粘委陵菜中的鞣质成分的研究

从枯委陵菜(potenjtilla viscosa J.Don)根中分离出七个鞣质成分, 经波谱分析, 化学降解和衍生物制备等手段确定了它们的化学结构, 分别为(+)-儿茶素(1), (+)-儿茶素3-O-β-D葡萄糖苷(2), afzelechin-(4α-8)-儿茶素(3), 原花色苷元B-3(4), 原花色苷元B-33'-O-β-D-葡萄吡喃糖苷(5), 原花色苷元C-2(6)和枯委陵菜素(potentillanin)(7), 其中5和7是首次发现的天然化合物,化合物1及2具有保肝作用。     

Versatile synthesis of epicatechin series procyanidin oligomers, and their antioxidant and DNA polymerase inhibitory activity

Proanthocyanidins, known as condensed tannins or oligomeric flavonoids, exist in many edible plants and show various interesting biological activities. We have developed a simple and versatile method of synthesizing procyanidin oligomers consisting of (−)-epicatechin and (+)-catechin. This method is applicable to the synthesis of various 3-O-substituted oligomers. We report here the stereoselective and length controlled synthesis of [4-8]-condensed (−)-epicatechin series procyanidin oligomers. We described the details of the synthesis of an two tetramers, (−)-epicatechin-(−)-epicatechin-(−)-epicatechin-(−)-epicatechin and (−)-epicatechin-(−)-epicatechin-(−)-epicatechin-(+)-catechin (arecatannin A1), (−)-epicatechin pentamer and two 3,3″,3?-tri-O-galloyl trimers, (−)-epicatechin-(−)-epicatechin-(−)-epicatechin-3,3″,3?-tri-O-gallate and (−)-epicatechin-(−)-epicatechin-(+)-catechin-3,3″,3?-tri-O-gallate with the condensation method using TMSOTf as a catalyst. The ability of DPPH radical scavenging activity and DNA polymerase inhibitory activity of these oligomeric compounds were investigated.     

Influence of an 8-trifluoroacetyl group on flavanol couplings

The effect of an electron attracting substituent in the Lewis acid catalyzed oligomerization of flavanols was investigated. The results showed that the presence of a COCF₃, at the 8 position of a (+)-catechin unit strongly influenced the attack of the 6 free nucleophile flavanol position by the electrophile generated from a 4-O-alkyloxy protected catechin unit. This was observed either with TiCl₄ or TMSOTf as Lewis acids in which the carbon-carbon bond formation was inhibited and the corresponding dimer was detected in small amount. On the contrary, the formation of a carbon-oxygen bond was observed and the corresponding C-4→O→C-3 ether linked procyanidin dimer was isolated in a good yield. In order to avoid the participation of the C-3 hydroxyl group in the dimerization reaction, the two flavanol units were forced into C-4→C-8 coupling by use of an internal link. The structural elucidation of the isolated compounds was achieved through MS and NMR spectroscopy.     

High-performance liquid chromatographic determination of oligomeric procyanidins from dimers up to the hexamer in hawthorn

An HPLC method using UV diode array detection was developed for analysing procyanidins qualitatively and quantitatively up to the hexameric level in hawthorn samples. The analysed compounds included procyanidin dimers B-2, B-4 and B-5, procyanidin trimers C-1, epicatechin-(4beta-->8)-epicatechin-(4beta-->6)-epicatechin and epicatechin-(4beta-->6)-epicatechin-(4beta-->8)-epicatechin, a tetramer D-1 and a pentamer E-1 both consisting of (-)-epicatechin units linked through C-4beta/C-8 bonds. The concentrations of two unknown tetramers and a hexamer F were also quantified. The oligomeric procyanidins (OPs) were specifically determined due to the development of a method for isolating them from hawthorn during sample preparation. The pattern of oligomeric procyanidins in the leaves, flowers and fruits was similar, but the concentrations varied depending on the part of the plant. The concentration in leaves was 1.6%, in flowers 1.2% and in fruits 0.2% of the dry mass. The method was validated with respect to repeatability, recovery, linearity, and sensitivity. The repeatability for the quantitative analytical method of all the OPs in leaves was 7.7%, in flowers 8.8%, and in fruits 12.3%. The recovery of the main OPs ranged from 91 to 97%. The correlation coefficients of calibration curves were between 0.997 and 1.000. The limits of quantitation for different procyanidin standards were 0.05-0.12 mg/ml, when 10 microl of each standard solution was injected into the HPLC.     

