tannins and epicatechin-gallate

Polyphenols possess antioxidant, anti-inflammatory and antimicrobial properties and have been used in the treatment of skin wounds and burns. We previously showed that tannic acid-modified AgNPs sized >26 nm promote wound healing, while tannic acid-modified AgNPs sized 13 nm can elicit strong local inflammatory response. In this study, we tested bimetallic Au@AgNPs sized 30 nm modified with selected flavonoid and non-flavonoid compounds for wound healing applications.. Bimetallic Au@AgNPs were obtained by growing an Ag layer on AuNPs and further modified with selected polyphenols. After toxicity tests and in vitro scratch assay in HaCaT cells, modified lymph node assay as well as the mouse splint wound model were further used to access the wound healing potential of selected non-toxic modifications.. Tannic acid, gallic acid, polydatin, resveratrol, catechin, epicatechin, epigallocatechin, epicatechin gallate, epigallocatechin gallate and procyanidin B2 used to modify Au@AgNPs exhibited good toxicological profiles in HaCaT cells. Au@AgNPs modified with 15 μM tannic acid, 200 μM resveratrol, 200 μM epicatechin gallate, 1000 μM gallic acid and 200 μM procyanidin B2 induced wound healing in vivo and did not lead to the local irritation or inflammation. Tannic acid-modified Au@AgNPs induced epithelial-to-mesenchymal transition (EMT) - like re-epithelialization, while other polyphenol modifications of Au@AgNPs acted through proliferation and wound closure.. Bimetallic Au@AgNPs can be used as a basis for modification with selected polyphenols for topical uses. In addition, we have demonstrated that particular polyphenols used to modify bimetallic nanoparticles may show different effects upon different stages of wound healing.

Topics: Animals; Antioxidants; Biflavonoids; Catechin; Gold; Metal Nanoparticles; Mice; Polyphenols; Proanthocyanidins; Silver; Tannins; Wound Healing

The aim of this work has been to determine the correlations between sensory analysis, colour and content of main flavanols present in seeds. For this, the flavanic composition of grape seeds with different degrees of maturity was analysed by HPLC-DAD-MS and the obtained results were correlated with CIELab colour parameters, perceived colour (C), hardness of the seed (HS), tannic intensity (TI) and astringency (A). Multiple linear regression analysis (MLR) with the variables showing significant correlations (p<0.05) was also performed. Grape seeds undergo important decreases in the content of catechins and procyanidin oligomers during ripening. Epicatechin-(4-8)-epicatechin-3-O-gallate (B2G) and (-)-epicatechin-3-O-gallate (ECG) are the flavanolic compounds whose contents decrease most. The changes in the phenolic composition accompany changes in TI, A and HS. The total content of flavanols in the seed is not the only factor affecting these attributes, since samples containing higher contents in flavanols can exhibit less astringency and tannic intensity than others with lower ones. The qualitative profile of the seeds is, therefore, also responsible for the sensations elicited in the mouth. A and HS parameters are more affected by the presence of galloylated dimeric procyanidins in the molecule than TI. CIELab colour parameters of seeds have high correlation coefficients with many flavanolic compounds. ECG was the compound most related to these parameters.

Topics: Antioxidants; Catechin; Chromatography, High Pressure Liquid; Color; Flavonoids; Grape Seed Extract; Mass Spectrometry; Proanthocyanidins; Regression Analysis; Tannins; Taste; Vitis

Collagen based cosmetic fillers require repeat treatments due to collagenase derived degradation of the filler in the intradermal injection site. The objective of this study was to investigate the inhibition of this degradation by the galloyl-containing compounds tannic acid, epigallocatechin gallate (EGCG), epicatechin gallate (ECG) and gallic acid (GA). A gel permeation chromatography assay was developed to quantitate the collagenase induced reductions in collagen molecular weight. The binding of the compounds to collagen was measured using HPLC. The stabilization of collagen was measured using Differential Scanning Calorimetry (DSC). Tannic acid, EGCG and ECG (but not GA) were found to strongly inhibit collagen degradation at concentrations in the low micromolar range. The compounds bound strongly to collagen and stabilized collagen. It is concluded that tannic acid, EGCG and ECG bind to collagen via extensive hydrogen bonding augmented by some hydrophobic interactions and prevent the free access of collagenase to active sites on the collagen chains.

