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PubMed2003

Phenolic constituents of shea (Vitellaria paradoxa) kernels.

Analysis of the phenolic constituents of shea (Vitellaria paradoxa) kernels by LC-MS revealed eight catechin compounds-gallic acid, catechin, epicatechin, epicatechin gallate, gallocatechin, epigallocatechin, gallocatechin gallate, and epigallocatechin gallate-as well as quercetin and trans-cinnamic acid. The mean kernel content of the eight catechin compounds was 4000 ppm (0.4% of kernel dry weight), with a 2100-9500 ppm range. Comparison of the profiles of the six major catechins from 40 Vitellaria provenances from 10 African countries showed that the relative proportions of these compounds varied from region to region. Gallic acid was the major phenolic compound, comprising an average of 27% of the measured total phenols and exceeding 70% in some populations. Colorimetric analysis (101 samples) of total polyphenols extracted from shea butter into hexane gave an average of 97 ppm, with the values for different provenances varying between 62 and 135 ppm of total polyphenols.

Africa↗
PubMed2002

Oxidative dimers produced from protocatechuic and gallic esters in the DPPH radical scavenging reaction.

DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging reactions of protocatechuic and gallic acids, and their methyl esters, have been investigated by NMR. In acetone, methyl protocatechuate was gradually converted to a Diels-Alder adduct of two molecules of the intermediate quinone in the reaction with DPPH radical, whereas methyl gallate rapidly gave a symmetrical dimer via a putative quinone precursor. Both dimers are rather unstable and their structures have been deduced by in situ NMR measurements of the reaction mixtures. Gallic acid also gave a corresponding symmetrical dimer in the same reaction as methyl gallate, although protocatechuquinone produced from protocatechuic acid did not yield a Diels-Alder adduct, unlike its methyl ester. Interestingly, these dimer formations were not observed in methanol solution.

Acetone↗
PubMed2000

Potent and selective inhibition of squalene epoxidase by synthetic galloyl esters.

n-Alkyl esters (ethyl, octyl, dodecyl, and cetyl) of gallic acid were evaluated as enzyme inhibitors of recombinant rat squalene epoxidase (SE), a rate-limiting enzyme of cholesterol biogenesis. Dodecyl (6) (IC(50) = 0.061 microM) showed the most potent inhibition, which was far more potent than those of previously reported naturally occurring gallocatechins. Octyl gallate (5) (IC(50) = 0.83 microM) and cetyl gallate (7) (IC(50) = 0.59 microM) also showed good inhibition, while gallic acid (IC(50) = 73 microM) itself was not so active. In addition, chemically synthesized galloyl ester of cholesterol (9) (IC(50) = 3.9 microM), farnesol derivative (10) (IC(50) = 0.57 microM), and dodecyl galloyl amide (8) (IC(50) = 3.0 microM) were also potent inhibitors of SE. Inhibition kinetics revealed that dodecyl gallate inhibited SE in competitive (K(I) = 0.033 microM) and no-time-dependent manner. The potent inhibition of the flavin monooxygenase would be caused by specific binding to the enzyme, and by scavenging reactive oxygen species required for the epoxidation reaction.

Animals↗
PubMed2003

Effects of several polyhydroxylated flavonoids on the growth of B16F10 melanoma and Melan-a melanocyte cell lines: influence of the sequential oxidation state of the flavonoid skeleton.

The response of B16F10 melanoma and Melan-a melanocyte cell lines to treatment with five polyhydroxylated flavonoids and gallic acid, after 24 and 72 h of exposure, was determined, and the relationship between any antiproliferative effects observed and the chemical structure is discussed. After 24 h, none of the studied compounds showed significant cytotoxic activity in the B16F10 cell line, whereas compounds with an adjacent trihydroxylated substitution pattern did affect the viability of the Melan-a cell line. After 72 h of exposure, myricetin, baicalein and gallic acid significantly inhibited both B16F10 and Melan-a cell cultures, whereas luteolin and quercetin had only a moderate effect. Eriodictyol only had an effect on Melan-a cell viability, which was reduced slightly. These results suggest that the presence of a C2-C3 double bond and three adjacent hydroxyl groups in the flavonoid A- or B-rings confers greater antiproliferative activity to the flavonoid.

