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'Quercetin' in keywords
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1Author    G. M. WasselRequires cookie*
 Title    On the Constituents of the Wild Egyptian Plant Onopordon alexandrinum Boiss  
 Abstract    The study of the nitrogenous bases of Onopordon alexandrinum Boiss. resulted on the isolation of stachydrine and choline. The flavonoid components detected are: Luteolin-7-monoglucoside, apigenin-7-glucoside and quercetin. 
  Reference    (Z. Naturforsch. 30c, 349 [1975]; received February 18 1975) 
  Published    1975 
  Keywords    O nopordon alexandrinum, Stachydrine, Choline, Flavonoids, Quercetin 
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 TEI-XML for    default:Reihe_C/30/ZNC-1975-30c-0349.pdf 
 Identifier    ZNC-1975-30c-0349 
 Volume    30 
2Author    Gunter Brunet, N. Ab, A. M. Saleh, R. Agai, K. IbrahimRequires cookie*
 Title    Stepw ise M ethylation of Quercetin by Cell-Free Extracts of Citrus Tissues  
 Abstract    The cell-free extracts of peel, root, or callus tissues of citrus catalyzed the stepwise O-methylation of quercetin to rham netin, isorham netin and rhamnazin. Both rham netin and isorham netin were further m ethylated to rhamnazin and possibly to a trim ethyl ether derivative of quercetin. The results seem to indicate the existence of both m eta and para directing enzymes that are involved in the biosynthesis of m ethylated flavonoids in citrus tissues. 
  Reference    Z. Naturforsch. 33c, 786 (1978); received August 7 1978 
  Published    1978 
  Keywords    O-M ethylation, Quercetin, Citrus tissues 
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 TEI-XML for    default:Reihe_C/33/ZNC-1978-33c-0786_n.pdf 
 Identifier    ZNC-1978-33c-0786_n 
 Volume    33 
3Author    M. J. Martín, C. La-Casa, C. Alarcón-De-La-Lastra, J. Cabeza, I. Villegas, V. MotilvaRequires cookie*
 Title    Anti-Oxidant Mechanisms Involved in Gastroprotective Effects of Quercetin  
 Abstract    The anti-ulcerogenic and anti-oxidant effects of various flavonoids have been frequently reported. We investigated the cytoprotective properties of quercetin, a natural flavone, in gastric mucosal injury induced by 50% ethanol, since in this experimental model the patho­ genesis of the lesions has been related with production of reactive oxygen species. The in­ volvement of neutrophil infiltration and the capacity of this flavonoid to restrain the oxida­ tive process produced in the gastric tissue after ethanol administration were also investigated. Oral pretreatment with the highest dose of quercetin (200 mg/kg), 120 min before absolute ethanol was the most effective anti-ulcer treatment. Thiobarbituric acid reactive substances in the gastric mucosa, an index of lipid peroxidation, were increased by ethanol injury, but the increase was inhibited by the administration of 200 mg/kg of quercetin. This dose also induced a significant enhancement in the levels of mucosal non-protein SH compounds (im­ portant anti-oxidant agents) and in glutathione peroxidase activity. Exposure of the gastric mucosa to 50% ethanol induced a significant increase in myeloperoxidase activity, an index of neutrophil infiltration. Flowever, quercetin was not able to modify the increase in enzy­ matic activity generated by the necrotizing agent. The activity of superoxide dismutase en­ zyme involved in several antioxidant processes was also not significantly modified after quer­ cetin treatment. These results suggest that the anti-ulcer activity of quercetin in this experimental model could be partly explained by the inhibition of lipid peroxidation, through decrease of reactive oxygen metabolites. However, the inhibition of neutrophil infiltration or the increase of su­ peroxide dismutase activity does not appear to be involved in gastroprotective effect of this flavonoid. 
  Reference    Z. Naturforsch. 53c, 82—8 (1998); received July 14/October 31 1997 
  Published    1998 
  Keywords    Flavonoids, Quercetin, Gastroprotection, Anti-Oxidant Effects, Neutrophils 
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 TEI-XML for    default:Reihe_C/53/ZNC-1998-53c-0082.pdf 
 Identifier    ZNC-1998-53c-0082 
 Volume    53 
4Author    Kim Thresh, RagaiK. IbrahimRequires cookie*
 Title    Are Spinach Chloroplasts Involved in Flavonoid O-Methylation?  
