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PubMed1990

[Propolis allergy].

The incidence of propolis contact sensitivity was 1.2-3.3% among 7483 hospital patients during the period 1981-1987, while the prevalence among 1,558 healthy volunteers was 0.64%. A group of 26 patients with contact allergy to propolis was challenged with identified substances isolated from propolis. The mixture of 3-methyl-2-butenylester (3M2B) and 3-methyl-3-butenylester (3M3B) from caffeic acid caused a positive reaction in 7 patients, and in 5 of 9 patients there was a positive reaction to the mixture of 3M2B and 3M3B from diacetyl-caffeic acid. Among the 19 patients challenged with the flavonoid group, 3 had positive reactions, and individual derivatives of cinnamic acid caused positive reactions in 3 and 4 patients each. When five components taken from poplar buds were tested, the one that provoked the largest number of positive reactions was the methanol component (15 of 19 patients). The results show that propolis contact allergy is not caused by one main allergen, but by several allergens varying in chemical composition; the presence of these in propolis depends on the nature of the source plant and the place and time of collection by the bees.

Adult↗
PubMed1976

Reactivation mechanisms of thiamine with thermostable factors.

It was observed, in vitro, that the water extract of the fermented-tea customarily chewed by Thai people has a similar thermostable thiamine-inactivating factor to that found in the water extract of fern. It was also observed that the percentage of thiamine disulfide formed from thiamine with some flavones, catechol, pyrogallol, caffeic acid, dihydroxyphenylalanine, and hemin is greater at pH 7.5 than at pH 7.0. With some flavonoids, such as quercetin, rutin, and 6,7,4'-trihydroxyisoflavone, and pyrogallol, hemin, catechol and caffeic acid at pH 7.5, around 30-100% of thiamine is changed into thiamine disulfide. Water extract of shiitake, okra, coffee, black tea and fukinoto have only weak activities of thermostable thiamine-inactivating factors as a large percentage of thiamine disulfide is formed from thiamine even at pH 7.0. 2-Methyl-4-amino-5-aminomethylpyrimidine was isolated from the reaction mixture of 1 g thiamine with 20 mg catechol (1:0.5 mole) at pH 7.0, 45 degrees C, and identified with the synthesized pyrimidine.

Antimetabolites↗
PubMed2006

N-Methyltransferase involved in gramine biosynthesis in barley: cloning and characterization.

The indole alkaloid gramine occurs in leaves of certain barley (Hordeum vulgare L.) cultivars but not in others. A gene sequence in barley that earlier was characterized as a jasmonate-induced O-methyltransferase (MT) (EC 2.1.1.6, GenBank accession U54767) was here found to be absent in some barley cultivars and breeding lines that all lacked gramine. The cDNA was cloned and expressed in Escherichia coli and the recombinant protein purified. The purified recombinant protein methylated two substrates in the pathway to gramine: 3-aminomethylindole (AMI) and N-methyl-3-aminomethylindole (MAMI) at a high rate, with Km-values of 77 microM and 184 microM, respectively. In contrast, the protein did not exhibit any detectable methylation with the earlier suggested substrate for O-methylation, caffeic acid. A number of cultivars and breeding lines of barley were analyzed for presence of the U54767 gene sequence and MT protein and the enzyme activity in vitro with MAMI or caffeic acid as substrates. The results showed a clear relationship between the presence of the MT gene, the MT protein and N-methyltransferase activity, and confirmed the identification of the gene as coding for an N-methyltransferase (NMT, EC 2.1.1) and being involved in gramine biosynthesis.

Alkaloids↗
PubMed2000

Enzymatic synthesis and purification of caffeoyl-CoA, p-coumaroyl-CoA, and feruloyl-CoA.