Animals↗
PubMed2004

Wine polyphenols and ethanol do not significantly scavenge superoxide nor affect endothelial nitric oxide production.

Epidemiological studies have shown that moderate intake of red wine reduces the risk of coronary heart disease. It has been proposed that the antiatherogenic effect be due to the scavenging of reactive oxygen species by polyphenols and ethanol or an effect on endothelial nitric oxide (NO) production. We have determined the reaction rates of superoxide with four different polyphenols and ethanol. The superoxide reaction rates were determined at 37 degrees C and pH 7.4 using competitive spin trapping and electron paramagnetic resonance (EPR) spectroscopy. Ethanol did not scavenge superoxide. For the polyphenols catechin, epicatechin, gallic acid, and quercetin, we find rate constants of respectively 2.3*10(4), 2.2*10(4), 2.3*10(3) and 1.9*10(4)(mole per second)(-1). Polyphenols can only exert a significant scavenging effect, if the plasma concentration reach sufficiently high levels. At concentrations found in vivo (low nanomolar range), the scavenging of superoxide by polyphenols and ethanol is negligible in comparison with endogenous protection against superoxide. Incubation of cultured endothelial cells with 5 micromol/L of catechin, epicatechin, gallic acid, quercetin, or ethanol 0.05% (v/v) did not influence the maximal production of NO by these cells as measured by fluorescent nitric oxide cheletropic traps (FNOCT). The observed antiatherogenic effects must be caused by a mechanism other than direct scavenging of superoxide or influence on maximal endothelial NO production.

Animals↗
PubMed2006

Assessment of the polyphenolic composition of the organic extracts of Mauritian black teas: a potential contributor to their antioxidant functions.

There is increasing interest in the emerging view that tea improves the antioxidant status in vivo and thereby helps to lower risk of certain types of cancer, coronary heart disease and stroke and its component biofactors could provide prophylactic potential for these diseases. The polyphenolic composition and the antioxidant properties of organic extracts (acetone/methanol) of Mauritian commercial black teas were evaluated. HPLC data of the individual compounds revealed remarkably high levels (+)-Catechin ((+)-C), (-)-epicatechin ((-)-EC), (-)-epicatechin 3-gallate ((-)-ECG), (-)-epigallocatechin ((-)-EGC), (-)-epigallocatechin 3-gallate ((-)-EGCG) and gallic acid. Analysis of hydrolysed extracts indicated that quercetin was the dominant flavonol aglycone with traces of myricetin and kaempferol. Based on the Ferric Reducing Antioxidant Power (FRAP) and the Trolox Equivalent Antioxidant Capacity (TEAC) assays Extra tea from Bois Chéri exhibited the highest antioxidant potential. Linear regression analyses showed that the antioxidant capacities of the organic extracts are strongly influenced by total phenols (TEAC: r=0.95 and FRAP: r=0.96) and to a lesser extent by total proanthocyanidin and total flavonoid contents. Catechins and gallic acid seem to add up to the overall antioxidant capacity of black tea extracts. The fresh tea leaves had high levels of total phenols, total flavonoids, total proanthocyanidin and exhibited greater antioxidant potential when compared with black teas. Organic extracts of endemic teas represent useful source of phenolic antioxidants supplements for prophylactic use.

Antioxidants↗
PubMed2005

Mineralization of some natural refractory organic compounds by biodegradation and ozonation.

