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At least 451 records · Page 25Linked to original sources
PubMed2003

Solid-phase spectrophotometric determination of trace amounts of vanadium using 2,3-dichloro-6(3-carboxy-2- hydroxynaphthylazo)quinoxaline.

Solid-phase spectrophotometry (SPS) has been applied to analysis for trace amounts of vanadium in several environmental water (potable and polluted), biological samples (human blood and urine), and soil samples. Vanadium was sorbed in a styrene-divinylbenzene-type anion-exchanger Dowex 1-X8 as a vanadium--2,3-dichloro-6(3-carboxy-2-hydroxynaphthylazo)quinoxaline. Resin phase absorbances at 606 and 800 nm were measured directly which allowed the determination of vanadium in the range 0.03-2.2 ng ml(-1) with a relative standard deviation (R.S.D.) of 1.4%. The comparison of the SPS method and the gallic acid persulphate method shows that the linearity, analytical sensitivity, and precision were better for the SPS method, and that the latter method has lower detection and quantification limits compared with the gallic acid persulphate method.

Gallic Acid↗
PubMed2006

Nitric oxide radical scavenging active components from Phyllanthus emblica L.

An activity-directed fractionation and purification process was used to identify the nitric oxide (NO) scavenging components of Phyllanthus emblica. Dried fruit rind of P. emblica was extracted with methanol and then separated into hexane, ethyl acetate, and water fractions. Among these only the ethyl acetate phase showed strong NO scavenging activity in vitro, when compared with water and hexane phases. The ethyl acetate fraction was then subjected to separation and purification using Sephadex LH-20 chromatography. Five compounds showing strong NO scavenging activity were identified by spectral methods (1H NMR, 13C NMR, and MS) and by comparison with literature values to be Gallic acid, Methyl gallate, Corilagin, Furosin, and Geraniin. In addition, HPLC identification and quantification of isolated compounds were also performed. Gallic acid was found to be a major compound in the ethyl acetate extract and Geraniin showed highest NO scavenging activity among the isolated compounds.

Antioxidants↗
PubMed1997

[Application of TLC to tannin measurement].

There has been little report on the use of in measuring tannin in traditional Chinese medicinal preparations by TLC. Gallic acid, the decomposd product of tannin, was in bright yellow and green color, showing a strong specificity. The measurement of gallic acid can provide reliable indexes for quality assay of TCM preparations.

Chromatography, Thin Layer↗
PubMed2003

Can black tea influence plasma total homocysteine concentrations?

BACKGROUND: Polyphenols can act as acceptors of methyl groups during the metabolism of methionine to homocysteine. This may result in elevations in plasma total homocysteine (tHcy) concentrations after ingestion of polyphenol-rich beverages such as tea. OBJECTIVES: Our major objective was to determine whether regular, moderate-to-high intakes of black tea alter tHcy concentrations. We also assessed the relation between the degree of O-methylation of tea-derived polyphenols and the change in tHcy with regular ingestion of tea. DESIGN: Twenty-two subjects completed a randomized, controlled crossover study. Subjects consumed 1250 mL black tea/d (5 cups each containing 2 g tea leaves in 250 mL boiled water) and 1250 mL hot water/d for 4 wk each. Fasting tHcy concentrations and 24-h urinary excretion of 4-O-methylgallic acid (4OMGA, the major O-methylated metabolite of gallic acid) were measured at the end of each period. 4OMGA was used as a marker of overall O-methylation of tea-derived polyphenols. RESULTS: Black tea did not significantly alter mean (+/- SEM) tHcy concentrations (9.9 +/- 0.5 and 10.0 +/- 0.5 micro mol/L for the hot water and black tea periods, respectively). However, the increased excretion of 4OMGA as a consequence of black tea consumption was positively associated with the change in tHcy from the hot water period to the black tea period (r = 0.55, P = 0.008). Subjects in the bottom quartile of increase in 4OMGA excretion had a significant decrease in tHcy (-0.28 +/- 0.10 micro mol/L; P = 0.046), and those in the top quartile had a significant increase in tHcy (0.78 +/- 0.16 micro mol/L; P = 0.005). CONCLUSIONS: Overall, regular ingestion of black tea did not alter mean tHcy concentrations. However, individual differences in O-methylation of polyphenolic compounds may influence the ultimate effects of black tea on tHcy.