An enzyme preparation from wheat seedlings containing p-coumaroyl:CoA ligase activity was used to synthesize caffeoyl-CoA, p-coumaroyl-CoA, and feruloyl-CoA. The same enzyme preparation also contains caffeic acid-3-O-methyl transferase and caffeoyl-CoA-3-O-methyl transferase activities. The maximum activity was found in enzyme preparation from 2-day-old seedlings, where 15-20% of the hydroxy cinnamic acid could be converted into the corresponding thioester. This yield is a result of an equilibrium between the ligase and a thioesterase also present in the crude enzyme preparation. The activity of caffeic acid 3-O-methyl transferase and caffeoyl-CoA 3-O-methyl transferase enables the production of (14)C-labeled feruloyl-CoA when using S-adenosyl-l-[methyl-(14)C]-methionine as methyl donor. The produced thioesters can be purified by reverse phase HPLC using a phosphoric acid-acetonitrile gradient.

Acetonitriles↗
PubMed2006

Inhibitory effects of polyphenolic compounds on human arylamine N-acetyltransferase 1 and 2.

Arylamine N-acetyltransferases (NAT) are important enzymes involved in the metabolic activation of aromatic and heterocyclic amines and inhibitors of NAT enzymes may be valuable as chemopreventive agents. Phytochemicals including cinnamic acid derivatives, various classes of flavonoids and coumarins were tested for the inhibitory activity on NAT1 and NAT2 from human liver and the human cholangiocarcinoma cell line: KMBC cells. Assays were performed using p-aminobenzoic acid and sulfamethazine as selective substrates for NAT1 and NAT2, respectively. NAT1 and NAT2 activities were present in liver cytosol. However, the KMBC cells showed only NAT1 activity. There was a marked difference in the ability of the test chemicals to inhibit NAT1 and NAT2. Caffeic acid, ferulic acid, gallic acid and EGCG inhibited NAT1 but not NAT2, whereas scopuletin and curcumin inhibited NAT2 but not NAT1. Quercetin, kaemferol and other flavonoids, except epicatechin and silymarin, inhibited both enzymes. The kinetics of inhibition of NAT1 by caffeic acid, EGCG and quercetin were of the non-competitive type, whereas that of NAT2 by quercetin, curcumin and kaemferol was also of the non-competitive type. The most potent inhibitor was quercetin, which has the inhibitory constants for NAT1 and NAT2 of 48.6 +/- 17.3 and 10.0 +/- 1.8 microM, respectively.

Arylamine N-Acetyltransferase↗
PubMed2002

Black cohosh (Cimicifuga racemosa L.) protects against menadione-induced DNA damage through scavenging of reactive oxygen species: bioassay-directed isolation and characterization of active principles.

The roots/rhizomes of Cimicifuga racemosa L. (Nutt.) (black cohosh) have traditionally been used to treat menopausal symptoms through an unknown mechanism of action. In an effort to determine if black cohosh had additional health benefits, methanol extracts were investigated for their potential to scavenge reactive oxygen species and to protect against menadione-induced DNA damage. These extracts effectively scavenged 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radicals. In addition, the extracts showed dose-dependent decreases in DNA single-strand breaks and oxidized bases induced by the quinone menadione using the comet (single-cell gel electrophoresis assay) and fragment length associated repair enzyme assays, respectively. Bioassay-directed fractionation of the methanolic extracts using the DPPH assay as a monitor led to the isolation of nine antioxidant active compounds: caffeic acid (1), methyl caffeate (2), ferulic acid (3), isoferulic acid (4), fukinolic acid (5), cimicifugic acid A (6), cimicifugic acid B (7), cimicifugic acid F (8), cimiracemate A (9), and cimiracemate B (10). Six of these antioxidants were found to reduce menadione-induced DNA damage in cultured S30 breast cancer cells with the following order of potency: methyl caffeate (2) > caffeic acid (1) > ferulic acid (3) > cimiracemate A (9) > cimiracemate B (10) > fukinolic acid (5). These data suggest that black cohosh can protect against cellular DNA damage caused by reactive oxygen species by acting as antioxidants.

Antioxidants↗
PubMed2005

Interactive effects of polyphenols, tocopherol and ascorbic acid on the Cu2+-mediated oxidative modification of human low density lipoproteins.

