An electrically conducting crystal composed of an octahedrally ligated porphyrin complex with high-spin iron(iii).

A porphyrin-based octahedrally ligated complex with high-spin iron(iii) was designed, and the resulting electrically conducting crystal TPP[FeIII(tbp)Br2]2 (TPP = tetraphenylphosphonium and tbp = tetrabenzoporphyrin) was synthesised. Although TPP[Fe(tbp)Br2]2 was isostructural to the reported TPP[Fe(Mc)L2]2 systems (Mc = macrocyclic ligands such as phthalocyanine (Pc) or tbp; and L = CN, Cl, or Br), the bond lengths between Fe and ligands in the [Fe(tbp)Br2] unit were evidently longer than those in the other units, because of the different spin states of Fe: high-spin in TPP[Fe(tbp)Br2]2 and low-spin in others. The magnetic anisotropy observed in the low-spin state vanished when the Fe is in the high-spin state. Based on reports for Pc-based systems, the negative magnetoresistance (MR) effect for TPP[Fe(tbp)Br2]2 was expected to be smaller than that for TPP[Fe(tbp)(CN)2]2. However, the former showed a giant negative MR effect similar to or larger than the latter, suggesting that the nature of iron is a crucial factor for the electrical properties of porphyrin-based materials.

A new strategy for inducing dipole moments in charge-transfer complexes: introduction of asymmetry into axially ligated iron phthalocyanines.

Introduction of asymmetry into charge-transfer complexes composed of axially ligated iron phthalocyanines was achieved. In the obtained crystals of TPP[FeIII(Pc)(CN)Cl]2, TPP[FeIII(Pc)(CN)Br]2, and TPP[FeIII(Pc)BrCl]2 (TPP = tetraphenylphosphonium and Pc = phthalocyanine), the axial positions of the iron atoms were occupied by 50/50 ratios of the ligands CN/Cl, CN/Br, and Br/Cl, respectively. The crystal structures of the obtained CT complexes were isostructural to those composed of the symmetric analogues of the type [FeIII(Pc)L2] (L = CN, Cl or Br); the [FeIII(Pc)LL'] units formed regular one-dimensional chains along the c-axis following the symmetry of the P42/n space group. Despite forming similar regular chains to the symmetric systems, the electrical resistivities and activation energies were enhanced in the obtained CT complexes compared to those in symmetric systems, indicating that the charge-ordered states were stabilised by the introduction of asymmetry. More specifically, the dielectric relaxation behaviour of the inhomogeneous disordered TPP[FeIII(Pc)(CN)Cl]2 probably suggests that a dipole moment was induced in this material.

A giant negative magnetoresistance effect in an iron tetrabenzoporphyrin complex.

By measuring the electrical resistivity in TPP[FeIII(tbp)(CN)2]2 (TPP = tetraphenylphosphonium and tbp = tetrabenzoporphyrin) under the application of a static magnetic field, a giant negative magnetoresistance (MR) effect with high anisotropy is observed. More specifically, the MR ratio at 13 K under a field of 9 T perpendicular to the c axis is -70%, whereas the MR ratio under a field parallel to the c axis is -40%. Furthermore, electron spin resonance (ESR) measurements indicate large anisotropy in the principal g-values of d spin (S = 1/2) in the [FeIII(tbp)(CN)2] unit; the g1 value almost perpendicular to the tbp plane and the g2 and g3 values almost parallel to the tbp plane are 3.60, 1.24, and 0.39, respectively. It is revealed that the anisotropy in the MR effect arises from the anisotropy in the d spin, suggesting that the d spins in TPP[FeIII(tbp)(CN)2]2 affect the π-conduction electron via the intramolecular π-d interaction. The anisotropy and magnitude in the giant negative MR effect for TPP[FeIII(tbp)(CN)2]2 are smaller than the corresponding values for the isostructural phthalocyanine (Pc) analogue TPP[FeIII(Pc)(CN)2]2. This is consistent with the fact that the intermolecular antiferromagnetic d-d interaction in TPP[FeIII(tbp)(CN)2]2 (suggested by the Weiss temperature: Θ = -8.0 K) is weaker than that in TPP[FeIII(Pc)(CN)2]2 (Θ = -12.3 K). This indicates that the minor modification in coordination complexes can significantly affect the MR effect via tuning the intermolecular d-d interaction as well as the intermolecular π-π overlap.

Neocimicigenosides A and B, cycloartane glycosides from the rhizomes of Cimicifuga racemosa and their effects on CRF-stimulated ACTH secretion from AtT-20 cells.

Two new cycloartane glycosides, named neocimicigenosides A (1) and B (2), were isolated from the rhizomes of Cimicifuga racemosa. The structures of 1 and 2 were determined on the basis of extensive spectroscopic analysis and enzymatic hydrolysis followed by chromatographic and spectroscopic analyses to be (16S,23R,24S)-24-acetoxy-16,23:16,25-diepoxy-15alpha-hydroxycycloartan-3beta-yl alpha-L-arabinopyranoside (1) and (16S,23R,24S)-24-acetoxy-16,23:16,25-diepoxy-15alpha-hydroxycycloartan-3beta-yl beta-D-xylopyranoside (2), respectively. Neocimicigenosides A and B enhanced CRF-stimulated ACTH secretion from AtT-20 cells.

Analytical separation of tea catechins and food-related polyphenols by high-speed counter-current chromatography.