Adult↗
PubMed1993

Visual reading method for detection of bacterial tannase.

Tannase activity of bacteria capable of degrading tannin-protein complexes was determined by a newly developed visual reading method. The method is based on two phenomena: (i) the ability of tannase to hydrolyze methyl gallate to release free gallic acid and (ii) the green to brown coloration of gallic acid after prolonged exposure to oxygen in an alkaline condition. The method has been successfully used to detect the presence of tannase in the cultures of bacteria capable of degrading tannin-protein complexes.

Journal Article↗
PubMed1999

Intramolecular synergism of the inhibiting action of polydisulfide antioxidants in the system ferritin--H2O2--tetramethylbenzidine.

Polydisulfides of urea (PDSU), thiourea (PDSTU), biuret (PDSB), and gallic acid (PDSG) and their monomer analogues (urea, biuret, and gallic acid) inhibited (in a competitive manner) tetramethylbenzidine (TMB) peroxidation catalyzed by ferritin in 0.1 M acetate buffer, pH 4.2, containing 10% dimethylformamide. Their efficiency characterized in terms of inhibition constants, Ki, increased in the following order PDSU < PDSB approximately PDSTU << PDSG. This order is determined by the reactivity of monomers with respect to HO* radicals which are the main oxidizing agents in the system ferritin--H2O2. Polydisulfide antioxidants exhibit the intramolecular synergism of the inhibiting action (non-additivity of antiradical activity relative to their monomers) that was quantitatively characterized by alpha = (Ki)pol/(Ki)mon x n, where n is the number of monomers in the polymeric inhibitors. The alpha values increased from 1.5 up to 5.18 in the following order: PDSG < PDSU < PDSB. Significantly higher inhibiting efficiency of polydisulfide antioxidants as compared to monomer forms and synergism of the inhibitory action offer promising opportunities of their use as quenchers of free radical processes in biochemical systems.

Animals↗
PubMedDate not supplied

Decline of superoxide dismutase activity during antioxidant-induced apoptosis in HL-60 cells.

Possible changes in Mn-containing superoxide dismutase (MnSOD) and Cu- and Zn-containing superoxide dismutase (CuZnSOD) activity during the apoptosis of human promyelocytic leukemia HL-60 cells, induced by three antioxidants, were investigated. Agarose gel electrophoresis of the DNA isolated from cells treated with sodium ascorbate, gallic acid or epigallocatechin gallate (EGCG) showed the internucleosomal DNA fragmentation, a biochemical hallmark of apoptosis. The optimum concentration for induction of DNA fragmentation was narrow and higher concentrations were rather inhibitory. Their effects were detected after 3 hours and reached a maximum level at 6 hours. Polyacrylamide gel electrophoresis and activity staining demonstrated that both MnSOD and CuZnSOD activities were significantly reduced at cytotoxic concentrations of all these compounds. Incubation of an intracellular MnSOD-enriched fraction with apoptosis-inducing concentrations of sodium ascorbate, gallic acid or EGCG did not significantly reduce the MnSOD activity, suggesting that their actions might be cell-mediated. These data suggest the mitochondrial dysfunction at the early stages of apoptosis.

Antioxidants↗
PubMed2004

Antioxidant phenolic constituents in roots of Rheum officinale and Rubia cordifolia: structure-radical scavenging activity relationships.