The objective of this study was to explore the extent of mineralization, reduction in color and reduction of COD of gallic acid, tannin and lignin by ozonation and a combination of aerobic biodegradation and ozonation. Ozonation of pure aliquots (phase I experiments) resulted in the decline in TOC, COD, COD/TOC ratio, UV absorbance at 280 nm and color of the three model compounds investigated, with COD removals of greater than 80% and high removals (>90%) of UV absorbance at 280 nm and color observed in all cases at an ozone dose of 6 mg ozone/mg initial TOC or higher. Aerobic biodegradation of pure gallic acid, tannin and lignin aliquots resulted in COD decline of approximately 36-38%. Subsequent ozonation (phase II experiments) resulted in further decline in TOC, COD, COD/TOC ratio, and increase in UV absorbance at 280 nm and color removals. COD and TOC removals comparable to phase I experiments were obtained with 30-40% lower ozone absorption in phase II experiments. The biodegradation step was quite effective in removing specific UV absorbance at 280 nm, with up to 75% removal observed. Subsequent ozonation increased overall specific UV absorbance at 280 nm to greater than 90%.

Bacteria, Aerobic↗
PubMed2002

Study of catechin and xanthine tea profiles as geographical tracers.

The contents of gallic acid, epigallocatechin gallate, epigallocatechin, epicatechin, epicatechin gallate, catechin, caffeine, theophylline, and theobromine were determined in a set of 45 tea samples, including fermented (black and red) and nonfermented (green) teas of different geographical origins (i.e., China, Japan, Kenya, Sri Lanka, and India). A reversed-phase high performance liquid chromatographic method with gradient elution and photometric detection at 275 nm was used to carry out the analysis. Before the HPLC determination, an extraction step was developed using a mixture of acetonitrile and water (60:40, v/v). Pattern recognition techniques involving principal component analysis (PCA) and linear discriminant analysis (LDA) were applied to differentiate the tea samples according to their geographical origins. Catechins, gallic acid, and tea alkaloids are adequate chemical descriptors to distinguish between fermented and nonfermented tea samples cultivated in different geographical areas.

Caffeine↗
PubMed2003

Analysis of three effective components in Fructus corni and its preparations by micellar electrokinetic capillary chromatography.

An efficient micellar electrokinetic capillary chromatography method was developed to analyze three major active components including morroniside, loganin and gallic acid in Fructus corni and its six preparations for the first time. The factors that could affect the separation were studied, such as the pH of the buffer, concentrations of SDS, organic modifier and beta-CD, and the applied voltage. The optimum analysis conditions were 10 mmol/L NaH(2)PO(4)-5 mmol/L Na(2)B(4)O(7) (pH 6.8) buffer containing 140 mmol/L SDS, 1 mmol/L beta-CD, 5% (v/v) methanol and 12.5 kV applied voltage. The linearity between the peak-areas and the concentrations of the analytes were investigated, and they exhibit excellent linear behavior over the concentration ranges (correlation coefficients 0.9953-0.9995). In addition, the pK(a) of gallic acid was determined using capillary zone electrophoresis. The result was consistent with that reported by the literature.

Buffers↗
PubMed2005

Antimutagenic effect of phenolic acids.

In the present study, the Salmonella typhimurium tester strain TA 100 was used in the plate-incorporation test to examine the antimutagenic potential of caffeic, ferulic and cichoric acids extracted from plant species of genera Echinacea (L) Moench, as well as of another phenolic acids, on 3-(5-nitro-2-furyl)acrylic acid (5NFAA) and sodium azide mutagenicity. All tested compounds possess antimutagenic activity. In the case of 5NFAA, the antimutagenic potency of tested compounds was in the order of gallic acid > ferulic acid > caffeic acid > syringic acid > vanillic acid. The mutagenic effect of sodium azide was inhibited by tested phenolic acids by about 20-35 %. The most effective compound, gallic acid inhibits this effect by 82 % in the concentration of 500 mug/plate. The only exception from favourable properties of tested phenolic acids is cichoric acid, which in the contrary significantly increased the mutagenic effect of 5NFAA.

