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PubMed2001

Green tea polyphenols: novel irreversible inhibitors of dopa decarboxylase.

The green tea gallocatechins, (-)-epigallocatechin-3-O-gallate (EGCG), and (-)-epigallocatechin (EGC) were found to be inhibitors of Dopa decarboxylase (DDC). EGCG and EGC inactivate the enzyme in both a time- and concentration-dependent manner and exhibit saturation of the rate of inactivation at high concentrations, with efficiency of inactivation values (k(inact)/K(i)) of 868 and 1511 M(-1) min(-1), respectively. In contrast, gallic acid behaves as a weak inhibitor of DDC. Protection against inactivation by EGCG and EGC was observed in the presence of the active site-directed inhibitor D-Dopa. Either EGCG or EGC induce changes in the absorbance and CD bands of the visible spectrum of enzyme-bound PLP. Taken together, these findings indicate the active site nature of the interaction of DDC with both polyphenols. On the basis of the properties of the EGCG-inactivated enzyme, it can be suggested that inactivation could be ascribed to a covalent modification of not yet identified residue(s) of the active site of DDC.

Animals↗
PubMed1996

Hormonal stimulation of calcium mobilization in the isolated perfused rat pancreas.

Hormone-stimulated cellular Ca2+ mobilization in the isolated perfused rat pancreas was investigated by analyzing the efflux profiles of 45Ca2+ from 45Ca(2+)-loaded pancreata following agonist stimulation. The increased 45Ca2+ efflux reflects the enhanced exchange of Ca2+ across the plasma membrane as a result of increased [Ca2+]i. Both high and low concentrations of the cholecystokinin analog, cerulein, applied to the isolated perfused pancreas gave rise to an increased release of 45Ca3+. The patterns of the increase in 45Ca2+ release were consistently different for high and low concentrations of the agonist. Cerulein infused at a concentration of 10(-11) M induced a release of a small but significant amount of 45Ca2+ which could be abolished by 8-(N,N-diethylamine)octyl-3,4,5-trimethoxy-benzoate (TMB-8), but was not affected by ethyleneglycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA). Cerulein stimulation at 10(-9) M elicited a marked increase in 45Ca2+ release which was minimized by EGTA, but not by TMB-8. Also, infusion of cerulein stimulated a concentration-dependent amylase secretion response which displayed the same TMB-8- and EGTA-sensitivity pattern as the 45Ca2+ release response. The present study suggests (i) that cellular Ca2+ influx is a prominent feature of the increased 45Ca2+ efflux (i.e., increased [Ca2+]i) induced by pharmacological concentrations of cerulein while physiological concentrations of cerulein cause an increase in [Ca2+]i which is due predominantly to a release of internal Ca2+; and (ii) [Ca2+]i changes are essential for pancreatic enzyme secretion. Although isolated pancreatic acini or cells may lose their sensitivity and physiological responses to various agonists during isolation and preparation, the isolated perfused pancreas is a suitable and very sensitive model in which to study the physiology of Ca2+ mobilization and enzyme secretion.

Amylases↗
PubMed1997

Effects of antioxidants and Ca2+ in cisplatin-induced cell injury in rabbit renal cortical slices.

