3-4-dihydroxyphenylpropionic-acid and caffeic-acid

Coffee is one of the most frequently consumed beverages worldwide. Research on effects of coffee drinking has focused on caffeine; however, coffee contains myriad biochemicals that are chemically unrelated to caffeine, including 3,4-dihydroxyphenyl compounds (catechols) such as caffeic acid and dihydrocaffeic acid (DHCA).. This prospective within-subjects study examined effects of drinking caffeinated or decaffeinated coffee on plasma free (unconjugated) catechols measured by liquid chromatography with series electrochemical detection (LCED) after batch alumina extraction. To confirm coffee-related chromatographic peaks represented catechols, plasma was incubated with catechol-O-methyltransferase and S-adenosylmethionine before the alumina extraction; reductions in peak heights would identify catechols.. Ten healthy volunteers drank 2 cups each of caffeinated and decaffeinated coffee on separate days after fasting overnight. With subjects supine, blood was drawn through an intravenous catheter up to 240 min after coffee ingestion and the plasma assayed by alumina extraction followed by LCED.. Within 15 min of drinking coffee of either type, >20 additional peaks were noted in chromatographs from the alumina eluates. Most of the coffee-related peaks corresponded to free catechols. Plasma levels of the catecholamines epinephrine and dopamine increased with both caffeinated and decaffeinated coffee. Levels of other endogenous catechols were unaffected. Plasma DHCA increased bi-phasically, in contrast with other coffee-related free catechols.. Drinking coffee-whether caffeinated or decaffeinated-results in the rapid appearance of numerous free catechols in the plasma. These might affect the disposition of circulating catecholamines. The bi-phasic increase in plasma DHCA is consistent with production by gut bacteria.

Topics: Adult; Caffeic Acids; Caffeine; Catechols; Coffee; Female; Humans; Male; Plasma; Prospective Studies; Young Adult

3',4'-Dihydroxycinnamic acid (aka caffeic acid) is a common dietary component found in a variety of plant-derived food products either in a free form or esterified as in chlorogenic acids such as 5-

Topics: Caffeic Acids; Chlorogenic Acid; Colon; Feces; Fermentation; Humans; Hydroxybenzoates; Microbiota; Quinic Acid

Amyloid-β (Aβ) deposition and oxidative stress observed in the brains of patients with Alzheimer's disease (AD) are important targets for therapeutic intervention. In this study, we conjugated the antioxidants caffeic acid (CA) and dihydrocaffeic acid (DHCA) to Aβ

Topics: Alzheimer Disease; Amyloid; Amyloid beta-Peptides; Antioxidants; Caffeic Acids; Cell Line, Tumor; Humans; Neuroprotective Agents; Oxidative Stress; Peptide Fragments; Protein Aggregates

