- The epimerase activity of anthocyanidin reductase from Vitis vinifera and its regiospecific hydride transfers
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Anthocyanidin reductase (ANR) from Vitis vinifera catalyzes an NADPH-dependent double reduction of anthocyanidins producing a mixture of (2S,3R)- and (2S,3S)-flavan-3-ols. At pH 7.5 and 30°C, the first hydride transfer to anthocyanidin is irreversible, and no intermediate is released during catalysis. ANR reverse activity was assessed in the presence of excess NADPq. Analysis of products by reverse phase and chiral phase HPLC demonstrates that ANR acts as a flavan-3-ol C3-epimerase under such conditions, but this is only observed with 2R-flavan-3-ols, not with 2S-flavan-3-ols produced by the enzyme in the forward reaction. In the presence of deuterated coenzyme 4S-NADPD, ANR transforms anthocyanidins into dideuterated flavan-3-ols. The regiospecificity of deuterium incorporation into catechin and afzelechin - derived from cyanidin and pelargonidin, respectively - was analyzed by liquid chromatography coupled with electrospray ionization-tandem mass spectrometry (LC/ESI-MS/MS), and it was found that deuterium was always incorporated at C2 and C4. We conclude that 3-epimerization should be achieved by tautomerization between the two hydride transfers and that this produces a quinone methide intermediate which serves as C4 target of the second hydride transfer, thereby avoiding any stereospecific modification of carbon 3. The inversion of C2 stereochemistry required for reverse epimerization suggests that the 2S configuration induces an irreversible product dissociation.
- Gargouri, Mahmoud,Chaudiere, Jean,Manigand, Claude,Mauge, Chloe,Bathany, Katell,Schmitter, Jean-Marie,Gallois, Bernard
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- PHYLLOFLAVAN, A CHARACTERISTIC CONSTITUENT OF PHYLLOCLADUS SPECIES
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Key Word Index - Phyllocladus alpinus; Podocarpaceae; catechin; epicatechin; phylloflavan; epimerization; configuration.Abstract - Selective visulaization of 2D TLC of extracts of Phyllocladus species with vanillin-hydrochloric acid showed a characteristic pattern of constituents attributable to catechin, epicatechin and phylloflavan, a new flavanoid compound.Optical rotation measurements showed that while catechin and epicatechin are of the normal type with the 2R configurations, the flavan moiety in phylloflavan is of the opposite 2S configuration.Spectroscopic data of the new compound and its hydrolysis products showed phylloflavan to be ent-epicatechin-3-δ-(3,4-dihydroxyphenyl)-β-hydroxypentanoate.
- Foo, Lai Yeap,Hrstich, Liana,Vilain, Christian
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- Effects of epigallocatechin gallate on the stability of epicatechin in a photolytic process
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Catechins belonging to polyhydroxylated polyphenols are the primary compounds found in green tea. They are associated with many physiological properties. Epicatechin (EC) is a non-gallate-type catechin with four phenolic hydroxyl groups attached. The changes in EC treated with color light illumination in an alkaline condition were investigated by chromatographic and mass analyses in this study. In particular, the superoxide anion radical (O2??) was investigated during the EC photolytic process. EC is unstable under blue light illumination in an alkaline solution. When EC was treated with blue light illumination in an alkaline solution, O2?? was found to occur via a photosensitive redox reaction. In addition, the generation of monomeric, dimeric, and trimeric compounds is investigated. On the other hand, epigallocatechin gallate (EGCG), which is a gallate-type catechin, is stable under blue light illumination in an alkaline solution. Adding EGCG, during the blue light illumination treatment of EC decreased photolytic formation, suggesting that gallate-type catechins can suppress the photosensitive oxidation of EC. Gallate-type catechins are formed via the esterification of non-gallate-type catechins and gallic acid (GA). The carbonyl group on the gallate moiety of gallate-type catechins appears to exhibit its effect on the stability against the photosensitive oxidation caused by blue light illumination.
- Huang, Shiuh-Tsuen,Hung, Yi-An,Yang, Meei-Ju,Chen, Iou-Zen,Yuann, Jeu-Ming P.,Liang, Ji-Yuan
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- Phenolic compounds from the rhizomes of Smilax China L. & their anti-inflammatory activity
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A new triflavanoid, kandelin B-5 (1), was isolated from the rhizomes of Smilax China L., together with six known phenylpropanoid substituted flavan-3-ols (2-7), nine flavonoids (8-16), two stilbenoids (17, 18), and two other compounds (19, 20). The structure of compound 1 was determined on the basis of 1D, 2D NMR and HR-ESI-MS data, as well as chemical method. Compounds 2-5, 8-12, 15, 17, and 19 were evaluated for anti-inflammatory activity. Only compounds 10, 15 and 17 showed slightly IL-1expression inhibitory activities on LPS induced THP-1 cells, with inhibition rate of 15.8%, 37.3%, and 35.8%, respectively, at concentration of 50 μg/mL.
- Zhong, Cheng,Hu, Deng,Hou, Lian-Bing,Song, Lu-Yao,Zhang, Ying-Jun,Xie, Yang,Tian, Li-Wen
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- POTENTILLANIN, A BIFLAVANOID AND A PROCYANIDIN GLYCOSIDE FROM POTENTILLA VISCOSA
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An investigation of the root of Potentilla viscosa has led to the isolation and characterization of a novel 6',8-linked bisflavanoid, potentillanin and a procyanidin B-3,3'-O-glucoside.Furthermore, the occurrence of (+)-catechin and its 3-O-glucoside, procyanidins B-3 and C-2 and afzelechin-(4α->8)-catechin was demonstrated.Key Word Index - Potentilla viscosa; Roseceae; potentillanin; bisflavanoid; flavan-3-ol glycoside; procyanidin glycoside; proanthocyanidin.
- Zhang, Ben,Gen-Ichiro Nonaka,Nishioka, Itsuo
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- Kinetics of Epimerization of (+)-Catechin and Its Rearrangement to Catechinic Acid
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The rates of epimerization of (+)-catechin (1) to (+)-epicatechin (2) and of (-)-epicatechin to (-)-catechin in aqueous solution were measuredthe pH range 5.4-11.0 and the temperature range 34-100 deg C.The rate of conversion of (+)-catechin to catechinic acid (3) also was measured under these conditions.First-order kinetics were observed for all three processes.At low pH, k(epimerization) >> k(rearrangement), and epimerization approached an equilibrium in which (+)-catechin predominated(+)-epicatechin.Near pH 11 and at elevated temperatures,k(epimerization) was only slightly greater than k(rearrangement), and the rapid, irreversible formation of catechinic acid under these conditions determined product composition.Both the epimerization of catechin and its rearrangement to catechinic acid can be rationalized in terms of a quinone methide intermediate (4).
- Kiatgrajai, Preecha,Wellons, J. D.,Gollob, Lawrence,White, James D.
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- Terpenoids of Boswellia neglecta oleo-gum resin
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Oleo-gum resin exudate from Boswellia neglecta afforded a new ursane-type triterpene characterized as 3α-acetoxy-28-hydroxy-11-oxours-12-en-24-ioc acid (1) together with twelve known compounds. Their structural elucidation was accomplished using physical, chemical and spectroscopic methods.
