Qualitative analysis and HPLC isolation and identification of procyanidins from Vicia faba

The soluble proanthocyanidins of the coloured seed coats of Vicia faba L. were isolated and separated by solvent partition. The chemical characteristics of the proanthocyanidins were elucidated by total oxidation and partial degradation in the presence of phloroglucinol followed by HPLC analysis. The native extract of proanthocyanidins contained (+)-gallocatechin, (-)-epigallocatechin, (+)-catechin and (-)-epicatechin units. Oligomeric procyanidins were purified by chromatography on Sephadex LH-20 and the accessible compounds were isolated by RP-HPLC using a Licrospher Li 100 Column. The structures of the purified oligomeric procyanidins were elucidated using a procedure involving TLC, UV spectroscopy, ESI-MS and HPLC analysis of the products from the phloroglucinol reaction. The major condensed tannins of Vicia faba comprise six compounds identified as two A-type procyanidin dimers, the procyanidin dimers B1, B2 and B3, and a procyanidin trimer.     

Acylated flavanols and procyanidins from Salix sieboldiana

An homologous series of acylated flavan-3-ols and procyanidins have been isolated, together with the known procyanidins B-1, B-3 and trimer, from the bark of Salix sieboldiana. Chemical and spectroscopic evidence led to the assignments of their structures as the 3-O-(1,6-dihydroxy-2-cyclohexene-1-carboxylic acid ester) of (+)-catechin and the 1-hydroxy-6-oxo-2-cyclohexene carboxylic acid esters of (+)-catechin and procyanidins B-1, B-3 and trimer.     

The first 2,3-trans-3,4-cis procyanidin

Condensation of (+)-leucocyanidin with (+)-catechin under acidic conditions afforded the novel 2,3-trans-3,4-cis: 2,3-trans [4,8]-bi-[(+)-catechin] as the first representative of a 3,4-cis procyanidin unit.     

7-O-Galloyl-(+)-catechin and 3-O-galloylprocyanidin B-3 from Sanguisorba officinalis

7-O-Galloyl-(+)-catechin and 3-O-galloylprocyanidin B-3, along with gambiriins A-1 and B-3 and four polygalloylglucoses, have been isolated fro     

PROANTHOCYANIDINS IN NEEDLES FROM SIX GENERA OF THE TAXODIACEAE

Proanthocyanidin contents of needles ranged from a mean of 150 to 300 μg per mg dry wt in five species from five genera of the Taxodiaceae, Sequoiadendron giganteum (Lindl.) Bucch., Metasequoiaglyptostroboides H. Hu and Cheng, Sequoia sempervirens (D. Don) Endl., Taxodium distichum L. Rich., and Sciadopitys verticillata Siebold and Zucc. However, significantly lower amounts (70 μg per mg dry wt) were found in Cryptomeria japonica (L.f.) D. Don. This latter species as well as Sciadopitys verticillata, contained little or no prodelphinidin, while the other four species contained a ratio of procyanidin to prodelphinidin up to about 1:5. These data were based on analyses from three trees from each species. In addition, one tree from each species was examined in more detail. The major flavan-3-ol in all cases was (+)-catechin, with only non-detectable or trace amounts of (–)-epicatechin. The triphenolic flavan-3-ol, (+)-gallocatechin, was a minor constituent in all species, except Sciadopitys and Cryptomeria. The (–)-epigallocatechin was detected in Metasequoia, Sequoiadendron and Sequoia. All contained either (–)-epicatechin-(+)-catechin or (+)-catechin-(+)-catechin as the major procyanidin dimer. Prodelphinidin dimers were only tentatively identified.     

Occurrence of procyanidins in Nelia meyeri

A novel natural 4-arylflavan-3-ol has been obtained from leaves of Nelia meyeri. The same extract contains two procyanidin dimers, B-2 and B-5, and trimer C-1. ¹H NMR studies furnish diagnostic chemical shift parameters for determining the points of linkage in these compounds. The polymeric procyanidin isolated consists mainly of monomeric units with the 2,3-cis configuration and is considered to represent a pentamer or hexamer. The flavan-3-ol sequence of the polymer is proposed on the basis of partial degradation.     

