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At least 649 records · Page 36Linked to original sources
PubMed1985

Polyphenol oxidase produced during encystation of Acanthamoeba castellanii.

Acanthamoeba castellanii has a phenol oxidase activity that is believed to be a laccase. Enzyme activity was found in the outer cyst wall, in the cytoplasm of encysting amoebae and in the encystment medium. Encystment procedures were modified to promote an increase in the amount of soluble enzyme secreted during encystation. Acanthamoeba polyphenol oxidase has a pH optimum of 6.0 and a Km value of 0.21 mM with dihydroxyphenylalanine. The enzyme does not oxidize tyrosine, and it is inhibited by chloride but not by inhibitors of peroxidase. Its synthesis coincides with encystation, and known inhibitors of polyphenol oxidase prevent encystation. Polyphenol oxidase may have a role in making the cyst resistant to mechanical and chemical breakdown.

Amoeba↗
PubMed1993

Inhibitory effect of oolong tea polyphenols on glycosyltransferases of mutans Streptococci.

Oolong tea extract (OTE) was found to inhibit the water-insoluble glucan-synthesizing enzyme, glucosyltransferase I (GTase-I), of Streptococcus sobrinus 6715. The GTase-inhibitory substance in the OTE was purified successive adsorption chromatography on Diaion HP-21 and HP-20 columns; this was followed by further purification by Sephadex LH-20 column chromatography. A major fraction that inhibited GTase activity (fraction OTF10) was obtained, and the chemical analysis of OTF10 indicated that it was a novel polymeric polyphenol compound that had a molecular weight of approximately 2,000 and differed from other tea polyphenols. Catechins and all other low-molecular-weight polyphenols except theaflavin derived from balck tea did not show significant GTase-inhibitory activities. It was found that OTE amd PTF10 markedly inhibit GTase-I and yeast alpha-glucosidase, but not salivary alpha-amylase. Various GTases purified from S. sobrinus and Streptococcus mutans were examined for inhibition by OTE and OTF10. It was determined that S. sobrinus GTase-I and S. mutans cell-free GTase synthesizing water-soluble glucan were most susceptible to the inhibitory action of OTF10, while S. sobrinus GTase-Sa and S. mutans cell-associated GTase were moderately inhibited; no inhibition of S. sobrinus GTase-Sb was observed. Inhibition of a specific GTase or specific GTases of mutants streptococci resulted in decreased adherence of the growing cells of these organisms. The inhibitory effect of OTF10 on cellular adherence was significantly stronger than that of OTE.

Bacterial Adhesion↗
PubMed1998

Comparison of the cariostatic effects between regimens to administer oolong tea polyphenols in SPF rats.

The cariostatic effect of oolong tea polyphenols administered according to several regimens was examined in specific pathogen-free (SPF) Sprague-Dawley rats given both a diet containing 20% sucrose and infected with S. sobrinus 6715. The crude preparation (OTE) of oolong tea polyphenols showed the most prominent effect on caries reduction in SPF rats when OTE was administered in the drinking water beginning 1 day prior to the inoculation of S. sobrinus 6715, when compared with chromatographically isolated polyphenol fractions (OTF1 and OTF6) of OTE. Reduction in caries development was found even when OTE was given 1 day after inoculation of the organism. OTE was shown to significantly inhibit dental caries in rats at the concentrations of either more than 5 microg/ml in drinking water or more than 10 microg/g in diet. OTF1 and OTF6 also showed significant inhibition of caries induction, with the minimum inhibitory concentration of OTF6 being 50 microg/ml in drinking water and the minimum inhibitory concentration of OTF1 being 100 microg/g in diet. These results indicate that cariostatic activity of OTE was effective even after the establishment of S. sobrinus in the oral cavity and was more effective in drinking water than in diet. Furthermore, OTE may contain some anticaries substances that affect the virulence of S. sobrinus other than glucosyltransferases.

Analysis of Variance↗
PubMed1997

Polyphenols as inhibitors of carcinogenesis.

