- Flavonoid glycosides from seeds of Hippophae rhamnoides subsp. Sinensis with α-glucosidase inhibition activity
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Hippophae rhamnoides subsp. Sinensis is a famous traditional medicinal plant in Tibet and Mongolia of China. Three novel flavonoid glycosides and ten known analogues were obtained from the seeds of H. rhamnoides. The structures of new compounds were elucidated by spectroscopics, chemical methods as well as literature data. In vitro assay, compounds 5–9, kaempferol and 70% ethanolic elution fraction showed prominent α-glucosidase inhibitory activities with IC50 values ranging from 8.30 to 112.11 μM, better than that of the positive control, acarbose, whose IC50 value was 1727.07 μM.
- Li, Rui,Wang, Qing,Zhao, Menghao,Yang, Peiming,Hu, Xiao,Ouyang, Danwei
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- Antioxidant flavonoids from Alhagi maurorum
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A new flavonoid, isorhamnetin-3-O-[-α-L-rhamnopyranosyl-(1→3)]- β-D-glucopyranoside (1), along with two known flavonoids 3′-O-methylorobol (2) and quercetin 3-O-β-D-glucopyranoside (3), was isolated from Alhagi maurorum. Their structures were established with the help of mass spectrometry, 1D and 2D NMR spectroscopy, and in comparison with the literature data. Compounds 1 and 2 exhibited moderate antioxidant activity in the 2,2-diphenyl-1-picrylhydrazyl free radical scavenging assay.
- Ahmad, Saeed,Riaz, Naheed,Saleem, Muhammad,Jabbar, Abdul,Nisar-Ur-Rehman,Ashraf, Mohammad
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- Antioxidant effects of isorhamnetin 3,7-di-O-β-D-glucopyranoside isolated from mustard leaf (Brassica juncea) in rats with streptozotocin-induced diabetes
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To investigate the effects of isorhamnetin 3,7-di-O-β-D-glucopyranoside (isorhamnetin diglucoside), a major flavonoid compound of mustard leaf, on oxidative stress due to diabetes mellitus, in vivo and in vitro studies were carried out. Oral administration of isorhamnetin diglucoside (10 or 20 mg/kg of body weight/day for 10 days) to rats with streptozotocin-induced diabetes significantly reduced serum levels of glucose and 5-(hydroxymethyl)furfural (5-HMF), which is glycosylated with hemoglobin and is an indicator of oxidative stress. After intraperitoneal administration, isorhamnetin diglucoside did not show these activities. In addition, after oral administration, the thiobarbituric acid-reactive substance levels of serum, and liver and kidney mitochondria declined significantly compared with the control group in a dose-dependent manner, whereas after intraperitoneal administration these levels fell only slightly. On the basis of the oral and intraperitoneal results, it was hypothesized that isorhamnetin diglucoside was converted to its metabolite in vivo, and its conversion to its aglycone, isorhamnetin, by β-glucosidase was confirmed; isorhamnetin acted as an antioxidant. Moreover, it was observed that isorhamnetin diglucoside had no effect on the 1,1-diphenyl-2-picrylhydrazyl radical, whereas isorhamnetin showed a potent antioxidant effect in vitro. In addition, intraperitoneal administration of isorhamnetin reduced serum glucose and 5-HMF levels. Furthermore, lipid peroxidation in blood, liver, and kidney associated with diabetes mellitus declined after the administration of isorhamnetin. These results suggest that isorhamnetin diglucoside is metabolized in vivo by intestinal bacteria to isorhamnetin and that isorhamnetin plays an important role as an antioxidant.
- Yokozawa, Takako,Kim, Hyun Young,Cho, Eun Ju,Choi, Jae Sue,Chung, Hae Young
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- Two new flavonol glycosides and biological activities of Diplotaxis harra (Forssk.) Boiss.
