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PubMed1997

Identification of phenolic acids and inositols in balms and tissues from an Egyptian mummy.

A number of samples taken from an Egyptian mummy (ca. 100 B.C.) from the Guimet Museum in Lyon have been analyzed by GC-MS. Derivatives of aromatic acids (hydroxyhydrocinnamic, vanillic, protocatechuic and gallic acids) and inositols (non-methylated and mono-O-methyl) have been found among the constituents of extracts prepared by methanolysis and trimethylsilylation. From the reported electron impact mass spectra, ion sets where proposed for a sensitive and selective profiling of these selected compounds by mass fragmentometry. The source of gallic acid and inositol was found to be a vegetable tannin, an ingredient which was not previously known to be used for mummification in ancient Egypt. The nature and abundance ratios of the detected inositols also appeared to be a promising criterion to further investigate the botanical source of the tannin employed.

Adult↗
PubMed2002

Toxic effect of tannic and related compounds on human plasma proteins.

OBJECTIVE: To investigate the toxicity of tannic acid related compounds such as gallic acid and polyphenol on the activity of plasma proteins in vitro. Their electrophoretic results show extremely important information, albumin and globulin levels are remarkably changed and characterized by disorder in their fractions avere which occurred frequently. METHODS: All plasma proteins samples of sets A, B and C were treated in sequences with known different concentrations of gallic acid, gallotannin and polypholes, which were separated chromatographically from phenolic extract of fruit peel of punicaceae. These were then treated, A, B and C were subjected to electrophoresis techniques, for identification and quantitation. RESULTS: The electrophoretic patterns of treated plasma proteins samples, sets A, B and C are arised with remarkable changes in their fraction levels, compared to normal. The results in were also characterized by disorders in their electrophoretic pattern. In this way 5 fractions of treated plasma proteins could be distinguished after sustaining which are ablumin and alpha1, alpha2 and beta and gamma globulins. CONCLUSION: The biological activity of tannic acid related compounds on plasma proteins in vitro, is important in determining their toxicity, and this toxicity may be depend upon their metabolic processes in the liver. In addition, the electrophoretic techniques used for separation and identification of plasma protein is extremely important for future work in the area.

Blood Proteins↗
PubMed2000

Adsorption and Chemical Modification of Phenols on a Silver Surface.

The adsorption of phenols of different natures on silver colloidal particles is studied here by surface-enhanced Raman spectroscopy (SERS). The studied compounds can be classified in three groups: (a) cinnamic acic derivatives: caffeic and isoferulic acids; (b) catechol; and (c) the phenols derived from benzoic acid: m- and p-hydroxybenzoic acids and salicylic, vanillic, and gallic acids. The interest of these compounds lies in the fact that they are naturally occurring molecules with significant importance in relation to plant metabolism, soil chemistry, and vegetal food stability. In addition, many of these compounds have antioxidant properties derived from their high affinity toward atmospheric oxygen. They exhibit high reactivity that may be enhanced in the presence of a metal surface such as those employed for SERS spectroscopy. From the SERS results it can be deduced that a clear chemical change of caffeic and gallic acid and catechol occurred. The chemical modification consists mainly of polymerization connected to existence in the molecule of o-diphenol moieties. In the case of m-hydroxybenzoic acid the chemical change may occur at low pH at which a reorientation of the molecule on the surface takes place, while in the o-hydroxybenzoic acid the only chemical change seems to be the internal H bond breakdown induced by the complexation with the metal. Finally, isoferulic and p-hydroxybenzoic acids do not show any chemical modification upon adsorption on the metal, which takes place through the carboxylate group adopting the molecule a standing up orientation. The case of vanillic acid is not so clear, although possible chemical modification is also possible for this adsorbate. From the results found in this work it can be inferred that the factors influencing possible chemical modification are the chemical structure of the adsorbate and its orientation and interaction with the surface. Copyright 2000 Academic Press.