BACKGROUND: Only limited knowledge is available about any interactions between phenolic compounds and other antioxidants in inhibiting LDL oxidation. Many foods and beverages contain high levels of phenolic compounds; therefore, these compounds should not be considered in isolation from each other. AIM OF THE STUDY: The aim of this study was to examine the structure-antioxidant activity relationship of quercetin, caffeic acid, epicatechin, hesperetin and phloretin as well as alpha-tocopherol and ascorbic acid through their ability to interact with copper ions. METHODS: Isolated human LDL were incubated with single antioxidants or a combination of two and the kinetics of lipid peroxidation were assessed by measurement of conjugated diene formation (lag phase) via monitoring the absorbance at 234 nm after addition of copper ions. In addition, the degree of oxidation of the LDL protein moiety was followed by tryptophan fluorescence and carbonyl content measurements. RESULTS: Alpha-tocopherol and ascorbic acid showed a lower antioxidant activity in all test systems as compared to polyphenols at equimolar concentrations. Quercetin was the most effective compound in all three systems (p < 0.001 for lag phase and carbonyl content determination). A significant (p < 0.001) prolongation of the lag phase was found when combinations of ascorbic acid/quercetin, ascorbic acid/epicatechin, epicatechin/caffeic acid, and quercetin/epicatechin were tested as compared to the sum of the individual effects. Concerning the effects on LDL protein oxidation, the results from carbonyl content and the tryptophan fluorescence measurements showed that the combination of quercetin and caffeic acid revealed the strongest inhibitory effect (p < 0.001 carbonyl content; p < or = 0.002 tryptohan fluorescence) on protein oxidation which was higher than the effect of the single compounds. CONCLUSIONS: The results of the present study indicate that a combination of different antioxidants can be superior to the action of single antioxidants in protecting LDL lipid and protein moiety against oxidation. However, the substances may act by different antioxidative mechanisms, which are not necessarily complementary.

Antioxidants↗
PubMed2002

Neuroimmune interactions in guinea pig stomach and small intestine.

Enteric neuroimmune interactions in gastrointestinal hypersensitivity responses involve antigen detection by mast cells, mast cell degranulation, release of chemical mediators, and modulatory actions of the mediators on the enteric nervous system (ENS). Electrophysiological methods were used to investigate electrical and synaptic behavior of neurons in the stomach and small intestine during exposure to beta-lactoglobulin in guinea pigs sensitized to cow's milk. Application of beta-lactoglobulin to sensitized preparations depolarized the membrane potential and increased neuronal excitability in small intestinal neurons but not in gastric neurons. Effects on membrane potential and excitability in the small intestine were suppressed by the mast cell stabilizing drug ketotifen, the histamine H(2) receptor antagonist cimetidine, the cyclooxygenase inhibitor piroxicam, and the 5-lipoxygenase inhibitor caffeic acid. Unlike small intestinal ganglion cells, gastric myenteric neurons did not respond to histamine applied exogenously. Antigenic exposure suppressed noradrenergic inhibitory neurotransmission in the small intestinal submucosal plexus. The histamine H(3) receptor antagonist thioperamide and piroxicam, but not caffeic acid, prevented the allergic suppression of noradrenergic inhibitory neurotransmission. Antigenic stimulation of neuronal excitability and suppression of synaptic transmission occurred only in milk-sensitized animals. Results suggest that signaling between mast cells and the ENS underlies intestinal, but not gastric, anaphylactic responses associated with food allergies. Histamine, prostaglandins, and leukotrienes are paracrine signals in the communication pathway from mast cells to the small intestinal ENS.

Anaphylaxis↗
PubMed2005

Effects of plant phenolics and grape extracts from Greek varieties of Vitis vinifera on Mitomycin C and topoisomerase I-induced nicking of DNA.