Effects of antioxidants, reactive oxygen species (ROS) scavengers, and Ca2+ on cisplatin-induced renal cell injury were studied in rabbit renal cortical slices in vitro. Cisplatin induced LDH release and lipid peroxidation, inhibition of PAH uptake, and GSH depletion. These changes were significantly prevented by thiols (DTT and GSH), antioxidants (DPPD and BHA), and an iron chelator (deferoxamine). Superoxide dismutase partially reduced the cisplatin-induced LDH release without affecting the lipid peroxidation and the GSH depletion. Catalase did not affect the LDH release and the lipid peroxidation induced by cisplatin. Hydroxyl radical scavengers prevented the lipid peroxidation, whereas they did not alter the LDH release, the inhibition of PAH uptake, and the GSH depletion induced by cisplatin. Removal of Ca2+ or addition of EGTA to the incubation medium did not alter cisplatin effects on LDH release and lipid peroxidation. Buffering intracellular Ca2+ with quin-2/AM or inhibition of intracellular Ca2+ release with TMB-8 significantly reduced the cisplatin effect on LDH release without any effect on the lipid peroxidation and the GSH depletion. Ruthenium red attenuated the LDH release, the lipid peroxidation, and the inhibition of PAH uptake mediated by cisplatin. La3+ prevented the cisplatin effect on the LDH release, whereas it did not affect the lipid peroxidation, the inhibition of PAH uptake, and the GSH depletion by cisplatin. These results suggest that cisplatin induces a lethal cell injury by lipid peroxidation-dependent and -independent mechanisms and that the cell injury and the lipid peroxidation by cisplatin are iron-dependent. In addition, the data indicate that the Ca2+ released from intracellular stores, but not the Ca2+ moved from extracellular space, plays a role in the cisplatin-induced cell injury independent of lipid peroxidation.

Animals↗
PubMed1998

Effect of processing on phenolics of wines.

Phenolics of grapes are the main compounds responsible for color, taste, mouth feel, oxidation and other chemical reactions in wine and juice. Phenolic levels in wine and juice are affected by numerous processing conditions (crushing, pressing, sulfite addition, skin contact, oak aging). Studies were conducted to better understand the effect of processing on phenolic composition of three varieties of grapes. Three different processing steps: immediate press, hot press, and hull treatment (skin contact) for 7 and 14 days were applied to three different grape varieties, Vitis rotundifolia cv. Noble, Vitis vinifer cv. Cabernet Sauvignon, and the French-American hybrid Chambourcin. Phenolic compounds were identified and quantified by High Performance Liquid Chromatography (HPLC) and bitterness/astringency were assessed using a trained sensory panel. V. rotundifolia wines had higher levels of epicatechin and gallic acid but lower caftaric acid and procyanidins compared to the other varieties and were more astringent and bitter. Processing treatment affected phenolics and color differently among the three varieties.

Beverages↗
PubMed1980

Effects of toxicants on T-cell subpopulations as determined by lymphokine activity.

Selective depletion of T1 and T2 lymphocyte subpopulations of mouse spleens was accomplished by injecting mice subcutaneously with 5 mg cortisone acetate (CA) or 0.1 ml antithymocyte serum (ATS), respectively. Selectively depleted and control spleen cells were cultured in vitro and were tested for their ability to produce the lymphokine immune interferon (IIF) in response to the following mitogens: staphylococcal enterotoxin A (SEA), concanavalin A (ConA), and phytohaemagglutinin-P (PHA). The data indicate that SEA and PHA induce IIF from T1 and T2 cells respectively; ConA induces IIF from both T1 and T2 cells. Mice were also injected subcutaneously with 10 mg gallic acid (GA) and the pattern of mitogen-induction of IIF from GA-treated spleen cells was compared with that of CA- and ATS-treated spleen cells. GA pretreatment of mice, like CA pretreatment, resulted in a significant decrease in SEA-induced IIF; GA probably exerts its effect on T1 suppressor cells.

Animals↗
PubMed1975

[On phenolic acids of vegetables. I. Hydroxycinnamic acids and hydroxybenzoic acids of brassica-species and leaves of other cruciferae (author's transl)].

The contents of phenolic acids in vegetables of the species Brassica almost totally consist of hydroxycinnamic acid compounds. In contrary to other species of vegetables sinapic acid is dominant. Leaves of radish (Rhaphanus sativus var. sativus and var. niger) mainly contain compounds of caffeic and p-coumaric acid; leaves of horse radish show only traces of hydroxycinnamic acids. In the group of hydroxybenzoic acid derivatives traces of salicylic and gentistic acid could be determined in almost all species and frequently vanillic acid. Protocatechnic acid was only identified in red cabbage, especially in the head, syringic acid in gardencress and p-hydroxybenzoic acid in horse radish leaves. No other hydroxybenzoic acids or hydroxycoumarins could be detected.