Avenanthramides (AVAs), which are found exclusively in oats, may play an important role in anti-inflammation and antiatherogenesis. Although the bioavailability of AVAs has been investigated previously, little is known about their metabolism.. The aim of the present study was to investigate the metabolism of avenanthramide-C (2c), one of the major AVAs, in mice and by the human microbiota, as well as to elucidate the bioactivity of its major metabolites with the goal of finding new exposure markers to precisely reflect oat consumption.. For the mouse study, 10 CF-1 female mice were divided into control (vehicle-treated) and 2c intragastrically treated (200 mg/kg) groups (5 mice/group). Twenty-four-hour urine and fecal samples were collected with use of metabolic cages. For the batch culture incubations, 2c was cultured with fecal slurries obtained from 6 human donors. Incubated samples were collected at various time points (0, 12, 24, 48, 72, 96, and 120 h). Metabolites were identified via HPLC with electrochemical detection and LC with electrospray ionization/mass spectrometry. To investigate whether 2c metabolites retain the biological effects of 2c, we compared their effects on the growth of and induction of apoptosis in HCT-116 human colon cancer cells.. Eight metabolites were detected from the 2c-treated mouse urine samples. They were identified as 5-hydroxyanthranilic acid (M1), dihydrocaffeic acid (M2), caffeic acid (M3), dihydroferulic acid (M4), ferulic acid (M5), dihydroavenanthramide-C (M6), dihydroavenanthramide-B (M7), and avenanthramide-B (M8) via analysis of their MS(n) (n = 1-3) spectra. We found that the reduction of 2c's C7'-C8' double bond and the cleavage of its amide bond were the major metabolic routes. In the human microbiota study, 2c was converted into M1-M3 and M6. Moreover, interindividual differences in 2c metabolism were observed among the 6 human subjects. Subjects B, C, E, and F could rapidly metabolize 2c to M6, whereas subject D metabolized little 2c, even up to 120 h. In addition, only subjects A, B, and F could cleave the amide bond of 2c or M6 to form the cleaved metabolites. Furthermore, we showed that 2c and its major metabolite M6 are bioactive compounds against human colon cancer cells. M6 was more active than 2c with the half-inhibitory concentration (IC50) of 158 μM and could induce apoptosis at 200 μM.. To our knowledge, the current study demonstrates for the first time that avenanthramide-C can be extensively metabolized by mice and the human microbiota to generate bioactive metabolites.

Topics: Adult; Animals; Apoptosis; Avena; Biotransformation; Body Mass Index; Caffeic Acids; Chromatography, High Pressure Liquid; Coumaric Acids; Feces; Female; HCT116 Cells; Healthy Volunteers; Humans; Male; Mice; Microbiota; ortho-Aminobenzoates; Spectrometry, Mass, Electrospray Ionization

Although ingestion of coffee and its constituent chlorogenic acid (CGA) protects the retina from oxidative stress, the bioaccessibility and bioavailability of coffee metabolites are not well understood. The aim of this study was to determine which coffee metabolites reach the retina and protect against retinal degeneration.. UPLC-MS/MS was used to detect CGA and coffee metabolites in the rat eye. The methyl thiazolyl tetrazolium assay and double staining with Hoechst and propidium iodide showed that CGA, caffeic acid (CA), and dihydrocaffeic acid (DHCA) protect retinal ganglion cells from hypoxia-induced damage. Western blots showed that treatment with coffee metabolites up-regulated anti-apoptotic proteins such as Bcl-2 and Bcl-XL and down-regulated pro-apoptotic proteins such as Bad, PARP, and cleaved caspase 3. Adult ICR mice were subjected to optic nerve crush-induced retinal ganglion cell death with intravitreal pre-treatment with coffee metabolites 1 day before and 1 h after the procedure. Retrograde Fluorogold(TM) labeling showed severe retinal ganglion cell loss after optic nerve crushing, and coffee metabolites significantly reduced damage to retinal ganglion cells.. CGA and coffee metabolites, especially, CA, and DHCA, reach the eye, where they can significantly reduce apoptosis induced by hypoxia and optic nerve crush stress, and thus prevent retinal degeneration.

Topics: Animals; Antioxidants; Caffeic Acids; Cell Hypoxia; Cell Survival; Chlorogenic Acid; Coffee; Free Radical Scavengers; Male; Mice, Inbred ICR; Neuroprotective Agents; Proteins; Rats, Sprague-Dawley; Retinal Degeneration; Tandem Mass Spectrometry

In our previous paper, we reported that rosmarinic acid (1) of Argusia argentea could neutralize snake venom induced hemorrhagic action. Rosmarinic acid (1) consists of two phenylpropanoids: caffeic acid (2) and 3-(3,4-dihydroxyphenyl)lactic acid (3). In this study, we investigated the structural requirements necessary for inhibition of snake venom activity through the use of compounds, which are structurally related to rosmarinic acid (1). By examining anti-hemorrhagic activity of cinnamic acid analogs against Protobothrops flavoviridis (Habu) venom, it was revealed that the presence of the E-enoic acid moiety (-CH=CH-COOH) was critical. Furthermore, among the compound tested, it was concluded that rosmarinic acid (1) (IC(50) 0.15 μM) was the most potent inhibitor against the venom.

