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PubMed1995

Metabolism and cytotoxicity of propyl gallate in isolated rat hepatocytes: effects of a thiol reductant and an esterase inhibitor.

The relationship between the metabolism and the cytotoxic effects of propyl gallate (PG) has been studied in freshly isolated rat hepatocytes. Addition of PG (0.5-2.0 mM) to the hepatocytes elicited concentration-dependent cell death, accompanied by decreases in intracellular ATP, adenine nucleotide pools, glutathione, and protein thiols. The rapid loss of ATP preceded the onset of cell death. PG in the hepatocyte suspensions was converted to gallic acid, 4-O-methyl-gallic acid, and other minor products over time. In addition, PG was converted to a dimer [dipropyl-4,4',5,5',6,6'-hexahydroxydiphenate (PG-dimer)] and ellagic acid via autooxidation. In comparisons of the toxic effects of PG and its metabolites at concentrations of 2 mM, the parent compound PG was the most toxic. Pretreatment of hepatocytes with diazinon (100 microM), an esterase inhibitor, enhanced PG-induced cytotoxicity. This was accompanied by delay of PG loss and inhibition of gallic acid formation. The cytotoxicity of PG was also enhanced by addition of the thiol reductant dithiothreitol (4 mM), although intracellular levels of glutathione and protein thiols were maintained during the incubation period. Dithiothreitol did not affect the hydrolysis of PG to gallic acid by esterases but did delay the conversion of PG and prevented the formation of PG-dimer. In isolated hepatic mitochondria, PG elicited a concentration-dependent increase in the rate of state 4 oxygen consumption, indicating an uncoupling effect. In contrast, PG-dimer inhibited the rate of state 3 oxygen consumption. Based on the respiratory control index, the order of potency for impairment of mitochondria was PG > PG-dimer > gallic acid = 4-O-methyl-gallic acid = ellagic acid - propyl alcohol. These results indicate (a) that PG-induced hepatotoxicity is mediated by the parent compound and not its metabolites, (b) that toxicity is associated with ATP depletion apparently independently of cellular thiol depletion, and (c) that mitochondria may represent critical targets of PG-induced cytotoxicity.

Adenosine Triphosphate↗
PubMed2000

Olive oil phenols inhibit human hepatic microsomal activity.

We have examined the inhibition of human hepatic microsomal androstenedione 6beta-hydroxylation and both reductive and oxidative 17beta-hydroxysteroid dehydrogenase (17beta-HSD) activity by complex phenols found in olive oil. Structurally similar compounds were also examined for comparison. Androstenedione 6beta-hydroxylase activity was inhibited by oleuropein glycoside, hydroxytyrosol and gallic acid. Oleuropein glycoside, hydroxytyrosol, gallic acid and dihydroxybenzoic acid also inhibited reductive 17beta-HSD activity. Oxidative 17beta-HSD activity was not inhibited by any of the compounds tested; however gallic acid stimulated activity by approximately 30%. Androstenedione 6beta-hydroxylase activity showed atypical kinetics. For oleuropein glycoside, hydroxytyrosol and gallic acid the apparent K(i) values were determined to be 80, 77 and 70 micromol/L, respectively. Analysis of structural features of inhibitory compounds established that a 3,4-dihydroxyphenyl ethanol structure was required for inhibition of androstenedione 6beta-hydroxylase for this group of compounds.

Cells, Cultured↗
PubMed1997

Plasma triglyceride-decreasing components of pine needles.

An ultrafiltrate (M.W. < 10000) of 0.1 M acetic acid extract from Japanese red pine needles was treated with Sep-Pak Vac C18, and an absorbable fraction (pine aqueous components fraction, PAC) was obtained. Since the intraperitoneal administration of PAC to rats decreased plasma triglyceride in a screening test for bioactivity, we tried to further isolate the active substances with respect to this triglyceride-decreasing action. Active substances were precipitated by acid, and we then divided them into fractions using reversed phase HPLC. The active fractions were hydrolyzed, then the hydrolysate was re-separated by the same HPLC system. Negative ion mode FAB-LC/MS of the bioactive fractions of this hydrolysate revealed an [M-H] molecular ion peak at m/z 169 and 321. The 13C-NMR spectra were consistent with those of authentic gallic acid and galloyl gallic acid, a dimer of gallic acid. Authentic gallic acid also showed a triglyceride-decreasing action, and galloyl gallic acid even more markedly decreased triglyceride. These findings suggest that the triglyceride-decreasing action of Japanese red pine needles is due to these polyphenol compounds. In addition, amino acids were also detected in the hydrolysate of PAC, indicating that the components in Japanese red pine needles that decrease triglycerides are complexes of a hydrolyzable tannin, which contains gallic acid and galloyl gallic acid as components and peptides.