Caffeic Acids↗
PubMed1982

Extra- and intracellular Ca2+ requirements for lysosomal enzyme secretion in human neutrophils.

Ca2+-EGTA combinations were utilized in Hank's buffers to fix extracellular free Ca2+ concentrations [Ca2+f] for the study of human neutrophil lysosomal enzyme secretion. Ca2+-dependent neutrophil secretion initiated by formyl-methionyl-leucyl-phenylalanine (FMLP) and C5a required small amounts of [Ca2+f] (1-3 x 10(-6) M) while that caused by ionophore A23187 required 10(-5) M or greater [Ca2+f]. The inhibition of FMLP- and C5a-induced lysosomal enzyme secretion by the intracellular Ca2+ antagonist, 8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate (TMB-8) was additive to lowering extracellular [Ca2+f] from 10(-4) M to 10(-6) M or blocking plasma membrane Ca2+ flux with verapamil. These results suggest that extracellular and intracellular Ca2+ flux may be coupled in the initiation of neutrophil secretion caused by FMLP and C5a.

Calcimycin↗
PubMed1984

Role of intracellular calcium in histamine release from rat mast cells.

Compound 48/80-induced histamine release may utilize both intracellular and extracellular calcium. The release is inhibited by La3+ and TMB-8 both in the presence and absence of calcium. The observations are consistent with a mobilization of calcium from the inner surface of the plasma membrane supporting the release. TMB-8 probably acts at more than one site. It has been shown to inhibit skeletal muscle contraction and this has been correlated to its inhibitory effect on the release of Ca2+ from the sarcoplasmic reticulum. TMB-8 also inhibits resting cellular influx and efflux of calcium in the ileum. Anaphylactic and dextran-induced histamine release is dependent on extracellular calcium; the inhibition of the release by TMB-8 seems to be primarily due to an interference with calcium transport across the plasma membrane. In the absence of extracellular calcium the inhibition of compound 48/80-induced histamine release by TMB-8 seems to be due to stabilization of Ca2+ binding to cellular stores.

Animals↗
PubMed2004

Antioxidant power of phytochemicals from Psidium guajava leaf.

Dried ground leaves of Psidium guajava L. (guava) were extracted by water and aqueous ethyl alcohol 50% (1:10) ratio, and the total phenolic content in the extracts was determined spectrophotometrically according to Folin- Ciocalteu's phenol method and calculated as gallic acid equivalent (GAE). Remarkably high total phenolic content 575.3 +/-15.5 and 511.6+/-6.2 mg of GAE/g of dried weight material (for ethanol guava leaf extracts and water guava leaf extracts, respectively) were obtained. The antioxidant activity of lyophilized extracts was determined at ambient temperature by means of a 2,2-diphenyl-1-picrylhydryzyl (DPPH*) colorimetry with detection scheme at 515 nm. The activity was evaluated by the decrease in absorbance as the result of DPPH* color change from purple to yellow. The higher the sample concentration used, the stronger was the free radical-scavenging effect. The results obtained showed that ascorbic acid was a substantially more powerful antioxidant than the extracts from guava leaf. On the other hand, the commercial guava leaf extracts and ethanol guava leaf extracts showed almost the same antioxidant power whereas water guava leaf extracts showed lower antioxidant activity. The parameter EC(50) and the time needed to reach the steady state to EC(50) concentration (T(EC(50))) affected the antiradical capacity of the sample. The antioxidant efficiency (AE) has been shown to be a more adequate parameter for selecting antioxidants than the widely used EC(50). This study revealed that guava leaf extracts comprise effective potential source of natural antioxidants.

Antioxidants↗
PubMed1987

Antimicrobial properties of aromatic compounds of plant origin.

The antimicrobial action of 11 compounds involving guaiacyl- and syringyl-like structures (low-molecular-weight part of lignin), gallic acid and its derivatives, cinnamic acid and its derivatives, veratric acid, anisic acid and crotonic acid (a total of 25 compounds) against bacteria, yeast-like organisms and protozoa was examined. Aromatic compounds modified in the C-side chain and aldehydes were effective preferentially against Trichomonas vaginalis, whereas against bacteria and yeast-like organisms eugenol was the most effective inhibitor.