Topics: Antioxidants; Catechin; Collagen; Collagenases; Extracellular Matrix; Flavonoids; Gallic Acid; Matrix Metalloproteinase Inhibitors; Phenols; Polyphenols; Tannins

Green tea catechins and hydrolyzable tannins are gaining increasing attention as chemopreventive agents. However, their mechanism of action is poorly understood. We investigated the effects of four green tea catechins and two hydrolyzable tannins on microsome-induced benzo[a]pyrene (BP)-DNA adducts and the possible structure-activity relationship. BP (1 microM) was incubated with rat liver microsomes and DNA in the presence of the test compound (1-200 microM) or vehicle. The purified DNA was analyzed by (32)P-postlabeling. The inhibitory activity of the catechins was in the following descending order: epigallocatechin gallate (IC(50) = 16 microM) > epicatechin gallate (24 microM) > epigallocatechin (146 microM) > epicatechin (462 microM), suggesting a correlation between the number of adjacent aromatic hydroxyl groups in the molecular structure and their potencies. Tannic acid (IC(50) = 4 microM) and pentagalloglucose (IC(50) = 26 microM) elicited as much DNA adduct inhibitory activity as the catechins or higher presumably due to the presence of more functional hydroxyl groups. To determine if the activity of these compounds was due to direct interaction of phenolic groups with electrophilic metabolite(s) of BP, DNA was incubated with anti-benzo[a]pyrene-7,8-diol-9,10-epoxide (anti-BPDE) (0.5 microM) in the presence of test compounds (200 microM) or vehicle. Significant inhibition of DNA adduct formation was found (tannic acid > pentagalloglucose > epigallocatechin gallate > epicatechin gallate). This notion was confirmed by analysis of the reaction products of anti-BPDE with the catechins and pentagalloglucose by electrospray ionization mass spectrometry and liquid chromatography-mass spectrometry. In conclusion, our data demonstrate that green tea catechins and the hydrolyzable tannins are highly effective in inhibiting BP-DNA adduct formation at least, in part, due to direct interaction of adjacent hydroxyl groups in their structures and that the activity is higher with an increasing number of functional hydroxyl groups.

Topics: Animals; Benzo(a)pyrene; Catechin; DNA; DNA Adducts; Hydrolyzable Tannins; Isotope Labeling; Microsomes, Liver; Rats; Structure-Activity Relationship; Tannins; Tea

The adsorption of components from black tea and of purified tea polyphenols onto a whole unstimulated salivary pellicle-like protein layer, formed in vitro on hydroxyapatite discs, was studied by in situ ellipsometry. It was found that components from black tea and the purified polyphenols epicatechin-3-gallate (ECG), epigallocatechin-3-gallate (EGCG) and theaflavin readily adsorbed onto the pellicle. Further investigations showed that under the experimental conditions of this study, no black tea- or purified polyphenol-modified pellicles were eluted by either phosphate buffer or sodium dodecyl sulphate rinses. Therefore, black tea and its polyphenol components are indicated to have a profound effect on in vitro pellicle modification. Similar effects were observed for tannic acid.

Topics: Adsorption; Adult; Antioxidants; Biflavonoids; Buffers; Catechin; Dental Pellicle; Detergents; Durapatite; Flavonoids; Humans; Male; Phenols; Polyphenols; Refractometry; Salivary Proteins and Peptides; Sodium Dodecyl Sulfate; Tannins; Tea; Urokinase-Type Plasminogen Activator

In the present study, we investigated the free radical scavenging effects of green tea extract and green tea tannin mixture and its components using a nitric oxide (NO) and superoxide (O(2)(-)) generating system in vitro. Green tea extract showed direct scavenging activity against NO and O(2)(-) and green tea tannin mixture, at the same concentration, showed high scavenging activity. Comparison of the activities of seven pure compounds isolated from green tea tannin mixture showed that (-)-epigallocatechin 3-O-gallate (EGCg), (-)-gallocatechin 3-O-gallate (GCg) and (-)-epicatechin 3-O-gallate (ECg) had higher scavenging activities than (-)-epigallocatechin (EGC), (+)-gallocatechin (GC), (-)-epicatechin (EC) and (+)-catechin (C), showing the importance of the structure of flavan-3-ol linked to gallic acid for this activity. Among the gallate-free tannins, EGC and GC were more effective O(2)(-) scavengers than EC and C, indicating the O-trihydroxy structure in the B ring is an important determinant of such activity. However, this structure did not affect the NO scavenging activity. These findings confirm that green tea tannin has excellent antioxidant properties, which may be involved in the beneficial effect of this compound.

