- Structural determination of abutilins A and B, new flavonoids from Abutilon pakistanicum, by 1D and 2D NMR spectroscopy
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Two new flavonoids, abutilin A and B, were isolated from the chloroform soluble fraction of Abutilon pakistanicum and their structures assigned from 1H and 13C NMR spectra, DEPT and by 2D COSY, HMQC and HMBC experiments. Ferulic acid (3), (E)-cinnamic acid (4), 5-hydroxy-4′,6,7,8- tetramethoxyflavone (5), kaempferol (6), luteolin (7) and luteolin 7-O-β-D-glucopyranoside (8) have also been reported from this species. Copyright
- Ali, Bakhat,Imran, Muhammad,Hussain, Riaz,Ahmed, Zaheer,Malik, Abdul
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- The fungal leaf endophyte Paraconiothyrium variabile specifically metabolizes the host-plant metabolome for its own benefit
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Fungal endophytes live inside plant tissues and some have been found to provide benefits to their host. Nevertheless, their ecological impact is not adequately understood. Considering the fact that endophytes are continuously interacting with their hosts, it is conceivable that both partners have substantial influence on each other's metabolic processes. In this context, we have investigated the action of the endophytic fungus Paraconiothyrium variabile, isolated from the leaves of Cephalotaxus harringtonia, on the secondary metabolome of the host-plant. The alteration of the leaf compounds by the fungus was monitored through metabolomic approaches followed by structural characterization of the altered products. Out of more than a thousand molecules present in the crude extract of the plant leaf, we have observed a specific biotransformation of glycosylated flavonoids by the endophyte. In all cases it led to the production of the corresponding aglycone via deglycosylation. The deglycosylated flavonoids turned out to display significant beneficial effects on the hyphal growth of germinated spores. Our finding, along with the known allelopathic role of flavonoids, illustrates the chemical cooperation underlying the mutualistic relationship between the plant and the endophyte.
- Tian, Yuan,Amand, Séverine,Buisson, Didier,Kunz, Caroline,Hachette, Fran?ois,Dupont, Jo?lle,Nay, Bastien,Prado, Soizic
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- Anti‐melanogenic properties of velutin and its analogs?
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Velutin, one of the flavones contained in natural plants, has various beneficial activities, such as skin whitening, as well as anti‐inflammatory, anti‐allergic, antioxidant, and antimicrobial activities. However, the relationship between the structure of velutin and its anti‐melanogenesis activity is not yet investigated. In this study, we obtained 12 velutin derivatives substituted at C5, C7, C3′, and C4′ of the flavone backbone with hydrogen, hydroxyl, and methoxy functionalities by chemical synthesis, to perform SAR analysis of velutin structural analogues. The SAR study revealed that the substitution of functional groups at C5, C7, C3′, and C4′ of the flavone backbone affects biological activities related to melanin synthesis. The coexistence of hydroxyl and methoxy at the C5 and C7 position is essential for inhibiting tyrosinase activity. However, 1,2‐diol compounds substituted at C3′ and C4′ of flavone backbone induce apoptosis of melanoma cells. Further, substitution at C3′ and C4′ with methoxy or hydrogen is essential for inhibiting melanogenesis. Thus, this study would be helpful for the development of natural‐derived functional materials to regulate melanin synthesis.