Journal Article↗
PubMedDate not supplied

[Stability and catalytic properties of o-diphenol oxidase. 1. Oxidation of o-diphenols].

o-Diphenoloxidase from potato tubers is inactivated in the course of the oxidation reaction of o-diphenols at the level of the enzyme-substrate complex. At 25 degrees C of the reaction mixture the enzyme inactivation rate constants (Kin) in oxidation of 10 mM solutions of the substrates were: for pyrocatechol--0.48 min-1; 3,4-dihydroxyphenylethylamine (DOP-amine)--0.52 min-1; 3,4-dihydroxyphenylalanine (DOPA)--0.17 min-1; noradrenaline--0.12 min-1; 3,4-dihydroxybenzaldehyde (DHBA)--0.032 min-1; 3,4-dihydroxybenzoic acid (DHBAc)--0.01 min-1; gallic acid--0.01 min-1. Kin of the enzyme in oxidation of pyrocatechol does not depend practically on pH, ionic strength and polarity of the medium, but rises with its temperature. For a temperature range from 20 to 40 degrees C the effective activation energy calculated in terms of the Arrhenius equation is equal to 28 kJ/mol and the preexponential value for the given preparation was 38 850 min-1. The enzyme activity is determined by the substituent nature in the substrate molecule: electron-donor groups (--CH2--) accelerate the oxidation as compared to nonsubstituted pyrocatechol and electron-acceptor groups (--COOH, --CHO) make it more difficult. If the o-diphenoloxidase activity in oxidation of a 10 mM solution of pyrocatechol is 100%, then the oxidation rate of DOP-amine taken in the same concentration would be 111, DOPA--61, noradrenaline--24, DOBA--2,7, DHBA--0.7, gallic acid--0.8%.(ABSTRACT TRUNCATED AT 250 WORDS)

Catalysis↗
PubMed2003

Factors affecting the ascorbate- and phenolic-dependent generation of hydrogen peroxide in Dulbecco's Modified Eagles Medium.

Ascorbate and several polyphenolic compounds have been reported to undergo oxidation in cell culture media to generate hydrogen peroxide (H2O2), but the mechanism underlying this has not been established. We therefore investigated the parameters affecting H2O2 production. H2O2 generation from ascorbate, gallic acid and other phenolic compounds in Dulbecco's Modified Eagles' Medium (DMEM) at 37 degrees C under 95% air - 5% CO2 was not significantly inhibited by high (5-10 mM) concentration of EGTA, o-phenanthroline or desferriox-amine, but partial inhibition by EDTA and diethylene-triaminepentaacetic acid (DTPA) was observed. Incubation of DMEM alone at 37 degrees C led to an upward drift of pH, even under an atmosphere of 95% air - 5% CO2. Prevention of this pH rise by increasing the concentration of N-[2-hydroxyethyl]piperazine-N'-[2-ethanesulfonic acid] (Hepes) buffer lowered the levels of H2O2 generated by ascorbate and phenolic compounds, but there was still substantial H2O2 generated at pH 7.4. Mixtures of ascorbate and phenolic compounds led to less H2O2 generation than would be expected from the rates observed with ascorbate or phenolic compounds alone. Ascorbate prevented the loss of gallic acid incubated in DMEM. The role of metal ions and other constituents of the culture medium in promoting H2O2 generation is discussed.

Ascorbic Acid↗
PubMed1998

Mechanism of inhibition of tannic acid and related compounds on the growth of intestinal bacteria.

Tannic acid, propyl gallate and methyl gallate, but not gallic acid, were found to be inhibitory to the growth of intestinal bacteria Bacteroides fragilis ATCC 25285, Clostridium clostridiiforme ATCC 25537, C. perfringens ATCC 13124, C. paraputrificum ATCC 25780, Escherichia coli ATCC 25922, Enterobacter cloacae ATCC 13047, Salmonella typhimurium TA98 and S. typhimurium YG1041 at 100-1000 microg/ml in culture broth. Neither Bifidobacterium infantis ATCC 15697 nor Lactobacillus acidophilus ATCC 4356 was inhibited by any of the above compounds up to 500 microg/ml. Tannic acid has a much greater relative binding efficiency to iron than propyl gallate, methyl gallate or gallic acid. The inhibitory effect of tannic acid to the growth of intestinal bacteria may be due to the strong iron binding capacity of tannic acid; whereas the effect of propyl gallate and methyl gallate probably occurs by a different mechanism. The growth of E. coli was restored by the addition of iron to the medium after the precipitate caused by tannic acid was removed. Neither B. infantis nor L. acidophilus require iron for growth. This probably contributes to their resistance to tannic acid. Because tannins are abundant in the human diet, tannins may affect the growth of some intestinal bacteria and thus may have an impact on human health.