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Two new flavonol glycosides, isorhamnetin 3-O-β-glucopyranoside- 4′-O-β-xylopyranoside (1) and kaempferol 3-O-β-glucopyranoside -4′-O-β-xylopyranoside (2), were isolated from the defatted aqueous methanol extract of the whole plant Diplotaxis harra along with 12 known flavonols (3-14). They were characterised by chemical and spectral methods. The 70% aqueous methanol, chloroform and defatted aqueous methanol plant extracts exhibited significant antioxidant effects (nitroblue tetrazolium reduction method). Their cytotoxic activity was carried out against 11 tumour cell lines (sulphorhodamine B assay). The three extracts expressed the greatest antiproliferative activity against colon 38, P388 and MKN-28 with GI50 (0.45, 0.4, 0.07 g/mL) and against P388 [3-(4,5-dimethylthiazol-2yl)-2,5- diphenyltetrazolium bromide assay] with IC50 (0.26, 0.24, 0.25 g/mL), respectively. The chloroform extract showed the highest activity as eukaryotic DNA topoisomerase II inhibitors of P388 with IC50 0.24 g/mL. Antiviral screening of the extracts and the pure compounds against foot-and-mouth disease virus types A and O revealed a prominent inhibition of its cytopathic effect. 2013
- Kassem, Mona E.S.,Afifi, Manal S.,Marzouk, Mona M.,Mostafa, Manal A.
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- A new isorhamnetin glycoside and other phenolic compounds from Callianthemum taipaicum
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A new flavonol glycoside together with five known phenolic compounds were isolated from the whole herb of Callianthemum taipaicum. The compounds were identified as isorhamnetin-3-O-α-L-arabinoside-7-O-β-D-glucoside (1), isorhamnetin-3-O-β-D-glucoside (2), dibutyl phthalate (3), (+)-1-hydroxylpinoresinol-4'-β-D-glucoside (4), pinoresinol-4'-O-β-D- glucoside (5) and 2-phenylethyl-β-primeveroside (6). Compound 1 was identified as a new flavonol glycoside. The compound 6 was isolated for the first time as natural product. All compounds were isolated for the first time from the Callianthemum genus. Furthermore, the 2D-NMR data of the four known compounds 2-5 are given for the first time in this paper. All the structures were identified on the basis of detailed spectral analysis. The compounds 1 and 4 exhibited certain antifungal activity.
- Wang, Dong-Mei,Pu, Wen-Jun,Wang, Yong-Hong,Zhang, Yu-Juan,Wang, Shan-Shan
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- FLAVONOL GLYCOSIDES FROM SEDUM ACRE
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Three new flavonol glycosides, isohamnetin 3-(2''-acetyl) glucoside, limocitrin 7-glucoside, and limocitrin 3,7-diglucoside were isolated from the aerial parts of Sedum acre.The known compounds quercetin, isohamnetin and their 3- and 3,7-di-glucosides, isohamnetin-7-glucoside an d limocitrin and its 3-glucoside were also identified.The structure of the compounds was determined by means of spectroscopic and chemical methods.
- Wolbis, Maria,Krolikowska, Maria
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- Isolation, characterization, complete structural assignment, and anticancer activities of the methoxylated flavonoids from rhamnus disperma roots
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Different chromatographic methods including reversed-phase HPLC led to the isolation and purification of three O-methylated flavonoids; 5,4’-dihydroxy-3,6,7-tri-O-methyl flavone (penduletin) (1), 5,3’-dihydroxy-3,6,7,4’,5’-penta-O-methyl flavone (2), and 5-hydroxy-3,6,7,3’,4’,5’-hexa-O-methyl flavone (3) from Rhamnus disperma roots. Additionlly, four flavonoid glycosides; kampferol 7-O-α-L-rhamnopyranoside (4), isorhamnetin-3-O-β-D-glucopyranoside (5), quercetin 7-O-α-L-rhamnopyranoside (6), and kampferol 3, 7-di-O-α-L-rhamnopyranoside (7) along with benzyl-O-β-D-glucopyranoside (8) were successfully isolated. Complete structure characterization of these compounds was assigned based on NMR spectroscopic data, MS analyses, and comparison with the literature. The O-methyl protons and carbons of the three O-methylated flavonoids (1–3) were unambiguously assigned based on 2D NMR data. The occurrence of compounds 1, 4, 5, and 8 in Rhamnus disperma is was reported here for the first time. Compound 3 was acetylated at 5-OH position to give 5-O-acetyl-3,6,7,3’,4’,5’-hexa-O-methyl flavone (9). Compound 1 exhibited the highest cytotoxic activity against MCF 7, A2780, and HT29 cancer cell lines with IC50 values at 2.17 μM, 0.53 μM, and 2.16 μM, respectively, and was 2–9 folds more selective against tested cancer cell lines compared to the normal human fetal lung fibroblasts (MRC5). It also doubled MCF 7 apoptotic populations and caused G1 cell cycle arrest. The acetylated compound 9 exhibited cytotoxic activity against MCF 7 and HT29 cancer cell lines with IC50 values at 2.19 μM and 3.18 μM, respectively, and was 6–8 folds more cytotoxic to tested cancer cell lines compared to the MRC5 cells.