- Manguro, Lawrence Onyango Arot,Wagai, Samuel Otieno,Onyango, Joab Otieno
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- FLAVONOID BIOCIDES: PHYTOALEXIN ANALOGUES FROM CONDENSED TANNINS
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Flavonoids containing a single alkyl chain can be synthesized from condensed tannins by thiolysis with an alkyl thiol to give epicatechin-4-alkylsulphides.A number of flavonoid derivatives were made with side chains ranging from C6 to C16 and tested for fungitoxic and bactericidal activities.Maximum activity was usually found for the decane derivative.Minimum inhibitory concentrations varied with the organism tested, from about 10 ppm for some rapidly growing fungi and Gram-positive bacteria, to over 500 ppm for other fungi and Gram-negative bacteria.The structural and toxicity characteristics of the epicatechin-4-alkylsulphides suggests they are acting as analogues of prenylated isoflavonoid phytoalexins.Key Word Index - Condensed tannins; phytoalexins; flavonoids; antifungal activity; antibacterial activity.
- Laks, Peter E.
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- Chemical and enzymatic synthesis of monomeric procyanidins (leucocyanidins or 3′,4′,5,7-tetrahydroxyflavan-3,4-diols) from (2R,3R)-dihydroquercetin
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The major product from the reduction of (2R,3R)-dihydroquercetin with sodium borohydride is the 2,3-trans-3,4-trans isomer of leucocyanidin [(2R,3S,4R-3,3′,4,4′,5,7-hexahydroxyflavan] whereas the enzymatic reduction product is the 2,3-trans-3,4-cis isomer [(2R,3S,4S)-3,3′,4,4′,5,7-hexahydroxyflavan]. The 3,4-trans isomer may be partly converted to the 3,4-cis isomer under mild acid conditions. The 3,4-cis isomer is more acid-labile, and more reactive both chemically with thiols and enzymatically with a diol reductase, than the 3,4-trans isomer.
- A. Stafford, Helen,H. Lester, Hope,J. Porter, Lawrence
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- Flavan-3-ols and procyanidins from the bark of Salix purpurea L.
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From a commercial aqueous ethanolic extract obtained from the bark of Salix purpurea L. the flavan-3-ols catechin, epicatechin, gallocatechin, catechin-3-O-(1-hydroxy-6-oxo-2-cyclohexene-1-carboxylic acid)-ester, the dimeric procyanidins B1, B3 and the trimeric procyanidins epicatechin- (4β→8)-catechin-(4α→8)-catechin and epicatechin- (4β→8)-epicatechin-(4β→8)-catechin were isolated. Structure elucidation was performed by NMR, CD, MS, degradation and optical rotation methods. A fraction containing higher oligomeric procyanidins was investigated by 13C NMR. Data indicate an average degree of oligomerization of 4 to 5 flavan-3-ol units with dihydroxylated B-rings and predominance of 2,3-cis-stereochemistry.
- Juergenliemk,Petereit,Nahrstedt, Adolf
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- DIMERIC FLAVANOLS OF Juniperus sabina. I.
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Procyanidins B2, B3, and B4 have been isolated from Juniperus sabina for the first time.On the basis of chemical transformations and the PMR spectroscopy of their decaacetates, and absolute configurations of the asymetric centers of each of the halves of the molecules of the dimer have been determined: 2R, 3R, 4R for the "upper" half and 2R, 3R for the "lower" half of B2, 2R, 3S, 4S for the "upper" half and 2R, 3S, for the "lower" half of B3; and 2R, 3S, 4S for the "upper" half and 2R, 3R for the "lower" haalf of B4.
- Pashinina, L. T.,Abil'kaeva, S. A.,Sheichenko, B. I.
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- Biochemical and functional characterization of anthocyanidin reductase (ANR) from Mangifera indica L.
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Mango (Mangifera indica L.) is abundant in proanthocyanidins (PAs) that are important for human health and plant response to abiotic stresses. However, the molecular mechanisms involved in PA biosynthesis still need to be elucidated. Anthocyanidin reductase (ANR) catalyzes a key step in PA biosynthesis. In this study, three ANR cDNAs (MiANR1-1,1-2,1-3) were isolated from mango, and expressed in Escherichia coli. In vitro enzyme assay showed MiANR proteins convert cyanidin to their corresponding flavan-3-ols, such as (—)-catechin and (—)-epicatechin. Despite high amino acid similarity, the recombinant ANR proteins exhibited differences in enzyme kinetics and cosubstrate preference. MiANR1-2 and MiANR1-3 have the same optimum pH of 4.0 in citrate buffer, while the optimum pH for MiANR1-1 is pH 3.0 in phosphate buffer. MiANR1-1 does not use either NADPH or NADH as co-substrate while MiANR1-2/1-3 use only NADPH as co-substrate. MiANR1-2 has the highest Km and Vmax for cyanidin, followed by MiANR1-3 and MiANR1-1. The overexpression of MiANRs in ban mutant reconstructed the biosynthetic pathway of PAs in the seed coat. These data demonstrate MiANRs can form the ANR pathway, leading to the formation of two types of isomeric flavan-3-ols and PAs in mango.
- Tan, Lin,Wang, Mei,Kang, Youfa,Azeem, Farrukh,Zhou, Zhaoxi,Tuo, Decai,Rojo, Lina María Preciado,Khan, Ikhlas A.,Pan, Zhiqiang
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- Ultraviolet B (UVB) photosensitivities of tea catechins and the relevant chemical conversions
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Ultraviolet B (UVB) photosensitivities of eight catechins were screened. In both water and ethanol, epicatechin (EC, 575 μM) and catechin (C, 575M) exhibited low photostabilities under 6 h UVB radiation with the generation of yellow photoproducts, while other catechins (epigallocatechin gallate, epigallocatechin, epicatechin gallate, gallocatechingallate, gallocatechin, catechin gallate) were relatively UVB-insensitive. Photoisomerization and photolysis were two important UVB-induced reactions to EC whereas photolysis was the dominant reaction for C. The influencing factors of time (2-10 h), solvent (water, ethanol) and substrate concentration (71.875-1150μM) on UVB-induced chemical conversions of EC and C were investigated, and eight photoproducts were identified through ultra performance liquid chromatography-diode array detection-Tandem mass spectrometry (UPLC-DAD-MS/MS) and 1H nuclear magnetic resonance (1H-NMR analysis). Photolysis reaction involved two pathways, including radical reaction and photo-induced electron transfer reaction. The 2,2-diphenylpicrylhydrazyl (DPPH) scavenging abilities of eight catechins did not change upon 6 h UVB irradiation. EC and C are photosensitive catechins among eight catechins causing deep color.