Amino Acids↗
PubMed2005

Spectroscopic investigation of the interaction between human serum albumin and three organic acids.

The interactions of human serum albumin (HSA) with sinapic acid (SA), gallic acid (GA) and shikimic acid (SI) were investigated by fluorescence and Fourier transformed infrared spectrometry. Fluorescence results showed that one molecule of protein combined with one molecule of GA at the molar ratio of drug to HSA ranging from 0.1 to 30, and their binding constant (K(A)) is 1.1x10(4) M(-1). While one HSA molecule combined with one or two molecule of SA at the molar ratio of drug to HSA ranging from 0.1 to 4.26 or 4.26 to 30, and their binding affinities (K(A)) are 1.92x10(3) M(-1) and 6.87x10(8) M(-1), respectively. There is no specific interaction between HSA and SI. Combining the curve-fitting results of infrared amide I and amide III bands, the alterations of protein secondary structures induced by drugs were estimated. The drug-protein combination brought gradual reductions of the protein alpha-helix structure with increasing the concentrations of SA and GA, but SI did not change the protein secondary structure. From the fluorescence and FT-IR results, the binding mode was discussed in relation to the structures of the organic acids.

Coumaric Acids↗
PubMed2005

[Studies on the chemical constituents from Fructus Rubi].

Five compounds have been isolated from Fructus Rubi. On the basis of spectral analysis and physicochemical properties, their structures were establised as 4-hydroxy-3-methoxybenzoic acid (I), p-hydroxybenzoic acid (II), gallic acid (III), tiliroside (IV) and ellagic acid (V). I, II and III were found from the plant for the first time.

Benzopyrans↗
PubMed1995

Characterization of tannin acylhydrolase activity in the ruminal bacterium Selenomonas ruminantium.

A strain of the anaerobe Selenomonas ruminantium subsp. ruminantium that is capable of growing on tannic acid or condensed tannin as a sole energy source has been isolated from ruminal contents of feral goats browsing tannin-rich Acacia sp. Growth on tannic acid was accompanied by release of gallic acid into the culture medium but the bacterium was incapable of using gallic acid as a sole energy source. Tannin acylhydrolase (EC 3.1.1.20) activity was measured in crude cell-free extracts of the bacterium. The enzyme has a pH optimum of 7, a temperature optimum of 30-40 degrees C and a molecular size of 59 kDa. In crude extracts, the maximal rate of gallic acid methyl ester hydrolysis was 6.3 micromol min(-1) mg(-1) of protein and the K(m) for gallic acid methyl ester was 1.6 mM. Enzyme activity was displayed in situ in polyacrylamide and isoelectric focusing gels and was demonstrated to increase 17-fold and 36-fold respectively when cells were grown in the presence of gallic acid methyl ester or tannic acid.

Journal Article↗
PubMed2005

Phenolic constituents of galla Rhois with hepatoprotective effects on tacrine- and nitrofurantoin-induced cytotoxicity in Hep G2 cells.

The bioassay-guided fractionation of the MeOH extract of Galla Rhois furnished two hepatoprotective compounds, an equilibrium mixture of 3-galloyl-gallic acid and 4-galloyl-gallic acid isomers (3), 1,2,3,4,6-penta-O-galloyl-beta-D-glucose (4), and two inactive phenolic compounds, gallic acid methyl ester (1) and gallic acid (2). Compounds 3 and 4 showed significant hepatoprotective effects with EC50 values of 70.39+/-5.4 and 29.51+/-0.7 microM, respectively, against tacrine-induced cytotoxicity, and 150.9+/-6.4 and 23.81+/-0.5 microM, respectively, against nitrofurantoin-induced cytotoxicity in Hep G2 cells.

Cell Line, Tumor↗
PubMed2006

Antioxidative and oxidative changes in the digestive gland cells of freshwater mussels Unio tumidus caused by selected phenolic compounds in the presence of H(2)O(2) or Cu(2+) ions.

