Pure Catechin Research Articles

Insights into Catechin-Copper Complex Structure and Biologic Activity Modulation.

Compounds of natural origin found in varying quantities in plant-based products constitute a highly significant category, possessing structural significance as well as the capacity to regulate oxidative processes. The activity of these compounds may be modulated by the composition of the biological environment in which they operate, the pH of the environment, or the presence of metal cations in plants or plant extracts. A successful complexation reaction was mainly confirmed by FT-IR, observing the shift from the original transmittance of catechin bonds, especially O-H ones. This work shows the synthetic methodology and the optimization process that took place to synthesize a catechin-copper complex, which demonstrated antioxidant activity. It was tested for iron chelation ability, hydroxyl radicals, and the inhibition of lipoxygenase (15-LOX). An antidiabetic assay was performed by determining the inhibition of alpha-amylase and alpha-glucosidase, finding that the synthesized complex had similar inhibitory potential as pure catechin. The antibacterial tests showed results against Staphylococcus aureus and the antifungal properties of the complex against Candida albicans.

A novel optimized eco-friendly simple spectrofluorimetric method for the determination of total catechins in green tea extract: Application to commercial tablet.

Green tea extract (GTE) contains antioxidants that are present in green tea. The active constituents of green tea extract are catechins. This study demonstrates a spectrofluorimetric method for measuring GTE's catechin concentration based on its native fluorescence. To design a quick, sensitive, and ecological spectrofluorimetric approach, all features were investigated and adjusted. This method relies on determining the GTE ethanolic solution's native fluorescence at 312 nm after excitation at 227 nm. The calibration graph displayed a linear regression for values between 0.05 and 1.0μg mL-1. The detection and quantification limits of the proposed technique were 0.008 and 0.026 μg mL-1, respectively. Two pure catechins present in GTE, (-)-epicatechin and (-)-epigallocatechin gallate, were examined by the proposed method. The analytical estimation of GTE in the pharmaceutical tablet was achieved effectively using this approach. An adequate degree of agreement was found when the findings were compared to those obtained by the comparative technique. Therefore, the novel strategy may be used in the GTE quality control study with minimal risks to people or the environment. The quantum yields of catechins were estimated. The validated technique was accepted by the International Council of Harmonization criteria.

Determination of Catechin Content in Green and Black Tea (Camellia sinensis L.) by UV-Vis Spectrophotometric Method

Tea is one of the most commonly consumed beverages around the world. The chemical compounds contained in tea have a good effect on health because they contain polyphenolic compounds, catechins. This study examined the catechin compound content of black tea and green tea from Karanganyar (A) and Malang (B). This research aims to determine the differences in catechin levels in black and green tea types in Malang, East Java, and Karanganyar, Central Java plantations. The research method used was experimental. Identification of catechin content was done using UV-Vis Spectrophotometry method. Tea is extracted by brewing, 4 grams of green tea is brewed using distilled water for 6 minutes, while 5.6 grams of black tea is brewed using distilled water for 10 minutes with the comparison used is pure catechin solution. The results obtained for green tea Karanganyar (A) had a catechin content of 3.61±0.083%, green tea Malang (B) had a level of 2.97±0.037%, black tea Karanganyar (A) had a level of 3.14±0.065%, and black tea Malang (B) had a level of 1.60±0.009%. It is concluded that the catechin content of green tea is higher than black tea, and of the two samples, the high catechin content comes from Karanganyar (A). Keywords: catechins, green tea, black tea, malang, karanganyar

Factorial design-assisted spectrophotometric methods for the determination of total catechins in green tea extract via reaction with MBTH. Application to commercial tablet

