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PubMed2000

Protective effect of olive oil and its phenolic compounds against low density lipoprotein oxidation.

The protective effect of phenolic compounds from an olive oil extract, and of olive oils with (extra-virgin) and without (refined) phenolic components, on low density lipoprotein (LDL) oxidation was investigated. When added to isolated LDL, phenolics [0.025-0.3 mg/L caffeic acid equivalents (CAE)] increased the lag time of conjugated diene formation after copper-mediated LDL oxidation in a concentration-dependent manner. Concentrations of phenolics greater than 20 mg/L inhibited formation of thiobarbituric-acid reactive substances after AAPH-initiated LDL oxidation. LDL isolated from plasma after preincubation with phenolics (25-160 mg/L CAE) showed a concentration-dependent increase in the lag time of conjugated diene formation after copper-mediated LDL oxidation. Refined olive oil (0 mg/L CAE) and extra-virgin olive oil (0.1 and 0.3 mg/L CAE) added to isolated LDL caused an increase in the lag time of conjugated diene formation after copper-mediated LDL oxidation that was related to olive oil phenolic content. Multiple regression analysis showed that phenolics were significantly associated with the increase in lag time after adjustment for effects of other antioxidants; alpha-tocopherol also achieved a statistically significant effect. These results indicate that olive oil phenolic compounds protect LDL against peroxyl radical-dependent and metal-induced oxidation in vitro and could associate with LDL after their incubation with plasma. Both types of olive oil protect LDL from oxidation. Olive oil containing phenolics, however, shows more antioxidant effect on LDL oxidation than refined olive oil.

Chromatography, High Pressure Liquid↗
PubMed1989

Formation of trans-caffeoyl-CoA from trans-4-coumaroyl-CoA by Zn2+-dependent enzymes in cultured plant cells and its activation by an elicitor-induced pH shift.

A novel hydroxylase activity catalyzing the formation of trans-caffeoyl-CoA from trans-4-coumaroyl-CoA was identified in crude extracts from cultured parsley cells. The extracts were less active (Vmax/Km) in converting trans-4-coumaric to trans-caffeic acid. Optimal hydroxylase activity was found at pH 6.5 with a steep decline toward both pH 7.4 and pH 5.0. The enzyme activity requires ascorbate and Zn2+ at optimal concentrations of 50 and 0.5 mM, respectively. No other reductant could replace ascorbate, whereas high concentrations of Ca2+ partially substituted for Zn2+. The enzyme is soluble and appears to be located in the cytoplasm. The unusual pH optimum suggests that the hydroxylase is inactive at the normal cytoplasmic pH. Upon treatment of parsley cells with an elicitor derived from Phytophthora megasperma f. sp. glycinea, the cytoplasmic pH dropped by approximately 0.25 pH unit within 55 min as determined by 31P NMR spectroscopy. Our results suggest that this shift in the cytoplasmic pH is sufficient for the activation of the hydroxylase, eventually leading to the formation of caffeoyl and feruloyl esters. Such esters may be a part of a very rapid resistance response of the plant cells, which would leave no time for de novo enzyme synthesis.

Acyl Coenzyme A↗
PubMed1991

alpha,beta-Dehydro-3,4-dihydroxyphenylalanine derivatives: potential schlerotization intermediates in natural composite materials.

Proteins containing the post-translationally modified amino acid L-3,4-dihydroxyphenylalanine (DOPA) undergo autosclerotization as a means of assuring cohesive resilience in many structural matrices found in nature. To explore the chemical mechanism of sclerotization, we examined the oxidation products of relatively simple analogs of a peptidyl DOPA residue, such as N-acetylDOPA ethyl ester and N-acetyldopamide, together with those of several oligopeptides. Oxidation, induced by either of two catecholoxidases or by sodium periodate, resulted in the Lewis base catalyzed formation of derivatives of the unusual amino acid 3,4-dihydroxy-alpha,beta-dehydroDOPA (delta DOPA). The N-acetyl delta DOPA ethyl ester representative of this group of derivatives was characterized by NMR and uv spectroscopy. A variety of peptides developed analogous uv spectra upon oxidation. A similar reaction was observed upon oxidation of 3,4-dihydroxyphenylpropanoic (dihydrocaffeic) acid, but not after oxidation of N-acetyldopamine. Evidence is presented that this conversion is the result of a rearrangement of the DOPA quinone moiety to its delta DOPA tautomer, and that this tautomerization can be a dominant fate for peptidyl DOPA quinone, provided a Lewis base catalyst is available and competing reactions are minimized. Formation of delta DOPA in natural or synthetic polymers would increase the variety of crosslinks available to sclerotizing matrices. delta DOPA has been found in naturally occurring oligopeptides isolated by other workers from several marine species.