Topics: Catechin; Dose-Response Relationship, Drug; Flavonoids; Free Radical Scavengers; In Vitro Techniques; Nitric Oxide; Oxidants; Oxidation-Reduction; Structure-Activity Relationship; Superoxides; Tannins; Tea

The most widely known health benefits of tea relate to the polyphenols as the principal active ingredients in protection against oxidative damage and in antibacterial, antiviral, anticarcinogenic, and antimutagenic activities, but polyphenols in tea may also increase insulin activity. The objective of this study was to determine the insulin-enhancing properties of tea and its components. Tea, as normally consumed, was shown to increase insulin activity >15-fold in vitro in an epididymal fat cell assay. Black, green, and oolong teas but not herbal teas, which are not teas in the traditional sense because they do not contain leaves of Camellia senensis, were all shown to increase insulin activity. High-performance liquid chromatography fractionation of tea extracts utilizing a Waters SymmetryPrep C18 column showed that the majority of the insulin-potentiating activity for green and oolong teas was due to epigallocatechin gallate. For black tea, the activity was present in several regions of the chromatogram corresponding to, in addition to epigallocatechin gallate, tannins, theaflavins, and other undefined compounds. Several known compounds found in tea were shown to enhance insulin with the greatest activity due to epigallocatechin gallate followed by epicatechin gallate, tannins, and theaflavins. Caffeine, catechin, and epicatechin displayed insignificant insulin-enhancing activities. Addition of lemon to the tea did not affect the insulin-potentiating activity. Addition of 5 g of 2% milk per cup decreased the insulin-potentiating activity one-third, and addition of 50 g of milk per cup decreased the insulin-potentiating activity approximately 90%. Nondairy creamers and soy milk also decreased the insulin-enhancing activity. These data demonstrate that tea contains in vitro insulin-enhancing activity and the predominant active ingredient is epigallocatechin gallate.

Topics: Adipocytes; Animals; Biflavonoids; Camellia sinensis; Catechin; Chemical Fractionation; Chromatography, High Pressure Liquid; Drug Synergism; Epididymis; Flavonoids; Glucose; Insulin; Male; Milk; Phenols; Plant Extracts; Polymers; Rats; Tannins; Tea

The polyphenols present in green tea or red wine comprise both regular flavon(ol)s and proanthocyanidins, i.e., derivatives of flavan-3-ols, whose distinct antioxidative potential is of great importance for explaining the beneficial effects of these nutrient beverages. Using EPR spectroscopy, we investigated radical structures obtained after oxidation of the parent compounds either by horseradish peroxidase/hydrogen peroxide or after autoxidation in moderately alkaline solutions. Both proanthocyanidins (monomers of condensed tannins, e.g., (+)-catechin, (-)-epicatechin, (-)-epicatechin gallate, (-)-epigallocatechin, (-)-epigallocatechin gallate, Pycnogenol) and gallate esters (hydrolyzable tannins, e.g., propylgallate, beta-glucogallin, pentagalloyl glucose and tannic acid) yielded predominantly semiquinone structures derived from the parent catechol or pyrogallol moieties. Evidence for a time-dependent oligomerization was obtained for (-)-epigallocatechin gallate, supporting our hypothesis that o-quinones formed from the initial semiquinone disproportionation are prone to nucleophilic addition reactions. Such phenolic coupling reactions would retain the numbers of reactive catechol/pyrogallol structures and thus the antioxidative potential. We therefore propose that proanthocyanidins are superior antioxidants as compared to flavon(ol)s proper, whose quinones are more likely to redox-cycle and act as prooxidants.