Green tea extract (GTE) is a supplement derived from the green tea plant which aids in weight loss along with other innumerable health. New analytical methods for determining GTE via its catechins using a design-assisted spectrophotometric methodologies are provided. The procedures are based on the formation of orange-colored products that are detectable at 473 or 455 nm, respectively, when catechins react with MBTH in the presence of FeCl3 (method I) or K2S2O8 (method II). Critical parameters were optimized using design of experiments (DOE). The absorbance-concentration plots were rectilinear over the ranges 4.0–20.0 or 4.0–40.0 µg cm−3 with limits of detection 0.393 or 0.493 µg cm−3 for methods I & II, respectively. Our methods were applied to pure catechins in GTE, namely (-)-epicatechin and (-)-epigallocatechin gallate. Moreover, the proposed methods were perfectly applied to the analysis of GTE in a commercial tablet. Good agreement between the collected data and those of the reported approach demonstrating that there were no significant variations. According to International Council for Harmonization (ICH) Guidelines, the procedures were validated.Graphical abstract

Vacuum-assisted biosorption for developing combined delivery formulations of live probiotics and plant-phenolic compounds and their in-vitro evaluation

This study focused on developing novel compositions for the simultaneous delivery of probiotics and phenolic bioactives. These novel compositions were generated by biosorption of phenolic-rich plant extracts produced using jabuticaba peel, guaraná seed, and pure catechin in three probiotic strains using vacuum-assisted and passive incubations. Vacuum-assisted biosorption using jabuticaba peel in 25% of ethanol solution (JP25%) provided the maximum loading of phenolic compounds (PC), around 9 mg Gallic Acid Equivalent (GAE)/g of cells in less than 5 min without significantly influencing probiotic cell viability. In contrast, the total phenolic content of probiotic cells loaded with guaraná seed extract (GSE) and catechin solution ranged between 3.5 and 5 mg GAE/g of cells. The PC content of probiotic cells using vacuum-assisted biosorption was around 2–4 fold higher than that obtained via passive biosorption for 24 h. The biosorption of PCs in probiotic cells was also confirmed by multiphoton microscopy. The viability of freeze-dried cells at 25 °C up to 30 days loaded with plant extracts by vacuum assisted biosorption was 1–2 log CFU/g higher than cells passively loaded with plant extracts. Furthermore, PC release from Lacticaseibacillus cells ranged between 55% and 75% of biosorbed PCs during simulated gastrointestinal digestions. Overall, this study illustrates a novel approach to formulate combination of probiotics and PCs and their potential to deliver viable probiotics and bioactive PCs.

Green Tea Catechin Potentiating Doxorubicine Effects against BE(2)C Neuroblastoma Cells In Vitro

Background: Neuroblastoma (NB), a malignant sympathetic nervous system cancer, is the second most common type of pediatric tumor. Increasing the number of NB death emerges to design a new strategy for NB treatment. Nowadays, the development of natural compounds has gradually increased due to their ability to apoptosis induction. Tea catechin, a flavonoid compound, is one of the natural combinations which inhibit tumor growth and enhance tumor cell apoptosis. In the current study, the effects of pure catechin, doxorubicin (DOX), and their combination on a cellular model of NB [BE(2)C cells] are perused. (NB) a malignant sympathetic nervous system cancer is the second most common type of pediatric tumor. Increasing the number of NB death emerges to design a new strategy for NB treatment. Nowadays, the development of natural compounds has gradually increased due to their ability to apoptosis induction. Tea catechin, a flavonoid compound, is one of the natural combinations which inhibit tumor growth and enhance tumor cell apoptosis. Objectives: In the current study, the effects of pure catechin, doxorubicin (DOX), and their combination on a cellular model of NB [BE(2)C cells] are perused. Methods: The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay was done to assess a response dose for each drug. Fluorescent Microscopic and cell cycle analyses were performed for apoptosis detection. Finally, Colony formation was performed to examine cell migration and invasion. Results: The MTT assay showed that catechin and DOX treatment inhibited the viability of the cells while the combination of their ineffective doses had more cytotoxic effects. However, these treatments could not inhibit the cell growth of the normal human fibroblast. Moreover, this combination reduced cell attachment, chromatin fragmentation, and G/S arrest in the cell cycle. The clonogenic assay demonstrated that colony size and numbers obviously reduced after ten days; therefore, Catchin and its combination with DOX suppressed cell capacities of clone formation and migration. Conclusions: These results suggest that catechin, DOX, and their combination may inhibit the proliferation, invasion, and migration of BE(2)C Neuroblastoma cells in vitro while inducing cell apoptosis by arresting the cell cycle.