Amino Acid Sequence↗
PubMed1992

Identification, purification, and characterization of S-adenosyl-L-methionine: isoliquiritigenin 2'-O-methyltransferase from alfalfa (Medicago sativa L.).

An O-methyltransferase (OMT) which methylates the 2'-hydroxyl of isoliquiritigenin (2',4,4'-trihydroxychalcone) was identified in alfalfa (Medicago sativa L.) seedlings and cell cultures. The OMT activity increased during early stages of seedling development and was predominantly located in roots. Treatment of alfalfa cell cultures with an elicitor from yeast resulted in a fivefold increase in chalcone OMT activity, whereas treatment of seedlings with CuCl2 caused a reduction in activity. The chalcone OMT was purified to near homogeneity from elicited alfalfa cell cultures. Only one form of the enzyme was found. It consisted of an active monomer of subunit Mr 43,000 which could be photoaffinity labeled with S-adenosyl-L-[methyl-3H]methionine. The purified OMT had a pH optimum of 9.0, pI of 4.7, and was highly specific for the 2'-hydroxyl of 2',4,4'-trihydroxychalcone, with essentially no activity toward narigenin chalcone, caffeic acid, or daidzein. Kinetic analysis indicated a sequential bi bi mechanism with Km values of 2.2 and 17.7 microM for 2',4,4'-trihydroxychalcone and S-adenosyl-L-methionine, respectively. S-Adenosyl-L-homocysteine was a potent inhibitor. The chalcone OMT represents the third distinct OMT isolated from alfalfa cell cultures.

Affinity Labels↗
PubMed1978

Studies on the reaction intermediate of protocatechuate 3,4-dioxygenase. Formation of enzyme-product complex.

The nature of the oxygenated intermediate observed (Fujisawa, H., Hiromi, K., Uyeda, M., Okuno, S., Nozaki, M. and Hayaishi, O. (1972) J. Biol. Chem. 247, 4422--4428) during the reaction of protocatechuate 3,4-dioxygenase (protocatechuate:oxygen 3,4-oxidoreductase (decyclizing), EC 1.13.11.3) was investigated. 3,4-Dihydroxyphenylpropionic acid and 3,4-dihydroxyphenylacetic acid were used as substrates of the enzyme to slow down the rate of the reaction. The enzyme reactions were performed under conditions where the concentration of the organic substrate was lower than those of the enzyme and oxygen in the reaction mixture. The reactions were stopped before completion by the addition of hydrochloric acid or guanidine hydrochloride and then the organic compounds were extracted from the reaction mixture to be analyzed. The qualitative analyses by thin-layer chromatography revealed that there was no species other than the organic substrate and the enzymatic reaction end-product during reaction. The quantitative spectrophotometric analyses revealed that the organic substrate which had participated in the formation of the oxygenated intermediate existed as a species indistinguishable from the reaction end-product, indicating that the oxygenated intermediate was not a simple complex of oxygen, substrate and the enzyme, i.e., a ternary complex, but a species rather close to a binary complex of product and the enzyme.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1994

Differential effect of growth- and differentiation-inducing factors on the release of eicosanoids and phospholipids from ML-1 human myeloblastic leukemia cells.

