Polyphenols from peanut skins and their free radical-scavenging effects

Separation of the water-soluble fraction of peanut skins led to the isolation of five proanthocyanidins. Based on the spectroscopic investigation and partial acid catalyzed degradation, their structures were determined to be epicatechin-(2beta-->O -->7, 4beta -->6)-[epicatechin-(4beta-->8)]-catechin (1), epicatechin-(2beta-->O -->7, 4beta-->8) epicatechin-(4beta-->8)-catechin-(4alpha-->8)-epicatechin (2), and procyanidins B2 (3), B3 (4) and B4 (5). The absolute configuration of the new compounds was determined from their circular dichroism curves and the (1)H NMR spectra of analysis of flavan-3-ols formed by thiolytic degradation of 1 and 2 in the presence of a chiral dirhodium complex (dirhodium tetra-(R)-(trifluoromethyl) phenyl acetate).     

(4-->6)-Coupled proteracacinidins and promelacacinidins from Acacia galpinii and Acacia caffra

The series of naturally occurring proanthocyanidins with 7,8-dihydroxylated A-rings is extended by identification of the proteracacinidins epioritin-(4beta-->6)-oritin-4alpha-ol, epioritin-(4beta-->6)-ent-oritin-4alpha-ol, ent-oritin-(4beta-->6)-epioritin-4alpha-ol, ent-oritin-(4beta-->6)-oritin-4alpha-ol, ent-oritin-(4alpha-->6)-epioritin-4alpha-ol, ent-oritin-(4alpha-->6)-oritin-4alpha-ol, ent-oritin-(4alpha-->6)-epioritin-4beta-ol, the 'mixed' pro-teracacinidins/-melacacinidins epioritin-(4beta-->6)-epimesquitol-4alpha-ol, epioritin-(4beta-->6)-epimesquitol-4beta-ol and epimesquitol-(4beta-->6)- epioritin-4alpha-ol, and the promelacacinidin epimesquitol-(4beta-->6)-epimesquitol-4beta-ol.     

Trimeric proteracacinidins and a (6-->6)-bis-leucoteracacinidin from Acacia galpinii and Acacia caffra

The rare series of trimeric proteracacinidins is extended by identification of the first analogs with exclusive C-C interflavanyl bonds, i.e. epioritin-(4beta-->6)-oritin-(4alpha-->6)-epioritin-4alpha-ol,oritin-(4beta-->6)-oritin-(4alpha-->6)-epioritin-4alpha-ol, and epioritin-(4beta-->6)-epioritin-(4beta-->6)-epioritin-4alpha-ol. These compounds are accompanied by the bis-leucoteracacinidin, epioritin-4alpha-ol-(6-->6)-epioritin-4beta-ol, the first naturally occurring bis-flavan-3,4-diol.     

Structure and stereochemistry of dimeric proteracacinidins possessing the rare C-4(C) --> C-5(D) interflavanyl linkage

The rare series of (4-->5)-linked proteracacinidins is extended by identification of oritin-(4alpha-->5)-epioritin-4beta-ol, ent-epioritin-(4alpha-->5)-epioritin-4beta-ol, epioritin-(4beta-->5)-epioritin-4alpha-ol and ent-oritin-(4beta-->5)-epioritin-4alpha-ol from the heartwoods of Acacia galpinii and Acacia caffra.     

Structure and stereochemistry of triflavanoids containing both ether and carbon-carbon interflavanyl bonds.

The first triflavanoids with both C-C and C-O-C interflavanyl bonds, epioritin-(4beta-->6)-epioritin-(4alpha-->4)-epioritin-4beta-ol, epioritin-(4beta-->3)-epioritin-(4beta-->6)-epioritin-4beta-ol and epioritin-(4beta-->3)-epioritin-(4beta-->6)-epimesquitol-4alpha-ol, were identified in the heartwood of Acacia caffra. The ethereal interflavanyl bond is readily susceptible to reductive cleavage with sodium cyanoborohydride in trifluoroacetic acid/dichloromethane which hence permits the unequivocal assignment of the absolute configuration of constituent flavanyl units.     