Application of green tea extract and catechin on the polyphenolic and volatile composition of Monastrell red wines

SummaryThe present work studies the effect of adding catechin and plant extract rich in catechin, Camellia sinensis (green tea) extract, on the volatile and polyphenolic composition of red wines made from Monastrell grapes. The aim of this research is to study the way to increase the red wine quality made with Monastrell variety of grapes. In one of them, the green tea extract was applied to grapes in vineyards 10 days before harvest. In another, catechin was applied to vineyards in the same way, and finally, catechin was applied during grape processing. Each trial was fermented by traditional vinification and prefermentative maceration for 5 days prior to alcoholic fermentation. A simple ANOVA analysis was used to evaluate if the application of copigments and winemaking techniques influenced wine composition. In addition, a multifactorial ANOVA was used to study the copigment treatment effect x winemaking technique interaction. Wine polyphenolic and volatile composition were analysed 12 months after fermentation. The application of green tea extract and catechin to vineyards increased (13%–16%) the concentration of anthocyanins in relation to the control to a greater extent when the initial polyphenolic concentration of grapes was lower. The volatile concentration rose when copigments (green tea extract and pure catechin) were applied to vineyards, in particular, hexyl acetate, ethyl octanoate and vanillin. The application of techniques like prefermentative maceration enhances the effects of copigments added to vineyards. The combination of the application of green extract or pure catechin with prefermentative cold maceration, had positive effects increasing polyphenols and volatile compounds concentration.

Antioxidant potential of biotransformed green tea catechin metabolites and their impact on peripheral blood mononuclear cells

ObjectiveCatechin absorption, bioavailability, and distribution in human tissue and excretion were low. Colonic bacteria degrade catechin and few studies suggest that biotransformed metabolites may increase or decrease biological activities. However, the antioxidant potential of biotransformed metabolites is still unexplored. Hence, it is necessary to investigate the antioxidant potential of colonic bacterial transformed catechin metabolites. MethodsThe In vitro antioxidant potential of biotransformed catechin metabolites was assessed by DPPH, Hydrogen peroxide, and ABTS assay. Cytotoxic effect of biotransformed catechin metabolites on human mesenchymal stem cells and their response to antioxidant genes GPX1 and POR expression in human peripheral blood mononuclear cells (PBMC) were evaluated. ResultsFree radical scavenging activity of partially purified bacterial transformed catechin metabolites was low compared to pure catechin. The results revealed that variations in the antioxidant potential of pure catechin and colonic bacterial altered catechin metabolites. The IC50 value of partially purified biotransformed catechin metabolites exhibits free radical scavenging activity at high concentrations, while pure catechins act as a potent inhibitor at lower concentrations. The expression of GPX1 and POR gene increased four folds in a concentration dependent manner in pure catechin-treated cells. In contrast, partially purified biotransformed catechin metabolites treated cells expressed the downregulation of GPX1 and upregulation of POR gene. ConclusionTherefore, it can be concluded that the functional group alteration in biotransformed catechin metabolites may reduce the hydrogen donating ability, thus In vitro antioxidant potential of biotransformed catechin metabolites was low compared to pure catechin. Hence, GPX1 and POR exhibit different expression patterns in treated peripheral blood mononuclear cells. These findings suggest that pure catechin and colonic bacterial transformed catechin metabolites differed functionally.

Development and characterization of catechin-in-cyclodextrin-in-phospholipid liposome to eradicate MRSA-mediated surgical site infection: Investigation of their anti-infective efficacy through in vitro and in vivo studies

