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At least 793 records · Page 44Linked to original sources
PubMed2004

Purification and characterization of tyrosinase from gill tissue of Portabella mushrooms.

A group of tyrosinase isoforms with isoelectric points between 4.9 and 5.2 was isolated from gill tissue of Portabella mushrooms. Use of protease inhibitors was not able to increase the amount of latent forms significantly in crude extracts or to preserve latent tyrosinase activity during purification. The tyrosinase in gill tissue extracts showed latent activity above pH 5.5 and suppressed or displayed no latent activity below pH 5.5 when assayed in the presence of SDS. The purified isoforms showed monophenolase activity toward 4-hydroxyanisole but practically no activity toward tyrosine or tyramine. The purified isoforms showed greater activity toward catechol than either 4-methylcatechol, dopa, dopamine, chlorogenic acid, t-butylcatechol, or catechin. The Km for catechol was similar for the group of isolated isoforms (4.3 mM) compared to the isoforms in crude extracts (5.3 mM). Crude extracts showed several isoforms ranging from 50 to 230 kDa after partially denaturing SDS PAGE, while the purified isoforms showed molecular weights of 70 kDa.

Agaricus↗
PubMed2006

Altitudinal variation of secondary metabolite profiles in flowering heads of Arnica montana cv. ARBO.

The altitudinal variation on the contents of secondary metabolites in flowering heads of Arnica montana was assessed. Plants of A. montana cultivar ARBO were grown in nine experimental plots at altitudes between 590 and 2230m at Mount Patscherkofel near Innsbruck/Austria. The total contents of sesquiterpene lactones and flavonoids were not positively correlated with the altitude of the growing site. However, the proportion of flavonoids with vicinal free hydroxy groups in ring B to flavonoids lacking this feature significantly increased with elevation. Additionally, the level of caffeic acid derivatives also positively correlated with the altitude of the growing site. In particular amounts of 1-methoxyoxaloyl-3,5-dicaffeoylquinic acid significantly increased in higher sites and samples from the summit region contained 85% more of this compound than samples from valley sites. These results are discussed with regards to chemosystematic studies comparing samples collected in different altitudes as well as in the light of a UV-B protective and radical scavenging function of phenolics and their significance for plant life in environments with elevated UV-B radiation.

Altitude↗
PubMed2006

Metabolite profiling of carotenoid and phenolic pathways in mutant and transgenic lines of tomato: identification of a high antioxidant fruit line.

Plant secondary metabolism is highly regulated within the major pathways to terpenoids, phenolics and alkaloids. Such regulation can occur at multiple levels from transcription through to the compartmentation of the product. However, the possibility exists for cross-talk between these pathways, the regulation of which is largely unknown at present. Such phenomena are important to understand in the application of plant breeding, where unintended effects of transgenesis or mutation can have an impact on the environment or human health. In an effort to improve dietary antioxidant content of crop plants, the tomato has been a major focus of effort for engineering both lipophilic antioxidants such as carotenoids and hydrophilic antioxidants such as flavonoid glycosides. In this study, a panel of transgenic and mutant tomato lines has been subjected to metabolite profiling in comparison with wild type Ailsa Craig for both carotenoids and phenolics. A range of mutants and transgenic lines were selected showing a range of phenotypes varying from down-regulation through to increased levels of lycopene and beta-carotene. All mutants altered in structural genes for carotenoid biosynthesis showed that perturbations in carotenoid biosynthesis do not generally alter phenolic or flavonoids content significantly even when devoid of carotenoids. Reciprocally, the down-regulation of ferulate 5-hydroxylase had no effect on carotenoid content. In contrast mutants defective in light perception such as the high pigment (hp-1) and LA3771 possess elevated chlorogenic acid and rutin as well as increased carotenoid content. These lines can act as the hosts for further genetic manipulation for increased antioxidant content.

Antioxidants↗
PubMed2006

Inhibition of MMP-2 secretion from brain tumor cells suggests chemopreventive properties of a furanocoumarin glycoside and of chalcones isolated from the twigs of Dorstenia turbinata.