- Shi, Meng,Nie, Ying,Zheng, Xin-Qiang,Lu, Jian-Liang,Liang, Yue-Rong,Ye, Jian-Hui
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- Study on in Vitro Preparation and Taste Properties of N-Ethyl-2-Pyrrolidinone-Substituted Flavan-3-Ols
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N-ethyl-2-pyrrolidinone-substituted flavan-3-ols (EPSFs) were prepared by an in vitro model reaction, and the taste thresholds of EPSFs and their dose-over-threshold factors in large-leaf yellow tea (LYT) were investigated. The effects of initial reactant
- Han, Zisheng,Ho, Chi-Tang,Jiang, Zongde,Lai, Guoping,Qin, Chunyin,Wan, Xiaochun,Wen, Mingchun,Zhai, Xiaoting,Zhang, Hui,Zhang, Liang
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- Structural Characterization and Assessment of Anti-Inflammatory Activities of Polyphenols and Depsidone Derivatives from Melastoma malabathricum subsp. normale
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The roots of Melastoma malabathricum subsp. normale (D. Don) Karst. Mey have been used in traditional ethnic medicine systems in China to treat inflammation-triggered ailments, such as trauma, toothache, and fever. Therefore, the aim of this study is to screen for compounds with anti-inflammatory activity in the title plant. The extract of M. malabathricum subsp. normale roots was separated using various chromatographic methods, such as silica gel, ODS C18, MCI gel, and Sephadex LH-20 column chromatography, as well as semi-preparative HPLC. One new complex tannin, named whiskey tannin D (1), and an undescribed tetracyclic depsidone derivative, named guanxidone B (2), along with nine known polyphenols (2–10) and three known depsidone derivatives (12–14) were obtained from this plant. The structures of all compounds were elucidated by extensive NMR and CD experiments in conjunction with HR-ESI-MS data. All these compounds were isolated from this plant for the first time. Moreover, compounds 1–4, 8, and 10–14 were obtained for the first time from the genus Melastoma, and compounds 1, 2, and 11–14 have not been reported from the family Melastomataceae. This is the first report of complex tannin and depsidone derivatives from M. malabathricum subsp. normale, indicating their chemotaxonomic significance to this plant. Compounds 1–12 were investigated for their anti-inflammatory activities on the production of the nitric oxide (NO) in lipopolysaccharide (LPS)-stimulated RAW264.7 cells, and compounds 1, 11, and 12 showed anti-inflammatory activities with IC50 values of 6.46 ± 0.23 μM, 8.02 ± 0.35 μM, and 9.82 ± 0.43 μM, respectively. The structure–activity relationship showed that the catechin at glucose C-1 in ellagitannin was the key to its anti-inflammatory activity, while CH3 O-at C-16 of aromatic ring A in depsidone derivatives had little effect on its anti-inflammatory activity. The study of structure–activity relationships is helpful to quickly discover new anti-inflammatory drugs. The successful isolation and structure identification of these compounds, especially complex tannin 1, not only provide materials for the screening of anti-inflammatory compounds, but also provide a basis for the study of chemical taxonomy of the genus Melastoma.
- He, Rui-Jie,Huang, Yong-Lin,Li, Dian-Peng,Liu, Zhang-Bin,Wang, Ya-Feng,Yang, Bing-Yuan,Zou, Bi-Qun
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- Benzophenone Glucosides and B-Type Proanthocyanidin Dimers from Zambian Cassia abbreviata and Their Trypanocidal Activities
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Two benzophenone glucosides (1 and 2), five flavan-3-ol dimers (5–9), and 17 known compounds (3, 4, and 10–24) were identified from the bark extract of Cassia abbreviata. The chemical structures display two points of interest. First, as an unusual charact
- Choongo, Kennedy,Ishikawa, Yoshinobu,Kikuchi, Takashi,Munsimbwe, Linous,Murata, Toshihiro,Shirakura, Izumi,Suganuma, Keisuke
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- Optimization of the biosynthesis of b-ring ortho-hydroxy lated flavonoids using the 4-hydroxyphenylacetate 3-hydroxylase complex (Hpabc) of escherichia coli
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Flavonoids are important plant metabolites that exhibit a wide range of physiological and pharmaceutical functions. Because of their wide biological activities, such as anti-inflammatory, antioxidant, antiaging and anticancer, they have been widely used in foods, nutraceutical and pharmaceuticals industries. Here, the hydroxylase complex HpaBC was selected for the efficient in vivo production of ortho-hydroxylated flavonoids. Several HpaBC expression vectors were constructed, and the corresponding products were successfully detected by feeding naringenin to vector-carrying strains. However, when HpaC was linked with an S-Tag on the C terminus, the enzyme activity was significantly affected. The optimal culture conditions were determined, including a substrate concentration of 80 mg·L?1, an induction temperature of 28?C, an M9 medium, and a substrate delay time of 6 h after IPTG induction. Finally, the efficiency of eriodictyol conversion from P2&3-carrying strains fed naringin was up to 57.67 ± 3.36%. The same strategy was used to produce catechin and caf-feic acid, and the highest conversion efficiencies were 35.2 ± 3.14 and 32.93 ± 2.01%, respectively. In this paper, the catalytic activity of HpaBC on dihydrokaempferol and kaempferol was demonstrated for the first time. This study demonstrates a feasible method for efficiently synthesizing in vivo B-ring dihydroxylated flavonoids, such as catechins, flavanols, dihydroflavonols and flavonols, in a bacterial expression system.
- Chen, Yang,Gao, Liping,Gui, Lin,Guo, Lina,Lei, Ting,Li, Yan,Ma, Xiubing,Ruan, Haixiang,Wang, Longji,Wang, Yunsheng,Xia, Tao
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- 11-β-hydroxysterols as possible endogenous stimulators of mitochondrial biogenesis as inferred from epicatechin molecular mimicry
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Currently, there is great interest in identifying endogenous (i.e. physiological) stimulators of mitochondrial biogenesis (MB), in particular, those that may mediate the effects of exercise. The molecular size of the cacao flavanols (epicatechin and catechin) highly resembles that of sterols and epicatechin has been reported to activate cells surface receptors leading to the stimulation of MB in endothelial and skeletal muscle cells translating into enhanced exercise capacity. We therefore hypothesize, that epicatechin may be acting as a structural mimic of an as yet unknown sterol capable of stimulating MB. We developed a new synthetic process for obtaining enantiomerically pure preparations of (-)-epicatechin and (+)-epicatechin. Applying spatial analytics and molecular modeling, we found that the two isoforms of epicatechin, (-) and (+), have a structural resemblance to 11-β-hydroxypregnenolone, a sterol with no previously described biological activity. As reported in this proof-of-concept study performed in primary cultures of endothelial and muscle cells, 11-β-hydroxypregnenolone is one of the most potent inducers of MB as significant activity can be detected at femtomolar levels. The relative potency of (-)/(+)-epicatechin isoforms and on inducing MB correlates with their degree of spatial homology towards the 11-β-hydroxypregnenolone. On the basis of these results, the detailed in vivo characterization of the potential for these sterols to act as endogenous modulators of MB is warranted.
