- Flavonol glycosides from Costus spicatus
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Two flavonol diglycosides, tamarixetin 3-O-neohesperidoside, kaempferide 3-O-neohesperidoside and the known quercetin 3-O-neohesperidoside, together with six other known flavonoids were isolated from the leaves of Costus spicatus and their structures were elucidated by a combination of spectroscopic and chemical methods. The flavonol diglycosides were evaluated for inhibitory activity of nitric oxide production by activated macrophages (Fig. 1).
- Da Silva, Bernadete P.,Bernardo, Robson R.,Parente, Jose P.
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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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- Synthesis and Biological Evaluation of 4-Substituted Kaempfer-3-ols
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The synthesis of two series of five kaempfer-3-ols was described. The first set all have a C-3 hydroxyl group and the second has a carboxymethoxy ether at the C-3 position. Both series have variable substitution at the C-4 position (i.e., OH, Cl, F, H, OMe). Both kaempferols and carboxymethoxy ethers were evaluated for their ability to inhibit ribosomal s6 kinase (RSK) activity and cancer cell proliferation.
- Kim, Sugyeom,Lannigan, Deborah A.,Li, Yu,Lin, Lin,O'Doherty, George A.,Sayasith, Peyton R.,Tarr, Ariel T.,Wright, Eric B.,Yasmin, Sharia
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p. 4279 - 4288
(2020/04/09)
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- Method for preparing icaritin intermediate
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The invention provides a method for preparing an icaritin intermediate. The method includes the steps of a, enabling phloroglucinol to react with one of a 2-benzyloxy acetylation reagent and 2-benzyloxy acetonitrile to obtain 2-benzyloxy-1-(2,4,6-trihydroxyphenyl)ethanone; b. subjecting a reaction product obtained from the step a and p-methoxybenzoyl halide to Baker-Venkataraman reaction so as toobtain 3-(benzyloxy)-5,7-dihydroxy-2-(4-methoxyphenyl)-4H-benzopyran-4-one; c. subjecting the reaction product obtained in the step b to hydrogenation so as to obtain the icaritin intermediate, namely 3,5,7-trihydroxy-2-(4-methoxyphenyl)-4H-benzopyran-4-one.
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Paragraph 0056; 0067-0071; 0082-0085; 0098-0101
(2019/08/07)
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- Selective methylation of kaempferol via benzylation and deacetylation of kaempferol acetates
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A strategy for selective mono-, di- and tri-O-methylation of kaempferol, predominantly on the basis of selective benzylation and controllable deacetylation of kaempferol acetates, was developed. From the selective deacetylation and benzylation of kaempferol tetraacetate (1), 3,4′,5,-tri-O-acetylkaempferol (2) and 7-O-benzyl-3,4′5,-tri-O-acetylkaempferol (8) were obtained, respectively. By controllable deacetylation and followed selective or direct methylation of these two intermediates, eight O-methylated kaempferols were prepared with 51-77% total yields from kaempferol.
- Mei, Qinggang,Wang, Chun,Yuan, Weicheng,Zhang, Guolin
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p. 288 - 293
(2015/03/31)
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- Total synthesis of icaritin via microwave-assistance Claisen rearrangement
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The novel total synthesis of icaritin (1), naturally occurring with important bioactive 8-prenylflavonoid, was performed via a reaction sequence of 8 steps including Baker-Venkataraman reaction, chemoselective benzyl or methoxymethyl protection, dimethyldioxirane (DMDO) oxidation, O-prenylation, Claisen rearrangement and deprotection, starting from 2,4,6-trihydroxyacetophenone and 4-hydroxybenzoic acid in overall yields of 23%. The key step was Claisen rearrangement under microwave irradiation. MS, 1H and 13C NMR techniques have been used to confirm the structures of all synthetic compounds.
- Nguyen, Van-Son,Shi, Ling,Li, Yue,Wang, Qiu-An
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p. 677 - 681
(2015/04/14)
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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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- 7-O-Arylmethylgalangin as a novel scaffold for anti-HCV agents
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In spite of potent antiviral activity, suboptimal physicochemical properties of aryl diketo acids (ADKs) necessitates modification of the core 1,3-diketo acid functionality into a novel scaffold. As the metal-binding affinity of the diketo acid is the key to the antiviral activity of ADKs, we anticipated 3,5-dihydroxy-4-oxo arrangement of galangin scaffold would serve as an excellent mimic for the diketo acid functionality. In this study, through synthesis and biological evaluation of various galangin derivatives, we have shown that the diketo acid functionality can be successfully replaced with the galangin scaffold by specific combination of the substituents to result in identification of a novel galangin derivative (3s) with anti-HCV activity (EC50 = 0.9 μM) comparable to the ADK counterpart.
- Lee, Hyo Seon,Park, Kwang-Su,Lee, Chaewoon,Lee, Bokhui,Kim, Dong-Eun,Chong, Youhoon
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scheme or table
p. 5709 - 5712
(2010/11/04)
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- Flavonoids from the leaves of actinidia kolomikta
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One new acetylated flavonoid, kaempferide-7-O-(4'-O-acetyl)-α-L- rhamnoside, and six known flavonoids were isolated from the EtOAc fraction of the leaves of Actinidia kolomikta (Rupr. et Maxim.) Planch. The chemical structures of the isolated compounds we
- Lu, Juan,Jin, Yongri,Liu, Guiying,Zhu, Na,Gui, Mingyu,Yu, Aimin,Li, Xuwen
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experimental part
p. 205 - 208
(2010/09/18)
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- A rare flavonol glycoside from Aerva tomentosa Forsk as antimicrobial and hepatoprotective agent
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From the perianth lobes of A. tomentosa, kaempferide 3-0-(6″O-acetyl-4?-O-α-methylsinapyl)neohesperidoside has been isolated which has shown marked antimicrobial and hepatoprotective activities.
- Jaswant,Ragunathan,Sulochana
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p. 956 - 958
(2007/10/03)
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- Novel use of flavones
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A pharmaceutical composition for inhibiting COX-2 biosynthesis comprising a therapeutically effective amount of the compound of formula I and a pharmaceutrically acceptable carrier. wherein R1 and R4 represent either Hydrogen or together a bond R5, R6, R7, R8 represent independently of each other Hydrogen, Hydroxy or Methoxy; in addition R7 represents a sugar substituent like glucoside, rutinosid, manno gluco pyransyl, aprosylglucoside R2 and R3 represent Hydrogen, Hydroxy, Methoxy or wherein R2′, R3′, R4′, R5′ and R6′ are independently or each other Hydrogen, Hydroxy or Methoxy with the proviso, that R2 or R3 is represented by the optionally substituted Phenylring.
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- TWO FLAVONOID GLYCOSIDES FROM THE BARK OF PROSOPIS JULIFLORA
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Key Word Index - Prosopis juliflora; Leguminoseae; flavonol glycoside; kaempferol 4'-methyl ether 3-O-β-D-galactopyranoside; isoflavone glycoside; retusin 7-O-neohesperidoside. Two new glycosides, kaempferol 4'-methyl ether 3-O-β-D-galactopyranoside and retusin 7-O-neohesperidoside, have been characterized from the bark of Prosopis juliflora.
- Shukla, Ranjana Vajpeyi Nee',Misra, Krishna
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p. 339 - 340
(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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