- Abd El-Wahab, Mohammed F.,Abdalla, Ashraf N.,Mohammed, Abd El-Salam I.,Mohammed, Hamdoon A.,Ragab, Ehab A.,Shaheen, Usama
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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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- 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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- Glucuronidation of Methylated Quercetin Derivatives: Chemical and Biochemical Approaches
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Botanical supplements derived from grapes are functional in animal model systems for the amelioration of neurological conditions, including cognitive impairment. Rats fed with grape extracts accumulate 3′-O-methyl-quercetin-3-O-β-d-glucuronide (3) in their brains, suggesting 3 as a potential therapeutic agent. To develop methods for the synthesis of 3 and the related 4′-O-methyl-quercetin-7-O-β-d-glucuronide (4), 3-O-methyl-quercetin-3′-O-β-d-glucuronide (5), and 4′-O-methyl-quercetin-3′-O-β-d-glucuronide (6), which are not found in the brain, we have evaluated both enzymatic semisynthesis and full chemical synthetic approaches. Biocatalysis by mammalian UDP-glucuronosyltransferases generated multiple glucuronidated products from 4′-O-methylquercetin, and is not cost-effective. Chemical synthetic methods, on the other hand, provided good results; 3, 5, and 6 were obtained in six steps at 12, 18, and 30% overall yield, respectively, while 4 was synthesized in five steps at 34% overall yield. A mechanistic study on the unexpected regioselectivity observed in the quercetin glucuronide synthetic steps is also presented.
- Docampo-Palacios, Maite L.,Alvarez-Hernández, Anislay,Adiji, Olubu,Gamiotea-Turro, Daylin,Valerino-Diaz, Alexander B.,Viegas, Luís P.,Ndukwe, Ikenna E.,De Fátima, ?ngelo,Heiss, Christian,Azadi, Parastoo,Pasinetti, Giulio M.,Dixon, Richard A.
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p. 14790 - 14807
(2020/12/23)
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- Chemical composition and biological activity of salicornia fruticosa L.
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Plants have been used as a source of traditional medicine to treat many diseases and conditions for many years. They considered as excellent source of phytochemicals which showed antioxidant and anticancer activities. The aim of the present study is to investigate the chemical composition and to determine the anticancer activity of Salicornia fruticosa (Chenopodiaceae) methanolic extract. S. fruticosa proved to be a source of isorhamnetin and its glycosides and showed anticancer activities. Seven major flavonoids were isolated and identified from the cytotoxic methanolic extract. The isolated compounds were identified, as quercetin 3',4'-dimethyl ether (1), isorhamnetin (2), isorhamnetin 3-O-rhamnoside (3), isorhamnetin 3-O-glucoside (4), isorhamnetin 3-O-rutinoside (5), isorhamnetin 3-O-neohesperidoside (6), isorhamnetin 3-O-rhamnosyl(1-2)arabinoside (7), by chromatographic analysis, chemical and spectroscopic tools (acid hydrolysis, UV, 1H and 13C NMR). Compounds 1 and 3-7 were isolated for the first time from the plant under investigation. The evaluation of cytotoxic activity of the methanolic extract against HCT-116, HepG2, A549 and MCF-7 human cancer cells, by MTT assay, revealed the higher potency of S. Fruticosa extract with IC50 [2.6. 10.9, 37.9, 5.4 (mg/ml)] respectively, comparable to that of doxorubicin. The obtained results suggested that the investigated plant could be used for future development of naturally occurring anticancer agent. Subclinical and clinical trials on polar fractions of S. fruticosa are mandatory to pave the way for its use in treatment of cancer diseases (HCT-116, HepG2, A549 and MCF-7).
