Enhancement of Annexin V in response to combination of epigallocatechin gallate and quercetin as a potent arrest the cell cycle of colorectal cancer / Aumento da anexina V em resposta à combinação de galato de epigalocatequina e quercetina como uma potente parada do ciclo celular do câncer colorretal

Abstract Colorectal cancer (CRC) is one of the most common cancers leading to comorbidities and mortalities globally. The rational of current study was to evaluate the combined epigallocatechin gallate and quercetin as a potent antitumor agent as commentary agent for therapeutic protocol. The present study investigated the effect of epigallocatechin Gallate (EGCG) (150mg) and quercetin (200mg) at different proportions on proliferation and induction of apoptosis in human colon cancer cells (HCT-116). Cell growth, colonogenic, Annexin V in addition cell cycle were detected in response to phytomolecules. Data obtained showed that, the colony formation was inhibited significantly in CRC starting from the lowest concentration tested of 10 µg/mL resulting in no colonies as visualized by a phase-contrast microscope. Data showed a significant elevation in the annexin V at 100 µg/mL EGCG(25.85%) and 150 µg/mL quercetin (48.35%). Moreover, cell cycle analysis showed that this combination caused cell cycle arrest at the G1 phase at concentration of 100 µg/mL (72.7%) and 150 µg/mL (75.25%). The combined effect of epigallocatechin Gallate and quercetin exert antiproliferative activity against CRC, it is promising in alternative conventional chemotherapeutic agent.

Resumo O câncer colorretal (CCR) é um dos cânceres mais comuns, levando a comorbidades e mortalidade em todo o mundo. O racional do presente estudo foi avaliar a combinação de galato de epigalocatequina e quercetina como um agente antitumoral potente como agente de comentário para protocolo terapêutico. O presente estudo investigou o efeito de galato de epigalocatequina (EGCG) (150 mg) e quercetina (200 mg) em diferentes proporções na proliferação e indução de apoptose em células de câncer de cólon humano (HCT-116). O crescimento celular, colonogênico, anexina V, além do ciclo celular foram detectados em resposta a fitomoléculas. Os dados obtidos mostraram que a formação de colônias foi inibida significativamente no CRC a partir da concentração mais baixa testada de 10 µg/mL, resultando em nenhuma colônia conforme visualizado por um microscópio de contraste de fase. Os dados mostraram uma elevação significativa na anexina V a 100 µg/mL de EGCG (25,85%) e 150 µg/mL de quercetina (48,35%). Além disso, a análise do ciclo celular mostrou que essa combinação causou parada do ciclo celular na fase G1 na concentração de 100 µg/mL (72,7%) e 150 µg/mL (75,25%). O efeito combinado da epigalocatequina galato e quercetina exerce atividade antiproliferativa contra o CCR, é promissor como agente quimioterápico alternativo convencional.

(+)-Catechin and (-)-epigallocatechin gallate: are these promising antioxidant therapies for frozen goat semen? / (+)-Catequina e (-)-epigalocatequina galato: essas são promissoras terapias antioxidantes para a congelação de sêmen caprino?

The aim of this study was to evaluate the effects of different concentrations of (+)-catechin or (-)-epigallocatechin gallate (EGCG) on goat semen freezability. Poolsof semen were processed (Experiment 1: 0, 15, 25, 50, 75, or 100µM (+)-catechin; Experiment 2: 0, 15, 25, 50, 75, or 100µM EGCG) and frozen. After thawing, the samples were evaluated for kinematics, plasma membrane (PMi) and acrosome integrity, morphology, and oxidative stress, at 0 and 1h. In Experiment 1, at 0h, VSL and VAP were greater (P<0.05) with 15µM than with 50 and 100; WOB was lower (P<0.05) with 100µM than with 0, 15, and 25; and BCF was higher (P<0.05) with 75 and 100µM than with 0. In turn, in Experiment 2, progressive motility was higher (P<0.05) with0 and 15µM than with50 and 75; LIN was lower (P<0.05) with75 and100µM than with0 and 15; WOB was higher (P<0.05) with0 and 15µM; and PMi was greater (P<0.05) with100µM than 0. Thus, (+)-catechin or EGCG at higher concentrations inhibits the kinematics of frozen goat sperm, in a transitory way, and 100µM of EGCG preserves the PMi.(AU)