Analyses of polyphenols in cacao liquor, cocoa, and chocolate by normal-phase and reversed-phase HPLC

The antioxidant polyphenols in cacao liquor, a major ingredient of chocolate and cocoa, have been characterized as flavan-3-ols and proanthocyanidin oligomers. In this study, various cacao products were analyzed by normal-phase HPLC, and the profiles and quantities of the polyphenols present, grouped by molecular size (monomers to approximately oligomers), were compared. Individual cacao polyphenols, flavan-3-ols (catechin and epicatechin), and dimeric (procyanidin B2), trimeric (procyanidin C1), and tetrameric (cinnamtannin A2) proanthocyanidins, and galactopyranosyl-ent-(-)-epicatechin (2alpha-->7, 4alpha-->8)-(-)-epicatechin (Gal-EC-EC), were analyzed by reversed-phase HPLC and/or HPLC/MS. The profile of monomers (catechins) and proanthocyanidin in dark chocolate was similar to that of cacao liquor, while the ratio of flavan-3-ols to the total amount of monomeric and oligomeric polyphenols in the case of pure cocoa powder was higher than that in the case of cacao liquor or chocolate.     

Evaluation of the antigenotoxic potential of monomeric and dimeric flavanols, and black tea polyphenols against heterocyclic amine-induced DNA damage in human lymphocytes using the Comet assay

The polyphenolic dimers, epicatechin-4beta-8-catechin (B1), epicatechin-4beta-8-epicatechin (B2), catechin-4beta-8-catechin (B3), catechin-4beta-8-epicatechin (B4), and the gallate ester epicatechin-4beta-8-epicatechin gallate (B'2G) were isolated from grape seeds, and theaflavins and theafulvins from black tea brews. The ability of these naturally-occurring polyphenols to afford protection against the genotoxicity of the heterocyclic amine 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) was compared with that of the monomeric tea flavanols, (+)-catechin (C), (-)-epicatechin (EC), (-)-epicatechin gallate (ECG), (-)-epigallocatechin (EGC) and (-)-epigallocatechin gallate (EGCG). Genotoxic activity was evaluated in human peripheral lymphocytes using the Comet assay. At the concentration range of 1-100 microM, neither the monomeric nor the dimeric flavanols prevented the lymphocyte DNA damage induced by Trp-P-2. In contrast, both of the black tea polyphenols, theafulvins and theaflavins, at a dose range of 0.1-0.5 mg/ml, prevented, in a concentration-dependent manner, the DNA damage elicited by Trp-P-2. Finally, neither the monomeric and dimeric polyphenols (100 microM) nor the theafulvins and theaflavins (0.5mg/ml) caused any DNA damage in the human lymphocytes. These studies illustrate that black tea theafulvins and theaflavins, if absorbed intact, may contribute to the anticarcinogenic potential associated with black tea intake.     

A-type proanthocyanidin antioxidant from Dioclea lasiophylla

The A-type proanthocyanidin, epigallocatechin-(2beta-->7,4beta-->8)-epicatechin, together with the known epicatechin, luteolin 3'beta-D-glucopyranoside, chrysoeriol 7beta-D-glucopyranoside and 2-methylpentan-2,4-diol, were isolated from leaves of Dioclea lasiophilla. The structures were established on the basis of their spectral data. Antioxidant activities of isolates were measured using the autooxidation of beta-carotene in a linolenic acid suspension method.     

Effect of tea catechins on cellular lipid peroxidation and cytotoxicity in HepG2 cells

Tea catechins inhibited TBARS accumulation in HepG2 cells, the order of effectiveness being (-)-epigallocatechin gallate (EGCG) > (-)-epigallocatechin (EGC) > or = (-)-epicatechin gallate (ECG) > (-)-epicatechin (EC). EGCG and EGC protected the depletion of alpha-tocopherol in the cells, and the glutathione content was enhanced by all four catechins. Moreover, all four catechins suppressed the formation of glutathione disulfide and the activation of glutathione peroxidase induced by tert-butylated hydroperoxide.     

Deodorizing effects of tea catechins on amines and ammonia

Deodorizing effects of tea catechins on amines were examined under alkaline conditions to eliminate the neutralization reaction. They showed deodorizing activity on ethylamine, but none on dimethylamine or trimethylamine. Deodorizing activity on ethylamine was found to be in the order of (-)-epigallocatechin gallate > gallic acid > (-)-epigallocatechin (EGC) > (-)-epicatechin gallate > ethyl gallate > (+)-catechin = (-)-epicatechin. Further, reaction products of EGC with methylamine, ethylamine, and ammonia were detected by HPLC, indicating that a deodorizing reaction other than neutralization occurs. From structural analysis of the reaction product with the methylamine isolated as a peracetylated derivative, the product was presumed to be methylamine substituted EGC, in which the hydroxyl group of EGC at the 4' position is replaced by the methylamino group. The same replacement reaction took place in the case of ethylamine and ammonia.     

Methylation of tea catechins by rat liver homogenates

Methylation of (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECg), and (-)-epigallocatechin gallate (EGCg) was carried out with a rat liver homogenate and S-adenosyl-L-methionine. A structural analysis of the reaction products by MS and NMR showed that 4'-O-methyl EGC, 4"-O-methyl ECg, and 4"-O-methyl EGCg had been formed from EGC, ECg, and EGCg, respectively. These results suggest that methylation may be one of the metabolic pathways to the catechins.     