Topics: Animals; Antivenins; Caffeic Acids; Cinnamates; Crotalid Venoms; Depsides; Hemorrhage; Humans; Male; Mice; Rosmarinic Acid; Snakes; Structure-Activity Relationship

Hydroxycinnamic acids are a class of phenolic antioxidants found widely in dietary plants. Their biotransformation in the human organism primarily involves Phase II conjugation reactions. In this study, activities of UDP-glucuronosyltransferases (UGTs) and sulfotransferases (SULTs) towards major dietary hydroxycinnamic acids (caffeic, dihydrocaffeic, dihydroferulic, ferulic and isoferulic acids) were investigated. Conjugate formation was evaluated using human liver and intestinal S9 homogenates, and in vitro characterization was carried out using recombinant human UGTs and SULTs. Analysis of the kinetics of hydroxycinnamic acid conjugation in human S9 homogenates revealed that intrinsic clearance (V(max)/K(m)) is much greater for sulfation than for glucuronidation. Assessment of activity using a panel of recombinant human SULTs showed that SULT1A1 is most active in the sulfation of caffeic, dihydrocaffeic and isoferulic acids, while SULT1E1 is most active in the sulfation of ferulic and dihydroferulic acids. Only isoferulic acid was significantly glucuronidated by human liver S9 homogenates, explained by the high activity of liver-specific UGT1A9. Studies on the kinetics of active SULTs and UGTs demonstrated a markedly lower K(m) for SULTs. To further corroborate our findings, we carried out an intervention study in healthy humans to determine the hydroxycinnamic acid conjugates in urine after consumption of hydroxycinnamate-rich coffee (200 ml). Analysis showed that sulfates are the main conjugates in urine, with the exception of isoferulic acid, which is mainly glucuronidated. These data suggest that sulfates are the predominant hydroxycinnamic acid conjugates in humans, and that SULT mediated sulfation is a major factor determining the bioavailability of hydroxycinnamic acids in vivo.

Topics: Adult; Biotransformation; Caffeic Acids; Cells, Cultured; Chromatography, High Pressure Liquid; Cinnamates; Coumaric Acids; Diet; Female; Glucuronosyltransferase; Humans; Kinetics; Male; Sulfates; Sulfotransferases; Young Adult

In the light of known HDAC inhibitors, 33 carboxylic acid derivatives were tested to understand the structural requirements for HDAC inhibition activity. Several modifications were applied to develop the structure-activity relationships of carboxylic acid HDAC inhibitors. HDAC inhibition activities were investigated in vitro by using HeLa nuclear extract in a fluorimetric assay. Molecular docking was also carried out for the human HDAC8 enzyme in order to predict inhibition activity and the 3D poses of inhibitor-enzyme complexes. Of these compounds, caffeic acid derivatives such as chlorogenic acid and curcumin were found to be highly potent compared to sodium butyrate, which is a well-known HDAC inhibitor.

Topics: Caffeic Acids; Carboxylic Acids; Catalytic Domain; Chlorogenic Acid; Curcumin; Enzyme Inhibitors; HeLa Cells; Histone Deacetylase Inhibitors; Histone Deacetylases; Humans; Models, Molecular; Molecular Structure; Protein Binding