In the absence of serum, growth of ML-1 human myeloblastic leukemia cells is induced by the insulin-like growth factor-1 (IGF1) together with transferrin (Tf), whereas monocytic differentiation is initiated by the transforming growth factor-beta (TGF-beta) in combination with Tf. Initiation of growth was followed by the rapid release of arachidonic acid (AA), hydroxyeicosatetraenoic acids (HETEs) and phospholipids into the culture medium. In contrast, induction of differentiation occurred without the release of these lipids beyond the level present in control. Inhibitors of enzymes involved in the formation of AA and of HETEs, including phospholipase A2 and lipoxygenases, caused interference with growth but not with differentiation, and an inhibitor of the cyclooxygenase path affected neither growth nor differentiation. These results indicate that the initiation of ML-1 cell growth but not of cell differentiation is dependent upon the increased formation of AA and its derivatives formed primarily via the lipoxygenase path.

Arachidonic Acid↗
PubMed1996

Cell protein cross-linking by erbstatin and related compounds.

The protein-tyrosine kinase inhibitor and stable erbstatin analogue methyl 2,5-dihydroxycinnamate (4) cross-links cell proteins by a non-physiological chemical mechanism (Stanwell et al., Cancer Res 55: 4950-4956, 1995). To determine the structural requirements for this effect, erbstatin (1) and fifteen related compounds, including caffeic acid phenylethyl ester (9) were synthesized and examined for their ability to induce cross-linking of cellular protein at concentrations ranging from low micromolar up to 1000 microM. Tests were conducted in NIH3T3 fibroblasts as well as mouse keratinocytes. Potent cross-linking of cellular protein was observed for a number of analogues, including erbstatin, at concentrations as low as 10-50 microM. The inactivity of methoxy and fluoro as compared with their corresponding dihydroxylated counterparts indicated that free aromatic hydroxyls were essential for cross-linking. Additionally, compounds containing phenyl rings with 1,4-dihydroxy substituents were more potent than those having 1,2-dihydroxylated patterns. As with the prototype compound 4, cross-linking was induced at both 37 degrees and 4 degrees, suggesting a chemical rather than physiological mechanism. Consistent with the data, a mechanism of action is proposed which involves initial oxidation to reactive quinone intermediates that subsequently cross-link protein nucleophiles via multiple 1,4-Michael-type additions. Similar alkylation of protein by protein-tyrosine kinase inhibitors, such as herbimycin A, has been invoked. While the latter benzoquinoid ansamycin antibiotics contain performed quinone moieties, results of the present study suggest that other hydroxylated kinase inhibitors can potentially participate in similar phenomena. A large number of potential therapeutics, including HIV integrase inhibitors, possess polyhydroxylated nuclei. The non-specific nature of the protein cross-linking reaction demonstrated for these erbstatin analogues, and the fact that cross-linking can occur at micromolar concentrations, may limit the therapeutic usefulness of such compounds to specific applications.

Animals↗
PubMed1996

Ascorbate is the natural substrate for plant peroxidases.

Ascorbate-dependent detoxification of hydrogen peroxide by guaiacol-type peroxidases is increased considerably in the presence of 3,4-dihydroxyphenolic compounds, suggesting that ascorbate is the natural substrate for many types of peroxidase in situ and not just the ascorbate-specific peroxidases. The ascorbate-dependent destruction of hydrogen peroxide in the more acidic cellular compartments such as the vacuole may be an important function of such non-specific peroxidases. The stress-induced production of phenolic compounds would render the guaiacol peroxidases in other less acidic-cellular sites effective as ascorbate-dependent H2O2-detoxifying enzymes.

Antibodies↗
PubMed1995

Analysis of the components of Lycopus europaeus L. in body fluids during metabolism studies. Comparison of capillary electrophoresis and high-performance liquid chromatography.

During pharmacokinetic studies with extracts obtained from medicinally used plants, analysis in body fluids is mainly performed by HPLC, an established separation method. In this paper high-performance capillary electrophoresis (HPCE) is investigated for its ability to separate such complex extracts. Crude extracts of Lycopus europaeus L. (Lamiaceae) are traditionally used against mild forms of hyperthyroidism. The metabolism of a 70% ethanolic extract with respect to some of its individual main components (rosmarinic and caffeic acid, luteolin-7-glucoside) and a mixture of the pure compounds were investigated using isolated perfused rat liver. After solid-phase extraction metabolites were determined using HPCE and HPLC separation techniques. A buffer solution composed of 0.05 mol l-1 Na2HPO4 at pH 7.0 with 30% acetonitrile was found to be the most suitable electrolyte for HPCE separation. The best mobile phase for isocratic HPLC was 0.03% TFA-acetonitrile (82:18, v/v). Data obtained with HPCE are in good accordance with those from HPLC; HPCE, however, is clearly more rapid and simple to perform.