- Abdel Elatif,Shabana,Ibrahim,Mansour,Awad,Sharaf
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p. 1713 - 1721
(2020/09/01)
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- Synthesis of Flavonols via Pyrrolidine Catalysis: Origins of the Selectivity for Flavonol versus Aurone
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A novel synthetic method for flavonol from 2′-hydroxyl acetophenone and benzaldehyde promoted by pyrrolidine under an aerobic condition in water is established. This protocol was supported by efficient synthesis of 44 common examples and three natural products. The α, β-unsaturated iminium ion (enimine ion E) was proved to be the key intermediate in the reaction. H218O and 18O2 isotope tracking experiments demonstrated that both water and the aerobic atmosphere were necessary to ensure the transformation. The selectivity for flavonol or aurone was originated from solvent-triggered intermediates, which were determined by UV-visible spectra from isolated enimine. The phenol-iminium E-A is dominant in water and the ketoenamine intermediate E-B is prevalent in acetonitrile. In the presence of pyrrolidine and oxygen, E-A leads to flavonol through E-I, a zwitterionic-like phenoloxyl-iminium ion, following the key steps of cyclization and a [2 + 2] oxidation; E-B proceeds through path II, a radical process induced by photolysis of E-B with both pyrrolidine and oxygen, to afford aurone. Preliminary mechanistic studies are reported.
- Xiong, Wei,Wang, Xiaohong,Shen, Xianyan,Hu, Cuifang,Wang, Xin,Wang, Fei,Zhang, Guolin,Wang, Chun
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p. 13160 - 13176
(2020/11/23)
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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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- Effects of Functional Groups and Sugar Composition of Quercetin Derivatives on Their Radical Scavenging Properties
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Quercetin derivatives are widespread in the plant kingdom and exhibit various biological actions. The aim of this study was to investigate the structure-activity relationships of quercetin derivatives, with a focus on the influence of functional groups and sugar composition on their antioxidant capacity. A series of quercetin derivatives were therefore prepared and assessed for their DPPH radical scavenging properties. Isoquercetin O-gallates were more potent radical scavengers than quercetin. The systematic analysis highlights the importance of the distribution of hydroxy substituents in isoquercetin O-gallates to their potency.
- Kato, Komei,Ninomiya, Masayuki,Tanaka, Kaori,Koketsu, Mamoru
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p. 1808 - 1814
(2016/08/02)
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- Synthetic method for isorhamnetin
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A provided synthetic method for isorhamnetin comprises the following steps: step 1, protecting 2,4,6-trihydroxyacetophenon with benzyl, so as to synthesize 2,4,6-tribenzyloxyacetophenone; step 2, performing addition reaction on 2,4,6-tribenzyloxyacetophenone and vanillin and then removing the protection group, so as to obtain 3'-methoxy-4',5,7-trihydroxychalcone; step 3, performing catalytic hydrogenation to remove a protection group; and step 4, employing an oxidation agent potassium peroxymonosulfate aqueous solution to perform oxidation cyclization reaction on 3'-methoxy-4',5,7-trihydroxychalcone. Isorhamnetin is synthesized by employing the above four steps, technology operation is simple, production cost is low, and the obtained product is high in purity and easy for industrialized production.
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- A new flavonol triglycoside derived from Anoectochilus elwesii on stimulating glucose uptake in insulin-induced human HepG2 cells
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A novel flavonol triglycoside (4), isorhamnetin-3-O-β-d-glucopyranosyl (1→2)-α-l-rhamnopyranosyl (1→6)-β-d-glucopyranoside, named elwesoside A, together with six known flavonols (1-3, 5-7) was isolated from Anoectochilus elwesii (Clarke ex Hook. f.) King et Pantl. and its structure was elucidated by extensive spectroscopic methods and comparison with the literature data. All compounds were first reported in this plant and two of them (4 and 5) were the first examples of flavonol triglycosides isolated from Anoectochilus genus. The effects of 1-7 were evaluated on insulin-treated human HepG2 cells under high glucose conditions for stimulating glucose uptake activities. The novel compound (4) displayed highly potent dose-dependent effect on the stimulation of glucose uptake in insulin-resistant human HepG2 cells.
- Cai, Jinyan,Zhao, Lin,Zhu, En
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p. 1414 - 1418
(2015/03/05)
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- Biological evaluation and SAR analysis of O-methylated analogs of quercetin as inhibitors of cancer cell proliferation
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Preclinical Research Using a high-throughout screening approach, the anticancer activities of 16 O-methylated (OMe) analogs of quercetin were assessed. The structure-activity relationships showed that OMe moieties at the 4′ and/or 7 positions were important for maintaining inhibitory activities against the 16 cancer cell lines. Furthermore, when the OH groups at the 3′ and 4′ positions were both replaced by OMe moieties, anticancer activity was enhanced.