Proanthocyanidins ofZiziphus jujuba

The catechin and proanthocyanidin compositions of the leaves and bark ofZiziphus jujuba have been studied over the vegetation periods. This has led to the isolation of 16 compounds, including 8 monomeric catechins — (–)-epiafzelechin, (–)-epicatechin, (–)-epigallocatechin, (–)-epicatechin gallate, (–)-epigal-locatechin gallate, (+)-catechin, (+)-catechin gallate, and (+)-gallocatechin; 4 dimeric proanthocyanidins — (–)-epiafzelechin-(4-8)-(–)-epicatechin, proanthocyanidin B-2, (–)-epicatechin-(4-8)-(–)-epigallocatechin, and (–)-epiafzelechin-(4-8)-(–)-epigallocatechin; and 4 oligomeric proanthocyanidins consisting of epiafzelechin, epigallocatechin, catechin, and epicatechin with different degrees of polymerization. Their structures have been established by a study of PMR and¹³C NMR spectra and the products of chemical transformation.The materials of this paper were presented at the Second International Symposium on the Chemistry of Natural Compounds (SCNC, Eskiehir, Turkey, October 22–24, 1996).Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 221–231, March–April, 1997.     

Procyanidin oligomers. A new method for 4→8 interflavan bond formation using C8-boronic acids and iterative oligomer synthesis through a boron-protection strategy

Interest in the synthesis of procyanidin (catechin or epicatechin) oligomers that contain the 4→8 interflavan linkage remains high, principally due to research into their health effects. A novel coupling utilising a C8-boronic acid as a directing group was developed in the synthesis of natural procyanidin B3 (i.e., 3,4-trans-(+)-catechin-4α→8-(+)-catechin dimer). The key interflavan bond was forged using a novel Lewis acid-promoted coupling of C4-ether 6 with C8-boronic acid 16 to provide the α-linked dimer with high diastereoselectivity. Through the use of a boron protecting group, the new coupling procedure was extended to the synthesis of a protected procyanidin trimer analogous to natural procyanidin C2.     

Chemical Constltuents from the Roots of Zizyphus jujuba Mill. var. spinosa (I)

The chemical constituents of the roots of Zizyphus jujuba Mill. var. spinosa were investigated with a combination of Sephadex LH-20 column, centrifugal partition chromatography and RP-18 low pressure liquid chromatography. We isolated seven flavonoids-quercetin ( 1 ), (+)-dihydroquercetin ( 2 ), (+)-dihydrokaempferol ( 7 ), quercetin-3-0-β-glucoside ( 8 ), 2-hydroxynaringenin ( 11 ), rutin ( 12 ), and quercetin 3-0-(2^G-β-D-xylopyranosylrutinoside) ( 13 ); four catechins-(-)-gallocatechin ( 3 ), (-)-epigallocatechin ( 4 ), (-)-catechin ( 5 ), and (-)-epicatechin ( 6 ); and two phenolic carboxylic acids-p-hydroxybenzoic acid ( 9 ) and protocatechuic acid ( 10 ) from the water soluble fraction of the ethanolic extract NMR date of 13 were assigned by 2D NMR techniques.     