Many polyphenolic compounds have demonstrated anticarcinogenic activities in animal models. These compounds include flavanone, flavonols, isoflavone, and catechins. In this article, tea catechins will be used as an example to illustrate current research in this area. Many laboratory studies have demonstrated the inhibition of tumorigenesis in animal models by different tea preparations. The animal models include tumorigenesis in the mouse lung, rat and mouse esophagi, mouse forestomach, mouse skin, mouse duodenum, rat small intestine, rat and mouse livers, and rat colon. In most of the studies, the inhibitory activity of tea could be demonstrated when tea preparations were given either during or after the carcinogen treatment period. Black tea was also effective, although the activity was weaker than green tea in some experiments. Decaffeinated tea preparations were also active in many model systems. The molecular mechanisms for these broad inhibitory actions are not fully understood. They are most likely related to the biochemical actions of the tea polyphenols, which include antioxidative activities and inhibition of cell proliferation and of tumor promotion-related activities. The effect of tea consumption on human cancers is not clear in spite of numerous investigations. The bioavailability and pharmacokinetics of tea polyphenols are being studied in animals and humans to provide a basis for more quantitative analyses on the effect of tea on carcinogenesis. More mechanistic and dose-response studies will help us to understand the effects of tea consumption on human carcinogenesis.

Animals↗
PubMed2001

Polyphenolic compounds: interactions with the gut and implications for human health.

Polyphenolic compounds are abundant throughout the plant kingdom and are found in a wide variety of human foods. The flavonoids, which are the best defined group of polyphenols in the human diet, themselves comprise a large and complex group, all of which contain a three-ring structure with two aromatic centres and a central oxygenated heterocycle. Recent evidence suggests that significant quantities of quercetin and possibly myricetin and kaempferol are absorbed in the gut. A larger fraction probably remains in the lumen, and thus a substantial proportion of the gastrointestinal mucosa is exposed to biologically significant concentrations of these compounds. A substantial body of experimental work has established that flavonoids can suppress carcinogenesis in animal models and there is considerable interest in the biological effects of these compounds at the cellular level. Flavonoids interact with cellular signal pathways controlling the cell cycle, differentiation and apoptosis. Their potentially antineoplastic effects include antioxidant activity, induction of Phase II enzyme activity, inhibition of protein kinases and interactions with Type II estrogen binding sites. Naturally occurring polyphenolic compounds may play a role in the protective effects of fruits and vegetables against cancers in general, and they appear to have considerable potential for pharmaceutical uses as chemopreventive agents against neoplastic changes in the alimentary tract. Future research should therefore focus on the biological effects of flavonoids in the human body, using biomarkers to define their effects at each stage in the onset of neoplasia.

Animals↗
PubMed2004

In vitro effects of the polyphenols resveratrol, mangiferin and (-)-epigallocatechin-3-gallate on the scuticociliate fish pathogen Philasterides dicentrarchi.

This study investigated the in vitro effects of the polyphenols resveratrol, mangiferin and (-)-epigallocatechin-3-gallate (EGCG) on the histiophagous ciliate Philasterides dicentrarchi, which causes fatal scuticociliatosis in farmed turbot Scophthalmus maximus L. Of the 3 polyphenols, resveratrol showed strongest antiprotozoal activity, reducing ciliate density after 1 wk culture by, on average, 91% at 50 microM, and 96% at 500 microM. EGCG reduced ciliate density by, on average, 93% at 500 microM, with no significant effect at 50 microM. Mangiferin reduced ciliate density by, on average, 56% at 500 microM, again with no significant effect at 50 microM. In view of these findings, we discuss the potential utility of chemotherapy with polyphenols as a strategy for the control of scuticociliatosis in farmed turbot.

Analysis of Variance↗
PubMed1998

Transformation of 3,5-dimethoxy,4-hydroxy cinnamic acid by polyphenol oxidase from the fungus Trametes versicolor: product elucidation studies.

Sinapic acid (SA), 3,5-dimethoxy,4-hydroxy cinnamic acid, was incubated with a crude polyphenol oxidase from the fungus Trametes versicolor. Some products of this transformation were isolated and their structures identified using mass spectrometry, nuclear magnetic resonance and Fourier transform infrared spectroscopy, and X-ray crystallography. It was found that the enzymatic oxidation of SA includes two distinct phases. In the initial phase SA is enzymatically transformed to r-1H-2c,6c-bis-(4'-hydroxy-3', 5'-dimethoxyphenyl)-3,7-dioxabicyclo-[3,3,0]-octane-4,8-dione, dehydrodisinapic acid dilactone. The mechanism of this reaction may involve coupling of two phenoxy radicals by the beta-beta mode and subsequent intramolecular nucleophilic attack. In the second phase dehydrodisinapic acid dilactone is transformed by polyphenol oxidase into several intermediate products, including 4-(4-(3, 5-dimethoxy-4-oxo-2,5-cyclohexadienyliden)-1, 4-dihydroxy-(E)-2-butenylidene)-2,6-dimethoxy-2, 5-cyclohexadien-1-one. The final product of the overall transformation of SA is 2,6-dimethoxy-p-benzoquinone. The obtained results were used to propose a part of the transformation pathway for the enzymatic oxidation of SA by polyphenol oxidase.