A validated method was developed for the simultaneous determination of the hydroxycinnamates caffeic acid (CA), dihydrocaffeic acid (DHCA), ferulic acid (FA), dihydroferulic acid (DHFA), and isoferulic acid (IFA) in human plasma as metabolites derived from coffee consumption. The method includes a protein precipitation step prior to enzymatic hydrolysis of the conjugated metabolites (sulfate, glucuronide, and/or ester) back to their aglycone forms. After liquid-liquid extraction, the reconstituted extract was analysed by high-performance liquid chromatography coupled to negative electrospray ionisation tandem mass spectrometry. Calibration curves were constructed from spiked human plasma samples in the range of 0-4800 nM for each of the targeted analytes. Two internal standards, 3-(4-hydroxyphenyl)-propionic acid (500 nM) and 1,3-dicaffeoylquinic acid (200 nM), were spiked at the beginning of the sample preparation and before analysis, respectively. Good performance data were obtained with limits of detection and quantification of the five hydroxycinnamates ranging between 1-15 nM and 3-50 nM, respectively. Within and between-days precisions were respectively calculated between 8-18% and 8-30% (at 50 nM added initially), between 6-9% and 6-12% (at 200 nM), and between 5-9% and 5-9% (at 500 nM). Precision calculated from different analysts ranged from 18% to 44% (at 50 nM), from 8% to 16% (at 200 nM), and from 4% to 8% (at 500 nM). Using this method, we determined plasma levels in humans and measured the efficiency of deconjugation using our enzymatic cocktail.

Topics: Area Under Curve; Caffeic Acids; Chromatography, Liquid; Cinnamates; Coumaric Acids; Humans; Hydrolysis; Kinetics; Limit of Detection; Reproducibility of Results; Spectrometry, Mass, Electrospray Ionization; Tandem Mass Spectrometry

The current growing interest for natural antioxidants has led to a renewed scientific attention for artichoke, due not only to its nutritional value, but, overall, to its polyphenolic content, showing strong antioxidant properties. The major constituents of artichoke extracts are hydroxycinnamic acids such as chlorogenic acid, dicaffeoylquinic acids caffeic acid and ferulic acid, and flavonoids such as luteolin and apigenin glycosides. In vitro studies, using cultured rat hepatocytes, have shown its hepatoprotective functions and in vivo studies have shown the inhibition of cholesterol biosynthesis in human subjects. Several studies have shown the effect on animal models of artichoke extracts, while information on human bioavailability and metabolism of hydroxycinnamates derivatives is still lacking. Results showed a plasma maximum concentration of 6.4 (SD 1.8) ng/ml for chlorogenic acid after 1 h and its disappearance within 2 h (P< 0.05). Peak plasma concentrations of 19.5 (SD 6.9) ng/ml for total caffeic acid were reached within 1 h, while ferulic acid plasma concentrations showed a biphasic profile with 6.4 (SD1.5) ng/ml and 8.4 (SD4.6) ng/ml within 1 h and after 8 h respectively. We observed a significant increase of dihydrocaffeic acid and dihydroferulic acid total levels after 8 h (P<0.05). No circulating plasma levels of luteolin and apigenin were present. Our study confirms the bioavailability of metabolites of hydroxycinnamic acids after ingestion of cooked edible Cynara scolymus L. (cultivar Violetto di Provenza).

Topics: Absorption; Adult; Antioxidants; Caffeic Acids; Chlorogenic Acid; Cinnamates; Cooking; Coumaric Acids; Cynara scolymus; Eating; Female; Humans; Male; Pilot Projects; Plant Extracts

Phenolic compounds are not completely absorbed in the small intestine and so enter the colon, where they might exert physiological effects. To identify phenolics that are present in normal human colon, fecal water was prepared from 5 free-living volunteers with no dietary restrictions and analyzed by gas chromatography-mass spectrometry. Daily measurements were also performed on a single individual to examine the variation more closely. Levels of polyphenols were variable between individuals. Naringenin and quercetin had mean concentrations of 1.20 and 0.63 microM. All other flavonoids examined were present < or =0.17 microM. Simple phenolic and other aromatic acids were present at much higher concentrations. The major components were phenylacetic acid, 479 microM; 3-phenylpropionic acid, 166 microM; 3-(4-hydroxy)-phenylpropionic acid, 68 microM; 3,4-dihydroxycinnamic acid, 52 microM; benzoic acid, 51 microM; 3-hydroxyphenylacetic acid, 46 microM; and 4-hydroxyphenylacetic acid, 19 microM. Other phenolic acids ranged from 0.04 to 7 microM. Decreased dietary phenolic intake caused a decrease in polyphenol and monophenolic acid concentration in fecal water 24 h later. This study is the first to measure the range of aromatic compounds in human fecal water and demonstrates that phenolic acid concentrations are high. The biological effects of phenolics may play an important role in colon function.