Anti-Bacterial Agents↗
PubMed2000

Antioxidative phenolic compounds from the roots of Rhodiola sachalinensis A. Bor.

The acetone extract of the roots of Rhodiola sachalinensis has furnished six phenolic compounds which exhibited significant scavenging effects against DPPH free radical. The structures of these compounds were identified and determined as gallic acid (1), (-)-epigallocatechin 3-O-gallate (2), kaempferol (3), kaempferol 7-O-alpha-L-rhamnopyranoside (4), herbacetin 7-O-alpha-L-rhamnopyranoside, (5) and rhodiolinin (6) by physico-chemical and spectral evidences.

Antioxidants↗
PubMed1994

Phenolic compounds from Duchesnea chrysantha and their cytotoxic activities in human cancer cell.

Five phenolic compounds were isolated from 80% aq. acetone extract of Duchesnea chrysantha. Their cytotoxicities were screened by the colorimetric tetrazolium assay (MTT assay). Gallic acid, methyl caffeate, protocatechuic acid and pedunculagin mildly inhibited the survival of PC14 and MKN45 human cancer cell. Brevifolin carboxylic acid showed a strong cytotoxic activity.

Antineoplastic Agents, Phytogenic↗
PubMed2003

Paclitaxel metabolism in rat and human liver microsomes is inhibited by phenolic antioxidants.

Paclitaxel is an important, recently introduced anti-neoplastic drug. Paclitaxel metabolites are virtually inactive in comparison with the parent drug. The study investigated whether phenolic antioxidants could inhibit metabolic inactivation sufficiently to increase paclitaxel effects. Cytochrome p450 (CYP)-catalysed metabolism of paclitaxel was investigated in rat and human liver microsomes. In rat microsomes, paclitaxel was metabolised mainly to C3'-hydroxypaclitaxel (C3'-OHP), less to C2-hydroxypaclitaxel (C2-OHP), di-hydroxypaclitaxel (di-OHP) and another monohydroxylated paclitaxel. In human liver microsomes, 6alpha-hydroxypaclitaxel (6alpha-OHP), formed by CYP2C8, was the main metabolite, while C3'-OHP, C2-OHP and another product different from di-OHP were minor metabolites, formed by CYP3A4. In individual human livers 6alpha-OHP was formed at 1.8-fold to 13-fold higher rates than C3'-OHP. Kinetic parameters (K(m) and V(max)) of production of various metabolites in rat and human liver microsomes revealed differences between species as well as human individual differences. Nine phenolic antioxidants ((+)-catechin, (-)-epicatechin, fisetin, gallic acid, morin, myricetin, naringenin, quercetin and resveratrol) were tested for inhibition of paclitaxel metabolism. In rat microsomes, resveratrol was more inhibitory than fisetin; the other phenolic antioxidants were without effect. In human microsomes, the inhibiting potency decreased in the order fisetin >quercetin >morin >resveratrol, while the other phenolic antioxidants were not inhibitory; the formation of 6alpha-OHP (CYP2C8) was generally more inhibited than that of C3'-OHP. The inhibition was mostly mixed-type. The results suggest that oral administration of some phenolic substances might increase paclitaxel blood concentrations during chemotherapy.

Adolescent↗
PubMed2002

Determination of polyphenols in wines by reaction with 4-aminoantipyrine and photometric flow-injection analysis.