Animals↗
PubMed1983

An intestinal cell-mediated chromosome aberration test for the detection of genotoxic agents.

The use of rat-liver S9 in genotoxicity tests may not reflect true metabolism by whole cells, particularly cells of target organs. We have tested mucosal cells of the mouse small intestine for the capacity to mediate activation/inactivation of chemical carcinogens. Mucosal cells were isolated by pronase digestion. Three million cells were co-cultured with Chinese hamster ovary fibroblasts during a 3-h exposure to chemical clastogens. In the presence of the mucosal cells, aflatoxin B1 (100 microM) was activated to produce chromosome aberrations in 30% of Chinese hamster ovary cell metaphases. 4-Nitroquinoline 1-oxide was deactivated by intestinal cells, while benzo[a]pyrene and dimethylbenz[a]anthracene were not activated by the cells. The clastogenicity of the phenolic compounds caffeic acid (0.28 mg/ml) and clorogenic acid (0.25 mg/ml) was eliminated by the mouse intestinal preparation. The pyrrolizidine alkaloid monocrotaline was activated by intestinal cells. The results suggest the presence of specific activation and deactivation enzymes in the intestinal mucosa. The intestine cell-mediated chromosome aberration test could provide a means to measure tissue-specific activation and deactivation capabilities.

4-Nitroquinoline-1-oxide↗
PubMed1992

Acylated pelargonidin glycosides in the red-purple flowers of Pharbitis nil.

Four acylated pelargonidin glycosides and pelargonidin 3-sophoroside-5-glucoside were isolated from 23 red-purple cultivars of Pharbitis nil. The acylated anthocyanins were all based on pelargonidin 3-sophoroside-5-glucoside and were identified as the 3-O-[2-O-(beta-D-glucopyranosyl)-6-O-(trans-caffeyl)-beta-D- glucopyranoside]-5-O-(beta-D-glucopyranoside), the 3-O-[2-O-(6-O-(trans-3-O-(beta-D-glucopyranosyl)caffeyl)-beta- D-glucopyranosyl)-beta-D-glucopyranoside]-5-O-(beta-D-glucopyranoside), the 3-O-[2-O-(6-O-(trans-3-O-(beta-D-glucopyranosyl)caffeyl)-beta- D-glucopyranosyl)-6-O-(trans-caffeyl)-beta-D-glucopyranoside]-5-O-(beta- D-glucopyranoside); and the 3-O-[2-O-(6-O-(trans-3-O-(beta-D-glucopyranosyl)caffeyl)-beta-D- glucopyranosyl)-6-O-(trans-4-O-(6-O-(trans-3-O-(beta-D- glucopyranosyl)caffeyl)- beta-D-glucopyranosyl)caffeyl)-beta-D-glucopyranoside]-5-O-(beta-D- glucopyranoside). By the analysis of these anthocyanin constituents variously in 23 cultivars, it was found that the red flower colour gradually changed into more bluish colour with increasing numbers of caffeic acid residues in the acylated pelargonidin glycosides. The stabilities of these anthocyanins increased in the order of increasing caffeyl substitution.

Anthocyanins↗
PubMed1995

Acylated cyanidin glycosides in the violet-blue flowers of Ipomoea purpurea.