- Choe, Jung-Won,Heo, Hee-Young,Jung, Se-Hui,Kim, Jaehyun,Lee, Kooyeon
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- New Flavonoids from Artemisia frigida
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New flavonoids were isolated from the aerial part of Artemisia frigida Willd. (Asteraceae). Their structures were elucidated using UV, IR, and NMR spectroscopy and mass spectrometry as chrysoeriol-7-O-(2′′-Oacetyl)-β-D-glucopyranoside (2′′-O-acetylthermop
- Olennikov
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p. 623 - 627
(2020/07/27)
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- Influence of Substrate Binding Residues on the Substrate Scope and Regioselectivity of a Plant O-Methyltransferase against Flavonoids
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Methylation of free hydroxyl groups is an important modification for flavonoids. It not only greatly increases absorption and oral bioavailability of flavonoids, but also brings new biological activities. Flavonoid methylation is usually achieved by a specific group of plant O-methyltransferases (OMTs) which typically exhibit high substrate specificity. Here we investigated the effect of several residues in the binding pocket of the Clarkia breweri isoeugenol OMT on the substrate scope and regioselectivity against flavonoids. The mutation T133M, identified as reported in our previous publication, increased the activity of the enzyme against several flavonoids, namely eriodictyol, naringenin, luteolin, quercetin and even the isoflavonoid genistein, while a reduced set of amino acids at positions 322 and 326 affected both, the activity and the regioselectivity of the methyltranferase. On the basis of this work, methylated flavonoids that are rare in nature were produced in high purity.
- Tang, Qingyun,Vianney, Yoanes M.,Weisz, Klaus,Grathwol, Christoph W.,Link, Andreas,Bornscheuer, Uwe T.,Pavlidis, Ioannis V.
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p. 3721 - 3727
(2020/06/02)
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- New Flavone Glycosides from Astragalus tanae Endemic to Georgia
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The new flavone glycosides tanoside I and II in addition to three known flavonoids and daucosterol were isolated from the Georgian endemic species Astragalus tanae Sosn. Their structures were elucidated as chrysoeriol-7-O-β-D-glucopyranosyl-4′ -O-α-L-rham
- Kavtaradze,Alaniya,Masullo,Cerulli,Piacente
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- Characterization of a Flavonoid 3’/5’/7-O-Methyltransferase from Citrus reticulata and Evaluation of the in Vitro Cytotoxicity of Its Methylated Products
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O-methylation of flavonoids is an important modification reaction that occurs in plants. O-methylation contributes to the structural diversity of flavonoids, which have several biological and pharmacological functions. In this study, an O-methyltransferase gene (CrOMT2) was isolated from the fruit peel of Citrus reticulata, which encoding a multifunctional O-methyltransferase and could effectively catalyze the methylation of 3’-, 5’-, and 7-OH of flavonoids with vicinal hydroxyl substitutions. Substrate preference assays indicated that this recombinant enzyme favored polymethoxylated flavones (PMF)-type substrates in vitro, thereby providing biochemical evidence for the potential role of the enzyme in plants. Additionally, the cytotoxicity of the methylated products from the enzymatic catalytic reaction was evaluated in vitro using human gastric cell lines SGC-7901 and BGC-823. The results showed that the in vitro cytotoxicity of the flavonoids with the unsaturated C2-C3 bond was increased after being methylated at position 3’. These combined results provide biochemical insight regarding CrOMT2 in vitro and indicate the in vitro cytotoxicity of the products methylated by its catalytic reaction.
- Liu, Xiaojuan,Wang, Yue,Chen, Yezhi,Xu, Shuting,Gong, Qin,Zhao, Chenning,Cao, Jinping,Sun, Chongde
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- Compounding method for chrysoeriol
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The invention provides a compounding method for chrysoeriol, solving the problems of operation complexity and low yield in the prior art. The compounding method includes mixing anhydrous phloroglucinol with 3-methoxy-4-hydroxy-benzoyl ethyl acetate and dimethyl sulfoxide, heating and stirring the mixture, stopping heating to remove vacuum after complete vacuum reaction, cooling the mixture to roomtemperature, adding water, and performing stirring and filtering to obtain a crude chrysoeriol solid; subjecting the crude chrysoeriol solid to recrystallization by ethyl alcohol, and performing decoloration, concentration, recrystallization, filtration and drying to obtain the refined chrysoeriol. The compounding method has the advantages of simple and convenient procedure, simplicity in post-treatment, high yield of the whole process and applicability to large-scale industrial production.