Antidepressant-like effect of Cecropia glazioui Sneth and its constituents – In vivo and in vitro characterization of the underlying mechanism

The present study aimed to characterize the antidepressant-like effect of a standardized aqueous extract (AE) of Cecropia glazioui Sneth and its purified fractions on in vivo (forced swimming test), ex vivo (hippocampal monoamines levels) and in vitro (serotonin, noradrenaline and dopamine uptake) tests, searching for the active principles and the underlying mechanisms of action. Treatment with AE, or with its butanolic fraction (BuF), the latter rich in catechins, procyanidins and flavonoids, reduced the immobility of rats in the forced swimming test indicating an antidepressant-like effect. Biochemical analysis of the hippocampal neurotransmitters in BuF-treated rats showed significant increase in monoamines levels. BuF and six of its purified constituents inhibited the uptake of [(3)H]-serotonin, [(3)H]-dopamine and [(3)H]-noradrenaline by synaptosomes of different brain regions. Catechin, catechin (4alpha-->8) ent-catechin (Procyanidin B3 isomer) and epicatechin (4beta-->8) epicatechin (Procyanidin B2) were the most active compounds. Comparatively, the uptake of [(3)H]-noradrenaline was the most affected. These results show that the antidepressant-like effect promoted by C. glazioui extract is most likely due to the blockade of the monoamines uptake in the CNS.     

Molecular characterization of a first human 3(alpha-->beta)-hydroxysteroid epimerase

In this report, we describe the isolation and characterization of a cDNA encoding an enzyme that exhibits catalytic characteristics of a 3(alpha-->beta)-hydroxysteroid epimerase (3(alpha-->beta)-HSE). The enzyme overexpressed in human 293 embryonic kidney cells transforms androsterone into epi-androsterone in two steps: the oxidation of androsterone to 5 alpha-androstane-3,17-dione, followed by the reduction of the latter to epi-androsterone. The reverse reaction, 3(beta-->alpha)-hydroxysteroid epimeration, is approximately 10-fold weaker. These results are confirmed by V(max)/K(m) determination, which shows that the enzyme catalyzes the oxidation of androsterone to 5 alpha-androstane-3,17-dione and the reduction of 5 alpha-androstane-3,17-dione to epi-androsterone more efficiently than the reverse reactions. The selective catalysis of the reaction following the 3(alpha-->beta) direction is also observed in intact transfected cells in culture, which better reflect physiological conditions. In vitro assays reveal that the recombinant enzyme prefers NAD(+) and NADH as cofactors and could recognize both C-19 and C-21 3 alpha-hydroxysteroids as substrates. DNA sequence analysis predicts a protein of 317 amino acids. Tissue distribution analysis using RT-PCR reveals that the mRNA of the enzyme is expressed in various tissues, including liver, brain, prostate, adrenal, and uterus, with the most abundant expression in the liver. Because active hydroxysteroids generally exert their effect in a stereo-specific manner, 3(alpha-->beta)-HSE could thus potentially play an important role in regulating the biological activities of various steroids.     

Browning Reaction between Phospholipids and Acetaldehyde

Tea catechins have strong bitterness and influence the taste of tea. Among the 25 human bitter-taste receptors (TAS2Rs), we found that hTAS2R14 responded to catechins, in addition to hTAS2R39, a known catechin receptor. Although hTAS2R14 responded to (?)-epicatechin gallate and (?)-epigallocatechin gallate, it did not respond to (?)-epicatechin and (?)-epigallocatechin.     

Crystal structure of Trematomus newnesi haemoglobin re-opens the root effect question

As new structural data have become available, somewhat contrasting explanations of the Root effect in fish haemoglobins (Hb) have been provided. Hb 1 of the Antarctic fish Trematomus newnesi has a nearly pH-independent oxygen affinity, in spite of 95 % sequence identity with Hb 1 of Trematomus (previously named Pagothenia) bernacchii that has a strong Root effect. Here, the 2.2 A R-state structure of Trematomus newnesi Hb 1 is presented. The structure is similar to that of Root effect fish Hbs from Spot and T. bernacchii, suggesting that the differences in the pH dependence cannot be related to the modulation of the R-state. In comparison to T. bernacchii Hb 1, the role of the three mutations Thr41 (C6)alpha-->Ile, Ala97 (G3)alpha-->Ser and His41 (C7)beta-->Tyr at the alpha1beta2-interface is discussed.     