- Dugar, Sundeep,Villarreal, Francisco,Hollinger, Frank H.,Mahajan, Dinesh,Ramirez-Sanchez, Israel,Moreno-Ulloa, Aldo,Ceballos, Guillermo,Schreiner, George
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- Preparation and evaluation of a triazole-bridged bis(β-cyclodextrin)–bonded chiral stationary phase for HPLC
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A triazole-bridged bis(β-cyclodextrin) was synthesized via a high-yield Click Chemistry reaction between 6-azido-β-cyclodextrin and 6-propynylamino-β-cyclodextrin, and then it was bonded onto ordered silica gel SBA-15 to obtain a novel triazole-bridged bis (β-cyclodextrin)–bonded chiral stationary phase (TBCDP). The structures of the bridged cyclodextrin and TBCDP were characterized by the infrared spectroscopy, mass spectrometry, elemental analysis, and thermogravimetric analysis. The chiral performance of TBCDP was evaluated by using chiral pesticides and drugs as probes including triazoles, flavanones, dansyl amino acids and β-blockers. Some effects of the composition in mobile phase and pH value on the enantioseparations were investigated in different modes. The nine triazoles, eight flavanones, and eight dansyl amino acids were successfully resolved on TBCDP under the reversed phase with the resolutions of hexaconazole, 2′-hydroxyflavanone, and dansyl-DL-tyrosine, which were 2.49, 5.40, and 3.25 within 30 minutes, respectively. The ten β-blockers were also separated under the polar organic mode with the resolution of arotinolol reached 1.71. Some related separation mechanisms were discussed preliminary. Compared with the native cyclodextrin stationary phase (CDSP), TBCDP has higher enantioselectivity to separate more analytes, which benefited from the synergistic inclusion ability of the two adjacent cavities and bridging linker of TBCDP, thereby enabling it a promising prospect in chiral drugs and food analysis.
- Shuang, Yazhou,Liao, Yuqin,Wang, Hui,Wang, Yuanxing,Li, Laisheng
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p. 168 - 184
(2019/11/25)
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- Metabolic characterization of the anthocyanidin reductase pathway involved in the biosynthesis of flavan-3-ols in elite Shuchazao tea (Camellia sinensis) cultivar in the field
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Anthocyanidin reductase (ANR) is a key enzyme in the ANR biosynthetic pathway of flavan-3-ols and proanthocyanidins (PAs) in plants. Herein, we report characterization of the ANR pathway of flavan-3-ols in Shuchazao tea (Camellia sinesis), which is an elite and widely grown cultivar in China and is rich in flavan-3-ols providing with high nutritional value to human health. In our study, metabolic profiling was preformed to identify two conjugates and four aglycones of flavan-3-ols: (-)-epigallocatechin-gallate [(-)-EGCG], (-)-epicatechin-gallate [(-)-ECG], (-)-epigallocatechin [(-)-EGC], (-)-epicatechin [(-)-EC], (+)-catechin [(+)-Ca], and (+)-gallocatechin [(+)-GC], of which (-)-EGCG, (-)-ECG, (-)-EGC, and (-)-EC accounted for 70-85% of total flavan-3-ols in different tissues. Crude ANR enzyme was extracted from young leaves. Enzymatic assays showed that crude ANR extracts catalyzed cyanidin and delphinidin to (-)-EC and (-)-Ca and (-)-EGC and (-)-GC, respectively, in which (-)-EC and (-)-EGC were major products. Moreover, two ANR cDNAs were cloned from leaves, namely CssANRa and CssANRb. His-Tag fused recombinant CssANRa and CssANRb converted cyanidin and delphinidin to (-)-EC and (-)-Ca and (-)-EGC and (-)-GC, respectively. In addition, (+)-EC was observed from the catalysis of recombinant CssANRa and CssANRb. Further overexpression of the two genes in tobacco led to the formation of PAs in flowers and the reduction of anthocyanins. Taken together, these data indicate that the majority of leaf flavan-3-ols in Shuchazao's leaves were produced from the ANR pathway.
- Zhao, Lei,Jiang, Xiao-Lan,Qian, Yu-Mei,Wang, Pei-Qiang,Xie, De-Yu,Gao, Li-Ping,Xia, Tao
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- A catechin preparation method of compound (by machine translation)
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The invention relates to a method for preparing a catechin compound. The method comprises the following steps: by taking 2,4,6-trihydroxy acetophenone and p-hydroxy benzaldehyde as raw materials, carrying out condensation reaction, restored deoxidation, cyclization reaction of acid catalysis, so as to obtain the catechin compound. The invention also provides a technology for producing the catechin compound. In the synthesis process of an immediate 9, reduction is carried out by using sodium borohydride which is catalyzed by a lewis acid, so that side reaction caused by double bond transfer is greatly reduced while a highly toxic reagent osmium tetroxide is replaced with hydrogen peroxide oxidation.
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Paragraph 0047; 0048
(2017/02/23)
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- Synthesis method of procyanidine compound Catechin
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The invention relates to a synthesis method of a procyanidine compound Catechin and belongs to the field of chemical synthesis. The method is as below: conducting benzyl protection reaction on trans-caffeic acid to produce O-Bz caffeic acid; subjecting O-Bz caffeic acid to an ester reduction reaction for synthesis of allyl alcohol; subjecting allyl alcohol to a Sharpless dihydroxylation reaction to synthesize a trihydroxy compound; subjecting the trihydroxy compound to a selective sulfonylation reaction to synthesize sulfonate; subjecting the sulfonate to an O-Ts leaving reaction to synthesize ternary epoxy; conducting a hydroxy mitsunobu reaction to synthesiz O-Ph epoxy; subjecting O-Ph epoxy to a ring-forming reaction to synthesize O-Bz Catechi; subjecting O-Bz Catechin to a palladium carbon deprotection reaction to synthesize the procyanidine compound Catechin (shown in figure). The invention has the characteristics of few reaction steps, high total yield, good product selectivity, and suitability for industrial production.
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Paragraph 0015; 0023
(2017/02/09)
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- A novel adduct of ECG fused to piceid and four new dimeric stilbene glycosides from: Polygonum cuspidatum
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Polyflavanostilbene B (1), an unusual adduct of epicatechin-3-O-gallate fused to piceid through a carbon-carbon bond, four new dimeric stilbene glycosides (2-5), three new stilbene glucosides (6-8), one new flavan glucoside (9), and six known compounds were isolated from the rhizome of Polygonum cuspidatum. The structures of these compounds were elucidated using spectroscopic data, including electronic circular dichroism (ECD) and Rh2(OCOCF3)4-induced CD spectra. All of the compounds were screened for their inhibitory activity against α-glucosidase using acarbose as a positive control (IC50 = 385 μM), and strong inhibitory activity against α-glucosidase was observed for compound 8 (IC50 = 3.04 μM).
- Yang, Ya-Nan,Li, Fu-Shuang,Liu, Fu,Feng, Zi-Ming,Jiang, Jian-Shuang,Zhang, Pei-Cheng
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p. 60741 - 60748
(2016/07/07)
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- NOVEL APPROACH FOR SYNTHESIS OF CATECHINS
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A process for synthesis of enatiomerically pure or enatiomerically enriched or racemic mixture of (+and/or?) epicatechin echm and its intermediates, comprising the steps of: (i) obtaining penta-protected quercetin; (ii) reducing the penta-protected quercetin obtained from step (i); (iii) optionally deprotecting the compound of step (ii); (iv) reducing the compound obtained from step (ii) or step (iii) in the presence of a chiral/achiral reducing agent to obtain a chiral intermediate; (v) deprotecting and/or hydrogenation of the chiral intermediate obtained from step (iv) to obtain (?)-epicatechin; (vi) optionally simultaneously deprotecting and by drogenation of the compound obtained from step (ii) to obtain racemic epicatechin.