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Paragraph 0026-0047
(2018/03/06)
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- Enzymatic production of oroxylin A and hispidulin using a liverwort flavone 6-O-methyltransferase
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Oroxylin A and hispidulin, compounds which are abundant in both Scutellaria and liverwort species, are important lead compounds for the treatment of ischemic cerebrovascular disease. Their enzymatic synthesis requires an O-methyltransferase able to interact with the related flavonoid's 6-OH group, but such an enzyme has yet to be identified in plants. Here, the gene encoding an O-methyltransferase (designated PaF6OMT) was isolated from the liverwort species Plagiochasma?appendiculatum. A test of alternative substrates revealed that its strongest preferences were baicalein and scutellarein, which were converted into, respectively, oroxylin A and hispidulin. Allowed a sufficient reaction time, the conversion rate of these two substrates was, respectively, 90% and 100%. PaF6OMT offers an enzymatic route to the synthesis of oroxylin A and hispidulin.
- Zhang, Yu-Ying,Xu, Rui-Xue,Gao, Shuai,Cheng, Ai-Xia
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p. 2619 - 2628
(2017/01/14)
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- A new synthesis for acacetin, chrysoeriol, diosmetin, tricin and other hydroxylated flavones by modified Baker-Venkataraman transformation
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Baker-Venkataraman (BV) rearrangement is the method of choice for the synthesis of flavones. The major limitation of BV is that it requires extensive protections and deprotections of hydroxyl groups which make the process lengthy and cumbersome. In the present study, a three step efficient method has been developed using simple protecting groups and easily available starting materials. New syntheses for acacetin, chrysoeriol, diosmetin, tricin and other hydroxylated flavones are described.
- Pandurangan
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p. 225 - 229
(2014/05/20)
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- Characterization of two candidate flavone 8-O-methyltransferases suggests the existence of two potential routes to nevadensin in sweet basil
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Regioselective 6-,7-,8-,3'-, and 4'-O-methylations underlie the structural diversity of lipophilic flavones produced in the trichomes of sweet basil (Ocimum basilicum L.). The positions 6, 7, and 4' are methylated by a recently described set of cation-independent enzymes. The roles of cation-dependent O-methyltransferases still require elucidation. Here, the basil trichome EST database was used to identify a Mg2+-dependent O-methyltransferase that was likely to accept flavonoids as substrates. The recombinant protein was found to be active with a wide range of o-diphenols, and methylated the 8-OH moiety of the flavone backbone with higher catalytic efficiency than the 3'-OH group of candidate substrates. To further investigate flavone 8-O-methylation, the activity of a putative cation-independent flavonoid 8-O-methyltransferase from the same EST collection was assessed with available substrate analogs. Notably, it was strongly inhibited by gardenin B, one of its expected products. The catalytic capacities of the two studied proteins suggest that two alternative routes to nevadensin, a major flavone in some basil cultivars, might exist. Correlating the expression of the underlying genes with the accumulation of 8-substituted flavones in four basil lines did not clarify which is the major operating pathway in vivo, yet the combined data suggested that the biochemical properties of flavone 7-O-demethylase could play a key role in determining the reaction order.
- Berim, Anna,Gang, David R.
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- Modulation of human neutrophils' oxidative burst by flavonoids
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Inflammation is a normal response towards tissue injury, but may become deleterious to the organism if uncontrolled. The overproduction of reactive species during the inflammatory process may cause or magnify the damage at inflammatory sites. Flavonoids have been suggested as therapeutic agents to avoid such damage, as these compounds exhibit anti-inflammatory activity, through the modulation of oxidative stress and signalling pathways. Both effects may attenuate neutrophils' activities at inflammatory sites. In this study,we investigated the structure/activity relationship of a series of flavonoids on the oxidative burst of human neutrophils in vitro, as a measure of its anti-inflammatory potential. Neutrophils were stimulated with phorbol-12-myristate-13-acetate, and fluorescence and chemiluminescence techniques were used to evaluate the generation of reactive oxygen species. All the tested flavonoids revealed the ability to modulate the neutrophil 's oxidative burst. From the obtained results, the pivotal role of the catechol group in the B-ringwas evidenced as well as the minor importance of the hydroxylations in the A-ring, which did not appear to be determinant for the activity, although clearly influencing the lipophilicity of the tested flavonoids. It is also clarified the importance of the methylation in the OH group at the B-ring catechol moiety. In conclusion, the obtained results uncover new possible strategies for the resolution of inflammatory processes, using flavonoids to modulate neutrophil's oxidative burst.
