Synthesis of condensed tannins. Part 4. A direct biomimetic approach to [4,6]- and[4,8]-biflavanoids

Botha, Jacobus J.; Ferreira, Daneel; Roux, David G.

doi:10.1039/p19810001235

Cited by 120 publications

(48 citation statements)

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“…Such asymmetric labeling supports the mechanism of a carbocationmonomer condensation for polymer formation rather than a condensation of similar units (5). Such asymmetry would also be expected, because the pool of carbocation would be very small relative to that of the flavan-3-ol monomers (2 (Fig. 4).…”

Section: Asymmetricmentioning

confidence: 79%

“…1). Several groups have demonstrated that dimers similar to natural products can be formed nonenzymically upon the addition of a diol formed as a reduction product of dihydroquercetin, or the appropriate carbocation (2)(3)(4). Studies with "C-labeled phenylalanine and cinnamic acid fed to intact shoots have provided direct evidence for this mechanism by demonstrating the greater incorporation of label into the 'upper' (derived from the carbocation) than into the 'lower' (derived from the flavan-3-ol) unit (5).…”

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confidence: 99%

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Incorporation of [¹⁴C]Phenylalanine into Flavan-3-ols and Procyanidins in Cell Suspension Cultures of Douglas Fir

Stafford

Shimamoto²,

Lester³

1982

Plant Physiol.

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L_I14CIPhenylalanine, fed to cell suspension cultures of Douglas fir, (Pseudotsuga menziesii Franco) was incorporated simulteously, but at different rates, into (+)-catechin, (-)-epicatechin, and procyaniins of increasing molecular weight. Asymmetric labeling of dimers and polymers was demonstrated, with more label appearing in the upper than in the lower or terminal unit. In addition, the total pool of free monomers was 10 to 30 times more highly labeled than was this lower, terminal unit of dimers and higher oligomers. Since the dimer, epicatechin-catechin, contabied more label than catechin-catechin, it is concluded that the carbocation with the 2,3-cis stereochemistry of (-)-epicatechin was formed more rapidly than was that of the 2,3-tras type of (+)-catechin.Procyanidins are believed to be formed by the sequential condensation of one of two stereospecific 4-carbocations with a terminal unit consisting of one of the flavan-3-ols, (+)-catechin or (-)-epicatechin (Fig. 1). Several groups have demonstrated that dimers similar to natural products can be formed nonenzymically upon the addition of a diol formed as a reduction product of dihydroquercetin, or the appropriate carbocation (2-4). Studies with "C-labeled phenylalanine and cinnamic acid fed to intact shoots have provided direct evidence for this mechanism by demonstrating the greater incorporation of label into the 'upper' (derived from the carbocation) than into the 'lower' (derived from the flavan-3-ol) unit (5).["4C]Phenylalanine has been fed to one of the Douglas fir cell suspension cultures studied previously (7,8) to study further the asymmetric labeling patterns reported by Haslam and coworkers (5) and to determine over a 48-h incubation period the pattern of labeling of monomers, dimers, and higher mol wt polymers of procyanidins found in these cell cultures. In addition, incorporation of label into the potential intermediate, eriodictyol-7-glucoside (8), was followed. MATERIALS AND METHODSThe cell suspension culture ofDouglas fir (Pseudotsuga menziesii Franco), clone V, has been maintained as described previously (7,8). identical to those in which the cultures are routinely maintained, the cells were rinsed with distilled H20, filtered and weighed, and then extracted with 3 x 1 ml of 70%o methanol. Three fractions were obtained as described previously (8) Purification Procedures. The two methanol-soluble fractions from the mini-column were separated into individual components for determination of A at 280 and 550 nm and for determination of radioactivity. Method I, involving HPLC and paper chromatography for purification, was used for the data in Figures 2 and 3. The 20:80 fraction was eluted into three portions by HPLC with a reversed phase C18 Partisil column (10 ODS3, 25 x 0.6 cm; Whatman Inc.). Portion 1, eluted in 5% acetic acid (v/v) between 16 and 24 ml, contained cat22 and cat3; portion 2, eluted between 24 and 32 ml, contained catechin and epi-cat; portion 3, eluted subsequently with methanol:H20 (70:30), contained epicatechin ...