Topics: Adult; Benzoic Acid; Caffeic Acids; Colon; Diet; Dose-Response Relationship, Drug; Feces; Flavanones; Flavonoids; Free Radicals; Gas Chromatography-Mass Spectrometry; Humans; Intestine, Small; Male; Models, Chemical; Phenol; Phenols; Phenylacetates; Phenylpropionates; Polyphenols; Quercetin; Time Factors

It was previously reported that m-coumaric acid, m-hydroxyphenylpropionic acid (mHPP), and 3,4-dihydroxyphenylpropionic acid (DHPP) are major metabolites of ingested caffeic acid formed by gut microflora and would be transported by the monocarboxylic acid transporter (MCT). We have directly measured their absorption characteristics in Caco-2 cells using a coulometric detection method involving HPLC-ECD. The proton-coupled directional transport of m-coumaric acid, mHPP, and DHPP was observed, and the transport was inhibited by an MCT substrate. The permeation of m-coumaric acid and mHPP was concentration-dependent and saturable: The Michaelis constant for m-coumaric acid and mHPP was 32.5 and 12.9 mM, respectively, and the maximum velocity for m-coumaric acid and mHPP was 204.3 and 91.2 nmol (min)(-1) (mg protein)(-1), respectively. By contrast, the permeation of DHPP was nonsaturable even at 30 mM and was inversely correlated with the paracellular permeability of Caco-2 cells. Our results demonstrate that these compounds are absorbed by the MCT, although DHPP is mainly permeated across Caco-2 cells via the paracellular pathway. MCT-mediated absorption of phenolic compounds per se and their colonic metabolites would exert significant impact on human health.

Topics: Biological Transport; Caco-2 Cells; Caffeic Acids; Chromatography, High Pressure Liquid; Coumaric Acids; Epithelial Cells; Humans; Intestinal Absorption; Intestines; Monocarboxylic Acid Transporters; Symporters

The effect of chlorogenic acid on the sleep-wakefulness cycle in rats was investigated in comparison with those of caffeic acid (the metabolite of chlorogenic acid) and dihydrocaffeic acid (the metabolite of caffeic acid). A significant prolongation of sleep latency was observed with chlorogenic acid and caffeic acid at a dose of 500 and 200 mg/kg, respectively. On the other hand, no remarkable effects were observed with dihydrocaffeic acid even at a dose of 500 mg/kg. Caffeine caused a significant increase in sleep latency and waking time and decrease in non-rapid eye movement sleep time at a dose of 10 mg/kg. In contrast, chlorogenic acid and its metabolites had no significant effects on each sleep state. From these results, it may be concluded that chrologenic acid caused a mild arousal effect compared with that of caffeine, and the effect of chlorogenic acid may have occurred through its metabolite caffeic acid.

Topics: Animals; Antioxidants; Caffeic Acids; Caffeine; Central Nervous System Stimulants; Chlorogenic Acid; Dose-Response Relationship, Drug; Electroencephalography; Electromyography; Male; Rats; Rats, Wistar; Sleep; Sleep, REM; Wakefulness

Seven representative compounds isolated from Salvia officinalis, among them caffeic acid, the dimer rosmarinic acid and oligomers of caffeic acid, were investigated with regard to their antioxidant potential both expressed by the radical scavenging activity and the stability and structure of the intermediate radicals. Pulse-radiolytic investigation revealed very high rate constants with both hydroxyl and azide radicals. Evidence from kinetic modelling calculations suggested unusual complex behavior due to the presence of both O(4)- and O(3)-semiquinones and - in two cases - formation and decay of a hydroxyl radical adduct at the vinyl side chain. EPR spectroscopy studies, which included dihydrocaffeic acid as a model for the saturated side chains of the oligomers, confirmed that the radical structures after oxidation in slightly alkaline solutions are representing dissociated O(4)-semiquinones. While according to calculations based on hybrid density-functional theory the other radical structures are valid intermediates, they cannot be observed except by pulse radiolysis due to their fast decay.