Bacteria↗
PubMed2006

Evaluation of free radical scavenging and antityrosinase activities of standardized longan fruit extract.

The protective effects of fruits and vegetables against chronic diseases have been attributed to the antioxidant properties of some secondary metabolites present in these foods. Plant polyphenols have been reported to exhibit bioactive properties, and in particular antioxidant activities. Longan seeds are found to contain high levels of some beneficial polyphenolic compounds such as corilagin, gallic acid and ellagic acid. The present study examined the free radical scavenging activity of longan seed extract by using three different assay methods. Longan extracts contained corilagin ranging from zero to 50.64 mg/g DW, gallic acid from 9.18 to 23.04 mg/g DW, and ellagic acid from 8.13 to 12.65 mg/g DW depending on the cultivars. Dried longan seed extracts of cultivar Edor contained high levels of gallic acid and ellagic acid and also exhibited the highest radical scavenging activities when comparing fresh seed and dried pulp extracts. For scavenging activity of DPPH and superoxide radicals, longan seed extract was found to be as effective as Japanese green tea extract while dried longan pulp and mulberry green tea extracts showed the least scavenging activities. In the ORAC assay, both fresh and dried longan seed also had higher activity than dried pulp and whole fruit. However, the results demonstrate that three polyphenolics may not be the major contributors of the high antioxidant activity of longan water extracts but this high activity may be due to other phenolic/flavonoid glycosides and ellagitannins present in longan fruit. In addition, longan seed also showed tyrosinase inhibitory activity with IC(50) values of 2.9-3.2 mg/ml. Therefore, the preliminary observations suggest that longan seed extract could be another potential source of potent natural dietary antioxidants and also in an application as a new natural skin-whitening agent.

Antioxidants↗
PubMed2005

Antiproliferative effects of dietary phenolic substances and hydrogen peroxide.

There has been controversy as to whether the antiproliferative activity of dietary phenolic substances on cancer cells is due to the bioactivities of phenolics or the generation of hydrogen peroxide (H2O2) in media as an artifact. This study was to investigate whether the formation of H2O2 by different phenolics induces acute toxicity and carcinogenicity in normal rat liver epithelial cells. Gallic acid, one of the major antioxidants present in fruits and vegetables, dose-dependently generated considerably more H2O2 in DMEM media without cells than did quercetin. Gallic acid exerted stronger antiproliferative activity than quercetin on both Caco-2 human colon cancer cells (Caco-2 cells) and WB-F344 normal rat liver epithelial cells (WB cells) cultured in DMEM media, and the effect was partially reduced by catalase. Furthermore, gallic acid (but not quercetin) also inhibited gap-junction intercellular communication (GJIC; a carcinogenic phenomenon), which was in part protected by the addition of catalase. Exogenous H2O2 addition also inhibited the proliferation of both Caco-2 cells and WB cells and inhibited GJIC in a dose-dependent manner, but these effects were almost abolished by the treatment with catalase. From these results it is concluded that the antiproliferative effects of some antioxidants on cancer cells are partially due to their prooxidant actions.

Animals↗
PubMed2006

Comparative cytotoxicity of alkyl gallates on mouse tumor cell lines and isolated rat hepatocytes.