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the prime pathogens responsible for surgical site infection (SSI). Treatment of SSI remains challenging because of resistant nature of MRSA, which is a major threat in recent years. Our previous work revealed the antibacterial potential of catechin isolated from cashewnut shell against MRSA. However, the application of catechin to treat MRSA-mediated SSI is hampered because of its poor solubility and low trans-dermal delivery. Hence, the present study focused on developing catechin-in-cyclodextrin-in-phospholipid liposome (CCPL) and evaluating its physicochemical characteristics and anti-infective efficacy through in vitro and in vivo models. Encapsulation of catechin with β-cyclodextrin and soybean lecithin was confirmed through UV–Vis spectroscopy, FTIR, and XRD techniques, while TEM imaging revealed the size of CCPL (206 nm). The CCPL displayed a higher level of water solubility (25.13%) and in vitro permeability (42.14%) compared to pure catechin. A higher level of encapsulation efficiency (98.9%) and antibacterial activity (19.8 mm of ZOI and 31.25 μg/mL of MIC) were noted in CCPL compared to the catechin/cyclodextrin complex. CCPL recorded significant and dose-dependent healing of the incision, significant reduction of bacterial count, improved epithelization, and effective prevention of inflammation in skin samples of SSI-induced Balb/c mice. Data of the present work suggest that the CCPL could be considered as a novel and potential candidate to mitigate MRSA-mediated SSI after clinical trials.

Catechin Extracted from Uncaria gambier Roxb for Nanocatechin Production: Physical and Chemical Properties

This research reports nanoparticles or nanocatechin produced from catechin extracted from gambier and the differences between the properties of the extracted catechin and nanocatechin. The study began with the preparation of >95% pure catechin through successive extraction. The catechin obtained was converted to nanocatechin with a high-speed homogenizer on a 1% suspension of catechin in water at 12,000 rpm for 30, 45, 60, 75 or 90 minutes. Results showed average diameters of the nanocatechin 90-minute homogenized colloids were then dried with a spray dryer so physical and chemical properties could be compared with those of the raw extracted catechin. Catechin content, water content, pH, refractive index, density, molecular weight and rotational angle were unaltered. Appearance, solubility, thermal properties, highest absorbance wavelength and antioxidant activity were measured. Initial degradation temperature and antioxidant activity of nanocatechin were higher than those in the originally extracted catechin.

Production Mechanisms of Black Tea Polyphenols.

Black tea accounts for 70-80% of world tea production, and the polyphenols therein are produced by enzymatic oxidation of four tea catechins during tea fermentation. However, only limited groups of dimeric oxidation products, such as theaflavins, theasinensins, and theacitrins, have been isolated from black tea and chemically characterized. This is largely because of the complexity and heterogeneity of the oxidation products. To determine structures and production mechanisms of uncharacterized black tea polyphenols, in vitro model fermentation experiments using pure catechins and polyphenol oxidase have been applied, and basic oxidation mechanisms have been established. Contemporary methods, such as LC-MS, are also effective to identify catechin oxidation products in black tea. Despite ongoing efforts, almost 60% of the solids in black tea infusion remain uncharacterized. These compounds include the so-called thearubigins, which are a heterogeneous mixture of uncharacterized catechin oxidation products with oligomeric structures. This review summarizes the current knowledge of the production mechanisms of representative black tea polyphenols and presents recent progress in characterization of thearubigins.

Encapsulation of grape seed phenolics from winemaking byproducts in hydrogel microbeads – Impact of food matrix and processing on the inhibitory activity towards α-glucosidase

Hydrogel-based encapsulation systems were developed for grape seed phenolics recovered from winemaking byproducts. Proanthocyanidins, monomeric flavanols, flavonols and anthocyanins were extracted from grape seeds with 60% ethanol. Encapsulation of solubilized grape seed phenolics in microbeads with alginate-Ca++ or alginate-chitosan-Ca++ achieved efficiency of 78 and 92%, respectively, higher than those of pure catechin and proanthocyanidins.Encapsulated phenolics showed inhibitory activity towards the brush border enzyme α-glucosidase, which was chosen as a model bioactivity assay. Grape seed phenolics were retained in the hydrogel structure after mixing of the microbeads with bovine milk or rice drink, pasteurization of these beverages to achieve 7 decimal reductions of Mycobacterium avium subsp. paratubercolosis (equivalent to 72 °C for 91 s) as well as after intense heat treatment of the rice beverage to achieve 7 decimal reductions of Bacillus cereus (95 °C for 20 min).

