- Formation of UV-honey guides in Rudbeckia hirta
-
The UV-honey guides of Rudbeckia hirta were investigated by UV-photography, reflectance spectroscopy, LC-MS analysis and studies of the enzymes involved in the formation of the UV-absorbing flavonols present in the petals. It was shown for the first time
- Schlangen, Karin,Miosic, Silvija,Castro, Ana,Freudmann, Karin,Luczkiewicz, Maria,Vitzthum, Florian,Schwab, Wilfried,Gamsjaeger, Sonja,Musso, Maurizio,Halbwirth, Heidi
-
-
Read Online
- New thiophene and flavonoid from tagetes minuta leaves growing in saudi arabia
-
Phytochemical investigation of the methanolic extract of Tagetes minuta L. (Asteraceae) leaves resulted in the isolation and identification of two new compounds: 5-methyl-2,2',5',2'',5'',2''',5''',2''''-quinquethiophene (1) and quercetagetin-6-O-(6-Ocaffe
- Al-Musayeib, Nawal M.,Mohamed, Gamal A.,Ibrahim, Sabrin R. M.,Ross, Samir A.
-
p. 2819 - 2828
(2014/04/17)
-
- Regioselective hydroxylation of diverse flavonoids by an aromatic peroxygenase
-
Aromatic peroxygenases are extracellular fungal biocatalysts that selectively oxidize a variety of organic compounds. We found that the peroxygenase of the fungus Agrocybe aegerita (AaeAPO) catalyzes the H 2O2-dependent hydroxylation of diverse flavonoids. The reactions proceeded rapidly and regioselectively yielding preferentially monohydroxylated products, e.g., from flavanone, apigenin, luteolin, flavone as well as daidzein, quercetin, kaempferol, and genistein. In addition to hydroxylation, O-demethylation of fully methoxylated tangeretin was catalyzed by AaeAPO. The enzyme was merely lacking activity on the quercetin glycoside rutin, maybe due to sterical hindrance by the bulky sugar substituents. Mechanistic studies indicated the presence of epoxide intermediates during hydroxylation and incorporation of H2O2-derived oxygen into the reaction products. Our results raise the possibility that fungal peroxygenases may be useful for versatile, cost-effective, and scalable syntheses of flavonoid metabolites.
- Barková, Kate?ina,Kinne, Matthias,Ullrich, René,Hennig, Lothar,Fuchs, Annett,Hofrichter, Martin
-
experimental part
p. 4874 - 4878
(2011/08/03)
-
- Studies of the selective O-alkylation and dealkylation of flavonoids. XVIII. A convenient method for synthesizing 3,5,6,7-tetrahydroxyflavones
-
In the demethylation of 6-hydroxy-3,4',7-trimethoxy-5-(tosyloxy)flavone with anhydrous aluminum bromide, the 5-tosyloxyl group was eliminated with bromination to give 8-bromo-3,6,7-trihydroxy-4'-methoxyflavone as the main product. When anhydrous aluminum chloride was used in the demethylation of the acetate, the 5-tosyloxyl group was cleaved prior to the demethylation to give 5,6,7-trihydroxy-3,4'-dimethoxyflavone. Demethylation of 6-hydroxy-4',5,7-trimethoxy-3-(tosyloxy)flavone and its acetate with the bromide or chloride afforded the 5,6,7-trihydroxyflavone without the cleavage of the 3-tosyloxyl group, but was not suitable for the general synthesis of the 3,5,6,7-tetrahydroxyflavones because of the difficulty in removing the protecting group. Consequently, it was found that the direct demethylation of 3,6-dihydroxy-5,7-dimethoxyflavones with anhydrous aluminum chloride-sodium iodide in acetonitrile was the most useful general method for synthesizing 3,5,6,7-tetrahydroxyflavones. Additionally, the reported structures of two natural flavones were revised.
- Horie,Kobayashi,Kawamura,Yoshida,Tominaga,Yamashita
-
p. 2033 - 2041
(2007/10/03)
-
- Flavanoids from the Rudbeckia Hirta L. Herb
-
Seven crystalline flavanoids: 6,7-dimethoxy-3,5,3',4'-tetrahydroxyflavone 3-O-rhamnoside 1; 3,5,6,7,3',4'-hexahydroxyflavone 7-O-glucoside (quecetagitrin) 2; 6-methoxy-3,5,7,3',4'-pentahydroxyflavone 7-O-glucoside (patulitrin) 3; 3,5,7,3',4'-pentahydroxyflavone 7-O-glucoside (quercimetrin) 4; 6,7-dimethoxy-3,5,3',4'-tetrahydroxyflavone 5; dimethoxy-3,5,4'-trihydroxyflavone 3-O-rhamnoside 6; and 6,7-dimethoxy-3,5,3',4'-tetrahydroxyflavone 3-O-glucoside 7; have been isolated from methanolic extract of the Rudbeckia hirta L. herb by column chromatography on cellulose and polyamide.These compounds were identified by using UV, 1H NMR, 13C NMR, EI-MS and FD-MS.Four compounds: 1, 4, 5, and 6 have been found for the first time in this plant.
- Cisowski, W.,Dembinska-Migas, W.,Luczkiewicz, M.
-
p. 829 - 836
(2007/10/02)
-
- FLAVONOID GLYCOSIDES OF ARTEMISIA MONOSPERMA AND A. HERBA-ALBA
-
Ten flavonoid glycosides were isolated and identified from Artemisia monosperma: vicenin-2, lucenin-2, acacetin 7-glucoside, acacetin 7-rutinoside, the 3-glucosides and 3-rutinosides of quercetin and patuletin, and the 5-glucosides of quercetin and isorhamnetin.From Artemisia herba-alba eight flavonoid glycosides were isolated and identified: isovitexin, vicenin-2, schaftoside, isoschaftoside and the 3-glucosides and 3-rutinosides of quercetin and patuletin.Key Word Index - Artemisia monosperma; A herba-alba; Compositae; flavone and flavonol glycosides.
- Saleh, Nabiel A. M.,El-Negoumy, Sabry I.,Abd-Alla, Mohamed F.,Abou-Zaid, Mamdouh M.,Dellamonica, G.,Chopin, J.
-
p. 201 - 203
(2007/10/02)
-