Alkyl esters of gallic acid inhibited the respiration rate of mouse sarcoma 786A and mouse mammary adenocarcinoma TA3 cell lines and its multiresistant variant TA3-MTX-R more effectively than gallic acid, both in the absence and in the presence of the uncoupler CCCP. The order of inhibition of the respiration rate by gallates in intact cells was n-octyl- approximately iso-amyl- approximately n-amyl- approximately iso-butyl->n-butyl->iso-propyl->n-propyl-gallate>>gallic acid. Sarcoma 786A was significantly more susceptible to all seven esters than the TA3 cell line. Respiration rates of the TA3-MTX-R cell line showed almost the same sensitivity to these esters as the TA3 cell line. However, hepatocytes were significantly less sensitive than all tumor cells tested. These alkyl gallates blocked mitochondrial electron flow, mainly at the NADH-CoQ segment, preventing ATP synthesis, which would lead to cellular death. These esters also inhibited, in the same order of potencies as respiration, the growth of 786A, TA3 and TA3-MTX-R cells in culture. In mice carrying TA3 or TA3-MTX-R tumor cells, an important decrease of the tumor growth rate and an increase of survival were observed when mice were treated with iso-butyl gallate alone or in combination with doxorubicin. These results indicate that alkyl gallates are selectively cytotoxic to tumor cells, which may be due to the mitochondrial dysfunctions of these cells.

Animals↗
PubMedDate not supplied

Effect of alpha-tocopherol on cytotoxicity induced by UV irradiation and antioxidants.

The addition of DL-alpha-tocopherol (vitamin E) at the time of UV irradiation only marginally protects cells from UV-induced cytotoxicity. However, a protective effect of alpha-tocopherol emerged when it was added to the cells before UV irradiation, alpha-Tocopherol was progressively and dose-dependently incorporated into the cells. Washout experiments showed that the intracellular concentration of alpha-tocopherol decreased with an approximate half-life of 14-20 hours, due to the release from the cells and dilution by cell proliferation. Pretreatment of the cells with alpha-tocopherol significantly increased the resistancy against the cytotoxic action of UV irradiation and antioxidants such as sodium ascorbate, gallic acid, n-propyl gallate and caffeic acid. ESR spectroscopy showed that alpha-tocopherol enhanced the ascorbyl radical intensity, whereas it reduced caffeic acid radical intensity, without affecting the radical intensity of gallic acid and n-propyl gallate. Both control and treated cell lysates scavenged superoxide anion (generated by xanthine-xanthine oxidase reaction) and hydroxyl radical (generated by Fenton reaction) to a comparable extent. The present study suggests that the protective effect of alpha-tocopherol might be derived from its incorporation into the cell membranes rather than its scavenging activity.

Antioxidants↗
PubMed1996

Antineoplastic agents 338. The cancer cell growth inhibitory. Constituents of Terminalia arjuna (Combretaceae).

By means of bioassay-guided separation methods, the cancer cell growth inhibitory constituents residing in the bark, stem and leaves of the Mauritius medicinal plant Terminalia arjuna (Combretaceae) were examined. The cancer cell line active components were found to be gallic acid, ethyl gallate, and the flavone luteolin. Only gallic acid was previously known to occur in this plant. Luteolin has a well established record of inhibiting various cancer cell lines and may account for most of the rationale underlying the use of T. arjuna in traditional cancer treatments. Luteolin was also found to exhibit specific activity against the pathogenic bacterium Neisseria gonorrhoeae.

Antineoplastic Agents↗
PubMed2003

Antioxidant activity of 3-dehydroshikimic acid in liposomes, emulsions, and bulk oil.

The antioxidant activity of 3-dehydroshikimic acid (DHS), an intermediate in the biosynthesis of aromatic amino acids, was evaluated in three assay systems: bulk oil (lard), liposomes, and a 10% corn oil-in-water emulsion. Upon initiation of peroxidation in the liposome or emulsion systems, DHS exhibited weak antioxidant activity. In contrast, DHS displayed strong antioxidant activity in lard, suppressing peroxidation with activity comparable to that of tert-butylhydroquinone, propyl gallate, and gallic acid and superior to that of alpha-tocopherol. Two major DHS oxidation products, gallic acid and protocatechuic acid, were identified by gas chromatography/mass spectral analysis of lard extracts; both compounds are effective antioxidants in the bulk oil system. In the liposome system, DHS remained intact throughout the assay period. A small amount of gallic acid was observed in extracts of the emulsion; however, protocatechuic acid was not detected. A mechanism to explain the different activities of DHS in the three lipid systems is proposed.

Antioxidants↗
PubMed2000

DNA-breaking versus DNA-protecting activity of four phenolic compounds in vitro.