Research on biomarkers as early bioindicators of perturbation in populations and individuals has received increasing interest during recent decades. These ecotoxicity studies allow us to measure the impact of environmental stressors and to monitor and evaluate the degradation or restoration of systems. In the present study we used bivalve molluscs (mussels), which are sensitive biomarkers of aquatic ecosystem pollution, to assess the effects of three polyphenols: tannic acid, ellagic acid and gallic acid. These compounds were used in the 1-60 microM concentration range, alone and in the presence of H(2)O(2) (40 and 100 microM) or Cu(2+) ions (50 microM). The fluorescence probe dichlorofluorescein-diacetate (DCFH-DA) was used to measure reactive oxygen species (ROS). The oxidation of DCFH-DA to the fluorescent DCF (dichlorofluorescein) by the phenolic compounds was investigated spectrofluorimetrically. The results showed that the polyphenols tested can act as antioxidants against the ROS present in the digestive gland cells, but their activity is decreased after incubation with hydrogen peroxide or copper ions. SH-groups were determined spectrophotometrically using Ellman's reagent. The results showed that oxidative modification of proteins increased in a concentration-dependent manner in cells incubated with polyphenols (above 15 microM) alone. Incubation of the cells with phenolic acids and H(2)O(2) or Cu(2+) ions revealed that the phenolic acids had prooxidant properties in all concentrations used except for 1 microM tannic and ellagic acid and 40 microM H(2)O(2). DNA fragmentation was estimated by a fluorescence method using Hoechst 33258/propidium iodine binding. The data showed that the phenolic acids alone and in the presence of hydrogen peroxide or copper ions can induce apoptosis and necrosis. The methods used and results obtained indicate that the polyphenols selected can act not only as antioxidants but also as prooxidants in digestive gland cells of Unio tumidus.

Animals↗
PubMed2005

Phytochemical phenolics in organically grown vegetables.

Fruit and vegetable intake is inversely correlated with risks for several chronic diseases in humans. Phytochemicals, and in particular, phenolic compounds, present in plant foods may be partly responsible for these health benefits through a variety of mechanisms. Since environmental factors play a role in a plant's production of secondary metabolites, it was hypothesized that an organic agricultural production system would increase phenolic levels. Cultivars of leaf lettuce, collards, and pac choi were grown either on organically certified plots or on adjacent conventional plots. Nine prominent phenolic agents were quantified by HPLC, including phenolic acids (e. g. caffeic acid and gallic acid) and aglycone or glycoside flavonoids (e. g. apigenin, kaempferol, luteolin, and quercetin). Statistically, we did not find significant higher levels of phenolic agents in lettuce and collard samples grown organically. The total phenolic content of organic pac choi samples as measured by the Folin-Ciocalteu assay, however, was significantly higher than conventional samples (p < 0.01), and seemed to be associated with a greater attack the plants in organic plots by flea beetles. These results indicated that although organic production method alone did not enhance biosynthesis of phytochemicals in lettuce and collards, the organic system provided an increased opportunity for insect attack, resulting in a higher level of total phenolic agents in pac choi.

Acids, Carbocyclic↗
PubMed1994

Interactions of astringent substances.

Two-component mixtures of astringent materials were rated for perceived intensity of astringent and taste attributes over time. Components included alum (a complex salt), gallic acid (the monomeric component of hydrolyzable tannins), catechin (the monomeric component of condensed tannins) and citric acid. Mixtures of alum and gallic acid showed mixture suppression, in that the 50/50 mixture was less intense than either component in astringency, drying, roughing and puckery/drawing sensations. Suppression was seen at concentration levels producing moderate to strong astringency but was absent or less pronounced at lower concentration levels. A similar pattern held for citric acid, although the suppressive effects were less pronounced. Catechin and gallic acid mixtures were additive. Sensory interactions between astringent materials appears to depend on the substances involved and their concentrations (or intensity levels).

Adult↗
PubMed2006

High-performance liquid chromatographic method for the quantification of phenolics in 'Chyavanprash' a potent Ayurvedic drug.

Quantification of bioactive principles through modern analytical tools is essential for establishing the authenticity, credibility, prescription and usage of Ayurvedic medicines/herbal formulations. 'Chyavanprash' is one of the oldest and most popular Ayurvedic preparations, used widely as a health promotive and disease preventive 'Rasayana' drug in India and elsewhere. The rejuvenating and tonic properties of 'Chavanprash' are considered mainly due to their antioxidant principles, which in turn is due to the presence of phenolic compounds. A simple high-performance liquid chromatography (HPLC) method for the separation and quantitative determination of the major antioxidant compounds from 'Chyavanprash' has been developed. The use of Waters Symmetry column and an acidic mobile phase enabled the efficient separation of phenolic compounds (catechin, quercetin-3-O-rutinoside, syringic acid and gallic acid) within a 35 min analysis. Validation of the method was done with a view to demonstrate its selectivity, linearity, precision, accuracy and robustness. In addition optimization of the complete extraction of phenolic compounds were also studied.