Topics: Anthocyanins; Catechin; Electron Spin Resonance Spectroscopy; Esters; Flavonoids; Free Radicals; Horseradish Peroxidase; Hydrogen Peroxide; Hydrogen-Ion Concentration; Molecular Conformation; Molecular Structure; Oxidation-Reduction; Tannins

Thiolysis of a wine tannin fraction yielded trihydroxylated flavanol units (as previously observed in grape skins) in addition to the well-known procyanidins (dihydroxylated units), usually described in the literature for grape condensed tannins. To determine how they occur in condensed tannins, the wine fraction was analyzed by liquid chromatography coupled to electrospray ionization mass spectrometry. Thus, various series of ion peaks containing a variable number of trihydroxylated units were detected as monocharged ions from dimers up to pentamers. From pentamers, oligomers were found as doubly charged ions. Heptamer species corresponded to the highest mass detected. These results showed that wine condensed tannins consist of, besides procyanidins, mixed tri- and dihydroxylated flavanol units and also of pure trihydroxylated flavanol units. These new data should be taken into account to interpret organoleptic properties of wines.

Topics: Catechin; Flavonoids; Spectrometry, Mass, Secondary Ion; Tannins; Wine

Reactivities of several proanthocyanidins (monomers of condensed tannins) and gallate esters (representing hydrolyzable tannins) with hydroxyl radicals, azide radicals, and superoxide anions were investigated using pulse radiolysis combined with kinetic spectroscopy. We determined the scavenging rate constants and the decay kinetics of the aroxyl radicals both at the wavelength of the semiquinone absorption (275 nm) and the absorption band of the gallate ester ketyl radical (400-420 nm). For most compounds second-order decay kinetics were observed, which reflect disproportionation of the semiquinones. In the case of the oligomeric hydrolysable tannins, pentagalloyl glucose and tannic acid, the decay kinetics were more complex involving sequential first-order and second-order reactions, which could only be resolved by kinetic modeling. A correlation of the reaction rates with hydroxyl radicals (k*OH) with the number of adjacent aromatic hydroxyl groups (i.e., representing catechol and/or pyrogallol structures) was obtained for both condensed and hydrolyzable tannins. Similar correlation for the reactions with azide radicals and superoxide anions are less obvious, but exist as well. We consider proanthocyanidins superior radical scavenging agents as compared with the monomeric flavonols and flavones and propose that these substances rather than the flavonoids proper represent the antioxidative principle in red wine and green tea.

Topics: Anions; Antioxidants; Azides; Catechin; Flavonoids; Flavonols; Free Radicals; Hydrolyzable Tannins; Hydroxyl Radical; Kinetics; Pulse Radiolysis; Spectrophotometry; Superoxides; Tannins

The effects of each of several tannins purified from Rhei Rhizoma on serum constituents were investigated in rats with adenine-induced renal failure. Blood levels of urea nitrogen, methylguanidine (MG), and guanidinosuccinic acid (GSA) were significantly decreased in rats given (-)-epicatechin 3-O-gallate at a dose of 2.5, 5 or 10 mg/kg body weight/day for 24 days. The creatinine (Cr) level was also significantly decreased in rats given 5 and 10 mg of this compound. A significant decrease in urea nitrogen, MG, and GSA was found in rats given 6.25 mg of procyanidin B-2 3,3'-di-O-gallate. However, unlike the former two components the administration of 12.5 mg of procyanidin C-1 3,3',3''-tri-O-gallate produced a considerable or significant increase in bLood levels of urea nitrogen, Cr, MG, and GSA. RG-tannin had a weaker overall effect on serum constituents except for GSA in comparison with the corresponding effect of (-)-epicatechin 3-O-gallate and 6.25 mg of procyanidin B-2 3,3'-di-O-gallate. Rhatannin tended to increase the serum nitrogen constituents.

Topics: Animals; Biflavonoids; Blood Urea Nitrogen; Catechin; Creatinine; Drugs, Chinese Herbal; Guanidines; Male; Methylguanidine; Plants, Medicinal; Proanthocyanidins; Rats; Rats, Inbred Strains; Rheum; Structure-Activity Relationship; Succinates; Tannins; Toxins, Biological; Uremia