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- NOVEL PROCESS FOR SYNTHESIS OF POLYPHENOLS
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The present invention provides synthetic processes for preparing racemic and/or optically pure epicatechin, epigallocatechin and related polyphenols as such or as their variously functionalized derivatives. A principle objective of the disclosure is to provide a new and useful method of synthesis to obtain polyphenols in isomerically pure and/or racemic forms.
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Paragraph 0150; 0151; 0152; 0153
(2014/02/16)
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- Structures and antioxidant and intestinal disaccharidase inhibitory activities of A-type proanthocyanidins from peanut skin
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Nine compounds including a new A-type proanthocyanidin trimer, epicatechin-(2β→O→7,4β→8)-[catechin-(6→4β)] -epicatechin (8), and a known trimer, epicatechin-(4β→8)-epicatechin- (2β→O→7,4β→8)-catechin (9), being reported for peanut skin for the first time, were isolated and purified. Their structures were determined by spectroscopic methods and by degradation reactions with l-cysteine in acidic conditions. The DPPH radical scavenging activity and the inhibitory activity on maltase and sucrase of the isolated compounds were investigated. All compounds showed strong DPPH scavenging activities (EC50 50 value of 0.088 mg/mL, while compound 9 exhibited the strongest inhibition on sucrase with an IC50 value of 0.091 mg/mL.
- Zhang, Huiwen,Yerigui,Yang, Yumei,Ma, Chaomei
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p. 8814 - 8820
(2013/10/01)
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- Photochemistry synthesis. Part 2: Enantiomerically pure polyhydroxy-1,1,3-triarylpropan-2-ols
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A new method to open the heterocyclic ring of flavan-3-ols via photolytic cleavage of the ether bond, with stereoselective trapping of the intermediates with phloroglucinol to obtain phloroglucinol grafted derivatives of flavan-3-ols, was developed. Photolysis of catechin and epicatechin, respectively, in the presence of phloroglucinol yielded the enantiomeric (1S,2S)- and (1R,2R)-1,3-di(2,4,6-trihydroxyphenyl)-1-(3,4-dihydroxyphenyl) propan-2-ols, respectively. The absolute configuration at C-1 and C-2 was determined by electronic circular dichroism (experimental and calculated) and these results confirmed that the trapping mechanism is controlled by the C-3 configuration of the flavan-3-ol.
- Wilhelm-Mouton, Anke,Bonnet, Susan L.,Ding, Yuanqing,Li, Xing-Cong,Ferreira, Daneel,Van Der Westhuizen, Jan H.
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experimental part
p. 18 - 24
(2012/03/26)
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- A NOVEL PROCESS FOR SYNTHESIS OF POLYPHENOLS
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The present invention provides synthetic processes for preparing racemic and/or optically pure epicatechin, epigallocatechin and related polyphenols as such or as their variously functionalized derivatives.
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Page/Page column 31
(2012/08/08)
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- Epimerization of tea catechins under weakly acidic and alkaline conditions
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Tea catechins in a buffer at pH 7 with N2 replacing O 2 epimerized rapidly at 80 °C with less than 10% of oxidative side reactions and gave catechin epimers in a 50-63% yield. The epimerization of catechins with three hydroxyl groups was faster than with two groups, and of galloyl-free catechins was faster than catechins with a galloyl ester.
- Ishino, Nobuyoshi,Yanase, Emiko,Nakatsuka, Shin-Ichi
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scheme or table
p. 875 - 877
(2011/07/30)
-
- New oligomeric proanthocyanidins from Alhagi pseudalhagi
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Two new oligomeric proanthocyanidin glucosides were isolated from the aerial part and roots of Alhagi pseudalhagi. Their structures and relative configurations were elucidated as 7-O-β-D-Glc p→6 galloyl-(+)catechin-(4α-8)-(+)-catechin-(4α-8)-(-
- Alimova,Nishanbaev,Vdovin,Abdullaev,Aripova
-
experimental part
p. 352 - 356
(2010/10/03)
-
- Composition for Topical Use
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The use, as a dermatological or cosmetic medicament, of compounds capable of transiently interacting with the AhR receptor (aryl hydrocarbon receptor) as agents for modulating skin functions such as sebaceous function, skin healing, skin atrophy termed “dermatoporosis”, estrogen deprivation and defense against infection, without inducing other toxic effects of the TCDD type. The compounds that interact with the AhR receptor are chosen in that they have a metabolism favorable to the dissociation of these effects, in particular by virtue of in situ production from a precursor and/or metabolization modulated in situ.
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- High molecular weight persimmon (Diospyros kaki L.) proanthocyanidin: A highly galloylated, a-linked tannin with an unusual flavonol terminal unit, myricetin
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MALDI-TOF MS suggested that the high molecular weight proanthocyanidin (condensed tannin) from persimmon (Diospyros kaki L.) pulp comprised a heteropolyflavanol series with flavan-3-O-galloylated extenders, flavan-3-ol and flavonol terminal units, and A-type interflavan linkages. Thiolysis-HPLC-ESI-MS with DAD, electrochemical, and ESI-MS detection confirmed a previously unreported terminal unit, the flavonol myricetin, in addition to the typical flavan-3-ols catechin and epigallocatechin gallate. The extender units were epicatechin, epigallocatechin, (epi)gallocatechin-3-O-gallate, and (epi)catechin-3-O-gallate. The crude tannin had a high prodelphinidin content (65%) and a high degree of 3-O-galloylation (72%). The material was fractionated on Toyopearl TSK-HW-50-F to yield fractions distinguished by degree of polymerization (DP). Thiolysis suggested that the persimmon tannin was composed of polymers ranging from 7 to 20 kDa (DP 19-47), but sizes estimated by GPC were 50-70% smaller. The crude material was chemically degraded with acid to yield products that were amenable to NMR and ESI-MS analysis, which were used to establish for the first time that persimmon tannin has a mixture of B-type and A-type linkages. 2010 American Chemical Society.
- Li, Chunmei,Leverence, Rachael,Trombley, John D.,Xu, Shufen,Yang, Jie,Tian, Yan,Reed, Jess D.,Hagerman, Ann E.
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experimental part
p. 9033 - 9042
(2011/05/05)
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- Proanthocyanidins and a phloroglucinol derivative from Rumex acetosa L.