Antioxidants↗
PubMed2001

Effect of hydrolysable and condensed tannins on growth, morphology and metabolism of Streptococcus gallolyticus (S. caprinus) and Streptococcus bovis.

Streptococcus gallolyticus (S. caprinus) was resistant in vitro to at least 7% (w/v) tannic acid and 4% (w/v) acacia condensed tannin, levels 10-fold greater than those tolerated by S. bovis. Growth of S. gallolyticus in liquid medium was characterized by a lag period which increased, and a growth rate which decreased, with increasing tannin concentration. S. gallolyticus was also more tolerant to the presence of simple phenolic acid monomers than was S. bovis, but the lag period was still concentration dependent. Gallate decarboxylase activity in S. gallolyticus was elevated in the presence of tannic acid or gallic acid but not with other phenolic acids. Scanning electron microscopic analysis showed that both the size and shape of S. gallolyticus and S. bovis changed in response to tannin but only S. gallolyticus was surrounded by an extracellular polysaccharide matrix which accumulated in a tannin-concentration-dependent fashion. Washing of the cells to remove extracellular polysaccharide increased the lag period of S. gallolyticus in the presence of 1% (w/v) tannic acid from 4 h to 6 h. In contrast, increasing extracellular polysaccharide synthesis in S. bovis did not increase its tolerance to tannic acid. These data demonstrate that S. gallolyticus has developed a number of mechanisms to reduce the potential effect of tannins on cell growth, and that these mechanisms provide the organism with a selective advantage over S. bovis when grown in the presence of tannins.

Carboxy-Lyases↗
PubMed2005

[Study on chemical constituents in seeds of Helicia nilagirica (II)].

OBJECTIVE: To study the chemical constituents in seeds of Helicia nilagirica. METHOD: The ethanol extract was seperated by petroleum ether, dichloromethane, n-butanol in sequence, then isolated by silica gel column chromatography. The structures were identified and elucidated by physicochemical properties and spectral analysis. RESULT: Five compounds were isolated from the dichloromethane and n-butanol extracts, identified as p-hydroxybenzaldehyde (1), p-hydroxybenzoic acid (2), gallic acid (3), helicide (4), 4-formylpymyl-O-beta-D-glucopyranoside (5). CONCLUSION: All the compounds except IV were isolated from the plant for the first time. The compounds I, II and III were isolated from the genus Helicia for the first time.

Benzaldehydes↗
PubMed2006

Biodegradation of gallotannins and ellagitannins.

Nowadays, many researches have been made on gallotannin biodegradation and have gained great success in further utilization. Some of industrial applications of these findings are in the production of tannase, the biotransformation of tannic acid to gallic acid or pyrogallol and detannification of food and fodder. Although ellagitannins have the typical C-C bound which is more difficult to be degraded than gallotannins, concerted efforts are still in progress to improve ellagitannin degradation and utilization. Currently, more attention is mainly focused on intestinal microflora biodegradation of tannins especially ellagitannins which can contribute to the definition of their bioavailability for both human beings and ruminants. Also there have been endeavours to utilize the tannin-degrading activity of different fungi for ellagitannin-rich biomass, which will facilitate application of tannin-degrading enzymes in strategies for improving industrial and livestock production. Due to the complicated structures of complex tannins and condensed tannins, the biodegradation of them is much more difficult and there are fewer researches on them. Therefore, the researches on the mechanisms of gallotannin and ellagitannin biodegradation can result in the overall understanding to the biodegradation of complex tannins and condensed tannins. Biodegradation of tannins is in an incipient stage and further studies have to be carried out to exploit the potential of various tannins for largescale applications in food, fodder, medicine and tannery effluent treatment.

Animals↗
PubMed2003

Effects of tannins on Chinese hamster cell line B14.

Tannins, naturally occurring plant phenols, have been recognized as antioxidants, but toxic effects have also been observed. In the current investigation, the interaction of this type of compounds with Chinese hamster cells (cell line B14) has been examined. This study reports on the results of experiments in which B14 cells were exposed to tannins: tannic, ellagic and gallic acids in the concentration range 15-240 microM. The cytotoxic and genotoxic effects of these compounds were studied. The colorimetric MTT assay to assess cytotoxicity and the Comet assay for detection of DNA damage were used. In this paper, we also demonstrated the influence of tannins on the fluidity of the plasma membrane. This experiment was carried out by a spectrofluorometric method using two fluorescent probes: 1-[4-(trimethylamino)phenyl]-6-phenyl-1,3,5-hexatriene (TMA-DPH) and 12-(9-anthroyloxy)stearic acid (12-AS). The tannins increased the fluidity in the internal region of the lipid bilayer, but no changes at the surface of the plasma membrane were observed. The results of the MTT assay showed that tannins could decrease the viability of cells and that their cytotoxicity was highest at the concentration of 60 microM. The degree of toxicity of these compounds was not correlated with the concentration used. The data obtained from the Comet assay showed that the tannins could also contribute to formation of DNA single-strand breaks.