A new flow-injection analytical procedure is proposed for the determination of the total amount of polyphenols in wines; the method is based on the formation of a colored complex between 4-aminoantipyrine and phenols, in the presence of an oxidizing reagent. The oxidizing agents hexacyanoferrate(III), peroxodisulfate, and tetroxoiodate(VII) were tested. Batch trials were first performed to select appropriate oxidizing agents, pH, and concentration ratios of reagents, on the basis of their effect on the stability of the colored complex. Conditions selected as a result of these trials were implemented in a flow-injection analytical system in which the influence of injection volume, flow rate, and reaction-coil length, was evaluated. Under the optimum conditions the total amount of polyphenols, expressed as gallic acid, could be determined within a concentration range of 36 to 544 mg L(-1), and with a sensitivity of 344 L mol(-1) cm(-1) and an RSD <1.1%. The reproducibility of analytical readings was indicative of standard deviations <2%. Interference from sugars, tartaric acid, ascorbic acid, methanol, ammonium sulfate, and potassium chloride was negligible. The proposed system was applied to the determination of total polyphenols in red wines, and enabled analysis of approximately 55 samples h(-1). Results were usually precise and accurate; the RSD was <3.9% and relative errors, by the Folin-Ciocalteu method, <5.1%.

Ampyrone↗
PubMed1998

Nickel uptake by Pseudomonas aeruginosa: role of modifying factors.

Pseudomonas aeruginosa cells growing in minimal medium were 40-fold more sensitive to Ni2+ than cells growing in enriched medium, suggesting a possible protective role of medium ingredients. Likewise, cells pre-grown in enriched medium showed a high Km (6.15 mM) and increased Ni2+ uptake (950 nmol mg-1 protein, 1h) over cells pre-sown in minimal medium (Km, 0.48 mM; 146 nmol mg-1 protein, 1 h). The overall pattern indicates that cells pre-grown in enriched medium were characterized by having lowered affinity towards Ni2+ than those with minimal medium background. The enhanced Ni2+ uptake by enriched medium-grown cells can be correlated with the improved metabolic state of the cells. Ni2+ uptake was optimum at neutrality (pH 7.0). A major Ni2+ transport system was competitively inhibited by Mg2+, Zn2+, Cd2+, or Co2+ (400 microM each). Noticeably, a minor Ni2+ transport pathway was still operative even in the higher concentration range of Mg2+ (4 mM and 40 mM). The stimulation of Ni2+ uptake monitored in the presence of different carbon sources (0.5% wt/vol, each) showed the sequence: glucose (1.6-fold) > phenol = gallic acid (1.5-fold). Succinate, in comparison, reduced Ni2+ uptake (0.5-fold) possibly because of its acting as a metal chelator as well. Sensitivity of Ni2+ transport towards methyl viologen, azide, 2-4 DNP, and DCCD suggested that transport was energy-linked.

Cations, Divalent↗
PubMed2003

Antiproliferative effect of antioxidant polyphenols from grape in murine Hepa-1c1c7.

BACKGROUND: Grapes and wine contain high concentrations of polyphenolic compounds. Although their cancer protective effect has been well documented, their activity as anticarcinogens should be cautiously considered since the molecular bases of action and their applicability to human cancer prevention are still unclear. AIM OF THE STUDY: We studied the antioxidant/antiradical activity and the antiproliferative effect in vitro of different polyphenolic mixtures, extracted from grapes and fractionated through RP-HPLC. METHODS: The polyphenolic fractions were chemically characterized and their antioxidant/antiradical activity was determined by the DPPH assay. Mouse hepatoma Hepa-1c1c7 cells were used to study the cell growth inhibition capacity of these fractions by MTT assay. Their capacity of altering cell cycle and possible induction of apoptosis was examined using FACS analysis. RESULTS: The original polyphenolic fraction OW, which contained gallic acid (GA), (+)-catechin (Cat), (-)-epicatechin (Ec), glycosylated flavonols (F) and procyanidin oligomers was fractionated into fraction I, composed of monomers and small oligomers, and fraction II that included flavonols and procyanidin oligomers of higher molecular weight. The three polyphenolic fractions tested showed quite similar antiradical activity, although fraction I was the most potent antiradical agent (lowest ED(50) value: 9 microg). Fraction II was the least potent cell growth inhibitor (highest IC(50) value: 100 microg/ml) but showed the strongest effect on the cell cycle of Hepa-1c1c7, inducing apoptosis in those cells. The original fraction OW was demonstrated to have the most potent cell growth inhibition effect (lowest IC(50) value: 43 microg/ml). However, it only appeared to alter cell cycle of Hepa-1c1c7 at concentrations higher than its IC(50) and did not induce apoptosis in those cells. A similar effect on cell cycle and apoptosis was encountered for fraction I. CONCLUSIONS: The polyphenolic fractions tested in this study were potent antiradical agents and exerted an antiproliferative effect in mouse hepatoma Hepa-1c1c7 cells; the fraction with the highest degree of polimerization and galloylation (fraction II) had the most influence on the cell cycle and induction of apoptosis on Hepa-1c1c7.