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Section: Asymmetricmentioning

confidence: 79%

mentioning

confidence: 99%

Incorporation of [¹⁴C]Phenylalanine into Flavan-3-ols and Procyanidins in Cell Suspension Cultures of Douglas Fir

Stafford

Shimamoto²,

Lester³

1982

Plant Physiol.

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“…Five mg (+)-dihydroquercetin was stirred into 1 ml ofethanol and 3 mg NaBH4 was added over a 30-min period (1). After 1 h, 2 ml of 0.1 N HCI and 10 ml of H20 were added.…”

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confidence: 99%

“…Nonenzymic Preparation of Flavan-3-ols (1,5). Five mg (+)-dihydroquercetin was stirred into 1 ml ofethanol and 3 mg NaBH4 was added over a 30-min period (1).…”

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confidence: 99%

Enzymic and Nonenzymic Reduction of (+)-Dihydroquercetin to Its 3,4,-Diol

Stafford¹,

Lester²

1982

Plant Physiol.

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A NADPH-dependent reductase activity, capable of converting (+) dihydroquercetin (2,3-trans) to its 3,4-diol (a leucocyanidin), has been demonstrated in crude, soluble protein extracts derived from cell suspension cultures of Douglas fir (Pseudotsuga menziessi). Neither NADH nor ascorbate substituted as the H-donor. Quantitative analyses were based on the production of cyanidin, the formation of an adduct with vanillin, and on absorbance at 280 nanometers. Nonenzymic reduction of (+)-dihydroquercetin with NaBH4 produced two presumably isomeric flavan-3,4,-diols. One of these was similar to the enzymically produced diol, based on products isolated by chromatography on paper, on thin-layer cellulose and on C18 reversed-phase columns (high performance liquid chromatography), and on the conversion of the diol to the all-trans dimer of (+)-catechin upon the addition of (+)-catechin.

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“…9 closely related to that of fisetinidol-(4a→6)-catechin, which has already been reported. 10) It showed negative Cotton effect at 200-220 nm in the CD spectrum defined as an a orientation at C-4, that is, the 4S configuration. However, the CD spectrum of compound 2 showed a strong positive Cotton effect at 216 nm, which defined a 4b orientation.…”

Section: Resultsmentioning

confidence: 99%

Three New Stereoisomers of Condensed Tannins from the Roots of Rosa multiflora

Park

Kim

Choi

et al. 2010

CHEMICAL & PHARMACEUTICAL BULLETIN

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Three new stereoisomers of condensed tannins (1-3), and four known phenolic compounds (4-7) were isolated from the 80% acetone extract of the roots of Rosa multiflora Thunberg. The structures of these compounds were elucidated using 1D/2D NMR, high resolution (HR)-MS, and circular dichroism (CD) spectra. In order to evaluate their anti-oxidative and anti-inflammatory activities, their 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity and inhibitory activity on nitric oxide (NO) production were determined.

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Synthesis of condensed tannins. Part 4. A direct biomimetic approach to [4,6]- and[4,8]-biflavanoids

Cited by 120 publications

References 0 publications

Incorporation of [¹⁴C]Phenylalanine into Flavan-3-ols and Procyanidins in Cell Suspension Cultures of Douglas Fir

Incorporation of [¹⁴C]Phenylalanine into Flavan-3-ols and Procyanidins in Cell Suspension Cultures of Douglas Fir

Enzymic and Nonenzymic Reduction of (+)-Dihydroquercetin to Its 3,4,-Diol

Three New Stereoisomers of Condensed Tannins from the Roots of Rosa multiflora

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Synthesis of condensed tannins. Part 4. A direct biomimetic approach to [4,6]- and[4,8]-biflavanoids

Cited by 120 publications

References 0 publications

Incorporation of [14C]Phenylalanine into Flavan-3-ols and Procyanidins in Cell Suspension Cultures of Douglas Fir

Incorporation of [14C]Phenylalanine into Flavan-3-ols and Procyanidins in Cell Suspension Cultures of Douglas Fir

Enzymic and Nonenzymic Reduction of (+)-Dihydroquercetin to Its 3,4,-Diol

Three New Stereoisomers of Condensed Tannins from the Roots of Rosa multiflora

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Incorporation of [¹⁴C]Phenylalanine into Flavan-3-ols and Procyanidins in Cell Suspension Cultures of Douglas Fir

Incorporation of [¹⁴C]Phenylalanine into Flavan-3-ols and Procyanidins in Cell Suspension Cultures of Douglas Fir