Conformational analysis of the sixteen C(4)-C(6) and C(4)-C(8) linked dimers of (+)-catechin and (−)-epicatechin

A conformational analysis has been performed for sixteen dimers of (+)-catechin and/or (?)-epicatechin using molecular mechanics (MM2). Monomer units are linked by 4α-6, 4α-8, 4β-6, and 4β-8 bonds. THe four possible combinations of (+)-catechin and/or(?)-epicatechin are used for each bonding pattern. The objectives are characterization of (1) the two rotational isomers at the bond between the two monomer units and (2) the conformations of the heterocyclic rings. There is a twofold rotation about the bond between monomer units. Differ4ences in the energies at the two minima range from a few tenths of a kcal/mol to several kcal/mol, depending on the dimer Heterocyclic rings occupy a range of conformations that can be described as half chairs with varying degrees of distoration toward C(2) or C(3) sofas. The more frequent distortion is toward the C(2) sofa. Interconversion between most of the heterocyclic ring conformations can be obtained by coordinated motion of C(2) and C(3), over a range of about 40 pm, with respect to the mean plane of the fused aromatic ring system.     

Procyanidins from Myrothamnus flabellifolia

From the ethyl acetate soluble fraction of an acetone-water extract of the twig tips of Myrothamnus flabellifolia Welw. (Myrothamnaceae), a variety of flavan-3-ols (epicatechin, epigallocatechin and their 3-O-galloylated analogues) and procyanidins (DP 8)-catechin], B4 [catechin-(4alpha --> 8)-epicatechin], B6 [catechin-(4alpha --> 6)-catechin] and catechin-(4alpha --> 8)-epigallocatechin along with the galloylated analogues B4-3'-O-gallate, procyanidin B2-3'-O-gallate [epicatechin-(4beta --> 8)-epicatechin-3-O-gallate], B2-3,3'-di-O-gallate, procyanidin B5-3,3'-O-gallate [epicatechin-3-O-gallate-(4beta --> 6)-epicatechin-3-O-gallate], catechin-(4alpha --> 8)-epigallocatechin-3-O-gallate, the trimer procyanidin C1-3'-O-gallate[epicatechin-(4beta --> 8)-epicatechin-(4beta --> 8)-epicatechin-3-O-gallate] and the new epicatechin-3-O-gallate-(4beta --> 6)-epicatechin-3-O-p-hydroxybenzoate. The structures were elucidated by 1D- and 2D-NMR experiments of their peracetylated derivatives, partial acid-catalysed degradation with phloroglucinol, ESI-MS and CD spectra.     

Densitometric determination of (+)-catechin and (−)-epicatechin by 4-dimethylaminocinnamaldehyde reagent

We report the optimization of a sensitive, selective and robust derivatization method using 4-dimethylaminocinnamaldehyde (DMACA) for densitometric determination of (+)-catechin and (−)-epicatechin. The separation of these compounds was achieved by thin-layer chromatography (TLC) on cellulose plates developed with water. With DMACA in HCl, both compounds gave blue bands, while under the same conditions, vanillin produced a fast fading red coloration of bands. Quantitation at 655 nm showed that for both compounds the calibration curve was linear from 2 to 12 ng and polynomial from 2 to 30 ng, and the repeatability of chromatography of 20 ng was 3.5% (RSD, n = 6). The visible limit of detection of both standards was 1 ng, but the densitometric limit of detection was lower (0.2 ng). The optimized DMACA reagent is superior to the more frequently used vanillin reagent and is applicable also for determination of mixtures containing other catechins ((−)-catechin, (−)-epicatechin gallate, (−)-epigallocatechin gallate, procyanidin A2, procyanidin B1 and procyanidin B2).     

Revised structures of gambiriins A1, A2, B1, and B2, chalcane-flavan dimers from gambir (Uncaria gambir extract)

Gambir, the aqueous extract from Uncaria gambir (Rubiaceae), has been used as an astringent medicine in Asian countries. Investigation of the constituents in the extract led to the isolation of four chalcane-flavan dimers, gambiriin A1 (6), A2 (7), B1 (8), and B2 (9), in addition to (+)-catechin (1), (+)-epicatechin (2), and dimeric proanthocyanidins, procyanidin B1 (3), procyanidin B3 (4), and gambiriin C (5). The spectroscopic and chemical data obtained in the present study indicated that their previously proposed structures 6a, 7a, 8a, and 9a should be revised to 6, 7, 8, and 9, respectively.     