Animals↗
PubMed2006

Diet supplementation for 5 weeks with polyphenol-rich cereals improves several functions and the redox state of mouse leucocytes.

BACKGROUND: Cereals naturally contain a great variety of polyphenols, which exert a wide range of physiological effects both in vitro and in vivo. Many of their protective effects, including an improvement of the function and redox state of immune cells in unhealthy or aged subjects come from their properties as powerful antioxidant compounds. However, whether cereal-based dietary supplementation positively affects the immune function and cellular redox state of healthy subjects remains unclear. AIM OF THE STUDY: To investigate the effects of supplementation (20% wt/wt) for 5 weeks with four different cereal fractions on healthy mice. METHODS: Several parameters of function and redox state of peritoneal leukocytes were measured. The cereals, named B (wheat germ), C (buckwheat flour), D (fine rice bran) and E (wheat middlings) contained different amounts of gallic acid, p-hydroxybenzoic acid, vanillic acid, sinapic acid, p-coumaric acid, ferulic acid, quercetin, catechin, rutin and oryzanol as major polyphenols. RESULTS: In general, all cereal fractions caused an improvement of the leukocyte parameters studied such as chemotaxis capacity, microbicidal activity, lymphoproliferative response to mitogens, interleukin-2 (IL-2) and tumor necrosis factor (TNFalpha) release, as well as oxidized glutathione (GSSG), GSSG/GSH ratio, catalase (CAT) activity and lipid oxidative damage. We observed similar effects among the cereal fractions. CONCLUSIONS: The results suggest that some of these effects may due, at least partially, to the antioxidant activity of the polyphenols naturally present in cereals. Since an appropriate function of the leukocytes has been proposed as marker of the health state, a short-term intake of cereals seems to be sufficient to exert a benefit in the health of the general population. However, further studies are needed to assess the optimal doses and to find out which active polyphenols are able to mediate the observed physiological effects before recommending their regular consumption.

Animals↗
PubMed2003

Volatile constituents of glutathione--ribose model system and its antioxidant activity.

Reaction between glutathione and ribose was carried out to study the volatiles formed via Maillard reaction and their antioxidant activity as well as their role in inhibition of LDL oxidation. The simultaneous distillation-extraction technique was used for trapping the volatile components followed by GC-MS analysis. Thirty six compounds were identified with the predominance of carbonyls and sulfur-containing compounds in the volatiles of this model system. Sensory evaluation was performed for the model system product according to the International Standard Methods (ISO). The results showed a high decrease in roasted and burnt attributes and remarkable increase in the like-boiled and roasted meat attributes. The sensory results of the model system product were confirmed by the presence of high concentrations of some volatile compounds having meat--like aroma such as 2-methyl-3-furanthiol and 2-furylmethanethiol. The radical scavenging activity of glutathione-ribose model system was quantified spectrophotometrically, using DPPH radical. The activity of the model system product was found to be slightly lower than that of gallic acid and BHA, but it was much higher than that of cinnamic acid (200 ppm. for each). A highly antioxidative activity was recorded by the model system product during the inhibition of LDL-oxidation in comparison with L-ascorbic acid as well as reduced glutathione (as a concentration of 0.5 micromol/L, for each) which may be due to the presence of some compounds such as 2-furylmethanethiol, 2-acetyl thiazole, 4-hydroxy-5-methyl-3(2H)-furanone.

Antioxidants↗