In recent years, a number of reports have shown the anticancer activity of grape extracts and wine against various types of cancer such as breast, lung and gastric cancer. This property is mainly attributed to the plant polyphenols identified in grapes. The aim of the present study was to investigate the mechanisms by which grape extracts and plant polyphenols found in them exert their chemopreventive and antitumour activities. Thus, aqueous and methanolic extracts from two Greek varieties of Vitis vinifera, fractions enriched in polyphenols of these extracts and polyphenolics (caffeic acid, ferulic acid, gallic acid, protocatechuic acid and rutin) found in grapes were screened using two in vitro assays: i) the topoisomerase I relaxation assay and ii) the mitomycin C-induced DNA strand breakage. The grape extracts, the polyphenol-rich fractions and some of the polyphenolics (caffeic acid and protocatechuic acid) were potent inhibitors of topoisomerase I, indicating that the inhibition of this enzyme may be one of the mechanisms accounting for the anticancer activity of these compounds. Moreover, the grape extracts inhibited the mitomycin C-induced DNA strand breakage suggesting that they could prevent ROS-mediated DNA damage. On the other hand, the polyphenol-rich fractions and the plant polyphenols enhanced the mitomycin C-induced DNA strand breakage indicating prooxidant activity. Thus, it is of interest that whole grape extracts act as chemopreventive agents by inhibiting topo I and mitomycin C-induced DNA damage, while polyphenol enriched fractions and plant polyphenolics exert prooxidant activity leading to enhancement of DNA damage which may account for the cytotoxic and apoptosis-inducing properties of plant polyphenols against cancer cells.

DNA Damage↗
PubMed1979

On the local anaesthetic action of propolis and some of its constituents.

An ethanolic propolis extract and some constituents isolated from propolis were tested on the cornea of the rabbit and of the mouse for local anaesthetic activity. Total anaesthesia was obtained with the total extract as well as with the compounds 5,7-dihydroxyflavanone (pinocembrin), 5-hydroxy-7-methoxyflavanone (pinostrobin) and with a mixture of caffeic acid esters. Each of these compounds was nearly thrice as potent as the total extract. Propoxypiperocaine which was tested for the purpose of comparison was still efficient in an almost 10-fold lower concentration. When applied subcutaneously, pinocembrin and the mixture of caffeic acid esters produced nearly the same anaesthesia as lidocaine.

Anesthesia, Intravenous↗
PubMed1998

Inhibitory effects of antioxidants on formation of heterocyclic amines.

It is important to search for effective antioxidants to suppress formation of mutagenic and carcinogenic heterocyclic amines (HCAs), like 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), because these HCAs are considered to be probable human carcinogens. The effects of various food-derived antioxidants on MeIQx formation were examined by their addition (0.2 mmol each) to mixtures of creatine (0.4 mmol), glycine (0.4 mmol) and glucose (0.2 mmol), and heating at 128 degreesC for 2 h. Glycine was replaced by l-phenylalanine in the case of PhIP formation. Among the 14 kinds of antioxidants tested, green tea catechins and the major component [(-)-epigallocatechin gallate], two flavonoids (luteolin and quercetin) and caffeic acid were found to clearly suppress the formation of both MeIQx and PhIP, being 3.2-75% of the level of the controls. These phenolic antioxidants also reduced the total mutagenicity of the heated mixtures. The results suggest that foodstuffs containing catechins, flavonoids and caffeic acid may suppress the formation of HCAs in cooked foods.

Animals↗
PubMed1991

Catecholamines decrease leukotriene B4 and increase thromboxane B2 synthesis in A23187-stimulated human whole blood.

Catecholamines (adrenaline, dopamine, isoprenaline, noradrenaline) and caffeic acid (catecholic compound without adrenergic receptor activity) decreased leukotriene (LT)B4 synthesis in A23187-stimulated human whole blood. Salbutamol, a non-catecholic beta 2-adrenergic agonist, did not influence LTB4 synthesis. Catecholamines stimulated thromboxane (TX)B2 synthesis with a concomitant inhibition of LTB4 synthesis; caffeic acid and salbutamol did not stimulate TXB2 synthesis. These results, obtained in A23187-stimulated whole blood, which also takes into account the complex interaction between different cell types, are similar to our previous results with polymorphonuclear leukocytes. Catecholamines show an opposite effect on lipoxygenase and cyclooxygenase pathways, which may give rise to a marked change in LT/TX ratio in physiological or pathological conditions where sufficient concentrations of catecholamines are present.