A furanocoumarin glycoside new named turbinatocoumarin (1) was isolated from the twigs of Dorstenia turbinata. The structure of turbinatocoumarin (1) was assigned as 5-methoxy-3-[3-(beta-glucopyranosyloxy)-2-hydroxy-3-methylbutyl]psoralen by means of spectroscopic analysis. Known compounds have also been isolated from this genus and identified as (2'S, 3'R)-3'-hydroxymarmesin (2), 5-methoxy-3-(3-methyl-2,3-dihydroxybutyl)psoralen (3), psoralen (4), kanzonol C (5) which was isolated for the first time from this genus, 4-hydroxylonchocarpin (6), umbelliferone, 4-hydroxy-3-methoxybenzaldehyde and 4-methoxyphenol. As part of our continuing search for potential naturally-occurring antitumor drug candidates, the inhibition of matrix metalloproteinase (MMP)-2 secretion from brain tumor-derived glioblastoma cells by the isolated compounds 1, 3, 5, and 6 was evaluated by zymography and compared to the documented naturally-occurring MMP secretion inhibitors chlorogenic acid (CHL) and epigallocatechin-3-gallate (EGCg). Among the compounds tested, the inhibiting MMP secretion concentrations ranged from 0.025 to 250 microM with up to 80% inhibition. The inhibitory activities of compounds 5 and 6 were found comparable to the common reference compounds CHL and EGCg. This suggests that alternate sources can be explored and exploited for the availability of chemopreventive molecules.

Antineoplastic Agents, Phytogenic↗
PubMed2026

Transcription factor NtELF3 promotes the polyphenol accumulation by targeting NtFLS-1 and NtCHIL-2 genes in tobacco.

Tobacco (Nicotiana tabacum L.) is an important economic crop, from which polyphenols are crucial for regulating its growth and development as well as shaping its quality. However, few genes associated with polyphenol accumulation have been cloned from tobacco, and the molecular mechanisms underlying this process remain poorly understood. Here, we found that the tobacco transcription factor EARLY FLOWERING 3 (NtELF3), which is highly expressed in tobacco leaves, positively regulates the accumulation of chlorogenic acid, neochlorogenic acid, cryptochlorogenic acid, rutin, scopoletin, and total polyphenols in tobacco middle leaves. The metabolomic and transcriptomic analyses of middle leaves showed that a total of 177 differentially accumulated metabolites and 7409 differentially expressed genes (DEGs) were identified in ntelf3-1 mutant versus wild type, respectively. Further investigation identified that 17 DEGs were involved in phenylpropanoid metabolic and flavonoid metabolic processes. Combined analysis indicated that the phenylpropanoid and flavonoid biosynthesis pathways were also co-enriched in kyoto encyclopedia of genes and genomes enrichment analysis. Molecular biology experiment demonstrated that NtELF3 directly binds to the promoters of NtFLS-1 and NtCHIL-2 that are both associated with phenylpropanoid and flavonoid biosynthesis, and promotes their expression. Taken together, our results not only provide new theoretical support for in-depth understanding of the regulatory mechanisms underlying polyphenol accumulation in tobacco, but also offer excellent genes and germplasm resources for tobacco quality breeding.

NtCHIL↗
PubMed2004

The catecholamine potentiates starch mobilization in transgenic potato tubers.

In human and animal cells, the catecholamines are involved in glycogen mobilization. Since the compounds are found in a potato, their function in starch mobilization was hypothesized. In order to verify this hypothesis, the transgenic potato plants Solanum tuberosum L. cv. Desiree overexpressing tyrosine decarboxylase (TD EC 4.1.1.25) cDNA from parsley has been generated. The cDNA expression was judged by the northern blot analysis and the enzyme activity measurements. Four independent transgenic lines with the highest TD mRNA expression were selected and analyzed. The expected substantial decrease in tyrosine content was followed by significant increase in tyramine and dramatic enhancement of norepinephrine synthesis was detected. The level of L-3,4-dihydroxyphenylalanin (L-Dopa) was only slightly increased and dopamine significantly decreased in most cases in these plants. The increase in norepinephrine was accompanied by changes in carbohydrate metabolism. The significant increase in glucose and sucrose and the decrease in starch content were characteristic features of TD overexpressed transgenic potato tubers. The features mentioned above indicate that catecholamines potentiate starch mobilization in potato plants in common with animal cells. The decrease in tyrosine content in transgenic plants is also compensated by significant increase in chlorogenic acid synthesis thus potentially increasing the antioxidant capacity of transgenic tubers. The glycoalkaloids content is changed in the transformants. This may originate from glucose accumulation and glycolysis activation. The obtained transgenic potato provides material for further detailed studies of the physiological function of catecholamines in plants.