Objetivou-se avaliar o efeito de diferentes concentrações de (+)-catequina ou (-)-epigalocatequina galato (EGCG) sobre a congelabilidade do sêmen caprino. Poolsseminais foram processados (experimento 1: 0, 15, 25, 50, 75 ou 100µM de (+)-catequina; experimento 2: 0, 15, 25, 50, 75 ou 100µM de EGCG) e congelados. Após a descongelação, foram avaliadas a cinética, a integridade de membrana plasmática (iMP) e acrossomal, a morfologia e o estresse oxidativo, a zero e a uma hora. No experimento 1, a zero hora, VSL e VAP foram maiores (P<0,05) com 15µM do que com 50 e100; WOB foi menor (P<0,05) com 100µM do que com 0, 15 e 25; e BCF foi maior (P<0,05) com 75 e 100µM do que com 0. No experimento 2, a motilidade progressiva foi maior (P<0,05) com 0 e 15µM do que com 50 e 75; LIN foi menor (P<0,05) com 75 e 100µM do que com 0 e 15; WOB foi maior (P<0,05) com 0 e 15µM; e iMP foi maior (P<0,05) com 100µM do que com 0. Assim, (+)-catequina ou EGCG em altas concentrações inibem, transitoriamente, a cinética de espermatozoides congelados caprinos, e 100µM de EGCG preserva a iMP.(AU)

Active compounds and derivatives of camellia sinensis responding to erosive attacks on dentin

Abstract This research explored the potential of Camellia sinensis-derived teas and active compounds to be used as treatments to prevent dentin wear. Human root dentin slabs were randomly assigned to 5 groups (n = 10) as follows: distilled water (DW, control), epigallocatechin-3-gallate (EGCG), theaflavin gallate derivatives (TF), commercial green tea (GT), and commercial black tea (BT). The samples were submitted to a pellicle formation and an erosive cycling model (5x/day, demineralization using 0.01 M hydrochloric acid/60 s) followed by remineralization (human stimulated saliva/60 min) for three days. The samples were treated for 5 min using the test group solutions between the erosive cycles. Dentin changes were assessed with profilometry analysis and FT-Raman spectroscopy. The data regarding wear were analyzed by ANOVA followed by Tukey's test (p < 0.05). EGCG, TF derivatives, and both regular teas significantly suppressed erosive dentin loss (38-47%, p < 0.05). No obvious changes in the Raman spectra were detected in the specimens; however, the DW group had a minor relationship of 2880/2940 cm−1. The phenolic contents in both green and black tea and the important catechins appear to have protective effects on dentin loss.

Effects of epicatechin, a crosslinking agent, on human dental pulp cells cultured in collagen scaffolds

ABSTRACT Objective The purpose of this study was to investigate the biological effects of epicatechin (ECN), a crosslinking agent, on human dental pulp cells (hDPCs) cultured in collagen scaffolds. Material and Method To evaluate the effects of ECN on the proliferation of hDPCs, cell counting was performed using optical and fluorescent microscopy. Measurements of alkaline phosphatase (ALP) activity, alizarin red staining, and real-time polymerase chain reactions were performed to assess odontogenic differentiation. The compressive strength and setting time of collagen scaffolds containing ECN were measured. Differential scanning calorimetry was performed to analyze the thermal behavior of collagen in the presence of ECN. Results Epicatechin increased ALP activity, mineralized nodule formation, and the mRNA expression of dentin sialophosphoprotein (DSPP), a specific odontogenic-related marker. Furthermore, ECN upregulated the expression of DSPP in hDPCs cultured in collagen scaffolds. Epicatechin activated the extracellular signal-regulated kinase (ERK) and the treatment with an ERK inhibitor (U0126) blocked the expression of DSPP. The compressive strength was increased and the setting time was shortened in a dose-dependent manner. The number of cells cultured in the ECN-treated collagen scaffolds was significantly increased compared to the cells in the untreated control group. Conclusions Our results revealed that ECN promoted the proliferation and differentiation of hDPCs. Furthermore, the differentiation was regulated by the ERK signaling pathway. Changes in mechanical properties are related to cell fate, including proliferation and differentiation. Therefore, our study suggests the ECN treatment might be desirable for dentin-pulp complex regeneration.