Synthesis and antioxidant activity of a procyanidin B3 analogue

Proanthocyanidin, an oligomer of catechin, is a natural antioxidant and a potent inhibitor of lectin-like oxidized LDL receptor-1, which is involved in the pathogenesis of arteriosclerosis. We synthesized proanthocyanidin analogue 1, in which the geometry of one catechin molecule in procyanidin B3, a dimer of (+)-catechin, is constrained to be planar. The antioxidant activities of the compounds were evaluated in terms of their capacities to scavenge galvinoxyl radicals, and results demonstrate that while procyanidin was 3.8 times more potent than (+)-catechin, the radical scavenging activity of proanthocyanidin analogue 1 was further increased to 1.9 times that of procyanidin B3. This newly designed proanthocyanidin analogue 1 may be a promising lead compound for the treatment of arteriosclerosis and related cerebrovascular diseases.     

Systematic synthesis of four epicatechin series procyanidin trimers and their inhibitory activity on the Maillard reaction and antioxidant activity

A systematic synthesis of four natural epicatechin series procyanidin trimers [[4,8:4",8"]-2,3-cis-3,4-trans: 2",3"-cis-3",4"-trans: 2,3-trans-(-)-epi-catechin-(-)-epicatechin-(+)-catechin, [4,8:4",8"]-2,3-cis-3,4-trans: 2",3"-cis-3",4"-trans: 2,3-cis-tri-(-)-epicatechin: procyanidin C1, [4,8:4",8"]-2,3-cis-3,4-trans: 2",3"-trans-3",4"-trans: 2,3-trans-(-)-epicatechin-(+)-catechin-(+)-catechin: procyanidin C4, and [4,8:4",8"]-2,3-cis-3,4-trans: 2",3"-trans-3",4"-trans: 2,3-cis-(-)-epicatechin-(+)-catechin-(-)-epicatechin] is described. Condensation of (2R,3R,4S)-5,7,3'4'-tetra-O-benzyl-4-(2"-ethoxyethyloxy)flavan derived from (-)-epicatechin as an electrophile with the dimeric nucleophiles in the presence of TMSOTf followed by deprotection yielded trimers. Inhibitory activities on the Maillard reaction and antioxidant activity on lipid peroxide of the synthesized oligomers were also investigated.     

Biosynthesis of (+)-catechin glycosides using recombinant amylosucrase from Deinococcus geothermalis DSM 11300

Amylosucrase (ASase, EC 2.4.1.4) is a glucosyltransferase that hydrolyzes sucrose into glucose and fructose and produces amylose-like glucan polymers from the released glucose. (+)-Catechin is a plant polyphenolic metabolite having skin-whitening and antioxidant activities. In this study, the ASase gene from Deinococcus geothermalis (dgas) was expressed in Escherichia coli, while the recombinant DGAS enzyme was purified using a glutathione S-transferase fusion system. The (+)-catechin glycoside derivatives were synthesized from (+)-catechin using DGAS transglycosylation activity. We confirmed the presence of two major transglycosylation products using TLC. The (+)-catechin transglycosylation products were isolated using silica gel open column chromatography and recycling-HPLC. Two (+)-catechin major transfer products were determined through ¹H and ¹³C NMR to be (+)-catechin-3′-O-α-d-glucopyranoside with a glucose molecule linked to (+)-catechin and (+)-catechin-3′-O-α-D-maltoside with a maltose linked to (+)-catechin. The presence of (+)-catechin maltooligosaccharides in the DGAS reaction was also confirmed via recycling-HPLC and enzymatic analysis. The effects of various reaction conditions (temperature, enzyme concentration, and molar ratio of acceptor and donor) on the yield and type of (+)-catechin glycosides were investigated.     

Tannins from Bendo Eucalyptus

The gallic acid, (+)-catechin and myricetin glucoside have been isolated and indentified from Bendo Eucalyptus, and two kinds of dimeric flavan-3-ol B1 and B3 were isolated as their peracetates and identified by chromatography on TLC and 1H NMR spectroscopic cha- racteristics. It is showed that condensed tannin is a procyanidin with (+)-catechin as terminal units and (–)-epicatechin as extension units by hydrolyzation anthocyanidin reaction, phloroglucinol degradation and polarimetry, UV and IR spectrometry, HPLC, 3C NMR. Linkage is C4–C8. Degree of polymerization is about 4–5.     