Inhibitory effect of tea polyphenols on histamine and leukotriene B4 release from rat peritoneal exudate cells

Summary The effect of tea polyphenols on the release of chemical mediators, histamine and leukotriene B₄ (LTB₄), from rat peritoneal exudate cells (PEC) was studied. Among polyphenols, (−)-epigallocatechin gallate (EGCG) most strongly inhibited the histamine release from the cells stimulated with a calcium ionophore, A23187 or compound 48/80. Though (+)-catechin (C) and (−)-epicatechin (EC) had no effect, (−)-epigallocatechin (EGC) and (−)-epicatechin gallate (ECG) moderately inhibited the histamine release. Similarly, EGCG, ECG, and EGC inhibited LTB₄ release from PEC, whereas C and EC were not effective. The magnitude of the inhibitory effect on the release of these mediators of tea polyphenols was in the order of EGCG>ECG>EGC. These results indicated an important role of the triphenol structure in the inhibitory activity. Therefore, the possible antiallergic effect of tea polyphenols can be expected.     

Radical scavenging activity of tea catechins and their related compounds

(-)-Epigallocatechin gallate was found to be the most effective scavenger among tea catechins for the superoxide anion, hydroxyl radical, and 1,1-diphenyl-3-picrylhydrazyl radical. Examination of the scavenging effects of tea catechins and their glucosides on superoxide anion showed that the presence of at least an ortho-dihydroxyl group in the B ring and a galloyl moiety at the 3 position was important in maintaining the effectiveness of the radical scavenging ability. Stoichiometric factors of tea catechins were estimated to be 2 for (+)-catechin and (-)-epicatechin, 5 for (-)-epigallocatechin, 7 for (-)-epicatechin gallate, and 10 for (-)-epigallocatechin gallate.     

Mechanism of Catechin Chemiluminescence in the Presence of Active Oxygen

The photon emission (chemiluminescence; CL) of catechin in the presence of active oxygen species (hydrogen peroxide, hydroxyl radical tert-butyl hydroperoxide and tert-butyl oxyl radical) and acetaldehyde was confirmed to occur non-enzymatically at room temperature in aqueous neutral conditions. The CL intensity [P] in the presence of active oxygen species (X), catalytic species (Y) and receptors (Z) is predicted by [P] = k [X] [Y] [Z]. The calculated photon constants (k) of 8 catechins and gallic acid were 8.23 × 10⁶ M⁻² s⁻¹ counts ((−)-epigallocatechin), 2.78 × 10⁶ ((−)-epigallocatechin gallate), 4.66 × 10⁵ ((−)-gallocatechin gallate), 4.36 × 10⁵ ((−)-gallocatechin), 2.70 × 10⁵ ((−)-epicatechin), 6.44 × 10⁴ ((−)-catechin), 5.85 × 10⁴ ((−)-epicatechin gallate), 4.78 × 10⁴ (gallic acid) and 3.54 × 10⁴ ((−)-catechin gallate), respectively. The system of active oxygen species, catalytic species and receptors is proposed to be a scavenging mechanism for active oxygen species. In the presence of acetaldehyde, (−)-epigallocatechin (maximum k value among catechins tested) reacted with tert-BuOOH to form tert-BuOH as determined by HPLC analysis.     

Stereospecificity in membrane effects of catechins

Green tea catechins consisting of catechin stereoisomers and their derivatives have been suggested to show biological activities through the interactions with cellular membranes. Their effects on membrane fluidity were comparatively studied by measuring fluorescence polarization of liposomal membranes prepared with phospholipids and cholesterol. All catechin stereoisomers reduced membrane fluidity by acting on the hydrophilic and hydrophobic regions of membrane bilayers at 20-500 microM. Both epicatechins in a cis form were more effective for reducing membrane fluidity than both catechins in a trans form. (-)-Epicatechin, (+)-epicatechin, (-)-catechin and (+)-catechin reduced membrane fluidity in increasing order of intensity. Such difference between optical isomers was increased by chiral cholesterol added to membrane lipids. In reversed-phase chromatographic evaluation, (-)-epicatechin and (+)-epicatechin were more hydrophobic than (-)-catechin and (+)-catechin, although hydrophobicity was not distinguishable between optical isomers. Stereospecificity in the membrane effects of catechin stereoisomers may be induced by the different hydrophobicity of geometrical isomers and the chirality of membrane lipid components. At lower concentrations (5-100 microM), (-)-epigallocatechin gallate and (-)-epicatechin gallate reduced membrane fluidity more significantly than (-)-epicatechin, suggesting that the intensive membrane effect contributes to the potent medicinal utility of (-)-epigallocatechin gallate.