Antimutagenic Agents↗
PubMed2004

[Antioxidative activity of propolis from Dalmatia (Croatia)].

AIM: The aim of this study was to determine the antioxidative activity of propolis from ecologically clean parts of Dalmatia. METHODS: Phenol concentration in ethanolic propolis extracts was determined by Folin-Ciocalteu reagent using gallic acid as the standard. Flavonoid phenolic compounds were analyzed after precipitation with formaldehyde. The residual non-flavonoid phenolics were also determined by Folin-Ciocalteu method. By determining the change of peroxide number (PN), of tiobarbiture acid reactive species (TBARS), and of DPPH-radical activity, antioxidative efficiency of propolis was tested and compared with well known and widely used synthetic antioxidants. Values of PN and TBARS were determined at 60 degrees C in samples of trigyceride substrate (lard) without and with the addition of antioxidants. Compared was the efficiency of three antioxidants: propolis (alcoholic extract), vitamin E, and (+)-catechin in a concentration of 1%. PN was monitored during 50 days. By the method of Sedlacek, TBARS were measured during 30 days. Antioxidative activity of propolis extract was also measured in terms of hydrogen donating ability using stable radical alpha,alpha-diphenyl-beta-picril hidrazyl (DPPH*) and compared with commercial synthetic antioxidants of butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), and (+)-cathecin. Inhibition degree of DPPH* was calculated by the formula of Yen and Duh. RESULTS: Total phenol content, expressed as gallic acid, in propolis extracts varied from 75.2 to 90.2 g/kg propolis. The proportion of flavonoids in total phenols ranged from 62% to 65%. Values of TBARS were not increased only in samples with added propolis. The inhibition of DPPH-radical by propolis extracts ranged from 93% to 96%, by catechin 95%, by BHT 49%, and by BHA 64%. Compared to BHT and BHA, propolis extracts showed greater reducing activity against DPPH-radical. DISCUSSION: The chemical composition of propolis, and thus its biological activity depend on the plant from which it has been collected, and on the macro- and microclimatic conditions. Many compounds in propolis exert antioxidative activity. A belief was expressed that the biological activity of propolis is very probably based mostly on its antioxidative efficiency. Dalmatian propolis showed high efficiency in the prevention of oxidative processes. This could be explained by the high proportion of polyphenol constituents, especially flavonoids. A very low and equal degree of increase of PN, as a measure of oxidative processes, was noticed in the samples of triglyceride substrate with the addition of propolis and (+)-catechin. The greatest rise of TBARS was measured in the samples of pure lard. There was no increase of TBARS only in the samples with added propolis. Propolis and (+)-catechin showed great efficiency in the inhibition of DPPH-radical, greater than BHT and BHA, which are widely used in food industry. CONCLUSION: The results indicate that Dalmatian propolis could be an efficient protective agent against oxidative processes in food. The high antioxidative activity of propolis, its natural origin, and present knowledge about its biological properties, make it a very promising nutritional additive for human diet.

Antioxidants↗
PubMed1989

Treatment of experimental acute uranium poisoning by chelating agents.

Sixteen chelating agents were examined to determine their relative efficacy as antidotes in acute uranyl acetate intoxication in mice after subcutaneous administration. Chelators were administered intraperitoneally to male Swiss mice at a dose equal to one-fourth of their respective LD50 and the therapeutic effectiveness was calculated. Eight compounds resulted in a significant enhancement of the survival rate: Tiron, gallic acid, DTPA, p-aminosalicylic acid, sodium citrate, EDTA, 5-aminosalicylic acid and EGTA. Therapeutic indices (TI) were then determined for these chelating agents. Tiron (TI: 158), gallic acid (TI: 116) and DTPA (TI: 44.9) were the most effective antidotes. In subsequent experiments, uranyl acetate dihydrate was administered subcutaneously (10 mg/kg) in a 24 hr excretion and distribution study. The previous eight chelators were given intraperitoneally ten min. after the uranium administration. 5-Aminosalicylic acid and tiron were consistently the most effective in increasing the urinary and faecal excretion of uranium respectively. A decrease of the uranium concentration in kidneys and bone was also noted with tiron. Tiron appears to be the most effective agent of those tested in the prevention of acute uranium intoxication.