Animals↗
PubMed2002

Interactions of lipoic acid radical cations with vitamins C and E analogue and hydroxycinnamic acid derivatives.

As a powerful natural antioxidant, lipoic acid exerts significant antioxidant activities in vivo and in vitro by deactivation of reactive oxygen and nitrogen species. In this study we present a novel synergistic interaction of lipoic acid with other endogenous or exogenous antioxidants. Antioxidants vitamins C and E analogue (Trolox C) and hydroxycinnamic acid derivatives were found to recycle lipoic acid by donating electrons to lipoic acid radical cations, thereby increasing the antioxidant capacity of lipoic acid in vivo and in vitro. The rate constant of the electron transfer is in the order 10(9)dm(3)mol(-1)s(-1), close to the diffusion-controlled limit, and transfer quantum yield is above 95%.

Ascorbic Acid↗
PubMed2002

Dicinnamoylquinides in roasted coffee inhibit the human adenosine transporter.

Preliminary screening of a minor, non-xanthine constituent of roasted coffee, 3,4-diferuloyl-1,5-quinolactone (DIFEQ), showed inhibition of the adenosine transporter at low micromolar concentration. DIFEQ is a neutral derivative of the chlorogenic acids, i.e. isomeric mono- and di-substituted coumaroyl-, caffeoyl-, and feruloyl-esters of quinic acid, formed in the roasting process of coffee. Displacement of the adenosine transporter antagonist [(3)H](S)-(nitrobenzyl)-6-thioinosine binding by DIFEQ in cultured U-937 cell preparations, expressing the human adenosine transporter protein (hENT1), showed a K(i) of 0.96+/-0.13 microM. Extracts of regular and decaffeinated coffee showed binding activities equivalent to 30-40 mg DIFEQ per three cups of coffee. Acute administration of a high dose of DIFEQ (100 mg/kg i.p.) reduced open field locomotion in mice for 20 min in correlation with brain levels of DIFEQ. Both 3,4-dicaffeoyl-1,5-quinide and 3,4-dicoumaroyl-1,5-quinide, two close structural analogs of DIFEQ also present in roasted coffee, showed similar affinities for the adenosine transporter, while the corresponding 3- and 4-mono caffeoyl- and feruloyl-quinides were one to two orders of magnitudes less active. This suggests that 3,4-dicinnamoyl-1,5-quinides in coffee could have the potential to raise extra-cellular adenosine levels, thereby counteracting the stimulant effect of caffeine.

Animals↗
PubMed2002

Evidence for glucose-6-phosphate transport in rat liver microsomes.

The existence of glucose-6-phosphate transport across the liver microsomal membrane is still controversial. In this paper, we show that S3483, a chlorogenic acid derivative known to inhibit glucose-6-phosphatase in intact microsomes, caused the intravesicular accumulation of glucose-6-phosphate when the latter was produced by glucose-6-phosphatase from glucose and carbamoyl-phosphate. S3483 also inhibited the conversion of glucose-6-phosphate to 6-phosphogluconate occurring inside microsomes in the presence of electron acceptors (NADP or metyrapone). These data indicate that liver microsomal membranes contain a reversible glucose-6-phosphate transporter, which furnishes substrate not only to glucose-6-phosphatase, but also to hexose-6-phosphate dehydrogenase.

Animals↗
PubMed1999

The small intestine can both absorb and glucuronidate luminal flavonoids.