Basidiomycota↗
PubMed2000

The effect of mycophenolate mofetil and polyphenolic bioflavonoids on renal ischemia reperfusion injury and repair.

PURPOSE: Chronic renal allograft nephropathy is associated with both immune and ischemic injury which may act synergistically to promote an inflammatory response. The immunosuppressant mycophenolic acid and the polyphenolic agents curcumin and quercetin possess properties that might ameliorate such injury. We studied the effects of these agents in models of ischemic renal injury and skin allograft rejection. MATERIALS AND METHODS: Ischemic acute tubular necrosis was produced in rats by renal pedicle occlusion with contralateral nephrectomy. Animals were treated with mycophenolic acid, quercetin and curcumin, or a combination of agents. Animals were killed on days 2 and 7 after operation and tissue samples were collected. Renal tubular apoptosis and cellular proliferation were assessed by immunohistochemistry. Expression of the cytokines RANTES and AIF were evaluated by semi-quantitative reverse transcription polymerase chain reaction (RT-PCR). RESULTS: Treatment with the polyphenolic compounds alone or in combination with mycophenolic acid was associated with less tubular damage, attenuation of renal inflammation, and prolongation of skin graft survival. A combination of agents decreased serum creatinine on day 2 from 4.5 to 0.9 mg./dl. (p< or =0.01) and at day 7 from 3.8 to 0.6 mg./dl. (p< or =0.01). Treatment with the polyphenolic compounds inhibited apoptosis at day 2. By RT-PCR, RANTES and AIF were detected at high levels on days 2 and 7. Treatment with these agents alone or in combination strongly attenuated this increased expression. CONCLUSIONS: The combination of mycophenolic acid with curcumin and quercetin reduces renal injury and facilitates repair. These agents may have a role in therapeutic regimens that are both immunosuppressive and renoprotective.

Animals↗
PubMed2000

O-Methylation of tea polyphenols catalyzed by human placental cytosolic catechol-O-methyltransferase.

In the present study, we evaluated the metabolic O-methylation of several catechol-containing tea polyphenols by human placental catechol-O-methyltransferase (COMT). (-)-Epicatechin, (+)-epicatechin, and (-)-epigallocatechin were good substrates for metabolic O-methylation by placental cytosolic COMT (150-500 pmol/mg of protein/min), but (-)-epicatechin gallate and (-)-epigallocatechin gallate were O-methylated at much lower rates (<50 pmol/mg of protein/min). When (-)-epicatechin was used as substrate, its O-methylation by human placental COMT showed dependence on incubation time, cytosolic protein concentration, incubation pH, and concentration of S-adenosyl-L-methionine (the methyl donor). Analysis of cytosolic COMT from six human term placentas showed that the O-methylation of increasing concentrations of (-)-epicatechin or (-)-epigallocatechin follows typical Michaelis-Menten kinetics, with K(m) and V(max) values of 2.2 to 8.2 microM and 132 to 495 pmol/mg of protein/min for (-)-epicatechin and 3.9 to 6.7 microM and 152 to 310 pmol/mg of protein/min for (-)-epigallocatechin, respectively. Additional analysis revealed that COMT-catalyzed O-methylation of (-)-epicatechin and (-)-epigallocatechin was strongly inhibited in a concentration-dependent manner by S-adenosyl-L-homocysteine (IC(50) = 3.2-5.7 microM), a demethylated product of S-adenosyl-L-methionine. This inhibition by S-adenosyl-L-homocysteine follows a mixed (competitive plus noncompetitive) mechanism of enzyme inhibition. In summary, several catechol-containing tea polyphenols are rapidly O-methylated by human placental cytosolic COMT. This metabolic O-methylation is subject to strong inhibitory regulation by S-adenosyl-L-homocysteine, which is formed in large quantities during the O-methylation of tea polyphenols.