Animals↗
PubMed2003

Isolation and structure elucidation of the major individual polyphenols in carob fibre.

Although it is already known that carob fibre contains several classes of polyphenolic substances, a comprehensive analysis of these has not been conducted to date. Therefore, the major polyphenolic compounds were extracted with organic solvents, and, following fractionation by normal-phase column chromatography on silicic acid, their structures were elucidated by liquid-chromatography electrospray-ionisation mass spectrometry (LC-ESI), nano-electrospray-ionisation mass spectrometry (ESI-MS), and gas-chromatography mass spectrometry (GC-MS). In addition, complete 1H and 13C NMR assignments were obtained for the isolated gallotannins 1,6-di-, 1,2,6-tri- and 1,2,3,6-tetra-O-galloyl-beta-D-glucose. Carob fibre was found to contain a rich variety of phenolic antioxidants. A total of 24 polyphenol compounds were identified with a yield of 3.94 g/kg (dry weight). The profile was dominated by gallic acid in various forms: free gallic acid (42% of polyphenols by weight), gallotannins (29%), and methyl gallate (1%), while simple phenols, mainly cinnamic acid, made up about 2% of the total. Flavonoids represented 26% of the polyphenols, and the major components were identified as the glycosides myricetin- and quercetin-3-O-alpha-L-rhamnoside (ca. 9% and 10%, respectively). These data indicate that carob fibre is rich in both amount and variety of phenolic antioxidant substances, and its inclusion in the diet may have chemopreventive properties.

Chromatography, Ion Exchange↗
PubMedDate not supplied

Identification of the main phenolic compounds in wood of Ceratonia siliqua by GC-MS.

The tannin composition of wood of Ceratonia siliqua (carob) was studied using GC-MS and classical chemical assays. Aqueous methanolic extracts of carob heartwood and sapwood were fractionated using organic solvents of increasing polarity, and GC-MS analyses were performed before and after hydrolysis. Prior to hydrolysis, gallic acid, catechin and its derivatives, methyl inositol and chalcone were determined as the major compounds found in the free form. Aqueous fractions of both wood types were hydrolysed with hydrochloric acid in methanol and extracted with organic solvents and water. These fractions were rich in methyl inositol, gallic acid, glucose and other monosaccharides. The results show that carob wood contains predominantly gallotannins and proanthocyanidins. The technique employed is shown to be a valuable tool and an alternative method to HPLC determination of hydrolysable tannin composition.

Fabaceae↗
PubMedDate not supplied

Interaction between antioxidants and hydroquinone/bisphenol.

We have investigated the stability of semiquinone radical (SQ .) produced from the mixture of hydroquinone (HQ) and bisphenol A (BPA) in the presence of various antioxidants, some of which induce apoptosis in tumor cell lines. BPA produced no detectable amount of ESR signal. The acceleration of HQ oxidation by BPA results in the production of SQ .. The BPA-enhanced SQ . production may occur through either SQ. regeneration by electron transfer from BPA working as an antioxidant or the O2- scavenging activity of BPA. SQ . intensity of HQ/BPA was reduced by lower concentrations of sodium ascorbate, epigallocatechin, gallate and quercetin, but significantly enhanced by gallic acid. The initial SQ . was replaced by the radicals of antioxidants except lignin and salicylic acid, at higher concentrations, due to their radical-radical coupling or dismutation process. Among these compounds, gallic acid enhanced the radical intensity of SQ . to the greatest extent. The results suggest that antioxidants from foods suppress the activity of xenobiotics such as HQ, however, they produce their own radical at higher concentrations, suggesting their bimodal actions. The present study demonstrates the usefulness of ESR spectroscopy for the interaction between HQ/BPA and antioxidants.