We have studied the perfusion of the jejunum and ileum in an isolated rat intestine model with flavonoids and hydroxycinnamates and the influence of glycosylation on the subsequent metabolism. Flavone and flavonol glucosides and their corresponding aglycones are glucuronidated during transfer across the rat jejunum and ileum and this glucuronidation occurs without the need for gut microflora. Furthermore, this suggests the presence of glycosidases as well as UDP-glucuronyl transferase in the jejunum. In contrast, quercetin-3-glucoside and rutin are mainly absorbed unmetabolised. The results suggest that the more highly reducing phenolics are absorbed predominantly as glucuronides (96.5%+/-4.6) of the amount absorbed, whereas monophenolic hydroxycinnamates and monophenolic B-ring flavonoids are less predisposed to glucuronidation and higher levels of aglycone (88.1%+/-10.1) are detected on absorption through both the jejunum and ileum.

Animals↗
PubMed2001

High-performance liquid chromatography-electrospray ionization mass spectrometry and multiple mass spectrometry studies of hyperforin degradation products.

The alcoholic extract of the aerial parts of Hypericum perforatum L. finds wide application because of its antidepressant activity. The extract contains a number of constituents with documented biological activity including chlorogenic acid, a broad range of flavonoids, naphthodianthrones and phloroglucinols. Hyperforin and adhyperforin are the major phloroglucinol constituents found in the lipophilic fraction of the extracts. Since the stability of hyperforin has been shown to be limited, an investigation of the hyperforin degradation products using HPLC-electrospray ionization mass spectrometry and multiple mass spectrometry was undertaken.

Bridged Bicyclo Compounds↗
PubMed2003

Separation of polyphenolic compounds extracted from plant matrices using capillary electrophoresis.

Phenolic compounds constitute a large group of secondary plant products whose chemical structure may range from quite simple compounds to highly polymerized substances. The polyphenols content have been investigated in the alcoholic extract of the fruits of three different plants: sweet gale, sea buckthorn, hiprose. The trans-resveratrol content we have studied in roots, stems, leaves and flowers of Japanese knotweed grown in Estonia. Plant material was pre-treated in two different ways: by infusing with methanol and by supercritical fluid extraction with carbon dioxide modified with different alcohols. The relationship between variables (pressure, temperature, modifier amount) and yields are examined. The capillary zone electrophoresis methods were developed for the separation of polyphenolic anti-oxidative compounds. Using both water based borate buffer and acetonitrile based non-aqueous media it was possible to get reliable separation of several polyphenolic compounds. Based on that there has been identified such as flavone, trans-resveratrol, catechin, chlorogenic acid, quercetin and myricetin in plant extracts. Changes in the relative concentrations of trans-resveratrol in different parts of the knotweed have been established.

Electrophoresis, Capillary↗
PubMed2000

Characterization of polyphenol oxidase in coffee.

Polyphenol oxidase (PPO) was characterized in partially purified extracts of leaves (PPO-L) and fruit endosperm (PPO-E) of coffee (Coffea arabica L.). PPO activity was higher in early developmental stages of both leaves and endosperm of fruits. Wounding or exposure of coffee leaves to methyl jasmonate increased PPO activity 1.5-4-fold. PPO was not latent and was not activated by protease treatment. PPO activity was stimulated 10-15% with sodium dodecyl sulphate (SDS) at 0.35-1.75 mM, but at higher concentrations activities were similar to the control samples, without detergent. Prolonged incubation of extracts with trypsin or proteinase K inhibited PPO activity but pepsin had no effect. Inhibition of PPO with proteinase K was increased in the presence of SDS. PPO activity from both tissues was optimal at pH 6-7 and at an assay temperature of 30 degrees C. Activity was highest with chlorogenic acid as substrate with a Km of 0.882 mM (PPO-L) and 2.27 mM (PPO-E). Hexadecyl trimethyl-ammonium bromide, polyvinylpyrrolidone 40. cinnamic acid and salicylhydroxamic acid inhibited PPO from both tissues. Both enzymes were inactivated by heat but the activity in endosperm extracts was more heat labile than that from leaves. The apparent Mr determined by gel filtration was 46 (PPO-L) and 50 kDa (PPO-E). Activity-stained SDS polyacrylamide gel electrophoresis (PAGE) gels and western blots probed with PPO antibodies suggested the existence of a 67 kDa PPO which is susceptible to proteolytic cleavage that generates a 45 kDa active form.