Catechins and proanthocyanidins ofAlhagi sparsifolia. I

Ten individual compounds have been isolated from the epigeal part ofAlhagi sparsifolia Shap. in various stages of vegetative growth. Their structures have been established by a study of PMR spectra, physicochemical properties, and the products of chemical transformations: (–)-epicatechin, (–)-epigallocatechin, (–)-epigallocatechin gallate, (+)-catechin, (+)-gallocatechin, proanthocyanidin B-2, (–)-epigallocatechin-(4–8)-(–)-epicatechin, epigallocatechin gallate-(4–8)-(–)-epicatechin, proanthocyanidin B-1, and (–)-epicatechin-(4–8)-gallocatechin.The materials of this paper were presented at the Second International Symposium on the Chemistry of Natural Compounds (SCNC, Eskiehir, Turkey, October 22–24, 1996).Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 232–237, March–April, 1997.     

Study of the catechins and proanthocyanidins ofQuercus robur

More than 20 compounds have been isolated from the bark ofQuercus robur. Monomers: (–)-epicatechin, (–)-epicatechin gallate, (+)-catechin, (+)-catechin gallate, (+)-gallocatechin, (–)-epigallocatechin, and (–)-epigallocatechin gallate; dimeric proanthocyanidins: (+)-catechin-(4-8)-(+)-catechin, 3-O-galloyl-(+)-catechin-(4-8)-3-O-galloyl-(+)-catechin, 3-O-galloyl-(+)-gallocatechin-(4-8)-(+)-gallocatechin, (–)-epicatechin-(4-8)-3-O-galloyl-(–)-epigallocatechin gallate, 3-O-galloyl-(–)-epicatechin-(4-8)-3-O-galloyl-(–)-epigallocatechin, 3-O-galloyl-(–)-epigallocatechin-(4-8)-(+)-catechin; and oligomeric proanthocyanidins: D14-D19.Materials presented at the IInd International Symposium on the Chemistry of Natural Compounds (SCNC, Eskiehir, Turkey, October, 22–24, 1996).Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (3712) 40 64 75. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 819–833, November–December, 1997.     

Interaction of Novel Anionic Gemini Surfactants with Dodecyl Sodium Sulfate in Aqueous NaCl Medium and the Performance of Their Mixtures

The interaction in two mixtures of two novel anionic gemini surfactants, sodium 2,2′-(6,6′-(ethane-1,2-diylbis(azanediyl)bis(4-(hexylamino)-1,3,5-triazine-6,2-diyl)bis(azanediyl)diethanesulfonate (C₆-2-C₆) and sodium 2,2′-(6,6′-(ethane-1,2-diylbis(azanediyl)bis(4-(octylamino)-1,3,5-triazine-6,2-diyl) bis(azanediyl) diethanesulfonate (C₈-2-C₈), and conventional anionic surfactants, sodium dodecyl sulfate (SDS), have been investigated in 0.1 M NaCl aqueous solutions. The mixed systems are C₆-2-C₆/SDS and C₈-2-C₈/SDS, and the mole factions (α_G) of geminis are 0.1, 0.3, 0.5, 0.7, and 0.9, respectively. Mixtures of both C₆-2-C₆/SDS and C₈-2-C₈/SDS exhibit synergism in surface tension reduction efficiency and mixed micelle formation. But, all mixtures except C₆-2-C₆/SDS (α_G = 0.7), C₆-2-C₆/SDS (α_G = 0.9), and C₈-2-C₈/SDS (α_G = 0.1) don't exhibit synergism in surface tension reduction effectiveness. The performances, such as wetting, emulsification, and dispersion were measured and the results showed all mixtures posses application properties.     