Catechin↗
PubMed1998

[Oxygen free radical scavening activity and anti-lipid peroxidation of tea polyphenol].

The oxygen free radical scavenging activity and anti-lipid peroxidation of tea polyshenol were studied in vitro. Tea polyphenol possessed significantly scavening effect on hydorxyl radical produced by Fenton recation and superoxide anion produced by xanthine-xanthine oxidase system (IC50 were 919.6 mg/L and 836 mg/L espectively). Tea polyphenol could significantly inhibit the lipid peroxidation of brain omogenate and cerbral mitochondrial membrane induced by hyderxyl radical. The results suggest that the anti-lipid peroxidation of tea polyphenol may be related to its scavenging effects on oxygen free radicals.

Animals↗
PubMed1992

[Aromatic and polyphenolic composition of infused peppermint, Mentha x piperita L].

The qualitative and quantitative composition of the main aromatic and polyphenolic constituents of Mitcham type peppermint (Mentha x piperita L.) tisane, were examined and compared with those of leaves before and after infusion. The original peppermint leaves contained 2.4% essential oil of which menthol was 0.99%, total polyphenolic compounds 19% and total flavonoid compounds 12% comprising eriocitrin 7%, luteolin-7-rutinoside 1.5%, hesperidoside 0.6% and total hydroxycinnamic compounds 7% (rosmarinic acid 1.4%). The tisane contained 21% of the original essential oil corresponding to 25 mg/l, with increased alcohol and ketone contents and lower contents of hydrophobic terpenecarbons, oxides and esters. It contained also a high proportion of the polyphenolic compounds (about 750 mg/l) corresponding to an extraction yield of 75%. In consequence the monograph "Peppermint leaf" of the Pharmacopoeia should be amended.

Oils, Volatile↗
PubMed1997

[The clinical effects of tea polyphenol varnish on caries prevention]

The aim of the present research is observing the effects of tea polyphenol varnish on caries prevention.107 children were in treated group,their first deciduous molars and deciduous incisors were treated by tea polyphenol varnish twice each.Other 110 children in control group did not receive any treatment.Two doctors examined their dental caries and recorded dmft and dmfs befoe treated and one year after treatment.The results indicate that the new caries incidence of the first deciduous molars and deciduous incisors in treatment group decreased 66% than that in control group.The results show that the new caries incidence of other untreated teethin treated group is lower significantly than that in control group.The effects of tea polyphenol varnish on preventing caries were more significant in deciduous molar than in deciduous incisor.The results also indicate that the effect of varnish is stronger in occlusal surface,and less in medial and distal surfaces of teeth.

Journal Article↗
PubMed1978

Serum polyphenol oxidase activity (ceruloplasmin) in conventional laboratory animals and man.

The optimum pH for ceruloplasmin as polyphenol oxidase (EC 1.10.3.2) activity was determined in human serum (pH 5.4) and the serum of conventional laboratory animals--the rat (pH 5.2), mouse (pH 5.2), hamster (pH 5.3), guinea pig (pH 5.4), multimammate mouse (pH 5.2) and rabbit (pH 5.4). Determined at the optimum pH in 0.1M acetate buffer polyphenol oxidase activity fell in the sequence: rat--man--rabbit--mouse--multimammate mouse--hamster--guinea pig. Ceruloplasmin polyphenol oxidase activity was inhibited by 0.1M phosphate buffer in the mouse, rat and multimammate mouse, but not in the other species. It was inhibited by 0.05M citrate and 0.1M phthalate buffer in all the species tested.

Animals↗
PubMed1994

Suppression of hydroperoxide-induced cytotoxicity by polyphenols.

A variety of synthetic and dietary polyphenols protect mammalian and bacterial cells from cytotoxicity induced by hydroperoxides, especially hydrogen peroxide (H2O2). Cytotoxicity of H2O2 on Chinese hamster V79 cells was assessed with a colony formation assay. Cytotoxicity and mutagenicity of H2O2 on Salmonella TA104 were assessed with the Ames test. SOS response induced by H2O2 was investigated in the SOS chromotest with Escherichia coli PQ37. The polyphenol-bearing o-dihydroxy (catechol) structure, i.e., nordihydroguaiaretic acid, caffeic acid ester, gallic acid ester, quercetin, and catechin, were effective for suppression of H2O2-induced cytotoxicity in these assay systems. In contrast, neither ferulic acid ester-bearing o-methoxyphenol structure nor alpha-tocopherol were effective, indicating that o-dihydroxy or its equivalent structure in flavonoids is essential for the protection. There are many reports describing that polyphenols act as prooxidants in the presence of metal ions. Our results suggest, however, that they act as antioxidants in the cells, when no metal ions are added to the medium.