- Shi, Zhi-Hao,Li, Nian-Guang,Tang, Yu-Ping,Shi, Qian-Ping,Tang, Hao,Li, Wei,Zhang, Xu,Fu, Hai-An,Duan, Jin-Ao
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p. 455 - 462
(2015/04/14)
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- New isorhamnetin glycosides and other phenolic compounds from calendula officinalis
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A total of 39 known compounds and two new flavonoid glycosides that were identified as isorhamnetin-3-O-(2″-acetyl)-β-D-glucopyranoside and isorhamnetin-3-O-(2″,6″-diacetyl)- β-D-glucopyranoside were isolated from florets of Calendula officinalis (Asteraceae). The distribution of phenolic compounds in morphological groups of C. officinalis was studied. It was found that peripheral florets had the highest flavonoid content (36.66 mg/g); tubular florets (9.95 mg/g) and leaves (9.65 mg/g), phenylpropanoids. Anthocyanins, among which cyanidin derivatives dominated, were identified for the first time in C. officinalis florets.
- Olennikov,Kashchenko
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p. 833 - 840
(2014/01/17)
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- Inhibitory effects of the constituents of hippophae rhamnoides on 3t3-l1 cell differentiation and nitric oxide production in RAW264.7 Cells
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Three new flavonol glycosides, hippophaeosides A-C (1-3), together with 27 known constituents, were isolated from Hippophae rhamnoides L. leaves. Their structures were determined by spectroscopic analyses. Their inhibitory activities on 3T3-L1 preadipocyte differentiation and triglyceride accumulation in maturing adipocytes, and nitric oxide production in RAW264.7 cells were examined.
- Yang, Zhi-Gang,Wen, Xiu-Feng,Li, Yong-Hai,Matsuzaki, Keiichi,Kitanaka, Susumu
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p. 279 - 285
(2013/05/08)
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- Metabolism-based synthesis, biologic evaluation and SARs analysis of O-methylated analogs of quercetin as thrombin inhibitors
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In blood, quercetin is mainly found in metabolized forms. In order to study the activities of these quercetin metabolites in cardiovascular disease, 17 methylquercetin derivatives were synthesized based on metabolism in vivo, their thrombin inhibition activity were evaluated through the analyzation of prothrombin time (PT), activated partial thromboplastin time (APTT), thrombin time (TT) and fibrinogen (FIB). The results showed that 6 methylquercetin derivatives had stronger inhibitory activities than that of quercetin. Preliminary SARs analysis showed that hydroxyl groups at C-3′ and C-4′ position in the B-ring and hydroxyl group at C-3 position in the C-ring played key roles in the thrombin inhibitory activity. The findings of this study would provide information for the exploitation and utilization of quercetin as thrombin inhibitor for thrombotic disease treatment.
- Shi, Zhi-Hao,Li, Nian-Guang,Tang, Yu-Ping,Wei-Li,Lian-Yin,Yang, Jian-Ping,Hao-Tang,Duan, Jin-Ao
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p. 210 - 222
(2012/09/07)
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- Phenolic constituents of the inflorescences of Sorbus torminalis (L.) Crantz
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Torminaloside, a new acylated flavonol glycoside (3,5,7,4′- tetrahydroxy-3′-methoxyflavone-3-O-[6″-O-(3?-hydroxy- 3?-methylglutaroyl)]-β-d-galactopyranoside, 6), together with five further methoxylated flavones 1-5, hyperoside (7), isoquercitrin (8), chlorogenic acid (9) and neochlorogenic acid (10), were isolated for the first time from Sorbus torminalis (L.) Crantz. The structures of the isolates were elucidated by extensive spectroscopic studies, including UV, IR, 1D- and 2D-NMR, LSI-MS and HR-LSI-MS experiments. In addition to torminaloside, three further flavonoids: 5,7,4′-trihydroxy-3′-methoxyflavone-7-O-β-d- glucopyranoside (1), 3,5,7,4′-tetrahydroxy-8,3′-dimethoxyflavone-3- O-β-d-glucopyranoside (2), and 3,5,7,4′-tetrahydroxy-3′- methoxyflavone-3-O-β-d-galactopyranoside (4) were found for the first time in the genus Sorbus.