Topics: Benzoquinones; Caffeic Acids; Cinnamates; Depsides; Electron Spin Resonance Spectroscopy; Free Radical Scavengers; Hydroxyl Radical; Linear Models; Mathematics; Molecular Structure; Phenols; Pulse Radiolysis; Rosmarinic Acid; Salvia officinalis

Ten esters each of caffeic acid and dihydrocaffeic acid have recently been synthesized. Cytotoxicity evaluations of these esters versus L1210 leukemia and MCF-7 breast cancer cells in culture have led to the delineation of substantially different QSAR for each series. The L1210 QSAR for dihydrocaffeic acid esters resembles the QSAR obtained for simple phenols and estrogenic phenols. However, the QSAR pertaining to the caffeic acid esters differs considerably from its sister QSAR. This difference may be attributed to the presence of the olefinic linkage in the side chain. The octyl ester of caffeic acid is nearly ten times as toxic to the leukemia cells than the widely studied phenethyl ester, CAPE.

Topics: Animals; Anticarcinogenic Agents; Breast Neoplasms; Caffeic Acids; Cell Division; Dose-Response Relationship, Drug; Drug Evaluation, Preclinical; Esters; Leukemia L1210; Mice; Models, Theoretical; Structure-Activity Relationship; Tumor Cells, Cultured

The antioxidant properties of the dietary dihydroxycinnamic acids [caffeic (CA), dihydrocaffeic (DHCA), and chlorogenic (CGA) acids] have been well studied but little is known about their metabolism. In this article, evidence is presented showing that CA, DHCA, and CGA form quinoids and hydroxylated products when oxidized by peroxidase/H(2)O(2) or tyrosinase/O(2). Mass spectrometry analyses of the metabolites formed with peroxidase/H(2)O(2)/glutathione (GSH) revealed that mono- and bi-glutathione conjugates were formed for all three compounds except CGA, which formed a bi-glutathione conjugate only when GSH was present. In contrast, the metabolism of the dihydroxycinnamic acids by tyrosinase/O(2)/GSH resulted in the formation of only mono-glutathione conjugates. In the absence of GSH, hydroxylated products and p-quinones of CA or CGA were formed by peroxidase/H(2)O(2). DHCA formed a hydroxylated adduct (even though GSH was present), as well as the corresponding p-quinone and dihydroesculetin, an intramolecular cyclization product. NADPH also supported rat liver microsomal-catalyzed CA-, CGA-, and DHCA-glutathione conjugate formation, which was prevented by benzylimidazole, a cytochrome P450 inhibitor. Furthermore, the cytotoxicity of CA, CGA, and DHCA toward isolated rat hepatocytes was markedly enhanced by hydrogen peroxide or cumene hydroperoxide-supported cytochrome P450 and was prevented by benzylimidazole. Cytotoxicity was also markedly enhanced by dicumarol, an NADPH/oxidoreductase inhibitor. These results suggest that dihydroxycinnamic acids were metabolically activated by P450 peroxidase activity to form cytotoxic quinoid metabolites.