Animals↗
PubMed1996

[Polyphenolic composition of the leaf of bilberry].

Dried leaves of 14 harvested batches and one batch from commercial origine of Vaccinium myrtillus L present a similar polyphenolic pattern. The mean levels of the harvested batches and the levels of the commercial batch were respectively: total polyphenol compounds 12.98 and 10.62%, tannins 7.84 and 7.43%, total flavonoid compounds 2.98 and 2.20% (spectrophotometry), 1.41 and 1.16% (HPLC), quercetin 3-glucuronide 1.02 and 0.83%, hyperoside 0.22 and 0.16%, chlorogenic acid 3.66 and 1.58%. The levels were higher in young leaves and lower in old leaves. A specific chromatographic profile of the flavonoid compounds and a determination method of the tannin or the total polyphenol content were proposed in a standardization purpose.

Chromatography, High Pressure Liquid↗
PubMed2004

Characteristics and physiological functions of polyphenols from apples.

Apples contain many kinds of polyphenols, and the main components are oligomeric procyanidins. Applephenon is apple polyphenol extract produced commercially from unripe apples, and has been used as food additive in order to prevent oxidation of components in foods and its application in functional foods is expected. In a lipid metabolism regulation study, administration of Applephenon has the potential to exert strong anti-oxidative activity and to inhibit consumption of vitamin E and anti-oxidative enzymes. Double blind clinical trials of Applephenon on pediatric patients with atopic dermatitis, and tests using type I allergic model mice suggested that Applephenon might regulate allergic reactions. We found the no observed adverse effect level (NOAEL) of Applephenon is greater than 2000 mg/kg in a 90~day consecutive oral administration toxicity test in rats, and Applephenon is safe and acceptable based on mutagenicity tests.

Animals↗
PubMed2006

The roles of polyphenols in cancer chemoprevention.

Oxidative stress imposed by reactive oxygen species (ROS) plays a crucial role in the pathophysiology associated with neoplasia, atherosclerosis, and neurodegenerative diseases. The ROS-induced development of cancer involves malignant transformation due to altered gene expression through epigenetic mechanisms as well as DNA mutations. Considerable attention has been focused on identifying naturally occurring antioxidative phenolic phytochemicals that are able to decrease ROS levels, but the efficacies of antioxidant therapies have been equivocal at best. Several studies have shown that some antioxidants exhibit prooxidant activity under certain conditions and potential carcinogenicity under others, and that dietary supplementation with large amounts of a single antioxidant may be deleterious to human health. This article reviews the intracellular signaling pathways that respond to oxidative stress and how they are modulated by naturally occurring polyphenols. The possible toxicity and carcinogenicity of polyphenols is also discussed.

Animals↗
PubMed2005

Dynamic ultrasound-assisted extraction of polyphenols in tobacco.

A novel extraction method, namely dynamic ultrasound-assisted extraction, is investigated. This technique is efficient with respect to both time and solvent consumption because it utilizes ultrasonic energy in dynamic mode during extraction. Polyphenols (chlorogenic acid, esculetin, rutin, scopoletin, and quercitrin) are extracted from a tobacco (Nicotina tobaccum L.) sample for 10 min with 6 mL of solvent. Fresh solvent is continuously pumped through the sample, with which the analytes can be rapidly extracted, and the possibility of degradation efficiently avoided. Methanol involving 0.5% w/v ascorbic acid was used as extraction solvent; optimal flow rate and extraction time were investigated. The extract was cleaned up by C18 disposable cartridge. The spiked and nonspiked tobacco samples were used for the evaluation of the proposed method. Recoveries obtained were varied from 96 to 108% and RSDs from 2.0 to 4.6%. This extraction technique was revealed to recover larger amounts of polyphenols from tobacco, compared to the static ultrasound-assisted extraction method.

Carbon↗