA through the generation of reactive oxygen species.

Green tea catechins have antimutagenic and anticarcinogenic activities. On the other hand, several epidemiological studies have indicated significant positive relationship between green tea consumption and cancer. Catechins enhance colon carcinogenesis in rats initiated with chemical carcinogen. To clarify the mechanism underlying the potential carcinogenicity, we investigated the DNA-damaging ability of catechins in human cultured cells. Catechin increased the formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), a characteristic oxidative DNA lesion, in human leukemia cell line HL-60 but not in HP100, a hydrogen peroxide (H2O2)-resistant cell line derived from HL-60. The catechin-induced formation of 8-oxodG in HL-60 cells significantly decreased by bathocuproine. Furthermore, we investigated DNA damage and its site-specificity induced by catechins, using 32P-labeled DNA fragments. Catechin and epicatechin induced extensive DNA damage in the presence of Cu(II). Catechin caused piperidine-labile sites at thymine and cytosine residues in the presence of Cu(II). Catalase and bathocuproine inhibited the DNA damage, indicating the involvement of H2O2 and Cu(I). NADH enhanced catechins plus Cu(II)-induced 8-oxodG formation in calf thymus DNA, suggesting the redox cycle between catechins and their corresponding quinones, the oxidized forms of catechins. The DNA-damaging ability of epicatechin is stronger than that of catechin, possibly due to the greater turnover frequency of the redox cycle. The difference in their redox properties could be explained by their redox potentials estimated form an ab initio molecular orbital calculation. The present study demonstrated that catechins could induce metal-dependent H2O2 generation during the redox reactions and subsequently damage to cellular and isolated DNA. Therefore, it is reasonably considered that green tea catechins may have the dual function of anticarcinogenic and carcinogenic potentials.

Animals↗