Six acylated cyanidin glycosides were isolated from violet-blue flowers of Ipomoea purpurea. These anthocyanins were all based on cyanidin 3-sophoroside-5-glucoside, acylated with caffeic acid and/or p-coumaric acid. Three anthocyanin structures were elucidated to be cyanidin 3-O(-)[2-O-(6-O-(trans-3-O-(beta-D-glucopyranosyl)caffeyl)-beta -D-glucopyranosyl)-6-O-(trans-4-O-(6-O-(trans-caffeyl)-beta-D-glucopyran osyl) caffeyl)-beta-D-glucopyranoside]-5-O(-)[beta-D-glucopyranoside], cyanidin 3-O(-)[2-O-(trans-3-O-(beta-D-glucopyranosyl)caffeyl)-beta-D-glucopyrano syl)- 6-O-(trans-caffeyl)-beta-D-glucopyranoside]-5-O(-)[beta-D-glucopyranosid e d and cyanidin 3-O(-)[2-O-(6-O-(trans-caffeyl)-beta-D-glucopyranosyl)-6-O- (trans-caffeyl)-beta-D-glucopyranoside]-5-O(-)[beta-D-glucopyranoside]. These three anthocyanins were present in all 12 violet-blue flower strains as major pigments. The colours of these acylated antocyanins were stabler in neutral solution than their deacyl analogues.

Anthocyanins↗
PubMed1989

In vivo murine studies on the biochemical mechanism of naphthalene cataractogenesis.

The polycyclic aromatic hydrocarbon naphthalene is bioactivated by cytochromes P450 to an electrophilic epoxide intermediate, which subsequently is metabolized to naphthoquinones (NQ) and possibly to a free radical intermediate. These reactive intermediates may bind covalently to lenticular tissues, cause oxidant stress and/or lipid peroxidation, thereby initiating cataracts. To evaluate this hypothesis, male C57BL/6 or DBA/2 mice were treated with naphthalene or one of several naphthoquinone and naphthol metabolites, in the presence or absence of modulators of chemical bioactivation and detoxification. In C57BL/6 mice, cataracts were caused by naphthalene (500-2000 mg/kg ip) in a dose-dependent fashion. The incidence of naphthalene-induced cataracts was decreased by pretreatment with the P450 inhibitors SKF 525A and metyrapone, the antioxidants caffeic acid and vitamin E, the glutathione (GSH) precursor N-acetylcysteine, and the free radical spin trapping agent alpha-phenyl-N-t-butylnitrone (p less than 0.05). Naphthalene cataractogenicity was enhanced by pretreatment with the cytochrome P450 inducer phenobarbital and the GSH depletor diethyl maleate (DEM) (p less than 0.05), and was unaffected by pretreatment with the prostaglandin synthetase inhibitors aspirin or naproxen, or the epoxide hydrolase inhibitor trichloropropene oxide. Cataracts were initiated by 1,2-NQ and 1,4-NQ (5-250 mg/kg ip) in a dose-dependent fashion, with a molar potency about 10-fold higher than that for naphthalene. NQ cataractogenicity was enhanced by pretreatment with DEM (p less than 0.05). 1-Naphthol (56 to 562 mg/kg ip) demonstrated a cataractogenic potency intermediary to that for naphthalene and NQ. DBA/2 mice treated with naphthalene (2000 mg/kg ip), 1,4-NQ (65-250 mg/kg ip), 1,2-NQ (30-250 mg/kg ip), or DEM followed by 1,4-NQ (125 mg/kg ip) did not develop cataracts. These results suggest that naphthalene cataractogenesis in C57BL/6 mice requires P450-catalyzed bioactivation to a reactive intermediate, which may be the NQ and/or a free radical derivative, either of which is dependent upon GSH for detoxification.

Animals↗
PubMed1985

Effects of chalcone derivatives on lipoxygenase and cyclooxygenase activities of mouse epidermis.

The effects of chalcone derivatives on 12-lipoxygenase and cyclooxygenase of mouse epidermis were investigated. The chalcone derivatives which have 3,4-dihydroxycinnamoyl structure in the molecule, such as 3,4-dihydroxychalcone, 3,4,2'-trihydroxychalcone, 3,4,4'-trihydroxychalcone and 3,4,2'4'-tetrahydroxychalcone, potently inhibited epidermal 12-lipoxygenase activity. Although some of them also inhibited cyclooxygenase activity at relatively high concentrations, the inhibitory effects of these chalcone derivatives on 12-lipoxygenase were 10 times or more potent than their effects on cyclooxygenase. The chalcone derivatives which have cinnamoyl or 4-hydroxycinnamoyl structure, instead of 3,4-dihydroxycinnamoyl structure, in the molecule, showed little or no inhibitory effects on either 12-lipoxygenase or cyclooxygenase activities. The inhibitory effects of chalcone derivatives on 12-lipoxygenase and cyclooxygenase of mouse epidermis are dependent on the particular structure, i.e. 3,4-dihydroxycinnamoyl structure, of the chalcone derivatives.