Effect of (+)-catechin hydrate on oxidative stress induced by high sucrose and high fat diet in male Wistar rats.

Increased lipid peroxidation and reduced glutathione levels in liver of rats fed high sucrose high fat (HSHF) diet were normalized by concomitant administration of (+)-catechin hydrate. Plasma non-enzymatic antioxidants viz. α-tocopherol, ascorbic acid and total thiols decrease were also significantly less in rats administered with (+)-catechin hydrate concomitantly with HSHF diet. Thus the present results indicate that (+)-catechin hydrate has antioxidant activity and is effective in reducing oxidative stress. The study is of clinical importance as oxidative stress is known to be the cause of many clinical manifestations viz. cancer, Parkinson’s disease, atherosclerosis, heart failure, myocardial infarction and many other diseases.

Effect of epigallocatechin-3-gallate on inflammatory mediators release in LPS-induced Parkinson's disease in rats.

Degeneration of dopamine (DA)-containing neurons in the substantia nigra of the midbrain causes Parkinson's disease (PD). Although neuroinflammatory response of the brain has long been speculated to play a role in the pathogenesis of this neurological disorder, the mechanism is still poorly understood. The aim of the present study was to examine the effect of epigallocatechin-3-gallate (EGCG) in prevention of inflammatory mediators release and protection of dopaminergic neurons from lipopolysaccharide (LPS)-induced neurotoxicity. A single intraperitoneal injection of LPS (15 mg/kg) in male Sprague Dawley rats resulted in an increase of midbrain content of TNF-α, NO and a decrease of DA level at 4, 24 h, 3 and 7 days compared to the control. In addition, LPS reduced the number and the density of tyrosine hydroxylase-immunoreactive (TH-ir) neurons in the midbrain at 7 days. Pretreatment with EGCG (10 mg/kg) 24 h before LPS for 7 days decreased TNF-α and NO compared to LPS-treated rats. Moreover, it increased DA level and preserved the number and the density of TH-ir neurons compared to LPS group. In conclusion, EGCG was found to have a potential therapeutic effect against LPS-induced neurotoxicity via reducing TNF-α and NO inflammatory mediators and preserving DA level in midbrain.

Catechin-incorporated dental copolymers inhibit growth of Streptococcus mutans

Objective: To test the inhibitory growth activity of green tea catechin incorporated into dental resins compared to resins containing the broad-spectrum antimicrobial compound chlorhexidine against Streptococcus mutans in vitro. Material and Methods: The minimum inhibitory concentrations (MICs) of epigallocatechin-gallate (EGCg) and chlorhexidine (CHX) were determined according to the microdilution method. Resin discs (5 mm × 3 mm) were prepared from Bis-GMA/TEGDMA (R1) and Bis-GMA/CH3Bis-GMA (R2) comonomers (n=9) containing: a) no drug, b) EGCg, c) CHX. Two concentrations of each drug (0.5× MIC and 1× MIC) were incorporated into the resin discs. Samples were individually immersed in a bacterial culture and incubated for 24 h at 37°C under constant agitation. Cell viability was assessed by counting the number of colonies on replica agar plates. Statistical analysis was performed using one-way ANOVA, Tukey and Student t-tests (α=0.05). Results: Both resins containing EGCg and CHX showed a significant inhibition of bacterial growth at both concentrations tested (p<0.05). A significantly higher inhibition was observed in response to resins containing CHX at 0.5× MIC and 1× MIC, and EGCg at 1× MIC when compared to EGCg at 0.5× MIC. Also, EGCg at 0.5× MIC in R1 had a significantly higher growth inhibition than in R2. Conclusions: Both EGCg and CHX retained their antibacterial activity when incorporated into the resin matrix. EGCg at 1× MIC in R1 and R2 resins significantly reduced S. mutans survival at a level similar to CHX. The data generated from this study will provide advances in the field of bioactive dental materials with the potential of improving the lifespan of resin-based restorations.