The phenolic constituents in the roots of Rheum officinale and Rubia cordifolia were identified with the aid of high-performance liquid chromatography and liquid chromatography-mass spectrometry and by comparison with authentic standards. A total of 17 hydroxyanthraquinones, gallic acid, and tannins were separated, and 14 of them were identified, being the main phenolic constituents present. Their antioxidant activity (Trolox equivalent antioxidant capacity) was evaluated using the improved 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)diammonium salt method. Hydroxyanthraquinones were the predominant antioxidant phenolic constituents in the roots of R. cordifolia, and tannins and gallic acid were the predominant antioxidant phenolic constituents in the roots of R. officinale. The structure-radical scavenging activity relationships of the tested hydroxyanthraquinones were systematically demonstrated as follows: Hydroxy groups on one benzene ring of the anthraquinone structure were essential for hydroxyanthraquinones to show activity, the ortho-dihydroxy structure in the hydroxyanthraquinone molecules could greatly enhance their radical scavenging effect, and glycosylation of the hydroxyanthraquinones reduced activity.

Anthraquinones↗
PubMedDate not supplied

Combination effect of lignin F and natural products.

We investigated the effect of lignin F, isolated from the alkaline extract of the cone of Pinus parviflora Sieb. et Zucc, on the cytotoxic activity and radical intensity (measured by ESR spectroscopy) of various natural products. Lignin F slightly inhibited the proliferation of human oral tumor cell lines (human squamous cell carcinoma HSC-2, human salivary gland tumor HSG), but not that of human gingival fibroblast HGF, suggesting its tumor specific cytotoxic action. Lignin F enhanced the cytotoxic activity of vitamin K2, vitamin K3, sodium ascorbate (vitamin C), epigallocatechin gallate (EGCG) (a major component of green tea), gallic acid (structural unit of tannin), chlorogenic acid, and 6 tea extracts (Japanese green tea, Japanese barley tea, black tea, Chinese green tea, Chinese Jasmin tea, Chinese Oolong tea), to various extents. On the other hand, lignin inhibited the cytotoxic activity of curcumin and dopamine. ESR spectroscopy demonstrated that combination of lignin and vitamin K3, EGCG or gallic acid synergistically augmented the radical intensity. Lignin F enhanced the bactericidal activity of EGCG against E. coli. These data suggest the beneficial effect of the combination of lignin F and natural products.

Antineoplastic Agents, Phytogenic↗
PubMed2002

Vitamin C equivalent antioxidant capacity (VCEAC) of phenolic phytochemicals.

To express the antioxidant capacity of plant foods in a more familiar and easily understood manner (equivalent to vitamin C mg/100 g), two stable radical species, ABTS(*)(-) and DPPH(*), commonly used for antioxidant activity measurements, were employed independently to evaluate their efficacies using apple polyphenolic extracts and seven polyphenolic standards including synthetic Trolox. Their antioxidant activities were expressed as vitamin C equivalent antioxidant capacity (VCEAC) in mg/100 g apple or mg/100 mL of the reference chemical compounds in 10 and 30 min using the ABTS(*)(-) and DPPH(*) scavenging assays, respectively. The antioxidant capacity of Gala apples and seven phenolic standards, determined by both ABTS(*)(-) and DPPH(*) scavenging assays, showed a dose-response of the first-order. Fresh Gala apples had a VCEAC of 205.4 +/- 5.6 mg/100 g using the ABTS assay, and the relative VCEACs of phenolic standards were as follows: gallic acid > quercetin > epicatechin > catechin > vitamin C > rutin > chlorogenic acid > Trolox. With the DPPH radical assay, the VCEAC of fresh Gala apples was 136.0 +/- 6.6 mg/100 g, and the relative VCEACs of seven phenolic standards were, in decreasing order, as follows: gallic acid > quercetin > epicatechin > catechin > or = vitamin C > Trolox > rutin > chlorogenic acid. Because the ABTS assay can be used in both organic and aqueous solvent systems, employs a specific absorbance at a wavelength remote from the visible region, and requires a short reaction time, it is a more desirable method than the DPPH assay. Therefore, it is recommended that antioxidant capacity be expressed as vitamin C mg/100 g equivalent (VCEAC) using the ABTS assay.

Antioxidants↗
PubMed1975

[V. The phenolics of strawberries and their changes during development and ripeness of the fruits (author's transl)].