Cocoa powder and catechins as natural mediators to modify carbon-black based screen-printed electrodes. Application to free and total glutathione detection in blood

In this work, for the first time, the direct usability of natural products, catechins (CT) and cocoa powder (CO), as electrochemical mediators able to modify a carbon black modified screen-printed electrode (SPE-CB) is proved, and, as proof of applicability, free (GSH) and total glutathione (GSH + GSSG) in blood samples is successfully determined. Noteworthy, the cocoa powder (naturally rich in catechins), dissolved in DMSO, was able to give rise to a useful highly redox-active catechol-quinone surface-confined system onto a carbon black nanoparticles modified screen-printed electrode (SPE-CB-CO – Cocoatrode), giving rise to a similar behaviour obtained with pure catechins (SPE-CB-CT). The electrodeposition process has been carefully studied, the resulting immobilized natural mediator (obtained using both CT and CO) features investigated, and the performance of the resulting sensors (SPE-CB-CT and Cocoatrode) tested and compared. Both modified electrodes (SPE-CB-CT and Cocoatrode) have a good inter-electrodes precision (RSD ip,a ≤ 4.2%, n = 3) and intra-electrodes repeatability (RSD ip,a ≤ 3.9%, n = 20), indicating a robust and stable ‘fabrication’ strategy. Finally, SPE-CB-CT and Cocoatrode have been employed for the detection of free (GSH) and total (GSH+GSSG) glutathione in blood samples, using differential pulse voltammetry decrease in the mediator's reduction peak (Δi %), as analytical signal. Analytical curves (R2 ≥ 0.998), for the GSH detection, have been determined both with SPE-CB-CT and Cocoatrode in the 2.5 × 10−8-6.0 × 10−5 M and 5.0 × 10−8-1.0 × 10−4 M concentration ranges, respectively. Limits of detections (LODs) were ≤2.6 × 10−8 M. GSH (free and total) determined in blood samples, by the proposed CT and CO sensors, showed a good intra-electrode repeatability (RSD ip,a ≤ 9.0%, n = 3), with good recoveries (from 88.3% to 117.7%). The values obtained were in agreement with a classical spectrophotometric method (GSH and GSSG concentration relative error between −4.7 and +9.8%). The SPE-CB-CT and the Cocoatrode platforms demonstrated high potentiality in sensing and biosensing scenario, opening new gates to the natural/food products employment as unconventional, eco-friendly and economically affordable analytical active tools.

Influence of time-based hot air-drying method on total polyphenols, total antioxidants and tannins of Jatropha zeyheri tea leaves

Phenols in tea are responsible for its antioxidant activity. The pure catechins and phenolic acids found in tea are more powerful than the antioxidant vitamins C, E and ?carotene in an in vitro lipoprotein oxidation model. The antioxidant properties have been shown to have a protective effect against several degenerative diseases. The objective of this study was to investigate effect of time-based hot air-drying method on tea phenolic compounds. Fully developed green leaves of Jatropha zeyheri were sampled randomly at Zebediela (Khureng village in Limpopo Province, South Africa). Khureng village is characterized by semi-arid climate, with rainfall of less than 400 mm per annum. The area is predominately clay with bushveld vegetation. Samples were transported to Limpopo Agro-Food Technology Station (LATS) laboratory for analysis. Four treatments, namely, 0, 24, 48 and 72 h, were arranged in completely randomized design (CRD), replicated five times. Total phenolic, total antioxidant capacity and tannin content were determined using Folin-Ciocalteu, phosphate-molybdate and Vanillin-HCl method, respectively. Total phenolic, total antioxidant capacity and tannin content were significantly increased by 63, 82 and 152%, respectively, when subjected to different drying periods.