Calcimycin↗
PubMed1994

Xanthine oxidase inhibitors from the leaves of Alsophila spinulosa (Hook) Tryon.

Diploptene(1), beta-sitosterol(2), a mixture of 6'-O-(E-P-coumaroyl)-alpha-glucopyranose and 6'-O-(E-P-coumaroyl)-beta-glucopyranose(3), a mixture of 6'-O-(E-P-caffeoyl)-alpha-glucopyranose and 6'-O-(E-P-caffeoyl)-beta-glucopyranose(4), caffeic acid(5) and astragalin(6) were isolated from an ethanolic extract of the leaves of Alsophila spinulosa Hook Tryon (Cyatheaceae). The plant has been used in folk medicine for hepatitis, gout, rheumatism, and tumor and these compounds were tested for their inhibitory effect on xanthine oxidase. Caffeic acid was the most potent constituent (IC50 = 39.21 microM; Ki = 28.2 microM) and was an uncompetitive inhibitor of the enzyme with respect to the substrate xanthine.

Magnetic Resonance Spectroscopy↗
PubMed1989

Regulation of T-lymphopoiesis by arachidonic acid metabolites.

The cloning efficiency of T-lymphocyte progenitor cells (CFU-T) is dependent on mononuclear cell concentration, with a triphasic growth curve. At low plating cell concentrations, hydrocortisone causes a dose-dependent decrease in cloning efficiency, whereas at high cell concentrations hydrocortisone causes increased cloning efficiency. To determine if the biphasic effects of hydrocortisone are through its inhibition of arachidonic acid metabolism, we tested the effects of various arachidonic acid metabolism inhibitors on cloning efficiency. Indomethacin, which inhibits cyclooxygenase, has no effect at low cell plating doses, but increases cloning efficiency at high cell doses. Prostaglandin E2 (PGE2) causes a dose-dependent inhibition of cloning efficiency at all cell doses. Caffeic acid, an inhibitor of lipoxygenase, causes a dose-dependent inhibition of CFU-T, particularly at lower cell concentrations. Leukotriene B4 (LTB4) restored caffeic acid-inhibited growth, as did addition of recombinant interleukins 1 and 2 (IL-1 and IL-2). These results support a regulatory role for arachidonic acid metabolites in T-lymphopoiesis. PGE2, a cyclooxygenase product, is inhibitory, whereas LTB4, a lipoxygenase product, is stimulatory through its role in IL-1 synthesis.

Arachidonic Acid↗
PubMed1999

Singlet oxygen quenching and the redox properties of hydroxycinnamic acids.

The singlet oxygen quenching rate constants (kq) for a range of hydroxycinnamic acids in acetonitrile and D2O solutions were measured using time resolved near infrared phosphorescence in order to establish their antioxidant activity. The magnitude of kq observed depends on both the nature of the substituent groups and solvent polarity. The variations in kq depend on the energy of the hydroxycinnamic acid/molecular oxygen charge transfer states, (O2delta- ...HCAdelta+). In D2O the values of kq range from 4x10(7) M(-1) s(-1) to 4x10(6) M(-1) s(-1) for caffeic acid and o-coumaric acid respectively. In acetonitrile, the charge transfer energy levels are raised and this is reflected in lower singlet oxygen quenching rate constants with a kq value of 5x10(6) M(-1) s(-1) for caffeic acid. The phenoxyl radical spectra derived from the hydroxycinnamic acids were determined using pulse radiolysis of aqueous solutions and the reduction potentials were found to range from 534 to 596 mV. A linear correlation is observed between reduction potential, and hence free energy for electron transfer, and log kq. These correlations suggest a charge transfer mechanism for the quenching of singlet oxygen by the hydroxycinnamic acids.