Topics: Animals; Antioxidants; Benzoquinones; Caffeic Acids; Cell Survival; Chlorogenic Acid; Glutathione; Hepatocytes; Kinetics; Male; Mass Spectrometry; Microsomes, Liver; Oxidation-Reduction; Rats; Rats, Sprague-Dawley; Spectrophotometry, Ultraviolet

The antioxidant activity of several plant catechol derivatives was tested in buffer, plasma, and human erythrocytes. In buffer, chlorogenic acid (CGA), caffeic acid (CA), and dihydrocaffeic acid (DCA) reduced ferric iron equally well in the ferric reducing antioxidant power (FRAP) assay. Low concentrations of the polyphenols enhanced the ability of plasma to reduce ferric iron by about 10%. In plasma, lipid hydroperoxide and F2-isoprostane formation induced by a water-soluble free radical initiator were reduced by CGA at concentrations as low as 20 microM. During incubation at 37 degrees C, human erythrocytes took up DCA, but not CGA, and intracellular DCA enhanced the ability of erythrocytes to reduce extracellular ferricyanide. When intact erythrocytes were exposed to oxidant stress generated by liposomes containing small amounts of lipid hydroperoxides, extracellular CGA at a concentration of 5 microM decreased both lipid peroxidation in the liposomes, and spared alpha-tocopherol in erythrocyte membranes. These results suggest that the catechol structure of these compounds convey the antioxidant effect in plasma and in erythrocytes.

Topics: alpha-Tocopherol; Antioxidants; Caffeic Acids; Catechols; Cell Membrane; Chlorogenic Acid; Dose-Response Relationship, Drug; Erythrocytes; Ferricyanides; Humans; Iron; Lipid Peroxidation; Lipid Peroxides; Liposomes; Models, Chemical; Plant Extracts; Time Factors

The antiradical activity of caffeic acid (1), dihydrocaffeic acid (5), and their corresponding n-alkyl esters was evaluated by using the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH(*)) method. Dihydrocaffeic acid (5) was the most potent compound, having an antiradical effect higher than that of (+/-)-alpha-tocopherol, whereas caffeic acid (1) was less efficient. Esterification of the carboxyl group of dihydrocaffeic acid (5) had a dramatic effect on its antiradical potency, but similar effects were not observed for caffeic acid (1) derivatives. The n-alkyl esters of both phenolic series had similar potencies, and their antiradical activities were independent of the alkyl chain length. Dose-dependent scavenger effects were found in both series. Acid-base properties of the compounds, evaluated by using potentiometry and spectrophotometry, showed that the catechol moiety had pK(a2) and pK(a3) values of 9. 24-9.02 and 11.38-10.99 in the dihydrocaffeic series and 8.48-8.24 and 11.38-11.07 in the caffeic series, respectively. Antiradical activity and pK(a) values of the compounds were not related.

Topics: Antioxidants; Caffeic Acids; Esters; Free Radical Scavengers; Free Radicals; Phenols; Potentiometry; Structure-Activity Relationship; Vitamin E

The reductive release of ferritin iron by several naturally occurring o-diphenols was studied. The initial rate of iron release was quantified by spectrophotometric measurement of the Fe(ferrozine)3(2+) complex, which absorbs maximally at 562 nm. The initial rate of iron release was dependent upon o-diphenol concentration, but not on the concentration of the chromophoric chelating agent, ferrozine, Stoichiometric measurements resulted in a ratio of 2Fe(II) released per molecule of o-diphenol. The series of o-diphenols studied included, caffeic acid, chlorogenic acid, dihydrocaffeic acid, 3,4-dihydroxybenzoic acid, and several analogs. These reductants represent an oxidation reduction potential range of 0.38 volts. A direct correlation between reducing power of the o-diphenols and rate of ferritin iron release was observed. Superoxide dismutase, catalase, mannitol, or general radical traps had no effect on the rate of iron removal; however, EDTA and oxalate inhibited iron release. A mechanism for ferritin iron reduction and release by o-diphenols consistent with the experimental observations is discussed.

Topics: Animals; Caffeic Acids; Chlorogenic Acid; Edetic Acid; Ferritins; Horses; Iron; Oxalates; Oxidation-Reduction; Phenols; Plant Extracts

Topics: Antiviral Agents; Caffeic Acids; Cinnamates; Oxidation-Reduction; Simplexvirus; Viral Plaque Assay