Catechol Oxidase↗
PubMed2001

Predicting quantitative phytochemical markers in single Echinacea plants or clones from their DNA fingerprints.

Amplified restricted fragment length polymorphism (AFLP) data analysis was found to be a statistically significant predictor of phytochemical markers in cultivated Echinacea purpurea germplasm and some related wild species. Over 50 accessions grown under greenhouse conditions were subjected to AFLP analysis and the same assessed for content of tetraene and cichoric acid by high pressure liquid chromatography. The first and second canonical correlation of DNA variables and the phytochemical variables were significant. Individual regressions of cichoric acid and dodeca-2E, 4E, 8Z, 10E/Z-tetraenoic acid isobutyl amide predicted by DNA polymorphism analysis against actual HPLC determined values were nearly linear. Mantel's test showed that there was a weak correlation but a strong association of values of the phytochemical variables and the DNA polymorphism data.

Arachidonic Acids↗
PubMed1999

Immunological and molecular comparison of polyphenol oxidase in Rosaceae fruit trees.

An antibody raised against apple polyphenol oxidase (PPO) cross-reacted with PPOs from Japanese pear (Pyrus pyrifolia), pear (Pyrus communis), peach (Prunus persica), Chinese quince (Pseudocydonia sinensis) and Japanese loquat (Eriobotrya japonica). Core fragments (681 bp) of the corresponding PPO genes were amplified and characterized. The deduced protein sequences showed identities of 85.3 to 97.5%. Chlorogenic acid oxidase activity of these PPOs showed higher activities when assayed at pH 4 than at pH 6. These results indicate that PPOs in Rosaceae plants are structurally and enzymatically similar.

Amino Acid Sequence↗
PubMedDate not supplied

Phenolics: blocking agents for heterocyclic amine-induced carcinogenesis.

Chemopreventive effects of synthetic and naturally occurring antioxidants on heterocyclic amine (HCA)-induced rat carcinogenesis and mechanisms of inhibition were assessed. In a medium-term liver bioassay, combined treatment with 0.03% 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and synthetic antioxidants such as 1-O-hexyl-2,3,5-trimethylhydroquinone (HTHQ), butylated hydroxyanisole (BHA), butylated hydroxutoluene (BHT), tert-butylhydroquinone (TBHQ) or propyl gallate, each at a dose of 0.25%, inhibited development of preneoplastic glutathione S-transferase placental form (GST-P) positive foci as compared with MeIQx alone, after initiation with diethylnitrosamine (DEN). Of these antioxidants, HTHQ showed the greatest activity. 8-Hydroxydeoxyguanosine (8-OHdG), a marker for DNA damage induced by active oxygen species, and malonedialdehyde and 4-hydroxynonenal levels were not largely influenced by the treatment with MeIQx or antioxidants, either alone or in combination. In the same medium-term liver bioassay, effects of some naturally occurring antioxidants, such as green tea catechins (GTC), hesperidin, chlorogenic acid, quercetin, rutin, curcumin, daidzin, ferulic acid and genistein were also examined. Of these antioxidants, only GTC tended to inhibit GST-P positive foci development, while quercetin, rutin, curcumin, daidzin, ferulic acid and genistein all exerted significant enhancing effects. Examination of HTHQ influence in a medium term liver bioassay with HCA Glu-P-1, in which the experimental period was extended for up to 26 weeks, also demonstrated a significant decrease in the incidence of liver tumours to 40% in the group treated with 0.5% HTHQ and 0.03% 2-amino-6-methyldipyrido[1,2-a:3',2'-d]imidazole (Glu-P-1) as compared with the Glu-P-1 alone value of 89%. Effects of HTHQ on colon carcinogenesis induced by 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) were evaluated in a two-stage colon carcinogenesis model using 1,2-dimethylhydrazine (DMH) as an initiator. At week 36, the multiplicity of colon tumours induced by 0.02% PhIP after DMH initiation (9.1+/-6.2/rat) was dose-dependently decreased by the combined treatment with 0.5% HTHQ (3.6+/-1.8, P < 0.001) and 0.125% HTHQ (6.2+/-3.2, not significant). Similarly, the incidence of mammary carcinomas in female F344 rats induced by oral administration of 0.02% PhIP (40%) for 52 weeks was significantly decreased by simultaneous treatment with 0.5% HTHQ (5%). Alpha-tocopherol and chlorophyllin only reduced the multiplicity of carcinomas. Analysis of the influence of HTHQ on metabolic activation of Glu-P-1 or PhIP after incubation with rat S9 mixture and NADPH by HPLC, revealed that each major metabolite was strongly reduced by the addition of HTHQ. Immunohistochemically detected PhIP-DNA adduct positive nuclei in the colon induced by continuous oral treatment with 0.02% PhIP for 2 weeks decreased by the combined treatment with 0.5 or 0.125% HTHQ. These results indicate that synthetic antioxidant HTHQ is a very strong chemopreventor of heterocyclic amine (HCA)-induced carcinogenesis and that depressed metabolic activation rather than antioxidant activity is responsible for the observed effect.

