Condensed tannins: direct synthesis, structure, and absolute configuration of four biflavonoids from black wattle bark (‘mimosa’) extract

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

doi:10.1039/c39780000700

Cited by 52 publications

(49 citation statements)

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“…The observation of the IH NMR spectra of such derivatives, lead to the suggestion of an empirical rule whereby i5 H8 -i5 H6 ~ 0. l ppm (2). In no case overlapping of these signal ranges was observed.…”

Section: H Outtrup ~S K Schaumburg: Ih Nmr Of Proanthocyanidinsmentioning

confidence: 87%

Structure elucidation of some proanthocyanidins in barley by1H 270 MHz NMR spectroscopy

Outtrup

Schaumburg

1981

Carlsberg Res. Commun.

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In the present paper the composition of proanthocyanidins isolated from barley is investigated. Separation by affinity chromatography and HPLC yields a large number of substances. Six of these have been isolated in this work. Based on the chromatographic preparation they are expected to be two dimers DI and D2 and four trimeric substances TI -T4. Studies by means of IH NMR spectroscopy at 270 MHz confirmed DI and D2 as being dimeric compounds, a prodelphinidin and procyanidin B3 respectively. The spatial structure of the prodelphinidin corresponds to procyanidin B3. The peracetates of all six compounds have also been studied by means of IH NMR spectrocopy. By comparison with data for the analogous peracetates of (+)-catechin and (-)-epicatechin and with literature data, T1 -T4 have been identified as trimeric proanthocyanidins and their structures have been elucidated.

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Section: H Outtrup ~S K Schaumburg: Ih Nmr Of Proanthocyanidinsmentioning

confidence: 87%

Structure elucidation of some proanthocyanidins in barley by1H 270 MHz NMR spectroscopy

Outtrup

Schaumburg

1981

Carlsberg Res. Commun.

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“…Determination of the "upper" 5-deoxyflavan-3-ol unit was facilitated by the long-range coupling between H-5(A) (d 6.89) and H-4(C) (Fletcher et al, 1977), the chemical shift of H-3(C) (d 5.79; t, SJ=19.5 Hz), the chemical shift of the B-ring protons and the high-amplitude negative Cotton effect in the 220-240 nm region of the CD spectrum of 8a, all confirmed a (4b→8) linkage and, thus, a 4S absolute configuration. Consequently, 8 was characterized as robinetinidol-(4b→8)-gallocatechin, previously reported as a prominent metabolite from Acacia mearnsii (Drewes et al, 1966b;Botha, Ferreira, Roux, 1978b;Botha et al, 1981b;Viviers et al, 1983) and also present in S. adstringens (Mello, Petereit, Nahrstedt, 1996a, 1996b, 1999 and in S. polyphyllum Mart. (Lopes, 2003).…”

Section: Resultsmentioning

confidence: 99%

Antioxidant capacity of extracts and isolated compounds from Stryphnodendron obovatum Benth

Zocoler

Sanches

Albrecht

et al. 2009

Braz. J. Pharm. Sci.