Flavanol derivatives from Rhizophora stylosa and their DPPH radical scavenging activity

A new acetylated flavanol, 3,7-O-diacetyl (-)-epicatechin (3), and seven known flavanol derivatives, (-)-epicatechin (1), 3-O-acetyl (-)-epicatechin (2), 3,3',4',5,7-O-pentaacetyl (-)-epicatechin (4), (+)-afzelechin (5), (+)-catechin (6), cinchonain Ib (7), and proanthocyanidin B2 (8), were isolated from the stems and twigs of the mangrove plant Rhizophora stylosa and identified. The crude extract, the different fractions and all of the purified compounds were evaluated for DPPH radical scavenging activity.     

Total synthesis of asymmetric flavonoids: the development and applications of 13C-labelling

This article compiles our results in the field of flavonoid chemistry with the aim to synthesise isotopically labelled products. Two strategies (C₆ + C₃–C₆ vs C₆–C₂ + C₁–C₆) and some organometallic (Pd⁰, Mo^IV) couplings were explored to build the C₆–C₃–C₆ flavonoid skeleton. Following this work, the gram scale has been reached in addition to the asymmetry of the targeted natural flavan-3-ols, i.e. (+)-catechin, (–)-epicatechin, and (–)-procyanidin B3. These characteristics were necessary in the event of using these molecules for pharmacokinetic and metabolic studies in human beings.     

Dimeric proanthocyanidins ofHibiscus cannabinus

Two dimeric proanthocyanidins have been isolated from the bark and roots of kenaf of variety Uzbekskii 1574. On the basis of chemical transformations and NMR and mass-spectral analyses it has been established that the proanthocyanidins have the structure of a dehydro dimer of 3,3′,4′,5,7-pentahydroxyflavan and that of 8-(3-galloyloxy-3′,4′,5,7-tetrahydroxyflavan-4-yl)-3,3′,4′,5,7-pentahydroxyflavan, respectively, with a C₄-C₈ (or C₆) bond between the flavan moieties.     

Biooxidation of (+)-catechin and (-)-epicatechin into 3,4-dihydroxyflavan derivatives by the endophytic fungus Diaporthe sp. isolated from a tea plant

The microbial transformation of (+)-catechin (1) and (-)-epicatechin (2) by endophytic fungi isolated from a tea plant was investigated. It was found that the endophytic filamentous fungus Diaporthe sp. transformed them (1, 2) into the 3,4-cis-dihydroxyflavan derivatives, (+)-(2R,3S,4S)-3,4,5,7,3',4'-hexahydroxyflavan (3) and (-)-(2R,3R,4R)-3,4,5,7,3',4'-hexahydroxyflavan (7), respectively, whereas (-)-catechin (ent-1) and (+)-epicatechin (ent-2) with a 2S-phenyl group resisted the biooxidation.     

Dimeric proanthocyanidins ofCotoneaster oligantha

Summary 1. Five flavans have been isolated from the stems ofCotoneaster oligantha A. Pojark, and have been identified; two of them are (+)-catechin and (–)-epicatechin and three are stereoisomeric dimeric procyanidins.2. The proanthocyanidins have the structure of dimers of 3,4,5,7-tetrahydroxyflavan-3-ol with C₄-C₈ (or C₆) bonds between the flavan moieties and with the cis (2R:3R) configuration of the asymmetric centers (flavans 3 and 5) and trans (2R:3S:4S) configuration of the upper half and the cis configuration of the lower half of the molecule (flavan 4).S. M. Kirov Kazakh State University, Alma-Ata. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 204–212, March–April, 1978.     

Structural characterization of a procyanidin tetramer and pentamer from the apple by low-temperature NMR analysis

The structures of a procyanidin tetramer and pentamer from unripe apple (Malus pumila) were elucidated by low-temperature NMR analysis at −34 °C. These structures were [epicatechin-(4β→6)-epicatechin-(4β→8)-epicatechin-(4β→8)-epicatechin (1)] and [epicatechin-(4β→8)-epicatechin-(4β→8)-epicatechin-(4β→8)-epicatechin-(4β→8)-epicatechin (2)].