Growth inhibition of Walker carcinosarcoma 256 with alcoholic extract of green tea leaves (Camellia sinensis) / Inibição do crescimento do carcinossarcoma 256 de Walker pelo extrato alcoólico de folhas de chá verde(Camellia sinensis)

PURPOSE: To evaluate the antitumor activity of alcoholic extracts of green tea (Camella sinensis). METHODS: Four groups of six Wistar rats were inoculated intramuscularly with 10(6) Walker tumor cells/mL. During 10 days, the animals received by gavage either 0.9% saline solution (Group I; negative control), solution containing 20 mg/Kg of tamoxifen (Group II; positive control), solution containing 0.07 g/Kg alcoholic extract of C. sinensis (Group III), or solution containing 0.14 g/Kg alcoholic extract of C. sinensis (Group IV). Following euthanasia on the tenth day, the tumor, liver, kidneys and spleen were excised and weighed, and tumor volume and tumor growth inhibition were quantified. RESULTS: The average weight of the animals was greater in Group IV than in Group II (p=0.0107). Tumor weight was smaller in Group IV than in Group I (p=0.0062), but did not differ from Group II. Tumor volume was smaller in Groups II and IV than in Group I (p=0.0131). Tumor growth inhibition was observed in Groups II (44.67% ± 32.47), III (16.83% ± 53.02) and IV (66.4% ± 25.82) (p>0.05). The groups did not differ with regard to the weight of the excised organs. CONCLUSION: Alcoholic extracts of green tea have antitumor activity.

OBJETIVO: Avaliar a atividade antitumoral do extrato alcoólico do chá verde (C. sinensis). MÉTODOS: Quatro grupos de seis ratos Wistar foram inoculados com 1x10(6) células/mL do tumor de Walker por via intramuscular. Os grupos foram tratados durante 10 dias, por gavagem, com salina 0,9 % (Grupo I, controle negativo), 20 mg/Kg de tamoxifeno (Grupo II, controle positivo) e extrato alcoólico de C. sinensis nas doses de 0,07 g/Kg (Grupo III) ou 0,14 g/Kg (Grupo IV). O volume e a inibição do crescimento tumoral foram calculados. RESULTADOS: A média dos pesos dos animais foi maior no Grupo IV do que no Grupo II (p=0,0107). O peso tumoral do Grupo IV foi menor do que o Grupo I (p=0,0062), mas não houve diferença quando comparado ao Grupo II. O volume tumoral foi menor nos grupos II e IV quando comparados ao Grupo I (p=0,0131). Inibição tumoral foi observada nos Grupos II = 44,67 ± 32,47, III = 16,83 ± 53,02 e IV = 66,4 ± 25,82 (p>0,05). Não houve diferença no peso dos órgãos entre os grupos. CONCLUSÃO: O extrato alcoólico do chá verde possui ação antitumoral.

Electron paramagnetic resonance study of lipid and protein membrane components of erythrocytes oxidized with hydrogen peroxide

Electron paramagnetic resonance (EPR) spectroscopy of spin labels was used to monitor membrane dynamic changes in erythrocytes subjected to oxidative stress with hydrogen peroxide (H2O2). The lipid spin label, 5-doxyl stearic acid, responded to dramatic reductions in membrane fluidity, which was correlated with increases in the protein content of the membrane. Membrane rigidity, associated with the binding of hemoglobin (Hb) to the erythrocyte membrane, was also indicated by a spin-labeled maleimide, 5-MSL, covalently bound to the sulfhydryl groups of membrane proteins. At 2% hematocrit, these alterations in membrane occurred at very low concentrations of H2O2 (50 µM) after only 5 min of incubation at 37°C in azide phosphate buffer, pH 7.4. Lipid peroxidation, suggested by oxidative hemolysis and malondialdehyde formation, started at 300 µM H2O2 (for incubation of 3 h), which is a concentration about six times higher than those detected with the probes. Ascorbic acid and α-tocopherol protected the membrane against lipoperoxidation, but did not prevent the binding of proteins to the erythrocyte membrane. Moreover, the antioxidant (+)-catechin, which also failed to prevent the cross-linking of cytoskeletal proteins with Hb, was very effective in protecting erythrocyte ghosts from lipid peroxidation induced by the Fenton reaction. This study also showed that EPR spectroscopy can be useful to assess the molecular dynamics of red blood cell membranes in both the lipid and protein domains and examine oxidation processes in a system that is so vulnerable to oxidation.