- Olszewska, Monika A.,Roj, Joanna Marta
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experimental part
p. 151 - 157
(2012/05/04)
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- Flavonoid oligosides from georgian astragalus falcatus
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New flavonoid oligosides were isolated from leaves and flowers of Astragalus falcatus Lam. It was found on the basis of chemical transformations, UV, IR, PMR, 13C NMR, HMBC, HSQC, 1D-TOCSY, and mass spectral properties that falcoside C had the structure quercetin 3-O-[β-D- glucopyranosyl(1→3)-α-Lrhamnopyranosyl( 1→6)]-β-D- galactopyranoside 7-O-β-D-glucopyranoside; falcoside D, isorhamnetin 3-O-[β-D-xylopyranosyl(1→3)-α-L-rhamnopyranosyl(1→6)] -β-D-galactopyranoside 7-O-α-Lrhamnopyranoside.
- Alaniya,Kavtaradze,Skhirtladze,Sutiashvili
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p. 377 - 381
(2011/10/09)
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- Synthesis and antioxygenic activities of seabuckthorn flavone-3-ols and analogs
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A practical synthesis of polyhydroxy- and regiospecifically methylated flavone-3-ols which are components of commercial 'seabuckthorn flavone' has been achieved by modified Algar-Flynn-Oyamada method. Antioxidant activities of seabuckthorn extracts, isolated products and a number of flavone-3-ols have been determined. Structure-activity relationships have been discussed. Amongst the compounds tested, gallic acid, which is also present in seabuckthorn, was found to be the most effective antioxidant and radioprotectant.
- Pandurangan,Bose, Chinchu,Banerji
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p. 5328 - 5330
(2011/10/09)
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- Two new flavonol glycosides from Sedum Aizoon L.
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Two new flavonol glycosides, Sedacins C (1) and D (2), and two known compounds (3-4), have been isolated from the whole plant of Sedum aizoon L. Their structures have been established as 6′-O-(E)-feruloylquercetin (1) and 6′-O-(E)-feruloylisorhamnetin (2) by means of spectroscopic analysis and chemical methods. The Japan Institute of Heterocyclic Chemistry.
- Li, Wei Lin,Luo, Qiu Yan,Wu, Li Qiang,Xiao, Lei
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experimental part
p. 135 - 141
(2011/04/22)
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- Selective monomethylation of quercetin
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Quercetin was monomethylated under mild conditions in moderate yields through selective deprotection. The combined effects of the protecting group and the heating mode on the reactivity were investigated. The presence of borax and the use of microwave irradiation significantly improved the yield and selectivity of alkylation. Georg Thieme Verlag Stuttgart - New York.
- Zhou, Zhong-Hua,Fang, Zhuan,Jin, Hui,Chen, Yue,He, Ling
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experimental part
p. 3980 - 3986
(2011/02/22)
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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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- Use of anoectochilus formosanus plant extracts and their derived fractions as herbal medicines or nutraceutical supplements for chemoprevention or treatment of human malignancies
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The present invention provides medicinally active extracts and fractions, and a method for preparing the same by extracting and fractioning constituents from the tissue of plant components of the Anoectochilus family. These active extracts and fractions are useful for preventing or inhibiting tumor growth.
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- Purification and characterization of a flavonol 3-O-β heterodisaccharidase from the dried herb of Fagopyrum esculentum Moench
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A flavonol-3-O-β-heterodisaccharide glycosidase (FHG I) was isolated from dried aerial tissues of Fagopyrum esculentum Moench (Fagopyri herba). It has a specific enzyme activity of ca. 3.5 nkat mg-1 protein in buffered extracts when rutin (quercetin-3-O-rutinoside) was used as substrate and an optimal enzyme activity was seen at around pH 4.8 and 30 °C. FHG I was purified about 156-fold to apparent homogeneity by hydrophobic interaction, anion exchange and size exclusion chromatographic steps. The apparent molecular mass of FHG I was 74.5 ± 2 kDa as determined by SDS-PAGE and it is a monomeric glycoprotein with a carbohydrate content of 23%. The isoelectric point as determined by isoelectric focusing was 5.7 and the energy of activation was 32 kJ mol-1. FHG I exhibits a high substrate specificity, preferring flavonol 3-O-glycosides comprising the disaccharide rutinose. The Km and Vmax values for the natural substrate rutin were calculated to be 0.561 μM and 745 nkat mg -1 protein, respectively. Two oligopeptide fragments obtained after enzymatic digestion of FHG I were sequenced and showed similarities to sequences of β-glucohydrolases from other plant species. Polyclonal antibodies were raised and their specificities determined. Another flavonol 3-O-β -heterodisaccharide glycosidase (FHG II) could also be detected in buckwheat herb, having a molecular mass of 85.3 ± 2 kDa and an isoelectric point between pH 6.0 and 6.5.