 Abstract    Intact spinach chloroplasts, which were isolated on a cushion of Percoll and purified on discon­ tinuous sucrose gradients, were found to adsorb appreciable amounts of high specific activity, cytosolic O-methyltransferases. The latter activity was readily eliminated after washing the chloroplast pellet with 0.1 m phosphate in sucrose gradient buffer and finally with 0 .1% nonidet. Furthermore, the OMT activity of spinach leaves was resolved by chromatography on DEAE-Sepharose CL-6B into caffeic acid (COMT) and flavonoid (FOMT) O-methyltransferase ac­ tivities, and purified to 30-and 50-fold, respectively. The similarities between the FOMT/COMT activity ratios and the methylation patterns of intact chloroplasts and their supernatants, as well as those of purified leaf preparations, suggest non-specific binding of cytosolic OMTs to chloroplast envelopes. It is concluded, therefore, that spinach chloroplasts are not involved in the methylation of phenylpropanoid or flavonoid compounds. These results call attention for the re-evaluation of the role of this organelle in the biosynthesis or accumulation of plant secondary metabolites. 
  Reference    Z. Naturforsch. 40c, 331 (1985); received December 11 1984/February 26 1985 
  Published    1985 
  Keywords    Spinacea oleracea, Chenopodiaceae, Chloroplasts, O-Methyltransferase, Caffeic Acid, Quercetin 
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 TEI-XML for    default:Reihe_C/40/ZNC-1985-40c-0331.pdf 
 Identifier    ZNC-1985-40c-0331 
 Volume    40 
5Author    K. Stich3, H. Halbwirth3, F. Wurst3, G. ForkmannbRequires cookie*
 Title    UDP-GIucose: Flavonol 7-O-glucosyItransferase Activity in Flower Extracts o f Chrysanthemum segetum  
 Abstract    The yellow colour of Chrysanthemum segetum petals is due to the presence o f the 7-0-glucosides of quercetin and particularly gossypetin (8-hydroxyquercetin). In petal extracts of C. segetum an enzyme was demonstrated which catalyzes the transfer o f the glucosyl moiety o f uridine 5'-diphosphoglucose (U D P G) to the 7-hydroxyl group of flavonols with gossypetin and quercetin as the best substrates. Besides flavonols flavanones and flavones were found to be glucosylated in the 7-position. The pH-optimum of the reaction highly depended on the substrate used. With quercetin as substrate, maximal enzyme activity occurred at a pH o f 8.25 and a temperature of 25 °C, but 7-O-glucosylation also proceeded at low temper­ atures. Studies on temperature stability revealed, that there was no influence on the glucosy-lation reaction up to 40 °C. Higher temperatures led to a loss of enzyme activity. Using gossypetin as a substrate a similar course of temperature stability was observed. Addition of M g2+, Ca2+ and K C N slightly stimulated 7-O-glucosylation, whereas C o2+, Cu2+, Fe2+, Hg2+, p-hydroxymercuribenzoate and N-ethylmaleimide showed a strong inhibitory effect. Addi­ tional enzymatic studies were performed with the commercial strain " Stern des Orients" where gossypetin 7-O-glucoside is restricted to the inner parts of the petals. For enzyme extracts from both parts of the petals gossypetin was found to be the most attractive sub­ strate. In comparison to quercetin (133.4 [.ikat / kg protein) an about three times higher specific activity of the 7-0-glucosyltransferase(s) was determined with gossypetin (382.1 (.ikat/ kg protein) as substrate, indicating that hydroxylation o f quercetin in 8-position to gossypetin precedes 7-O-glucosylation. 
  Reference    Z. Naturforsch. 52c, 153—158 (1997); received November 11/ 
  Published    1997 
  Keywords    Chrysanthemum segetum, UDP-Glucose: Flavonol 7-O-glucosyltransferase, Quercetin, Gossypetin, Flavonoids 
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 TEI-XML for    default:Reihe_C/52/ZNC-1997-52c-0153.pdf 
 Identifier    ZNC-1997-52c-0153 
 Volume    52