Monitoring the antioxidant effects of catechin using single-walled carbon nanotubes: Comparative analysis by near-infrared absorption and near-infrared photoluminescence

We measured the optical responses of single-walled carbon nanotubes (SWNTs) after adding Japanese green tea or catechin. SWNTs were covered with DNA in aqueous solution, and tea or catechin solution was added to the DNA–SWNT suspension. The antioxidant effects of tea and catechin were detected as changes in the near-infrared (NIR) absorption (ABS) and NIR-photoluminescence (PL) spectra of the SWNTs. Commercial Japanese tea, diluted 100 times and containing 15μg/mL catechin, was sufficient for recovering NIR-ABS and NIR-PL spectra when the DNA–SWNT suspension was pre-treated with 0.03% hydrogen peroxide(H2O2). Similar results were obtained with 15μg/mL of pure catechin solution. SWNTs with specific chirality were sensitive to the NIR-ABS and NIR-PL changes. The (10, 5)/(8, 7) and (9, 4) SWNTs showed the highest recovery in NIR-ABS and NIR-PL, respectively. NIR-PL recovery was higher than that of NIR-ABS for (10, 5)/(8, 7) and (9, 4). Spectral changes could be monitored thoroughly at pH 8.0, contrary to pH 6.0 and 7.3. However, the most dynamic recovery of NIR-ABS and NIR-PL was observed at pH 6.0. Furthermore, time-lapse measurements revealed that recovery was faster with tea or catechin addition than H2O2-induced oxidation.

Goitrogenic and Antithyroid Potential of Green Tea of Indian Origin

Polyphenolic flavonoids, specially catechins are major constituents of tea. Antithyroidal and goitrogenic effect of flavonoids have been reported however such effects of green tea on thyroid physiology has not been explored earlier. Green tea is derived from the tea leaves of Camellia sinensis and widely consumed globally. The green tea extracts(GTE) at different concentrations (1.25g% a” 5 cups of tea/ day; 2.5g% a” 10 cups of tea/ day and 5.0g% a” 20 cups of tea/ day) were orally fed to male rats for 30 days. Similarly, pure catechin was administered orally to male albino rats for 30 days at doses of 25, 50 and 100 mg/kg body weight that are equivalent to above doses of green tea extract in terms of its total catechin content and the morphological and functional changes of the thyroid have been investigated. The overall results reveal that oral administration of green tea extract at 2.5g% and 5.0g% concentrations for 30 days changed the morphology and histology resembling hypertrophy of thyroid follicles with differential colloid sizes as found in hypothyroid due to environment influences associated with significant inhibited activities of thyroid peroxidase(TPO) and 5’ monodeiodinase (5’ DI1) with elevated Na+,K+ ATPase and concomitant decrease in serum thyroxine (T4), triiodothyronine (T3) and increase in serum thyrotropin (TSH) levels developing a state of absolute biochemical hypothyroidism. All these suggest that catechin present in green tea has the antithyroidal as well as goitrogenic potential and its regular consumption at relatively high doses pose a threat to the functioning of thyroid. DOI: http://dx.doi.org/10.3329/jbsp.v9i2.22807 Bangladesh Soc Physiol. 2014, December; 9(2): 105-116

Assessment of white grape pomace from winemaking as source of bioactive compounds, and its antiproliferative activity

The antiproliferative effects of a purified white grape pomace extract (PWGPE), as well as of some phenolic standards on colon cancer cells were examined. The phenolic composition of the PWGPE was determined by rapid resolution liquid chromatography/mass spectrometry (RRLC/MS). The PWGPE had 92.6, 43.3 and 6.01mg/g of flavanols, flavonols and phenolic acids, respectively and, along with pure catechin, epicatechin, quercetin and gallic acid, they were all found capable of inhibiting cellular proliferation. PWGPE (100μg/ml) inhibited the proliferation of cells by 52.1% at 48h, whilst catechin, epicatechin, quercetin and gallic acid (60μg/ml) inhibited growth by 65.2%, 62.2%, 81.0% and 71.0%, respectively, at 72h. The PWGPE is an interesting source of phenolic compounds with antiproliferative properties, that could be of interest in the food and pharmaceutical industries.