- Baumgertel, Andreas,Grimm, Rudi,Eisenbeiss, Wilhelm,Kreis, Wolfgang
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p. 411 - 418
(2007/10/03)
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- Hemisynthesis of all the O-monomethylated analogues of quercetin including the major metabolites, through selective protection of phenolic functions
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A new methodology for the hemisynthesis of all the five O-monomethylated analogues of quercetin (3′-O-methylquercetin (isorhamnetin), 4′-O-methylquercetin (tamarixetin), 3-O-methylquercetin, 5-O-methylquercetin (azaleatin) and 7-O-methylquercetin (rhamnetin)) through sequential protection of the different phenolic functions of quercetin is reported.
- Bouktaib, Mohamed,Lebrun, Stéphane,Atmani, Aziz,Rolando, Christian
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p. 10001 - 10009
(2007/10/03)
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- Acylated flavonol diglucosides from Lotus polyphyllos
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Three acylated flavonol diglucosides, kaempferol 3-O-β -(6″-O-E-p-coumaroylglucoside)-7-O-β-glucoside; quercetin 3- O-β-(6″-O-E-p-coumaroylglucoside)-7-O-β-glucoside; isorhamnetin 3-O-β-(6″-O-E-p-coumaroylglucoside)-7-O-β-glucoside were isolated from the
- El Mousallami, Amani M.D.,Afifi, Manal S.,Hussein, Sahar A.M.
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p. 807 - 811
(2007/10/03)
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- Flavonol glycosides from Vernonia galamensis ssp. nairobiensis
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A new flavonol glycoside has been isolated from the leaves of Vernonia galamensis ssp. nairobiensis. Its structure has been established as isorhamnetin 3-O-β-D-apio-D-furanosyl(1 → 2)-β-D-galactopyranoside on the basis of spectral data (UV, 1H and 13C NMR, D/CIMS) and by acid hydrolysis. Characterization of the peracetate derivative confirmed the configuration of the apiosyl moiety. In addition, the known flavonol glycosides; quercetin 3-galactoside, quercetin 3-apiosyl(1 → 2)galactoside and quercetin 3-rhamnosyl(1 → 6)galactoside have been isolated and identified.
- Miserez, Francois,Potterat, Olivier,Marston, Andrew,Mungai, Geoffrey M.,Hostettmann, Kurt
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p. 283 - 286
(2007/10/03)
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- QUERCETIN 3-RHAMNOSYL (1->2) GALACTOSIDE FROM LYSIMACHIA VULGARIS VAR DAVURICA
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Key Word Index - Lysimachia vulgaris var davurica; Primulaceae; flavanol glycosides; quercetin 3-O-α-rhamnopyranosyl(1->2)-β-galactopyranoside.Abstract - From the whole plant of Lysimachia vulgaris var davurica, a new flavanol glycoside was isolated together with astragalin, hyperin, isorhamnetin 3-galactoside, syringetin 3-galactoside and isorhamnetin-3-robinobioside.The structure of the new compound was established as quercetin 3-rhamnosyl(1-2>)galactoside
- Yasukawa, Ken,Takido, Michio
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p. 3017 - 3018
(2007/10/02)
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- ISORHAMNETIN 7-GLUCOSIDE FROM CNICUS WALLICHI
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Key Word Index - Cnicus wallichi; Compositae; isorhamnetin 7-glucoside; flavonol glycoside.Isorhamnetin 7-glucoside was characterized from Cnicus wallichi.This is the first report of this glycoside in the Compositae and the second in nature.
- Singh, K. N.,Pandey, V. B.
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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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