Given the paradoxical effects of phenolics in oxidative stress, we evaluated the relative pro-oxidant and antioxidant properties of four natural phenolic compounds in DNA nicking. The phenolic compounds differed dramatically in their ability to nick purified supercoiled DNA, with the relative DNA nicking activity in the order: 1,2,4-benzenetriol (100% nicking) > gallic acid > caffeic acid > gossypol (20% nicking). Desferrioxamine (0.02 mM) decreased DNA strand breakage by each phenolic, most markedly with gallate (85% protection) and least with caffeic acid (26% protection). Addition of metals accelerated DNA nicking, with copper more effective (approximately 5-fold increase in damage) than iron with all four phenolics. Scavengers revealed the participation of specific oxygen-derived active species in DNA breakage. Hydrogen peroxide participated in all cases (23-90%). Hydroxyl radicals were involved (32-85%), except with 1,2,4-benzenetriol. Superoxide participated (81-86%) with gallic acid and gossypol, but not with caffeic acid or 1,2,4-benzenetriol. With 1,2,4-benzenetriol, scavengers failed to protect significantly except in combination. Thus, in the presence of desferrioxamine, catalase or superoxide dismutase inhibited almost completely. When DNA breakage was induced by Fenton's reagent (ascorbate plus iron) the two catechols (caffeic acid and gossypol) were protective, whereas the two triols (1,2,4-benzenetriol and gallic acid) exacerbated damage.

Antioxidants↗
PubMed1998

Tannins and human health: a review.

Tannins (commonly referred to as tannic acid) are water-soluble polyphenols that are present in many plant foods. They have been reported to be responsible for decreases in feed intake, growth rate, feed efficiency, net metabolizable energy, and protein digestibility in experimental animals. Therefore, foods rich in tannins are considered to be of low nutritional value. However, recent findings indicate that the major effect of tannins was not due to their inhibition on food consumption or digestion but rather the decreased efficiency in converting the absorbed nutrients to new body substances. Incidences of certain cancers, such as esophageal cancer, have been reported to be related to consumption of tannins-rich foods such as betel nuts and herbal teas, suggesting that tannins might be carcinogenic. However, other reports indicated that the carcinogenic activity of tannins might be related to components associated with tannins rather than tannins themselves. Interestingly, many reports indicated negative association between tea consumption and incidences of cancers. Tea polyphenols and many tannin components were suggested to be anticarcinogenic. Many tannin molecules have also been shown to reduce the mutagenic activity of a number of mutagens. Many carcinogens and/or mutagens produce oxygen-free radicals for interaction with cellular macromolecules. The anticarcinogenic and antimutagenic potentials of tannins may be related to their antioxidative property, which is important in protecting cellular oxidative damage, including lipid peroxidation. The generation of superoxide radicals was reported to be inhibited by tannins and related compounds. The antimicrobial activities of tannins are well documented. The growth of many fungi, yeasts, bacteria, and viruses was inhibited by tannins. We have also found that tannic acid and propyl gallate, but not gallic acid, were inhibitory to foodborne bacteria, aquatic bacteria, and off-flavor-producing microorganisms. Their antimicrobial properties seemed to be associated with the hydrolysis of ester linkage between gallic acid and polyols hydrolyzed after ripening of many edible fruits. Tannins in these fruits thus serve as a natural defense mechanism against microbial infections. The antimicrobial property of tannic acid can also be used in food processing to increase the shelf-life of certain foods, such as catfish fillets. Tannins have also been reported to exert other physiological effects, such as to accelerate blood clotting, reduce blood pressure, decrease the serum lipid level, produce liver necrosis, and modulate immunoresponses. The dosage and kind of tannins are critical to these effects. The aim of this review is to summarize and analyze the vast and sometimes conflicting literature on tannins and to provide as accurately as possible the needed information for assessment of the overall effects of tannins on human health.

Anti-Bacterial Agents↗
PubMed1989

Iron absorption and phenolic compounds: importance of different phenolic structures.