Animals↗
PubMed2006

Determination of total content of phenolic compounds and their antioxidant activity in vegetables--evaluation of spectrophotometric methods.

This research studies in detail the contents of phenolic compounds determined by the Folin-Ciocalteu reagent and the antioxidant activities determined by the TEAC (Trolox equivalent antioxidant capacity), DPPH (using diphenyl-p-picrylhydrazyl radical), and FRAP (ferric reducing antioxidant power) methods, and their correlations for used standards with these methods (catechine, gallic acid, caffeic acid, ferulic acid, Trolox, ascorbic acid, and ferrous sulfate) and extracts from several species of commonly consumed vegetables were studied in detail. The comparison of absolute values of absorption coefficients for used standards and for individual methods allows one to choose optimal common standards for methods to be compared. The procedures applied for the same sets of the extracts using identical calibration procedures and common standards allowed better comparison of the results obtained by the TEAC, DPPH, and FRAP methods. The values of content of phenolic substances and total antioxidant activity of the sets of samples correlate very well for all used methods. The very high values of antioxidant activity were found in intensely colored vegetables (red cabbage, red onion, etc.), and the values were very low in watery vegetables such as potato, marrow, and cucumber.

Antioxidants↗
PubMed1987

Induction of forestomach lesions in rats by oral administrations of naturally occurring antioxidants for 4 weeks.

The effects of naturally occurring antioxidants on rat forestomach epithelium were compared with those of synthetic antioxidants, butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT), of which the former is a known forestomach carcinogen. Groups of five F344 male rats were given diet containing BHA, BHT, gallic acid, syringic acid, sesamol, caffeic acid, chlorogenic acid, ferulic acid, eugenol or esculin for 4 weeks at a level of 0.7% for BHT or 2% for other compounds. Histological examination of the forestomach showed that BHA induced hyperplasia mainly in the prefundic region near the esophageal orifice, caffeic acid induced pronounced hyperplasia throughout the forestomach epithelium, and sesamol induced large ulcers and hyperplasia in the central region. Thus, these naturally occurring antioxidants showed different toxicities and abilities to induce hyperplasia in the rat forestomach.

Animals↗
PubMed2003

Phenolic content and antioxidant capacity of muscadine grapes.

Fruits of 10 cultivars of muscadine grapes (five bronze skin and five purple skin) grown in southern Georgia were separated into skin, seed, and pulp. Each fruit part and the leaves from the corresponding varieties were extracted for HPLC analysis of major phenolics. Total phenolics were determined colorimetrically using Folin-Ciocalteu reagent. Total anthocyanins were determined according to a pH-differential method, using a UV-visible spectrophotometer. Antioxidant capacity was determined by the Trolox equivalent antioxidant capacity (TEAC) assay. Gallic acid, (+)-catechin, and epicatechin were the major phenolics in seeds, with average values of 6.9, 558.4, and 1299.4 mg/100 g of fresh weight (FW), respectively. In the skins, ellagic acid, myricetin, quercetin, kaempferol, and trans-resveratrol were the major phenolics, with respective average values of 16.5, 8.4, 1.8, 0.6, and 0.1 mg/100 g of FW. Contrary to previous results, ellagic acid and not resveratrol was the major phenolic in muscadine grapes. The HPLC solvent system used coupled with fluorescence detection allowed separation of ellagic acid from resveratrol and detection of resveratrol. Reported here for the first time are the phenolic content and antioxidant capacity of muscadine leaves. Major phenolics in muscadine leaves were myricetin, ellagic acid, kaempferol, quercetin, and gallic acid, with average concentrations of 157.6, 66.7, 8.9, 9.8, and 8.6, respectively. Average total phenolics were 2178.8, 374.6, 23.8, and 351.6 mg/g gallic acid equivalent in seed, skin, pulp, and leaves, respectively. Total anthocyanin contents were 2.1 and 132.1 mg/100 g of FW in the skins of bronze and purple grapes, respectively, and 4.3 and 4.6 mg/100 g of FW in seeds and pulps, in that order. Antioxidant capacity values were, on average, 2.4, 12.8, 281.3, and 236.1 microM TEAC/g of FW for pulps, skins, seeds, and leaves, respectively.

Antioxidants↗