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From the ethyl acetate soluble fraction of an acetone-water extract of the aerial parts of Rumex acetosa L. (Polygonaceae), a variety of monomeric flavan-3-ols (catechin, epicatechin, epicatechin-3-O-gallate), A- and B-type procyanidins and propelargonidins (15 dimers, 7 trimers, 2 tetramers) were isolated with 5 so far unknown natural products. Dimers: procyanidin B1, B2, B3, B4, B5, B7, A2, epiafzelechin-(4β→8)-epicatechin, epiafzelechin-(4β→8)-epicatechin-3-O-gallate (new natural product), epiafzelechin-(4β→6)-epicatechin-3-O-gallate (new natural product), epiafzelechin-3-O-gallate-(4β→8)-epicatechin-3-O-gallate, B2-3′-O-gallate, B2-3,3′-di-O-gallate, B5-3′-O-gallate, and B5-3,3′-di-O-gallate. Trimers: procyanidin C1, epiafzelechin-(4β→8)-epicatechin-(4β→8)-epicatechin (new natural product), epicatechin-(4β→8)-epicatechin-(4β→8)-catechin, cinnamtannin B1, cinnamtannin B1-3-O-gallate (new natural product), tentatively epicatechin-(2β→7, 4β→8)-epiafzelechin-(4α→8)-epicatechin (new natural product), and epicatechin-3-O-gallate-(4β→8)-epicatechin-3-O-gallate-(4β→8)-epicatechin-3-O-gallate. Tetramers: procyanidin D1 and parameritannin A1. All compounds were elucidated by ESI-MS, CD spectra, 1D- and 2D-NMR experiments as free phenols or peracetylated derivatives and, in part, after partial acid-catalysed degradation with phloroglucinol. A more abundant proanthocyanidin polymer was also isolated, purified and its chemical composition studied by 13C NMR. In addition a so far unknown phloroglucinolglycoside (1-O-β-d-(2,4-dihydroxy-6-methoxyphenyl)-6-O-(4-hydroxy-3,5-dimethoxybenzoyl)-glucopyranoside) was isolated.
- Bicker,Petereit,Hensel
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experimental part
p. 483 - 495
(2010/06/15)
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- Identification of autoxidation oligomers of flavan-3-ols in model solutions by HPLC-MS/MS
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Autoxidation of flavan-3-ols was carried out in aqueous/methanol model solutions under mildly acidic conditions (pH 6.0), and these autoxidation products were analyzed by using high performance liquid chromatography (HPLC) coupled with tandem mass spectro
- He, Fei,Pan, Qiu-Hong,Shi, Ying,Zhang, Xue-Ting,Duan, Chang-Qing
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experimental part
p. 633 - 640
(2010/04/30)
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- ACTIVE COMPONENT FRACTION OF HIGH ANTIVIRAL ACTIVITY
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A method of producing active component fractions from dried and ground root material of a species of the rheum family by extraction with ethanol, removal of lipophilic minor components and methanol, followed by shaking in ethyl acetate and separating the combined ethyl acetate phase into a limited number of fractions by columnar chromatography in the presence of an eluant.
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-
- Structure of polymeric polyphenols of cinnamon bark deduced from condensation products of cinnamaldehyde with catechin and procyanidins
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Structures of two condensation products obtained by the reaction of cinnamaldehyde with (+)-catechin were determined by spectroscopic methods. One had two phenylpropanoid units at the C-6 and C-8 positions of the catechin skeleton. The other product had a dimeric structure with two catechin and two phenylpropanoid units. Matrix-assisted laser desorption time-of-flight mass spectrometric analysis of the reaction products of cinnamaldehyde with procyanidin B1 suggested that procyanidins were oligomerized in a manner similar to the reaction with catechin. Furthermore, 13C NMR spectral comparison of the condensation products with the polymeric procyanidins obtained from commercial cinnamon bark strongly suggested that the procyanidins in the cinnamon bark also were polymerized by reaction with cinnamaldehyde.
- Tanaka, Takashi,Matsuo, Yosuke,Yamada, Yuko,Kouno, Isao
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experimental part
p. 5864 - 5870
(2010/03/04)
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- METHOD OF PRODUCING PROANTHOCYANIDIN OLIGOMER
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The present invention relates to a composition containing as its main component proanthocyanidin oligomer to which a substance having a phloroglucinol ring structure or resorcinol ring structure has been bonded and reduced in the molecular weight, which is obtained by heating plant materials containing proanthocyanidin polymer or extract thereof with a substance having a phloroglucinol ring structure or resorcinol ring structure in an acidic aqueous solution, production method thereof, and uses of the composition in health products and pharmaceutical products. According to the invention, proanthocyanidin oligomer having physiological activity, to which a substance having a phloroglucinol ring structure or resorcinol ring structure has been bonded and reduced in the molecular weight to such a level that the oligomer can be absorbed into living body, which has been conventionally difficult to obtain at high yield from plant raw materials, can be produced efficiently and easily.
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Page/Page column 10
(2008/06/13)
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- PREPARATION OF (+)-CATECHIN, (-)-EPICATECHIN, (-)-CATECHIN, (+)-EPICATECHIN, AND THEIR 5,7,3',4'-TETRA-O-BENZYL ANALOGUES
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Processes for preparing racemic mixtures of 5,7,3',4'-tetra-O-benzyl-(±)-catechin and (±)-epicatechin involves (i) condensing 2-hydroxy-4,6-bis(benzyloxy)-acetophenone and 3,4-bis(benzyloxy)benzaldehyde, cyclizing the resulting compound, oxidizing the resulting compound; (ii) dihydroxylating (E)-3-(3',4'-bis(benzyloxy)phenyl)prop-2-ene-1 -ol and reducing the 1 ,2-diol; or (iii) coupling 3,5-bis(benzyloxy)phenol with (£)-3,5-bis(benzyloxy)-2-(3',4'-bis(benzyloxy)phenyl)allyl)phenol and cyclizing the resulting chalcone. A process for preparing the benzylated epimers of catechin and epicatechin involves seven steps. 3,4-Bis(benzyloxy)benzaldehyde is coupled with 2-hydroxy-4,6-benzyloxy-acetophenone to form a chalcone. The chalcone is selectively reduced to an alkene. The phenolic group of the alkene is protected. The protected alkene is asymetrically dihydroxylated. The resulting compound is deprotected, cyclized, and finally hydrolyzed. Epimers resulting from these processes are chemically resolved or separated by chiral high pressure liquid chromatography. Also disclosed is a method for preparing enantiomerically pure 5,7,3',4'-tetra-O-benzyl-(+)-catechin from a racemic mixture using dibenzoyl-L-tartaric acid monomethyl ester. Further, disclosed is an improved process for preparing dibenzoyl-L-tartaric acid monomethyl ester.
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Page/Page column 13; 36-37
(2010/11/25)
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- Polyphenols from peanut skins and their free radical-scavenging effects
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Separation of the water-soluble fraction of peanut skins led to the isolation of five proanthocyanidins. Based on the spectroscopic investigation and partial acid catalyzed degradation, their structures were determined to be epicatechin-(2β→O→7, 4β→6)-[epicatechin- (4β→8)]-catechin (1), epicatechin-(2β→O→7, 4β→8) epicatechin-(4β→8)-catechin-(4β→8)- epicatechin (2), and procyanidins B2 (3), B3 (4) and B4 (5). The absolute configuration of the new compounds was determined from their circular dichroism curves and the 1H NMR spectra of analysis of flavan-3-ols formed by thiolytic degradation of 1 and 2 in the presence of a chiral dirhodium complex (dirhodium tetra-(R)-(trifluoromethyl) phenyl acetate).