(+)-catechin 3-rhamnoside from Erythroxylum novogranatense

A new flavanol glycoside has been isolated from stems of Erythroxylum novogranatense and its structure has been elucidated on the basis of MS and ¹H NMR spectroscopy and hydrolytic studies as (+)-catechin 3-O-α-L-rhamnopyranoside. On a similar basis of chemical and spectroscopic evidence, the presence of ombuin 3-O-rutinoside has been established. Furthermore, the occurrence of procyanidin biflavanoids has been demonstrated by the characterization of B₁ and B₃ as the first representatives of B-type proanthocyanidins in the genus Erythroxylum.     

A furan-2-carbonyl C-glucoside and an alkyl glucoside from the parasitic plant,Dendrophthoe pentandra

A new furan-2-carbonyl C-(6′-O-galloyl)-β-glucopyranoside (scleropentaside F, 1) and a new alkyl glucoside [butane-2,3-diol 2-(6′-O-galloyl)-O-β-glucopyranoside, 2] were isolated from the entire hemi-parasitic plant, Dendrophthoe pentandra growing on Tectona grandis together with ten known compounds including, benzyl-O-β-d-glucopyranoside (3), benzyl-O-α-l-rhamnopyranosyl-(1 → 6)-β-d-glucopyranoside (4), benzyl-O-β-d-apiofuranosyl-(1 → 6)-β-d-glucopyranoside (5), methyl gallate 3-O-β-d-glucopyranoside (6), methyl gallate 3-O-(6′-O-galloyl)-β-d-glucopyranoside (7), (+)-catechin (8), procyanidin B-1 (9) and procyanidin B-3 (10), bridelionoside A (11), and kiwiionoside (12). In addition, compounds 1, 3–9 were isolated from this species growing on the different host, Mangifera indica. The structure elucidations were based on physical data and spectroscopic evidence including 1D and 2D experiments.     

Changes and importance of oligomeric procyanidins during maturation of grape seeds

Flavans and procyanidins from the seeds of different grape varieties were separated and identified using HPLC techniques. The compounds identified were (+)-catechin and (?)-epicatechin, dimeric procyanidins B1, B2, B3 and B4, trimeric procyanidin C2 and gallic acid. During maturation of the grape berries, the flavan-3-ol content fell in the seeds whereas procyanidin levels increased. This suggests an interrelationship between the compounds. There was also evidence of varietal differences in the amounts of phenolic compounds in grape seeds.     

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

L-[¹⁴C]Phenylalanine, fed to cell suspension cultures of Douglas fir, (Pseudotsuga menziesii Franco) was incorporated simultaneously, but at different rates, into (+)-catechin, (−)-epicatechin, and procyanidins 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, contained 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-trans type of (+)-catechin.     

Inhibition of β-Glucosidase (Amygdalae dulces) by (+)-Catechin Oxidation Products and Procyanidin Dimers

The sensitivity and specificity of the inhibition of β-glucosidase (Amygdalae dulces) by (+ )-catechin, an oxidized (+)-catechin solution, three dimeric procyanidins, and five (+)-catechin dimers obtained by enzymatic oxidation were evaluated by using a chromatographic method. All the polyphenols tested presented a significant inhibitory effect. Non-competitive inhibition was observed for the oxidized (+)-catechin solution. Some oxidation products were at least as powerful inhibitors as procyanidins which are known for their tanning effect. Yellow oxidation products were among the strongest inhibitors. No marked role of the number of hydroxyl and o-diphenol groups nor of the nature or position of the interflavanic linkage in the inhibitory effect was apparent.     

A new approach to procyanidins synthesis with potent anti-adipogenic effects

Convenient structure modification of (+)-catechin (1) induced by nonthermal dielectric barrier discharge (DBD) plasma treatment afforded three novel methylene-linked flavan-3-ol oligomers, methylenetetracatechin (2), methylenetricatechin (3), and methylenedicatechin (4), together with two known catechin dimers, bis 8,8′-catechinylmethane (5) and bis 6,8′-catechinylmethane (6). The structures of the three new catechin oligomers 2–4 with methylene bridges were elucidated by detailed 1D- and 2D-NMR analysis, and the absolute configurations were established by the observation of circular dichroism (CD). The novel products 2 and 3 showed significantly enhanced anti-adipogenic capacities against both pancreatic lipase and differentiation of 3T3-L1 preadipocytes compared to the parent (+)-catechin.     