16 strawberry varieties contained ca. 10--70 mg (+)-catechin per kg freshweight, frequently up to 10 mg (-)-epicatechin, seldom (+)-gallocatechin and never (-)-epigallocatechin. The phenolic contents after hydrolysis were up to ca. 10 mg caffeic acid, ca. 10--15 mg p-coumaric acid, ca. 10--35 mg 4-hydroxybenzoic acid, up to 6 mg protocatechuic acid and ca. 10--40 mg gallic acid per 1000 g freshweight. From "Senga Sengana" ca. 10 mg/kg methyl gallate and ellagic acid were isolated. Salicylic acid, gentisic acid and vanillic acid were found in traces (1 mg/kg). The concentrations of all the examined phenolic acids, relating to the whole fruit (mg per fruit) increased, and, relating to fresh weight (mg per kg) decreased during the growth of the fruits with exception of 4-hydroxybenzoic acid. This acid appeared only in a relatively late stage of the fruit. The changes in catechins were similar. In the ripe fruit the catechin level was reduced a little.

Benzopyrans↗
PubMed2003

[Studies on the chemical constituents of Chinese herb Melastoma dodecandrum].

OBJECTIVE: To investigate the chemical constituents of Chinese herb Melastoma dodecandrum. METHOD: The chemical constituents were isolated by solvent extraction and chromatography. Their structure were identified on the basis of physic-chemical constants and specral data. RESULT: Five compounds were isolated and identified as hexacosanoic acid (I), quercetin(II), avicularin(III), gallic acid (IV), kaempferol(V). CONCLUSION: The above-mentioned compounds were separated from the plant for the first time.

Fatty Acids↗
PubMed2000

Study of interactions between food phenolics and aromatic flavors using one- and two-dimensional (1)H NMR spectroscopy.

Changes in flavor release and aroma characteristics in a medium including food phenolics may be attributed to an intermolecular interaction between flavor compounds and phenolics. To investigate the interaction, one- and two-dimensional NMR studies have been carried out on the binding of two phenolics, gallic acid and naringin, with three aroma compounds, 2-methylpyrazine, vanillin, and ethyl benzoate. Evaluation of thermodynamic parameters and intermolecular nuclear Overhauser effects reveals that gallic acid can interact more strongly with aromatic flavors than naringin. The supramolecular complexation is also dependent on the structural nature of the flavors, with 2-methylpyrazine and vanillin interacting more strongly than ethyl benzoate. The interaction is principally pi-pi stacking between the galloyl ring and the aromatic ring of the aroma compounds, but secondary hydrogen-bonding effects help to stabilize the complex and enhance the specificity.

Benzaldehydes↗
PubMed1997

13C-CP-MAS-NMR studies of flavonoids. I. Solid-state conformation of quercetin, quercetin 5'-sulphonic acid and some simple polyphenols.

13C-CP-MAS-NMR spectra were measured in order to characterise the orientation of hydroxyl groups of quercetin, quercetin-5'-sulphonic acid and polyphenol-type compounds such as catechol, pyrogallol and gallic acid. The locked conformation of the OH group in the solid results in an increased shielding of carbon proxime to C-OH hydrogen. Carbon shieldings suggest that there is orientational disorder of three OH groups of pyrogallol and gallic acid and that two OH groups of catechol are not equivalent. In solid quercetin and quercetin-5'-sulphonic acid the C7-OH points towards C6-H and the C3'-OH hydrogen is near C2'-H.

Carbon Isotopes↗
PubMed2005

Effects of alkyl gallates on P-glycoprotein function.