Té verde, fitomedicamento contra la influenza A: rol de las catequinas / Green tea, phytomedicine against influenza A: role of catechins

The highly variable Influenza A is constantly changed in new forms, like avian influenza or actual pandemic swine flu, has forced to massive use of antiviral drugs. Neuraminidase inhibitors are those with acceptable risk – efficacy profile. However, high variability of neuraminidase among different Influenza A viruses has resulted in viral resistance. Searching for new therapeutic resources, green tea (Camelia sinensis) has been reported to inhibit Influenza A virus replication, due to its catechines that bind to the active pocket endonuclease domain of viral RNA-dependent RNA polymerase. This enzyme is highly conserved among influenza A virus variants. So, a Camelia sinensis catechine standardized extract could become an anti endonuclease herbal drug.

La constante aparición de nuevas variantes de la Influenza A, como la denominada influenza aviar y la más reciente gripe porcina, de características pandémicas, ha obligado al uso masivo de fármacos antivirales. Los únicos con un perfil riesgo – eficacia aceptable son los inhibidores de la neuraminidasa. Sin embargo, la poca conservación entre la neuraminidasa de las diferentes cepas de virus Influenza A, han evidenciado resistencia viral. En la búsqueda de nuevos recursos terapéuticos, se ha reportado que el té verde (Camelia sinensis), gracias a su contenido de catequinas, puede inhibir la replicación de virus Influenza A, al unirse específicamente al bolsillo activo del dominio endonucleasa de la polimerasa de ARN dependiente de ARN viral, una enzima que posee un alto grado de conservación entre las diferentes variantes del virus de la Influenza A. Un extracto de Camelia sinensis estandarizado en catequinas podría constituirse en un fitofármaco antiendonucleasa.

Anti-inflammatory effect of the epigallocatechin gallate following spinal cord trauma in rat

Spinal cord injury [SCI] stimulates an inflammatory reaction that causes substantial secondary damage inside the injured spinal tissue. The purpose of this study was to determine the anti-inflammatory effects of epigallocatechin gallate [EGCG] on traumatized spinal cord. Methods: Rats were randomly divided into four groups of 12 rats each as follow: sham-operated group, trauma group, and EGCG-treatment groups [50 mg/kg, i.p., immediately and 1 hour after SCI]. Spinal cord samples were taken 24 hours after injury and studied for determination of myeloperoxidase [MPO] activity, histopathological assessment and immunohistochemistry of tumor necrosis factor-a [TNF-alpha], interleukin-1 beta [IL-1beta], Nitrotyrosine, inducible nitric oxide synthase [iNOS], cyclooxygenase-2 [COX-2], and poly [ADP-ribose] polymerase [PARP]. The results showed that MPO activity was significantly decreased in EGCG-treatment groups. Attenuated TNF-alpha, IL-1beta, Nitrotyrosine, iNOS, COX-2, and PARP expression could be detected in the EGCG treated rats. Also, EGCG attenuated myelin degradation. On the basis of these findings, we propose that EGCG may be effective in protecting rat spinal cord from secondary damage by modulating the inflammatory reactions

Antinociceptive effect on mice of the hydroalcoholic fraction and (-) epicatechin obtained from Combretum leprosum Mart & Eich