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The extract from stem bark of Stryphnodendron obovatum Benth. was chromatographed on a Sephadex ® LH-20 column, and yielded nine compounds: gallic acid (GA), p-hydroxybenzoic acid (PHB), gallocatechin (GC), epigallocatechin (EPG), 4'-O-methylgallocatechin (MGC), epigallocatechin-(4b→8)-epigallocatechin (EPEP), epigallocatechin-(4b→8)-gallocatechin (EPGC), robinetinidol-(4a→8)-gallocatechin (ROGC) and robinetinidol-(4b→8)-epigallocatechin (ROEP). Evaluation of the antioxidant capacity in vitro by the methods of DPPH free radical (IC 50 ; mg/mL) and reduction of the phosphomolybdenum complex (RAC) gave the following results, respectively: crude extract 4.52 and 0.8242; ethyl-acetate fraction 4.04 and 0.9537; aqueous fraction 5.58 and 0.9275. The crude extract and ethyl-acetate fraction were shown to possess an antioxidant capacity comparable to that of vitamin C (4.93 and 1.0). The values obtained by the DPPH free-radical method for the isolated compounds were IC 50 (μM): GA=8.89; PHB=10.12; GC=16.46; EPG=13.20; MGC=21.00; EPEP=6.89; EPGC=4.91; ROGC=7.78 and ROEP=6.20. Vitamin C and trolox showed 30.11 and 30.10, respectively. Dimers showed greater activity in scavenging free radicals, possibly related to the number of hydroxyls. However, compounds without a hydroxyl at position 5 of the A-ring (5-deoxy-proanthocyanidins) did not change the antioxidant activity of the DPPH free radical, as evaluated here for the first time. Among the monomers, there appeared to be a direct relationship in scavenging of free radicals because of the stereochemistry of the compounds. The presence of a methyl radical on the B-ring significantly reduced the scavenging of free radicals of gallocatechin. All compounds showed greater scavenging of radicals than vitamin C and trolox, and these two compounds showed no significant difference from each other.Uniterms: Stryphnodendron obovatum. Antioxidant capacity. Condensed tannins. DPPH free radical. Phosphomolybdenum complex.O extrato das cascas de Stryphnodendron obovatum submetido à cromatografia em coluna, Sephadex ® LH-20, forneceu nove substâncias: ácido gálico (GA), ácido p-hidróxibenzóico (PHB), galocatequina (GC), epigalocatequina (EPG), 4'-O-metilgalocatequina (MGC), epigalocatequina-(4b→8)-epigalocatequina (EPEP), epigalocatequina-(4b→8)-galocatequina (EPGC), robinetinidol-(4a→8)-galocatequina (ROGC) e robinetinidol-(4b→8)-epigalocatequina (ROEP). A capacidade antioxidante in vitro pelos métodos do radical livre DPPH (IC 50 ; mg/mL) e do complexo fosfomolibdênio (CAR) apresentou os seguintes resultados, respectivamente: extrato bruto 4,52 e 0,8242; fração acetato de etila 4,04 e 0,9537 e fração aquosa 5,58 e 0,9275 demonstrando possuírem capacidade antioxidante quando comparados com vitamina C 4,93 e 1,0. Os valores obtidos pelo método do radical livre DPPH com as substâncias isoladas foram: IC 50 (μM): GA=8,89; PHB=10,12; GC=16,46; EPG=13,20; MGC=21,00; EPEP=6,89; EPGC=4,91; ROGC=7,78 e ROEP=6,20 tendo sido avaliadas aqui pela primeira vez. Entre os monômeros, parece haver uma ...

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“…The epoxy chalcone racemates (8) - (10), (12), and (13) were almost completely separated (resolution factor, R$ ~ 1). A 3-methoxymethoxy-or 4'-methoxy group is beneficial in improving resolution.…”

Section: Resolution Of Racemic Chalcone Epoxides Dihydroflavonols Amentioning

confidence: 96%

Enantioselective Synthesis of Flavonoids

Bezuidenhoudt

Ferreira

1992

Plant Polyphenols

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Enantiopure (scalemic) flavonoid monomers such as permethoxylated chalcone epoxides and dihydroflavonols are available via HPLC resolution of the racemates using a Chiralpack OT( +) column. Depending on the oxygenation pattern, epoxy chalcones can also be prepared in enantiomeric purity up to 96 percent by the utilization of synthetic poly(peptide) or cinchona alkaloid catalyzed epoxidation with hydrogen peroxide, aqueous sodium hypochlorite, or tert-butyl hydroperoxide. Transformation of these oxiranes into dihydroflavonols and ultimately flavan-3,4-diols without 'loss' in optical purity is possible by treatment with hydrogen chloride in absolute methanol, followed by sodium borohydride reduction. Direct catalytic hydrogenation of the epoxides leads to a-hydroxydihydrochalcones of comparable enantiomeric purity that can be used for determination of the absolute configuration of naturally occurring analogues by comparison of CD data.

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Condensed tannins: direct synthesis, structure, and absolute configuration of four biflavonoids from black wattle bark (‘mimosa’) extract

Cited by 52 publications

References 1 publication

Structure elucidation of some proanthocyanidins in barley by1H 270 MHz NMR spectroscopy

Structure elucidation of some proanthocyanidins in barley by1H 270 MHz NMR spectroscopy

Antioxidant capacity of extracts and isolated compounds from Stryphnodendron obovatum Benth

Enantioselective Synthesis of Flavonoids

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