- Ribeiro, Daniela,Freitas, Marisa,Tomé, Sara M.,Silva, Artur M. S.,Porto, Gra?a,Fernandes, Eduarda
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p. 280 - 292
(2013/10/01)
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- A new antiviral flavone glycoside from vernonia cinerea less
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A new flavone glycoside (A) m.p. 258-260 °C, m.f. C33H 40O19, [M] 740 (FABMS), has been isolated from roots of Vernonia cinerea Less. It was characterized as 5,7,4'-trihydroxy 3'-methoxy flavone-4'-O-a-L-rhamnopyranosyl-(14)-O-a-L-arabino-pyranosyl-(1 3)-O-b- D-galactopyranoside by various chemical degradations and spectral analysis which showed antiviral activity alongwith two known compounds luteolin (B) and taxifolin (C).
- Yadava,Raj, Mamta
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p. 3542 - 3544
(2013/05/08)
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- Synthesis and antidiabetic activity of 5,7-dihydroxyflavonoids and analogs
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In a study to evaluate the structural elements essential for the antidiabetic activity of flavonoids, we synthesized two series of flavonoids, 5,7-dihydroxyflavanones and 5,7-dihydroxyflavones. In a screening for potential antidiabetic activity, most of the flavonoids showed a remarkable in vitro activity, and compounds 1f, 2d, and 3c were significantly more effective than the positive control, metformin. The biological activity was mainly affected by structural modification at the ring B moiety of the flavonoid skeleton. The results suggest that 5,7-dihydroxyflavonoids can be considered as promising candidates in the development of new antidiabetic lead compounds. Copyright
- Chang, Liu-Shuan,Li, Chun-Bao,Qin, Nan,Jin, Mei-Na,Duan, Hong-Quan
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p. 162 - 169
(2012/04/04)
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- Flavonoid 3′-O-methyltransferase from rice: cDNA cloning, characterization and functional expression
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Plant O-methyltransferases (OMTs) are known to be involved in methylation of plant secondary metabolites, especially phenylpropanoid and flavonoid compounds. An OMT, ROMT-9, was cloned and characterized from rice using a reverse transcriptase polymerase chain reaction (RT-PCR). The blast results for ROMT-9 showed a 73% identity with caffeic acid OMTs from maize and Triticum aestivum. ROMT-9 was expressed in Escherichia coli and its recombinant protein was purified using affinity chromatography. It was then tested for its ability to transfer the methyl group of S-adenosyl-l-methionine to the flavonoid substrates, eriodictyol, luteolin, quercetin, and taxifolin, all of which have a 3′-hydroxyl functional group. The reaction products were analyzed using TLC, HPLC, HPLC/MS, and NMR spectroscopy. The NMR analysis showed that ROMT-9 transferred the methyl group specifically to the 3′-hydroxyl group of quercetin, resulting in the formation of its methoxy derivative. Furthermore, ROMT-9 converted flavonoids containing the 3′-hydroxy functional group such as eriodictyol, luteolin, quercetin and taxifolin into the corresponding methoxy derivatives, suggesting that ROMT-9 is an OMT with strict specificity for the 3′-hydroxy group of flavonoids.
- Kim, Bong-Gyu,Lee, Youngshim,Hur, Hor-Gil,Lim, Yoongho,Ahn, Joong-Hoon
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p. 387 - 394
(2008/02/04)
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- Flavonoid glycoside from Leucas lavandulaefolia (Rees) aerial parts
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Chrysoeriol-4′-O-α-L-rhamnopyranosyl (1→2) β-D-galacto-pyranosyl (1→6) β-D-glucopyranoside has been isolated from Leucas lavandulaefolia Rees aerial parts and its structure has been determined by UV-Vis, IR, 1H and 13C NMR and mass spectroscopic methods.