Investigation of the interaction between soluble antioxidants in green tea and insoluble dietary fiber bound antioxidants

This work investigates the possibility of interaction between insoluble dietary fiber bound antioxidants, specifically of wheat bran, and soluble antioxidants like those provide by aqueous infusions of green tea. Solutions of pure catechins were also assayed for comparison with those naturally found in tea. To accomplish this, the aqueous and alcohol soluble fractions as well as the lipid components of wheat bran were firstly removed and the freeze-dried insoluble residue was then treated with different concentrations of green tea infusions or aqueous solutions of epicatechin (EC) and epigallocatechin-3-gallate (EGCG) for certain time. Treatment with EC (0–200μM) had no significant effect on the antioxidant capacity of insoluble bran fraction. However, treatment with EGCG significantly (p<0.05) increased linearly the antioxidant capacity as a function of concentration (0–100μM). Treatment with great tea infusions (1–3g/100ml) also increased the resulting antioxidant capacity of insoluble bran fraction, but the effect was lesser at higher infusion concentrations. Liquid chromatography couple to mass spectrometry (LC–MS) analyses of aqueous phases after treatment indicated comparable levels of decrease in the concentrations of catechins confirming their reaction with the radical forms of antioxidants bound to insoluble bran matrix.

Antioxidant/Prooxidant and antibacterial/probacterial effects of a grape seed extract in complex with lipoxygenase.

In an attempt to determine the antioxidant/prooxidant, antibacterial/probacterial action of flavan-3-ols and procyanidins from grape seeds, pure catechin (CS), and an aqueous grape seed extract (PE), were applied in the absence and presence of pure lipoxygenase (LS) or in extract (LE) to leucocyte culture, Escherichia coli B 41 and Brevibacterium linens, and observed whether there was any effect on lipid peroxidation, cytotoxicity, or growth rate. Short time periods of coincubation of cells with the polyphenols, followed by the exposure to LS and LE, revealed a high level of lipid peroxidation and a prooxidative effect. Longer coincubation and addition of LS and LE resulted in the reversal of the prooxidant action either to antioxidant activity for CS + LS and PE + LS or to the control level for CS + LE and PE + LE. Lipid peroxidation was significantly reduced when cells were exposed to polyphenols over a longer period. Longer exposure of E. coli to CS or PE followed by addition of LS for 3 h resulted in bactericidal activity. Significant stimulatory effect on microbial growth was observed for PE + LS and PE + LE treatments in B. linens, illustrating the potential probacterial activity in B. linens cultures. Lipoxygenase-polyphenols complex formation was found to be responsible for the observed effects.

Catechin induced modulation in the activities of thyroid hormone synthesizing enzymes leading to hypothyroidism

Catechins, the flavonoids found in abundance in green tea, have many beneficial health effects such as antioxidative, anticarcinogenic, anti-inflammatory, antiallergic, and hypotensive properties. However, flavonoids have antithyroid/goitrogenic effect, although less information is available about the effect of pure catechin on thyroid physiology. The present investigation has been undertaken to explore the effect of catechin administration on thyroid physiology in rat model. For the in vivo experiment catechin was injected intraperitoneally (i.p.) at doses of 10, 20 and 30 mg/kg body to male albino rats for 15 and 30 days, respectively, and thyroid activities were evaluated with respect to determination of serum levels of thyroid hormones, thyroid peroxidase, 5'-deiodinase I (5'-DI), and Na(+), K(+)-ATPase activities that are involved in the synthesis of thyroid hormone. Catechin decreased the activities of thyroid peroxidase and thyroidal 5'-deiodinase I, while Na(+), K(+)-ATPase activity significantly increased in dose-dependent manner; substantial decrease in serum T3 and T4 levels coupled with significant elevation of serum TSH were also noted. Histological examinations of the thyroid gland revealed marked hypertrophy and/or hyperplasia of the thyroid follicles with depleted colloid content. In in vitro study, short-term exposure of rat thyroid tissue to catechin at the concentrations of 0.10, 0.20, and 0.30 mg/ml leads to decrease in the activities of thyroid peroxidase and 5'-deiodinase I, while the activity of thyroidal Na(+), K(+)-ATPase remains unaltered even at high concentration of catechin treatment. The present study reinforces the concept that catechin, tea flavonoids possess potent antithyroid activity as evidenced from in vivo and in vitro studies.