High-speed counter-current chromatography (HSCCC) using the type-J coil planet centrifuge was applied to compositional analysis of tea catechins and separation of other food-related polyphenols. The HSCCC separation of nine different standard compounds and those from extracts of commercial tea leaves was performed with a two-phase solvent system composed of tert-butyl methyl ether-acetonitrile-0.1% aqueous trifluoroacetic acid (TFA) (2:2:3, v/v/v) by eluting the upper organic phase at a flow rate of 2 ml/min. The main compounds in the extract of non-fermented green tea were found to be monomeric catechins, their galloylated esters and caffeine. In addition to these compounds, oxidized pigments, such as hydrophobic theaflavins (TFs) and polar thearubigins (TRs) were also separated and detected from the extracts of semi-fermented oolong tea and fermented black tea. Furthermore, several food-related polyphenols, such as condensed catechin oligomers (procyanidins), phenolic acids and flavonol glycosides were clearly separated under the same HSCCC condition. These separation profiles of HSCCC provide useful information about the hydrophobic diversity of these bioactive polyphenols present in various types of teas and food products.

Dose-dependent hypocholesterolemic actions of dietary apple polyphenol in rats fed cholesterol.

The dose-dependent hypocholesterolemic and antiatherogenic effects of dietary apple polyphenol (AP) from unripe apple, which contains approximately 85% catechin oligomers (procyanidins), were examined in male Sprague-Dawley rats (4 wk of age) given a purified diet containing 0.5% cholesterol. Dietary AP at 0.5 and 1.0% levels significantly decreased the liver cholesterol level compared with that in the control (AP-free diet-fed) group. Dietary AP also significantly lowered the serum cholesterol level compared with that in the control group. However, the HDL cholesterol level was significantly higher in the 1.0% AP-fed group than in the control group. Accordingly, the ratio of HDL-cholesterol/total cholesterol was significantly higher in the 0.5% AP-fed group and 1.0% AP-fed group than in the control group. Moreover, the atherogenic indices in the 0.5 and 1.0% AP-fed groups were significantly lower than those in the control group. The activity of hepatic cholesterol 7alpha-hydroxylase tended to be increased by dietary AP in a dose-dependent manner. In accord with this observation, dietary AP increased the excretion of acidic steroids in feces. Dietary AP also significantly promoted the fecal excretion of neutral steroids in a dose-dependent manner. These observations suggest that dietary AP at a 0.5 or 1.0% level exerts hypocholesterolemic and antiatherogenic effects through the promotion of cholesterol catabolism and inhibition of intestinal absorption of cholesterol.

Inhibitory effect of polyphenol-enriched apple extracts on mast cell degranulation in vitro targeting the binding between IgE and FcepsilonRI.

Extracts from immature fruit of the apple (Rosaceae, Malus sp.), which contain procyanidins (polymers of catechins) as the major ingredients, are known to inhibit histamine release from mast cells. We analyzed in this study the mechanism for the anti-allergic activity of two polyphenol-enriched apple extracts. These extracts, termed "crude apple polyphenol (CAP)" and "apple condensed tannin (ACT)", reduced the degranulation of mast cells caused by cross-linking of the high-affinity receptor for IgE (FcepsilonRI) with IgE and the antigen in a dose-dependent manner. Furthermore, western blotting revealed that phosphorylation of the intracellular signal-transduction molecules caused by cross-linking of FcepsilonRI was markedly decreased by the addition of CAP or ACT. We then analyzed the effects of CAP and ACT on the binding of the IgE antibody to FcepsilonRI on mast cells, which is the first key step in the allergic reaction mediated by mast cells, and found that this binding was markedly inhibited by both CAP and ACT. These results indicate that the inhibition of binding between FcepsilonRI and IgE by either CAP or ACT was the probable cause of the suppression of mast cell activation. This is the first report demonstrating the molecular mechanism for the anti-allergic effect of procyanidin-enriched extracts from apples.

Inhibitory effects of polyphenols on gastric injury by Helicobacter pylori VacA toxin.

BACKGROUND: Helicobacter pylori induces gastric damage and may be involved in the pathogenesis of gastric cancer. H. pylori-vacuolating cytotoxin, VacA, is one of the important virulence factors, and is responsible for H. pylori-induced gastritis and ulceration. The aim of this study is to assess whether several naturally occurring polyphenols inhibit VacA activities in vitro and in vivo. MATERIALS AND METHODS: Effects of polyphenols on VacA were quantified by the inhibition of: 1, vacuolation; 2, VacA binding to AZ-521 or G401 cells or its receptors; 3, VacA internalization. Effects of hop bract extract (HBT) containing high molecular weight polymerized catechin on VacA in vivo were investigated by quantifying gastric damage after oral administration of toxins to mice. RESULTS: HBT had the strongest inhibitory activity among the polyphenols investigated. HBT inhibited, in a concentration-dependent manner: 1, VacA binding to its receptors, RPTP(alpha) and RPTP(beta); 2, VacA uptake; 3, VacA-induced vacuolation in susceptible cells. In addition, oral administration of HBT with VacA to mice reduced VacA-induced gastric damage at 48 hours. In vitro, VacA formed a complex with HBT. CONCLUSIONS: HBT may suppress the development of inflammation and ulceration caused by H. pylori VacA, suggesting that HBT may be useful as a new type of therapeutic agent for the prevention of gastric ulcer and inflammation caused by VacA.