In this study, we examined the effects of the food antioxidants, alkyl gallates, on the function of P-glycoprotein (P-gp) and elucidated the importance of alkyl chains and gallic acid moieties on the activity of P-gp. We examined the effects of three alkyl (n-butyl, n-octyl and n-dodecyl) gallates and their related compounds on the cellular accumulation and efflux of rhodamine 123 and daunorubicin in P-gp overexpressing KB-C2 cells. Alkyl gallates increased the cellular accumulation of these P-gp substrates dependent on their alkyl chain lengths by inhibiting the efflux of the substrates. n-Dodecylresorcinol also increased the accumulation, but its effect was less than that of n-dodecyl gallate. However, either lauric acid or n-dodecyl-beta-d-maltoside, which does not have a phenol group, did not increase the accumulation. The results indicated that both the gallic acid moiety and a long alkyl chain play important roles in the modification of P-gp function. The cytotoxicity of daunorubicin was recovered in the presence of alkyl gallates possibly due to their inhibition of P-gp function.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2000

Molecular design of antibrowning agents.

Tyrosinase inhibitory and antioxidant activity of gallic acid and its series of alkyl chain esters were investigated. All inhibited the oxidation of L-3,4-dihydroxyphenylalanine (L-DOPA) catalyzed by mushroom tyrosinase. However, gallic acid and its short alkyl chain esters were oxidized as substrates yielding the colored oxidation products. In contrast, the long alkyl chain esters inhibited the enzyme activity without being oxidized. This indicates that the carbon chain length is associated with their tyrosinase inhibitory activity, presumably by interacting with the hydrophobic protein pocket in the enzyme. On the other hand, the esters, regardless their carbon chain length, showed potent scavenging activity on the autoxidation of linoleic acid and 1,1-diphenyl-2-p-picryhydrazyl (DPPH) radical, suggesting that the alkyl chain length is not related to the activity. The effects of side-chain length of gallates in relation to their antibrowning activity are studied.

Agaricales↗
PubMed2003

Toward targeted oral vaccine delivery systems: selection of lectin mimetics from combinatorial libraries.

PURPOSE: Various lectins bind specifically to oligosaccharides on intestinal cells. Exploiting this specificity, Ulex europaeus agglutinin I (UEA1) has been used as a ligand for targeted oral vaccine delivery to M cells (antigen-presenting cells) in follicle-associated epithelium. In this study we characterized compounds identified from mixture-based positional scanning synthetic combinatorial libraries, which mimic UEA1 and, thus, may have properties applicable to targeted drug delivery. METHODS: Two UEA1 mimetics were synthesized and their activity was verified on live cells. The ability of the lead compound, a tetragalloyl D-Lysine amide construct (4-copy gallic acid construct), to deliver dye-loaded polystyrene particles to M cells was assessed in an in situ mouse gut loop model. RESULTS: The 4-copy gallic acid construct inhibited UEA1 binding to Caco-2 cell membranes with an IC50 of 3 microM, a 650- to 5000-fold increase over the natural UEA1 substrate alpha-L-fucose. The biotin-labeled derivative of this construct demonstrated comparable binding activity as verified on live cells by fluorescence-activated cell sorting. Preclinical studies confirmed its ability to mediate M cell-specific delivery of streptavidin-coated particles in vivo. CONCLUSIONS: Polyphenolic compounds, D-Lysine scaffolds with multiple galloyl groups, can mimic functional activities of UEA1. Properties of such molecules, including low molecular weight, stability, ease of synthesis and low cost, highlight their potential for application in targeted vaccine delivery.

Administration, Oral↗
PubMed2005

In vitro bioactivity-guided fractionation and characterization of polyphenolic inhibitory fractions from Acacia nilotica (L.) Willd. ex Del.

The present study was undertaken to evaluate antimutagenic and cytotoxic effects of different extracts/fractions of Acacia nilotica prepared by maceration method. The potency order of different extracts was more or less similar in Ames assay as well as in cytotoxic assay. Considering the maximum potential of acetone extract in both the assays, the studies were initiated to fractionate this extract. Two pure fractions, namely AN-1 and AN-2, were obtained from acetone extract, of which AN-2 was found to be of gallic acid and AN-1 fraction is still to be identified. In conclusion, the antimutagenic and cytotoxic activities exhibited by acetone extract may partially be ascribed to the presence of gallic acid and other polyphenols.

Acacia↗