Animals↗
PubMed1992

Prostaglandin profile and synthetic capacity of the colon: comparison of tissue sources and subcellular fractions.

Although there has been intense interest in the physiology and pathophysiology of prostaglandins (PGs) synthesized in the colon, little is known about the PG profile and synthetic capacity of different tissue sources and subcellular fractions as enzyme sources. Subcellular fractions prepared from the mucosa and muscle layer of rat colon were incubated with or without exogenous arachidonic acid ([3H]20:4n-6) for 30 min. In experiments with exogenous [3H]20:4n-6, the prostaglandin synthetic capacity of the colonic muscle layer was significantly higher than that of the mucosa. Among the subcellular fractions, microsomes had the highest PG synthetic capacity in both mucosa and muscle. The major PG product was PGI2 and PGD2 in the mucosal microsomes and PGI2 and PGE2 in the muscularis microsomes. However, production of PGI2 in the mucosa and PGE2 in the muscle was significantly reduced in the fractions containing both cytosol and microsome, resulting in an alteration of the PG profile. Substrate availability (exogenous vs endogenous supply) appears to influence the PG profile of the colon. In the colonic mucosa with exogenous [3H]20:4n-6, the production of PGI2 was 5 times higher than that of PGE2, whereas the production of PGE2 was twice higher than that of PGI2 in experiments with endogenous 20:4n-6. These observations indicate: 1) different PG profile and synthetic capacity of tissue sources and subcellular fractions; 2) alteration of PG profile due to the variation of 20:4n-6 availability. Thus, the outcome of experiments on the physiological role of PG in the colon may be determined, in part, by the tissue source and subcellular fraction selected for analysis. The present study also suggests that the variation of substrate availability in physiological and pathophysiological processes may affect the PG profile of the colon.

4,5-Dihydro-1-(3-(trifluoromethyl)phenyl)-1H-pyraz↗
PubMed1990

Mutagenic and genotoxic effects of aqueous extracts of Achyrocline satureoides in prokaryotic organisms.

Aqueous extracts of Achyrocline satureoides (Marcela and/or Macela) were tested for the presence of genotoxic activity in microorganisms. This species belongs to the family Compositae and is used on a large scale by the population of South Brazil. The extracts showed genotoxic activity in the presence of S9 mix in the Ames test TA100, TA98 and TA102 strains, 'SOS' spot chromotest and Microscreen phage-induction assay. The positive results were related to the presence of quercetin and caffeic acid in the aqueous extracts.

Animals↗
PubMed1987

Lipoxygenase inhibitors suppress IL-2 synthesis: relationship with rise of [Ca++]i and the events dependent on protein kinase C activation.

The present study was performed in an attempt to understand the mechanism involved in the inhibition of interleukin 2 (IL-2) synthesis by lipoxygenase (LO) pathway inhibitors. Using the two IL-2-producing lymphoid cell lines, (Jurkat and EL4 cells), we showed first that the inhibitory effect of the phenolic compounds tested (NDGA, BHA and caffeic acid) acted on lymphoid cells themselves and not on eventual monocytic or granulocytic contaminant cells. Secondly, these inhibitors were demonstrated as exerting their effect on two levels: they affected the events controlled by both second messengers implicated in T cell activation, namely rise of intracellular free calcium concentration [( Ca++]i) and protein kinase C (PKC) activation. For this purpose, LO inhibitor effects have been compared: (a) on IL-2 production by the two different lines: Jurkat cells, which need both signals, and EL4 cells, which require only PKC activation for the induction of this production; and (b) on the events induced by the different ways of Jurkat cell activation: PHA (or anti-CD3 monoclonal antibody) versus calcium ionophore. These results are discussed with respect to an eventual involvement of arachidonic acid [AA] derivatives in IL-2 synthesis.

Animals↗