Previous studies on Combretum leprosum, a tree growing in the Northeastern states of Brazil, have shown antinociceptive effects of the ethanol extract of its leaves and bark, but studies examining its constituents are rare. The objective of this study was to evaluate the antinociceptive effect of the hydroalcoholic fraction (HF) of one of its constituents, the flavonoid (-) epicatechin (EPI), administered orally to mice (20-30 g) in models of chemical nociception, and the possible mechanisms involved. Different doses of HF (62.5 to 500 mg/kg) and EPI (12.5 to 50 mg/kg) were evaluated in models of abdominal writhing, glutamate, capsaicin, and formalin in animals pretreated with different antagonists: naloxone, ondansetron, yohimbine, ketanserin, pindolol, atropine, and caffeine in the abdominal writhing test. To determine the role of nitric oxide, the animals were pretreated with L-arginine (600 mg/kg, ip) in the glutamate test. The HF was effective (P < 0.05) in all protocols at different doses and EPI was effective in the abdominal writhing, capsaicin and glutamate tests (P < 0.05) at doses of 25 and 50 mg/kg. However, in the formalin test it was only effective in the second phase at a dose of 25 mg/kg. The antinociceptive effect of HF was inhibited when HF was associated with yohimbine (0.15 mg/kg), ketanserine (0.03 mg/kg), and L-arginine (600 mg/kg), but not with the other antagonists. HF and EPI were effective in models of chemical nociception, with the suggested participation of the adrenergic, serotonergic and nitrergic systems in the antinociceptive effect of HF.

Protective Effect of Catechin on Apoptosis of the Lens Epithelium in Rats with N-methyl-N-nitrosourea-induced Cataracts

PURPOSE: To investigate the effect of catechin on apoptotic cell death in the lens epithelium of rats with cataract. METHODS: Cataract was induced by intraperitoneal injection of 100 mg/kg N-methyl-N-nitrosourea (MNU) to ten day-old Sprague-Dawley rats. The neonatal rats were randomly divided into five groups (n=15 in each group): a control group, and four cataract-induction groups, treated with either 0, 50, 100, 200 mg/kg catechin. We performed slit-lamp biomicroscopic analysis, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay, Western-blot for Bcl-2 and Bax, and immunohistochemistry for caspase-3. RESULTS: Apoptotic cell death in lens epithelial cells that increased following cataract formation in rats was suppressed by cathechin. CONCLUSIONS: Catechin inhibited cataract-induced apoptotic cell death in the lens epithelium and may prove useful for the prevention of cataract progression.

Antioxidant and nitric oxide synthase activation properties of Ganoderma applanatum.

In vitro evaluation of antioxidant activities of Ganoderma applanatum showed significant inhibition of lipid peroxidation, and potent hydroxyl radical scavenging activity when compared with standard drug catechin. IC50 values of crude, boiled and ethanolic extracts of G. applanatum were 604.8, 624 and 267 microg/ml, respectively in case of hydroxyl radical scavenging activity, and 441, 520.5 and 166.16 microg/ml, respectively in case of lipid peroxidation. Furthermore, crude, boiled and ethanolic extracts also increased significantly nitric oxide production (156.67, 121.88 and 742 pmole/mg dry wt/hr, respectively) over the control. The results of present investigation revealed that G. applanatum have potential therapeutic use.

Ascorbate protects (+)-catechin from oxidation both in a pure chemical system and human plasma

We evaluated the interaction between ascorbic acid (AA) and (+)-catechin (CTCH) in potassium phosphate solution, pH 7.4 (PPS) and in human plasma. In both systems, the oxidation was started by adding 2,2'-azobis-(2-amidinopropane) clorhidrate (AAPH). The concentrations of AA and CTCH were determined by HPLC using electrochemical detection. In PPS, CTCH was oxidized by AAPH (50 mM), in either the absence or presence of different initial concentrations of AA (25-200 microM). In the presence of AA, CTCH depletion was delayed, an effect that was dependent upon the initial concentration of AA. When 100 microM AA was added after the oxidation had begun, CTCH depletion was arrested for 30 min. The kinetics of AA oxidation by AAPH was also characterized in PPS. AA (100 microM) was completely consumed after 60 min of reaction at 37 degrees C, in both the absence and presence of 100 mM CTCH. When human plasma was incubated with 50 mM AAPH in the absence of added CTCH, AA was completely consumed after 45-60 min. CTCH did not prevent AA depletion in human plasma at the concentrations tested (10, 50 100 microM). The results point out that AA is able to protect other aqueous soluble antioxidants, e.g.: CTCH.