- Lou, Hongxiang,Yuan, Huiqing,Ma, Bin,Ren, Dongmei,Ji, Mei,Oka, Syuichi
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p. 2391 - 2399
(2007/10/03)
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- Enantioselective synthesis of (2R,3S)-(+)-catechin
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A new enantioselective synthetic method for catechin from trans-methyl cinnamate derivative was developed via asymmetric dihydroxylation (ADH), the addition of an aryllithium species, followed by the Barton-McCombie reaction and an intramolecular Mitsunobu reaction as key steps.
- Jew, Sang-sup,Lim, Doo-yeon,Bae, So-young,Kim, Hyun-ah,Kim, Jeong-hoon,Lee, Jihye,Park, Hyeung-geun
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p. 715 - 720
(2007/10/03)
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- New oligomeric proanthocyanidine from Ziziphus jujuba
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Chemical and spectral data establish the structure of an oligomeric proanthocyanidine PZ-5 isolated from Ziziphus jujuba.
- Malik, Aibek,Kuliev,Akhmedov,Vdovin,Abdullaev
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- Process for the production of a compound (+) catechin penta acetate useful as a precursor for the production of (+) catechin
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This invention relates to a process for the production of a compound (+) catechin penta acetate of formula I fromTaxus wallichianatissue cultures which comprises : (a) inoculation of explants on different media compositions supplemented with combinations of auxins (1-5 mg/l) and cytokinins (0.1-1.0 mg/l); (b) incubation of the cultures under continuous light or dark conditions for 4-6 weeks for callus cultures followed by subculturing at 4-6 weeks intervals; (c) harvesting of the calli at different growth phases ranging from 12-36 months; (d) extraction of fresh pulverized calli with polar solvents at room temperature; (e) evaporating the solvent to give a residue; and partitioning of the residue between water and chlorinated solvents and evaporating the solvent to a semisolid mass; (f) subjecting the resultant mass to column chromatography over suitable adsorbent and (g) eluting with organic solvent/mixtures of organic solvents to get (+) catechin penta acetate.
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- Methods in synthesis of flavonoids. Part 2: High yield access to both enantiomers of catechin
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Resolution of racemic synthetic tetra-O-benzylcatechin 2 is described, through the formation of esters S and 6 derived from dibenzoyl-L-tartaric acid. The diastereoisomer of the natural series 6 was separated by crystallization, the other one being an oil. This process allowed us to prepare enantiomerically pure (+)-catechin 8 in high yield. The pure isomer in the ent-series 9 could be obtained, following the same scheme of reactions. (C) 2000 Elsevier Science Ltd.
- Nay,Monti,Nuhrich,Deffieux,Merillon,Vercauteren
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p. 9049 - 9051
(2007/10/03)
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- Determination of condensed Tannin Monomers in environmental samples by capillary gas chromatography of acid depolymerization extracts
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A method for molecular-level quantification of condensed tannin is described that uses acid depolymerization and carbocation capture by phloroglucinol. Resulting monomers and phloroglucinol adducts are trimethylsilyl derivatized, separated by capillary gas chromatography, detected by flame ionization, and quantified relative to standards. Optimal depolymerization conditions were determined for acid strength, phloroglucinol concentration, time, and temperature. The method gives reproducible results in leaf litter that are linear over 2 orders of magnitude with detection limits down to ~100 ng condensed tannin. In addition to tannin, triterpenoids were also identified and can be quantified with this method. Analyses of soils and sediments indicate that mineral interactions with condensed tannin are important both analytically and environmentally.
- Hemes, Peter J.,Hedges, John I.
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p. 5115 - 5124
(2007/10/03)
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- Competition between (+)-catechin and (-)-epicatechin in acetaldehyde- induced polymerization of flavanols
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The reactions of (+)-catechin and (-)-epicatechin in the presence of acetaldehyde were studied in model solution systems. When incubated separately with acetaldehyde and at pH values varying from 2.2 to 4.0, reactions were faster with (-)-epicatechin than with (+)-catechin. In mixtures containing both (+)-catechin and (-)-epicatechin with acetaldehyde, new compounds besides the homogeneous bridged derivatives were detected. These compounds were concluded to be heterooligomers consisting of (+)- catechin and (-)-epicatechin linked with an ethyl bridge. In this case, the reaction of (-)-epicatechin was faster than that of (+)-catechin. This was also observed in solutions containing the two flavanols and the (+)-catechin- ethanol intermediate. Under these conditions, the homogeneous (+)-catechin bridged dimers and heterogeneous dimers were obtained by action of the intermediate on (+)-catechin and (-)-epicatechin, respectively. In addition, the homogeneous (-)-epicatechin ethyl-bridged dimers were also detected, showing that ethyl linkages underwent depolymerization and recombination reactions.
- Es-Safi, Nour-Eddine,Fulcrand, Helene,Cheynier, Veronique,Moutounet, Michel
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p. 2088 - 2095
(2007/10/03)
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- Oligomeric proanthocyanidin glycosides of Clementsia semenovii
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Five new proanthocyanidins have been isolated from the roots of Clementsia semenovii A. Bor. The structures of two of these compounds have been established by various chemical and physical methods: 7-0-[6-0-galloyl-β-D-Glcp →6 O-βD-Glcp →6O-β-D-Glcp → 6O-β-D-Glcp]-(+)-gallocatechin-(4α-8)-(+)-gallocatechin- (4α-8)-(-)-epigallocatechin-(4β-8)-(-)-epigallocatechin-(4β-8)- (-) -epigallocatechin-(4β-8)-(+)-catechin - CS-1 and 3-O-galloyl-7-O-(β-D-Glcp → 6O-β-D-Glcp)-(-)-epigallocatechin-(4β-8)-[3-O-galloyl-(-)- epigallocatechin]-(4β-8)-[3-O-galloyl-(-)-epigallocatechin]-(4β-8)-[3- O-galloyl-5-O-(6-O-galloyl-O-β-D-Glcp)]-(-)-epicatechin - CS-2.
- Matamarova,Kuliev,Vdovin,Abdullaev,Murzubraimov
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p. 676 - 682
(2007/10/03)
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- Tannins from Betel Nuts
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From the acetone extract of fresh betel nuts, two procyanidin pentamers, two procyanidin tetramers and three procyanidin trimers, along with (+)-catechin, (-)-epicatechin, procyanidin A-1, procyanidin B-1, procyanidin B-2, and procyanidin B-7 were isolated. Based on 1H NMR and 13C NMR spectral data as well as the results of thiolysis degradation, the chemical structures of two series of oligomeric arecatannins A and B have been established. The arecatannins from betel nuts were found to be condensed-type tannins which possess (-)-epicatechin unit and (+)-catechin units. All arecatannins had C4-C8 linked (-)-epicatechin in the upper units whereas the (+)-catechin in the terminal unit had C4-C8 or C4-C6 linkage.