Potential α-glucosidase inhibitors from thermal transformation of (+)-catechin

Thermal transformation of the (+)-catechin (1) with heating processing afforded a new oxidation product, gambiriin D (2), along with catechin [6′–8]-catechin (3), and (+)-epicatechin (4). The structure of a new catechin dimer with C–C linkage was determined on the basis of spectroscopic data interpretation. The catechin dimers 2 and 3 exhibited significantly improved inhibitory activities against α-glucosidase, with IC₅₀ values of 0.16 ± 0.2 and 0.14 ± 0.2 μM, respectively, when compared to parent (+)-catechin. Kinetic analysis showed that the two effective compounds 2 and 3 have noncompetitive modes of action.     

Oxidation of phenolic compounds by the bifunctional catalase–phenol oxidase (CATPO) from Scytalidium thermophilum

The thermophilic fungus Scytalidium thermophilum produces a novel bifunctional catalase with an additional phenol oxidase activity (CATPO); however, its phenol oxidation spectrum is not known. Here, 14 phenolic compounds were selected as substrates, among which (+)-catechin, catechol, caffeic acid, and chlorogenic acid yielded distinct oxidation products examined by reversed-phase HPLC chromatography method. Characterization of the products by LC-ESI/MS and UV–vis spectroscopy suggests the formation of dimers of dehydrocatechin type B (hydrophilic) and type A (hydrophobic), as well as oligomers, namely, a trimer and tetramer from (+)-catechin, the formation of a dimer and oligomer of catechol, a dimer from caffeic acid with a caffeicin-like structure, as well as trimeric and tetrameric derivatives, and a single major product from chlorogenic acid suggested to be a dimer. Based on the results, CATPO oxidizes phenolic compounds ranging from simple phenols to polyphenols but all having an ortho-diphenolic structure in common. The enzyme also appears to have stereoselectivity due to the oxidation of (+)-catechin, but not that of epicatechin. It is suggested that CATPO may contribute to the antioxidant mechanism of the fungus and may be of value for future food and biotechnology applications where such a bifunctional activity would be desirable.     

Study on the inhibitory effects of Korean medicinal plants and their main compounds on the 1,1-diphenyl-2-picrylhydrazyl radical

A 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-generating system was used to evaluate the antioxidant properties of Korean medicinal plants that have been used widely as folk medicines for several disorders, as well as compounds isolated from them. Among the Rosaceae, Rosa rugosa and Rosa davurica showed strong DPPH radical-scavenging activity. The most effective medicinal plant from families other than Rosaceae was Cedrela sinensis, followed in order by Nelumbo nucifera, Eucommia ulmoides, Zanthoxylum piperitum, Cudrania tricuspidata and Houttuynia cordata. These results serve as a good index of the free radical-scavenging activities of Korean medicinal plants. Furthermore, the polyphenols isolated from these plants, procyanidin B-3, (+)-catechin, gallic acid, methyl gallate, quercetin, quercetin-3-O-beta-D-glucoside, quercetin-3-O-beta-galactoside, quercetin-3-O-rutinose and kaempferol, exerted strong DPPH radical-scavenging activity. These results suggest that the Korean medicinal plants and the polyphenols isolated from them that exhibited effective radical-scavenging activity may be promising agents for scavenging free radicals and treating diseases associated with excess free radicals.     

Phenolic constituents from the roots of Rosa laevigata (Rosaceae)

Chemical investigation of the root of Rosa laevigata led to the isolation of sixteen phenolic compounds, including seven flavonoids (1–7), five condensed tannins (8–12), two stilbenes (13 and 14) and two benzoic acid derivatives (15 and 16). Their structures were identified as (+)-catechin (1), (+)-gallocatechin (2), (2R, 3S, 4S)-cis- leucocyanidin (3), (2R, 3S, 4S)-cis-leucofisetinidin (4), (2S, 3R, 4R)-cis- leucofisetinidin (5), dehydrodicatechin A (6), phloridzin (7), procyanidin B3 (8), fisetinidol-(4α, 8)-catechin (9), guibourtinidol- (4α, 8)-catechin (10), ent- isetinidol -(4α, 6)-catechin (11), fisetinidol-(4β, 8)-catechin (12), (Z)-3-methoxy-5-hydroxy- stilbene (13), (Z)-piceid (14), gallic acid (15) and 4-hydroxybenzoic acid- 4-O-β-D-glucopyranoside (16). Among them, compounds 3–7, 9–14, and 16 were isolated from R. laevigata for the first time, and compounds 3–7, 9, 10, 12–14 and 16 were reported for the first time from the genus Rosa. The chemotaxonomic significance of these compounds was summarized.