Antioxidants↗
PubMed1996

Inhibitory effects of alkyl gallate and its derivatives on fatty acid desaturation.

Alkyl gallate, which is known as an antioxidant, intensively inhibited delta 5 and delta 6 desaturation in both rat liver microsomes and an arachidonic acid-producing fungus Mortierella alpina 1S-4. The rat liver microsomal delta 5 and delta 6 desaturases were inhibited by gallic acid esterified with alcohols with various numbers of carbons, suggesting that the necessary structure in an esterified alcohol for the inhibition is not so strict. Among the three hydroxy groups in gallic acid, the m-hydroxy group was shown to be the necessary structure. Kinetic analyses revealed that propyl gallate is a noncompetitive inhibitor of delta 5 desaturase (Ki = 2.6.10(-5)M) and delta 6 desaturase (Ki = 1.7.10(-4) M). These data indicate that alkyl gallate is a new type of desaturase inhibitor and different from known natural inhibitors, i.e., sesamin and curcumin.

Animals↗
PubMed2002

Antioxidant properties of ferulic acid and its related compounds.

Antioxidant activity of 24 ferulic acid related compounds together with 6 gallic acid related compounds was evaluated using several different physical systems as well as their radical scavenging activity. The radical scavenging activity on 1,1-diphenyl-2-picrylhydrazyl (DPPH) decreased in the order caffeic acid > sinapic acid > ferulic acid > ferulic acid esters > p-coumaric acid. In bulk methyl linoleate, test hydroxycinnamic acids and ferulic acid esters showed antioxidant activity in parallel with their radical scavenging activity. In an ethanol-buffer solution of linoleic acid, the activity of test compounds was not always associated with their radical scavenging activity. Ferulic acid was most effective among the tested phenolic acids. Esterification of ferulic acid resulted in increasing activity. The activity of alkyl ferulates was somewhat influenced by the chain length of alcohol moiety. When the inhibitory effects of alkyl ferulates against oxidation of liposome induced by AAPH were tested, hexyl, octyl, and 2-ethyl-1-hexyl ferulates were more active than the other alkyl ferulates. Furthermore, lauryl gallate is most effective among the tested alkyl gallates. These results indicated that not only the radical scavenging activity of antioxidants, but also their affinity with lipid substrates, might be important factors in their activity.

Antioxidants↗
PubMed2006

Chemical composition of clarified bayberry (Myrica rubra Sieb. et Zucc.) juice sediment.

Clarified bayberry juice turned hazy upon storage at 25 degrees C for 6 months, and the chemical composition of centrifugally separated sediment was analyzed. Bayberry juice haze was mainly protein-tannin haze. The lyophilized sediment contained 20.4 +/- 4.3% of protein, 70.2 +/- 2.6% of total polyphenols, 7.2% of monosaccharides, and 6.7 +/- 0.6% of ash. Amino acid analyses and molecular weight distribution estimation indicated that bayberry proteins were haze-active proteins with a molecular weight less than 8 kDa. Gallic acid, quercetin hexoside, quercetin deoxyhexoside, and quercetin were found in the methanol-dissolved sample, while gallic acid, protocatechuic acid, cyanidin, ellagic acid, and quercetin were detected in the acid-hydrolyzed sample. Ellagic acid was the dominant individual phenolic (9.9 +/- 0.19 g/100 g dry weight, 55.3% of the total amount) in the sediment. Monosaccharides of rhamnose, arabinose, mannose, glucose, and galactose in the sediment were most probably the glycoside moieties of the anthocyanins, flavonols, and elllagitannins. Metal ions of calcium, magnesium, potassium, iron, and copper also indicated the heterogeneous characteristics of the sediment.

Amino Acids↗