Zinc in the prevention of Fe2+-initiated lipid and protein oxidation

In the present study we characterized the capacity of zinc to protect lipids and proteins from Fe2+-initiated oxidative damage. The effects of zinc on lipid oxidation were investigated in liposomes composed of brain phosphatidylcholine (PC) and phosphatidylserine (PS) at a molar relationship of 60:40 (PC:PS, 60:40). Lipid oxidation was evaluated as the oxidation of cis-parinaric acid or as the formation of 2-thiobarbituric acid-reactive substances (TBARS). Zinc protected liposomes from Fe2+ (2.5-50 microM)-supported lipid oxidation. However, zinc (50 microM) did not prevent the oxidative inactivation of glutamine synthetase and glucose 6-phosphate dehydrogenase when rat brain supernatants were oxidized in the presence of 5 microM Fe2+ and 0.5 mM H2O2. We also studied the interactions of zinc with epicatechin in the prevention of lipid oxidation in liposomes. The simultaneous addition of 0.5 microM epicatechin (EC) and 50 microM zinc increased the protection of liposomes from oxidation compared to that observed in the presence of zinc or EC separately. Zinc (50 microM) also protected liposomes from the stimulatory effect of aluminum on Fe2+-initiated lipid oxidation. Zinc could play an important role as an antioxidant in biological systems, replacing iron and other metals with pro-oxidant activity from binding sites and interacting with other components of the oxidant defense system.

Effect of catechin on intestinal lipid metabolism.

On analysing the effect of catechin on intestinal lipid metabolism, an increase in the concentration of cholesterol in the duodenum and jejunum was observed along with an increase in the HMGCoA reductase activity. In the in vitro experiments also it was found that cholesterol and free fatty acid (FFA) levels were increased in these two regions. Binding of catechin with cholesterol in the lumen, reduces the availability of cholesterol for absorption which may in turn stimulate cholesterol biosynthesis and a rise in the HMGCoA reductase activity. These alterations produced by catechin may also be related to the degradation of cholesterol to bile acids, as endogenous cholesterol is the preferred substrate for bile acid synthesis.

Effect of catechin on carbohydrate metabolism.

Effect of varying concentrations of catechin on blood glucose levels was examined in male rats. Catechin exerted maximum hypoglycemic action at a dose of 10 mg/kg BW/day. Above this dose, the activity decreased gradually and blood sugar returned to almost normal levels at a concentration of 100 mg/kg BW/day. At optimum dose of catechin there was increase in the hepatic glycogen levels. Incorporation of [14C] glucose into glycogen in vitro was also increased. Glycogen synthase activity was found increased significantly whereas glycogen phosphorylase showed a decrease showing that hypoglycemic effect of catechin is due to increased glycogenesis and decreased glycogenolysis.

Factors affecting longevity.

In view of the fact that hypercholesterolemia occurs in 31.4%, hypertension in 16.7% and the smoking rate is 58.8% in males (Table 8), risk factors are not low. Despite this, we Japanese preserve a leading position regarding longevity. I hope that I have provided some evidence supporting the proposal that apparently not only a low fat intake but other factors including genetic make up and a relatively high antioxidant intake contribute to our longevity.

Insulin-mimetic effect of (-) epicatechin on osmotic fragility of human erythrocytes.

(-) Epicatechin, a benzopyran extracted from the bark of Pterocarpus marsupium, is reported to have insulin like activity. The present work is undertaken to study the effect of insulin on erythrocyte osmotic fragility (OF) and then to evaluate the insulin-like role of (-) epicatechin on human erythrocytes. Insulin exerts a protective effect on erythrocyte OF and shows a dose response which is similar to other typical insulin effects i.e. a maximum at 0.1 nM and a lower effect at higher and lower concentration. (-) Epicatechin (1 mM) also shows protective effect, similar to insulin, on the OF. Ouabain (1 mM) has completely abolished the insulin effect on OF, and failed to have any effect on the action of (-) epicatechin, showing that (-) epicatechin and insulin act by a different mechanism of action while eliciting their protective effects on red cell OF.