- Ma, Ying-Tsun,Hsu, Feng-Lin,Lan, Shu-Jan J.,Chen, Chieh-Fu
-
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- Proanthocyanidins from Lotus Corniculatus
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The chemical structure of the purified proanthocyanidin polymers of Lotus corniculatus was analysed by 13CNMR and by mild acid catalysed degradation in the presence of excess of phloroglucinol. The NMR data showed that the polymer was partially glycosidated with a number average Mr in the range 1800-2100 (six to seven flavanoid units). The products from phloroglucinol scission reaction indicated the extender flavan units to consist mostly of epicatechin (67%) and epigallocatechin (30%), with minor amounts of catechin and epiafzelechin units, which were linked together predominantly by C-4/C-8 interflavanoid bonds. The polymer chains were terminated mostly by catechin (83%) and, to a lesser extent, by epicatechin (16%). Copyright
- Foo,Newman,Waghorn,Mcnabb,Ulyatt
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p. 617 - 624
(2007/10/03)
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- Oligomeric flavanoids. Part 19. Reductive cleavage of the interflavanyl bond in proanthocyanidins
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The interflavanyl bond in profisetinidins 1, 4 and 6, and methyl ethers 3, 5, 28 and 29 procyanidins 24 and 26, and their methyl ethers 25 and 27 is readily subject to cleavage with sodium cyanoboranuide in trifluoroacetic acid at 0 deg C.This method will contribute significantly to the structure elucidation of the 5-deoxy (A-ring) proanthocyanidins from important commercial sources.Boltzmann-averaged heterocyclic ring coupling constants as determined by a conformational global search routine (GMMX) and NOE difference spectroscopy were used to assign unequivocally the diastereotopic methylene protons in the 1H NMR spectra of flavan-3-ols, a prerequisite for corroboration of the cleavage mechanism.
- Steynberg, Petrus J.,Steynberg, Jan P.,Bezuidenhoudt, Barend C. B.,Ferreira, Daneel
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p. 3005 - 3012
(2007/10/03)
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- Cleavage of the Interflavanyl Bond in 5-Deoxy (A Ring) Proanthocyanidins
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The fisetinidol-(4,8) and (4,6)-catechin profisetinidin biflavonoids 1, 4 and 5 respectively, are subject to facile cleavage of the interflavanyl linkage with sodium cyanoborohydride in trifluoroacetic acid at 0 deg C.
- Steynberg, Petrus J.,Steynberg, Jan P.,Bezuidenhoudt, Barend C. B.,Ferreira, Daneel
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- POLYPHENOLIC COMPOUNDS FROM CROTON LECHLERI
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The blood-red sap of Croton lechleri was found to contain proanthocyanidins as major constituents which accounted for up to 90percent of the dried weight.In addition to (+)-catechin, (-)-epicatechin, (+)-gallocatechin, (-)-epigallocatechin and dimeric procyanidins B-1 and B-4, five novel dimers and trimers were isolated and characterized as catechin-(4α->8-epigallocatechin, gallocatechin-(4α->8)-epicatechin, gallocatechin-(4α->6)-epigallocatechin, catechin-(4α->8)-gallocatechin-(4α->8)-gallocatechin and gallocatechin-(4α->8)-gallocatechin-(4α->8)-epigallocatechin.Higher oligomers were also obtained.A new procedure combining chemical degradation with 1H NMR spectroscopy has been developed for determination of the composition and molecular size of oligomeric/polymeric proanthocyanidins.The oligomers of the sap were shown to have the mean degree of polymerization of 4,5-6 and 6-7, respectively, and Mr up to 2130.The heterogeneity of the oligomers was clearly indicated by the presence of a variety of flavan-3-ols as extension and terminal units.An exceptionally high content of gallocatechin and epigallocatechin in the oligomers was observed.Key Word Index: Croton lechleri; Euphorbiaceae; Sangre de Grado; Dragon's blood; polyphenol; proanthocyanidins; flavan-3-ols; procyanidins; prodelphinidins.
- Cai, Y.,Evans, F. J.,Roberts, M. F.,Phillipson, J. D.,Zenk, M. H.,Gleba, Y. Y.
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p. 2033 - 2040
(2007/10/02)
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- THIOLYSIS OF BIRCH BARK PROCYANIDINES: STRUCTURAL DEPENDENCE IN FORMATION OF 2,3-CIS-3,4-CIS-FLAVAN-4-BENZYLTHIOETHERS FROM PROCYANIDINS
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Thiolytic studies of the birch bark procyanidins, epicatechin-(4β->8)-catechin (B1), epicatechin-(4β->6)-catechin (B7) and epicatechin-(4β->8)-epicatechin-(4β->8)-catechin, provided, in addition to known β-thioethers, evidence for the presence of the first 2,3-cis-3,4-cis-flavan-4-benzylthioethers.Their formation is dependent on the 2,3-stereochemistry of the 'lower' terminal flavan unit and apparently on the relative lability of the interflavanoid linkage.By contrast, epicatechin-(4β->8)-epicatechin (B2), epicatechin-(4β->6)-epicatechin (B5) and epicatechin-(4β->8)-epicatechin-(4β->8)-epicatechin (C1), afforded only 2,3-cis-3,4-trans-flavan-4-benzylthioethers.
- Kolodziej, Herbert
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p. 1671 - 1674
(2007/10/02)
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- Oligomeric flavanoids. Part 7. Novel base-catalysed pyran rearrangements of procyanidins
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Procyanidin B-3 (1) is subject to readily occurring c-ring isomerizations in NaHCO3-Na2CO3 buffer solution to form a novel 8,9-cis-9,10-trans-3,4,9,10-tetrahydro-2H,8H-pyrano[2,3-h;]chromene (3) and a series of 2,3-cis-3,4-trans-4-aryl-2-flavanylbenzopyrans (6), (9), and (12) in which the C-2 pyrocatechol and C-4 ( + )-catechin moieties are interchanged relative to their positions in the biflavanoid (1). These compounds presumably originate via 1,3-aryl migrations in intermediate quinone-methides with concomitant inversion of the absolute configuration at C-3. The lability of the interflavanyl bond at alkaline pH is reflected by the presence of considerable quantities of (+)-catechin as well as high-molecular-mass analogues of precursor (1).
- Steynberg, Jan P.,Bezuidenhoudt, Barend C. B.,Burger, Johann F. W.,Young, Desmond A.,Ferreira, Daneel
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p. 203 - 208
(2007/10/02)
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- PROCYANIDIN DIMERS AND TRIMERS FROM DOUGLAS FIR INNER BARK
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The aqueous fraction of the inner bark extract of Douglas fir (Pseudotsuga menziesii) yielded two novel natural procyanidin trimers, epicatechin-(4β->8)-catechin-(4α->8)-catechin and epicatechin-(4β->6)-epicatechin-(4β->8)-epicatechin, and two known trimers, epicatechin-(4β->8)-epicatechin-(4β->8)-epicatechin and epicatechin-(4β->8)-epicatechin-(4β->8)-catechin.Catechin, epicatechin and procyanidin dimers B1, B2, B3 and B4 were also isolated.The structures of all of these procyanidins were elucinated from their 13C NMR data and by partial acid catalysed degradation with benzylthiol.Key Word Index - Pseudotsuga mentiesii; Pinaceae; flavon-3-ols; procyanidin; dimers; trimers; benzylthiol; degradation.
- Foo, Lai Yeap,Karchesy, Joseph J.
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p. 1743 - 1748
(2007/10/02)
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