Animals↗
PubMed2002

Prolonged blood glucose reduction in mrp-2 deficient rats (GY/TR(-)) by the glucose-6-phosphate translocase inhibitor S 3025.

Chlorogenic acid derivatives are potent inhibitors of hepatic glucose production by inhibition of the glucose-6-phosphate translocase component of the hepatic glucose-6-phosphatase system. The pharmacological proof of concept was clearly demonstrated during i.v. infusion of potent derivatives (S 4048, S 3483) in rats. However, the blood glucose lowering effect of S 4048 after bolus i.v. injection lasted only 60-90 min. Plasma clearance of S 4048 was very high, and the parent compound was rapidly and efficiently excreted into the bile of Wistar and GY/TR(-) rats, indicating that mrp-2 was not involved in this hepatobiliary elimination process. About 72% of the total administered radioactivity appeared in the bile within 20 min after i.v. bolus injection of the radiolabeled analogue [(3)H]S 1743 in a Wistar rat. However, in GY/TR(-) rats the dicarboxylic analogue of S 4048, S 3025, was cleared from the plasma less rapidly than its parent compound and its biliary elimination was comparatively low. In contrast, S 3025 exhibited comparable pharmacokinetics and biliary elimination profile as S 4048 in Wistar rats, suggesting that biliary elimination of S 3025 is facilitated by mrp-2, functionally absent in GY/TR(-) rats. Targeting to mrp-2 resulted in a significantly prolonged reduction of blood glucose levels in GY/TR(-) rats after i.v. bolus administration of S 3025.

Animals↗
PubMed1999

Quercetin inhibits hydrogen peroxide-induced oxidation of the rat lens.

Cataract results from oxidative damage to the lens. The mechanism involves disruption of the redox system, membrane damage, proteolysis, protein aggregation and a loss of lens transparency. Diet has a significant impact on cataract development, but the individual dietary components responsible for this effect are not known. We show that low micromolar concentrations of the naturally-occurring flavonoid, quercetin, inhibit cataractogenesis in a rat lens organ cultured model exposed to the endogenous oxidant hydrogen peroxide. Other phenolic antioxidants, (+)epicatechin and chlorogenic acid, are much less effective. Quercetin was active both when incubated in the culture medium together with hydrogen peroxide, and was also active when the lenses were pre-treated with quercetin prior to oxidative insult. Quercetin protected the lens from calcium and sodium influx, which are early events leading to lens opacity, and this implies that the non-selective cation channel is protected by this phenolic. It did not, however, protect against formation of oxidized glutathione resulting from H2O2 treatment. The results demonstrate that quercetin helps to maintain lens transparency after an oxidative insult. The lens organ culture/hydrogen peroxide (LOCH) model is also suitable for examining the effect of other dietary antioxidants.

Animals↗