Synthesis of condensed tannins. Part 1. Stereoselective and stereospecific syntheses of optically pure 4-arylflavan-3-ols, and assessment of their absolute stereochemistry at C-4 by means of circular dichroism

Botha, Jacobus J.; Young, Desmond A.; Ferreira, Daneel; Roux, David G.

doi:10.1039/p19810001213

Cited by 115 publications

(85 citation statements)

References 2 publications

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“…In addition, the 4b → 8-linkage and thus the R-configuration at C-4(C) was confirmed by the strong positive Cotton effect observed between 220 and 230 nm, and 280 nm in the CD spectrum. [22][23][24][25][26][27] The missing NOE effect between H-2(C) and H-4(C) strongly supported the proposed 4b orientation of the interflavanoid bond. The high-amplitude positive Cotton effect was caused by the phenylpropanoid substituent with an S-configuration at C-7".…”

Section: Structure Of Phenylpropanoid Substituted Flavan-3-olsmentioning

confidence: 87%

“…In general, the 4S-linkage between two flavan units produces negative Cotton effects at 220-240 and 275 nm in the CD spectra. [22][23][24][25][26][27] Such negative Cotton effects can be observed in the spectrum of compound 9a, in addition to a positive Cotton effect at 255 nm. The latter effect is (probably) due to the S-configuration of the phenylpropanoid substituent.…”

Section: Structure Of Phenylpropanoid Substituted Flavan-3-olsmentioning

confidence: 99%

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Phenylpropanoid substituted flavan-3-ols from Trichilia catigua and their in vitro antioxidative activity

Resende¹,

Rodrigues‐Filho²,

Luftmann³

et al. 2011

J. Braz. Chem. Soc.

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O novo flavan-3-ol contendo um substituinte fenilpropanoide apocinina E, juntamente com oito substâncias conhecidas, epicatequina, procianidina B2, procianidina B4, procianidina C1, cinchonaína Ia, cinchonaína Ib, cinchonaína IIb e cinchonaína IIa foram isoladas a partir do extrato acetona-H 2 O das cascas secas de Trichilia catigua. As substâncias cinchonaína Ib e cinchonaína IIb foram reavaliadas em relação à sua estereoquímica. Todas as substâncias foram caracterizadas por análises espectroscópicas incluindo ressonância magnética nuclear (NMR) 1D e 2D e espectrometria de massa (MS) de seus derivados acetilados. A configuração absoluta do substituinte fenilpropanoide foi determinada por espectropolarimetria de dicroísmo circular (CD) e pela análise do efeito anisotrópico empregando modelo de Dreiding, e por experimento de espectroscopia de efeito nuclear Overhauser (NOESY NMR). As nove substâncias mostraram maior atividade sobre o sequestro de radical livre e poder de redução do que o ácido ascórbico e Trolox frente ao radical livre 2,2-difenil-1-picrilhidrazila e no sistema do teste de redução do ferro (Fe 3+ -Fe 2+ ).The new phenylpropanoid substituted flavan-3-ol apocynin E, together with eight known compounds, epicatechin, procyanidin B2, procyanidin B4, procyanidin C1, cinchonain Ia, cinchonain Ib, cinchonain IIb, and cinchonain IIa were isolated from an acetone-H 2 O extract of the air-dried stem bark of Trichilia catigua. The cinchonain Ia e Ib were reevaluated to its estereochemistry. All the compounds were characterized by spectroscopic analysis including 1D and 2D nuclear magnetic resonance (NMR) and mass spectrometry (MS) of their peracetate derivatives. The absolute configuration of the phenylpropanoid moiety was determined by circular dichroism (CD) spectra and by analyzing the anisotropic effects in the Dreiding model and nuclear Overhauser effect (NOESY NMR) experiments. The nine isolated compounds showed higher radical scavenging activity and reducing power than ascorbic acid and Trolox in the free-radical 2,2-diphenyl-1-picrylhydrazyl and Fe 3+ -Fe 2+ reduction assay systems. Keywords:Trichilia catigua, Meliaceae, cinchonains, proanthocyanidins, antioxidative activity IntroductionTrichilia catigua A. Juss. (Meliaceae), commonly known as "catuaba", is a plant native to South and Central America and widely distributed in Brazil. 1 However, the identity of the plant source is often uncertain, and stem barks from several different species of Erythroxylum or Anemopaegma, all regionally known as "catuaba", are sold commercially. Marques 2 described the differences among the species known as "catuaba" and Phenylpropanoid Substituted Flavan-3-ols from Trichilia catigua J. Braz. Chem. Soc. 2088 determined that T. catigua is the main species that is sold as "catuaba" in Brazil. The same conclusion was reached by Kletter et al. 3 and Daolio et al. 4 The bark of T. catigua has been traditionally used as a health and mental tonic, and especially as a sexual stimulant. 3,5 Some pharmacological studies o...