The phenolic compounds (phenolic monomers, polyphenols, tannins) are considered to interfere with iron absorption by complex formation with iron in the gastro-intestinal lumen, making the iron less available for absorption. Very little is known about the extent to which different types of phenolic compounds of different size and chemical structure inhibit iron absorption. The relationship between iron absorption and the amount and type of phenolic compounds was studied by the extrinsic tag method. The aims of the studies were as follows: (i) To study the effect of small phenolic compounds with different hydroxylation patterns (gallic acid, catechin, chlorogenic acid) on iron absorption, (ii) To study the effect of different amounts of a hydrolysable tannin containing ten gallic acid residues (tannic acid) on iron absorption. (iii) To study the degree of inhibition of iron absorption by some foods and beverages (oregano, spinach, coffee and tea) in relation to their respective content of iron-binding phenolic groups, measured by a newly developed method. The inhibition of iron absorption by tannic acid was strongly dose-related. The smallest amount (5 mg) inhibited absorption by 20 per cent, 25 mg by 67 per cent and 100 mg by 88 per cent. Gallic acid inhibited iron absorption to the same extent as tannic acid, per mol galloyl groups, whereas no inhibition was observed when catechin was added to the test meal. Chlorogenic acid inhibited iron absorption to a lesser extent. Oregano and tea inhibited iron absorption in proportion to their respective content of galloyl groups, whereas the inhibitory effect of spinach was less marked. The inhibiting effect of coffee was explained mainly by its content of galloyl groups, but also by some other factor, probably chlorogenic acid. It is concluded that the content of iron-binding galloyl groups might be a major determinant of the inhibitory effect of phenolic compounds on iron absorption from the diet, whereas the phenolic catechol groups seem to be of minor importance. The results further suggest that the group of condensed tannins do not interfere with iron absorption.

Absorption↗
PubMed2005

Microencapsulated mycelium-bound tannase from Aspergillus niger: an efficient catalyst for esterification of propyl gallate in organic solvents.

Microencapsulated Aspergillus niger with mycelium-bound tannase activity was employed to investigate the esterification of propyl gallate from gallic acid and propanol in organic solvents. The effects of various organic solvents (log P: -1.0 to 6.6) on the enzymatic reactions showed that benzene (log P: 2.0) was the suitable solvent, for which the conversion reached 26.8%. The optimum catalyst concentration and water concentration was found at 25 capsules in 10 mL of benzene and 0.04 g of water/capsule. The external mass transfer effect could be eliminated at stirring speeds of 180 rpm or higher. Both substrates 1-propanol and gallic acid had significant inhibition effects on the tannase activity. Maximum molar conversion (36.2%) was achieved with 9.1% (v/v) 1-propanol and 8 mM gallic acid and decreased with increasing amounts of substrates.

1-Propanol↗
PubMed1990

Effectiveness of chelation therapy with time after acute uranium intoxication.

The effect of increasing the time interval between acute uranium exposure and chelation therapy was studied in male Swiss mice. Gallic acid, 4,5-dihydroxy-1,3- benzenedisulfonic acid (Tiron), diethylenetriaminepentaacetic acid (DTPA), and 5-aminosalicylic acid (5-AS) were administered ip at 0, 0.25, 1, 4, and 24 hr after sc injection of 10 mg/kg of uranyl acetate dihydrate. Chelating agents were given at doses equal to one-fourth of their respective LD50 values. Daily elimination of uranium into urine and feces was determined for 4 days after which time the mice were killed, and the concentration of uranium was measured in kidney, spleen, and bone. The excretion of uranium was especially rapid in the first 24 hr. Treatment with Tiron or gallic acid at 0, 0.25, or 1 hr after uranium exposure significantly increased the total excretion of the metal. In kidney and bone, only administration of Tiron at 0, 0.25, or 1 hr after uranium injection, or gallic acid at 1 hr after uranium exposure significantly reduced tissue uranium concentrations. Treatment at later times (4 to 24 hr) did not increase the total excretion of the metal and did not decrease the tissue uranium concentrations 4 days after uranyl acetate administration. The results show that the length of time before initiating chelation therapy for acute uranium intoxication greatly influences the effectiveness of this therapy.

1,2-Dihydroxybenzene-3,5-Disulfonic Acid Disodium ↗