Antioxidants↗
PubMed1991

Effects of phenolic antioxidants in low dose combination on forestomach carcinogenesis in rats pretreated with N-methyl-N'-nitro-N-nitrosoguanidine.

The combined effects of low doses of promoters or carcinogens on two-stage forestomach carcinogenesis were examined in rats pretreated with N-methyl-N'-nitro-N-nitrosoguanidine. Groups of 15 rats were given a single 150 mg/kg body weight intragastric dose of N-methyl-N'-nitro-N-nitrosoguanidine. Starting 1 week later they were fed a diet containing low doses of known forestomach promoters/carcinogens (0.5% caffeic acid, 0.2% catechol, 0.5% butylated hydroxyanisole, or 0.25% 2-tert-butyl-4-methylphenol), alone or in combination, or basal diet without antioxidant supplement for 35 weeks. Histopathological examination revealed the incidences of forestomach squamous cell carcinomas in animals treated with N-methyl-N'-nitro-N-nitrosoguanidine followed by caffeic acid, catechol, butylated hydroxyanisole, 2-tert-butyl-4-methylphenol, and basal diet to be 27, 20, 13, 13, and 7%, respectively, whereas the incidence increased to 80% by the combined treatment with these four chemicals. The present results thus show that although the low doses of individual promoters/carcinogens did not have significant promoting activity, their combination exerted a strong enhancing influence on rat forestomach carcinogenesis. The findings indicate the importance of summation and synergism at a low dose for agents present in the human environment.

Animals↗
PubMed1989

Antioxidants--carcinogenic and chemopreventive properties.

Synthetic and naturally occurring antioxidants have a wide variety of biological actions in rodents in addition to their primary antioxidant activity. Some of the included biological effects are of direct interest in relation to studies of carcinogenicity and/or modulation of carcinogenesis. Since the synthetic antioxidant BHA was first found to exert carcinogenic potential in rat and hamster forestomach epithelium, many other synthetic and naturally occurring antioxidants have been examined for their ability to induce proliferative activity in the alimentary canal. These studies have revealed that caffeic acid and sesamol are also tumorigenic for rat forestomach epithelium, whereas catechol and p-methylcatechol induce neoplasia in rat glandular stomach epithelium. Although the proliferative response is very rapid, with inflammation and ulceration, it takes a very long time before carcinomas develop. The proliferative lesions in the forestomach induced by BHA or caffeic acid are largely reversible, in contrast to those induced by genotoxic carcinogens, which generally persist and develop into cancer. Therefore, chronic irritation is considered to be responsible for the induction of stomach cancer by antioxidants. Butylated hydroxyanisole can undergo oxidative metabolism in vitro, and some of the metabolites formed have the potential for binding to proteins. Neither BHA nor its metabolites binds to DNA in vivo, but protein binding in the forestomach was greater than 10 times higher than that in the glandular stomach. It is thus conceivable that BHA is oxidatively metabolized in the forestomach epithelium (possibly entering into redox cycling), and reactive metabolites including semiquinone radicals or active oxygen species are responsible for the carcinogenesis by a mechanism involving binding to macromolecules. Many antioxidants have been shown to modify carcinogenesis, and as a rule, they inhibit the initiation stage by reducing the interaction between carcinogen and DNA. However, both promotion and inhibition have been reported for second-stage carcinogenesis, depending on the organ site, species of animal, or initiating carcinogen. They can also block reaction of amine and nitrite to form nitrosamines or reduce TPA promotion of skin carcinogenesis. Generally high doses of antioxidants are required for carcinoma induction or modification of chemical carcinogenesis. The significance of the reported tumorigenicity and strong promoting activity of antioxidants for forestomach epithelium of animals to the development of human cancer appears limited mainly because humans do not have a forestomach. The carcinogenic and strong promoting activities of catechol and its structurally related compounds on rat glandular stomach epithelium are of greater concern because this tissue is directly analogous to human gastric epithelium.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