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Section: Structure Of Phenylpropanoid Substituted Flavan-3-olsmentioning

confidence: 87%

Section: Structure Of Phenylpropanoid Substituted Flavan-3-olsmentioning

confidence: 99%

Phenylpropanoid substituted flavan-3-ols from Trichilia catigua and their in vitro antioxidative activity

Resende¹,

Rodrigues‐Filho²,

Luftmann³

et al. 2011

J. Braz. Chem. Soc.

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“…These degradation products were identified by co-chromatography in comparison with authentic compounds (Qa'dan et al, 2006). The high amplitude positive cotton effect at low wavelengths (210-240 nm) in the CD spectrum of compound 7a confirmed the absolute configuration of the extender units as 4R (Barrett et al, 1979;Botha et al, 1981). In conjunction with the optical rotation [α] 20 = +107.6° (c = 1.65, MeOH), compound 7 was characterized as epigallocatechin-(4β→8)-epigallocatechin-(4β→8)-catechin.…”

mentioning

confidence: 96%

Proanthocyanidins from Ginkgo biloba leaf extract and their radical scavenging activity

Qadan

Mansoor

Al-Adham

et al. 2011

Pharmaceutical Biology

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“…Finally, the absolute stereochemistry of 1 was elucidated by circular dichroism (CD) spectrum, which showed a negative Cotton effect in the short wavelength region (Δε −37.54 at 214 nm), indicating that the orientation of the 4-position in the flavan-3-ol unit is S configuration. 21,[44][45][46][47] This evidence indicated that the absolute configuration of 1 was determined to be 2R, 3S, 4S, 3″S, and 4″S orientations. Consequently, the absolute stereostructure of 1 was determined to be as shown.…”

mentioning

confidence: 96%

Structures of Two New Phenolic Glycosides, Kaempferiaosides A and B, and Hepatoprotective Constituents from the Rhizomes of <i>Kaempferia parviflora</i>

et al. 2012

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Two new phenolic glycosides, kaempferiaosides A and B were isolated from the rhizomes of Kaempferia parviflora (Zingiberaceae) together with 24 known compounds. Their structures including absolute stereochemistry were elucidated on the basis of chemical and spectroscopic evidence. Among the isolates, 5,3′-dihydroxy-3,7,4′-trimethoxyflavone showed higher activity than silybin, a commercial hepatoprotective agent.Key words Kaempferia parviflora; Zingiberaceae; kaempferiaoside; hepatoprotective activity; Krachai Dum A Zingiberaceae plant, Kaempferia parviflora WALL. ex BAKER, is widely distributed in Thailand and is known as Krachai Dum.1,2) The rhizomes of this plant are tinged with-dark purple to black, and have traditionally been used for the treatment of hypertension, [3][4][5] allergy, 6) gastrointestinal disorders, 7) and impotence. 8,9) The extract of the rhizomes of K. parviflora and its constituents were revealed to exhibit several pharmacological activities, such as antiplasmoidal, antifungal, 2) antiinflammatory, [10][11][12] α-glucosidase inhibitory, 13) and xanthine oxidase inhibitory 1) activities and cytotoxicity of several tumor cell lines 14,15) as well as effect of P-glycoprotein function 16) and modulation of multi-drug resistance in cancer cells. 17)Recently, rhizomes of K. parviflora powder was found to show preventive effect from obesity and its downstream symptoms. 18) By a previous chemical study on K. parviflora, presence of several methoxyflavones and related phenolic constituents have been revealed. 2,5,6,[10][11][12][13][14][15]17,[19][20][21][22] During the course of our characterization studies on Thai natural medicines, [23][24][25][26][27][28][29][30][31][32] two new phenolic glycosides named kaempferiaosides A (1) and B (2) were isolated from the rhizomes of K. parviflora together with 24 known compounds. This paper deals with the structure elucidation of 1 and 2, as well as hepatoprotective effect of the constituents from the rhizomes of K. parviflora on D-galactosamine (D-GalN)-induced cytotoxicity in primary cultured mouse hepatocytes.The dried rhizomes of K. parviflora cultivated at Loei province, Thailand were extracted with methanol to give a methanolic extract (7.10% from the dried rhizomes). The methanolic extract was partitioned into an EtOAc-H 2 O (1 : 1, v/v) mixture to furnish an EtOAc-soluble fraction (3.82%) and an aqueous phase. The aqueous phase was subjected to Diaion HP-20 column chromatography (H 2 O → MeOH) to give H 2 O-and MeOH-eluted fractions (2.04, 1.23%, respectively). As shown in Table 1, the EtOAc-soluble fraction and the MeOH-eluted fraction exhibited hepatoprotective activity, but the H 2 Oeluted fraction lacked the activity. The EtOAc-soluble fraction was subjected to normal-and reversed-phase column chromatographies, and finally HPLC to give 5-hydroxy-7-methoxyflavone 33) (3, 0.113%), 5,7-dimethoxyflavone rel-(5aS, 10bS)-5a,10b-dihydro-1,3,5a,9-tetrahydroxy-8-methoxy-6H-benz[b]

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Synthesis of condensed tannins. Part 1. Stereoselective and stereospecific syntheses of optically pure 4-arylflavan-3-ols, and assessment of their absolute stereochemistry at C-4 by means of circular dichroism

Cited by 115 publications

References 2 publications

Phenylpropanoid substituted flavan-3-ols from Trichilia catigua and their in vitro antioxidative activity

Phenylpropanoid substituted flavan-3-ols from Trichilia catigua and their in vitro antioxidative activity

Proanthocyanidins from Ginkgo biloba leaf extract and their radical scavenging activity

Structures of Two New Phenolic Glycosides, Kaempferiaosides A and B, and Hepatoprotective Constituents from the Rhizomes of <i>Kaempferia parviflora</i>

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