- Chandrashekar,Arun,Satyanarayana,Subramanyam
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p. 1968 - 1969
(2007/10/03)
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- FLAVONOIDS OF Thermopsis alterniflora. CROTONOYLTHERMOPSOSIDE AND CROTONOYLCOSMOSIIN - NEW ACYLATED FLAVONE GLYCOSIDES
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From the epigeal part of Thermopsis alterniflora Rgl. et Schmalh. (Fabaceae), in addition to formononetin, ononin, cynaroside, and rothindin, two new acylated flavone glycosides have been isolated and, on the basis of chemical transformations and spectral characteristics, their structures have been established as 4',5,7-trihydroxy-3'-methoxyflavone 7-O-(6"-O-crotonoyl-β-D-glucopyranoside) and 4',5,7-trihydroxyflavone 7-O-(6"-O-crotonoyl-β-D-glucopyranoside).
- Yuldashev, M. P.,Batirov, E. Kh.,Vdovin, A. D.,Malikov, V. M.,Yagudaev, M. R.
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p. 303 - 308
(2007/10/02)
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- FLAVONOIDS FROM PHLOMIS LYCHNITYS
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The new naturally occurring acylated flavone glucoside chrysoeriol-7-β-D-(3''-E-p-coumaroyl)glucoside and other flavonoids have been isolated from the aerial parts of Phlomis lychnitys, and identified by spectral techniques.Relationships between flavonoid pattern, phylogeny and geography in Phlomis are discussed. Key Word Index - Phlomis lychnitys; Labiatae; acylated flavonoids; chrysoeriol-7-β-D-(3''-E-p-coumaroyl)-glucoside; phylogeny.
- Tomas, F.,Nieto, J. L.,Barberan, F. A. T.,Ferreres, F.
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p. 1253 - 1254
(2007/10/02)
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- On a Thermal Transmethylation Reaction with Flavon-5-methylethers
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Upon heating to 300 deg C partial luteolinemethylethers undergo transmethylation.A reaction mechanism is put foreward. - Key words: Flavonemethylethers, Thermal Transmethylation, TLC, HPLC, Reaction Mechanism
- Geiger, Hans,Casteele, Karel Vande,Sumere, Christiaan F. Van
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p. 393 - 396
(2007/10/02)
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- CHRYSOERIOL 7-(2''-O-β-D-ALLOPYRANOSYL)-β-D-GLUCOPYRANOSIDE FROM SIDERITIS GRANDIFLORA
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The aerial parts of Sideritis grandiflora yielded a new flavone glycoside, identified as chrysoeriol 7-(2''-allosylglucoside).Key Word Index - Sideritis grandiflora; Labiatae; 13C-NMR; chrysoeriol 7-(2''-O-β-D-allopyranosyl-β-D-glucopyranoside)
- Rabanal, Rosa M.,Valverde, S.,Martin-Lomas, M.,Rodriguez, B.,Chari, V. M.
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p. 1830 - 1832
(2007/10/02)
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- O-methylation of flavonoids by cell-free extracts of calamondin orange
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Cell-free extracts of calamondin orange (Citrus mitis) catalysed the O-methylation of almost all hydroxyls of a number of flavonoids, indicating the existence in citrus tissues of ortho, meta, para and 3-O-methyltransferases. The latter, hitherto unreported enzyme, catalysed the formation of 3-O-methyl ethers of galangin and quercetin. The stepwise O-methylation of a number of compounds, especially quercetin and quercetagetin, tends to suggest a coordinated sequence of O-methylations on the surface of a multienzyme complex. The methyl acceptor abilities of the flavonoid substrates used are discussed in relation to their hydroxyl substitution patterns and their negative electron density distribution.
- Brunet, Gunter,Ibrahim, Ragai K.
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p. 741 - 746
(2007/10/02)
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