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C Ring (c + ring)
Selected AbstractsStudies Directed Toward the Synthesis of Terreulactone A: Rapid Construction of the A, B, C Rings.CHEMINFORM, Issue 24 2006Haibo Liu Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Hypochlorite scavenging activity of flavonoidsJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 6 2004Omidreza Firuzi Scavengers of hypochlorite, a highly reactive oxidant produced by activated phagocytes, could have potential therapeutic effects in diseases in which this oxidant plays a pathogenic role. Flavonoids are polyphenolic substances present in food plants and have been extensively studied for their antioxidant properties against various free radicals. Less is known about their reactivity with hypochlorite. In this study, the hypochlorite scavenging activity of flavonoids was investigated using a microplate assay recently developed in our laboratory. This method evaluates the ability of a substance to inhibit the formation of chloramines in human serum albumin upon oxidation by hypochlorite. Thirteen flavonoids were tested. Most of them inhibited human serum albumin oxidation at micro-molar concentrations and appeared more active than Trolox, a water-soluble equivalent of vitamin E. It was observed that the greater the number of hydroxyl substitutions, the greater the scavenging activity. The 3-hydroxy substitution seemed to be particularly important for scavenging activity, whereas the presence of a 2,3-double bond in the C ring did not. Flavonoids were found to be good hypochlorite scavengers in-vitro and further information is provided about the chemical aspects important for scavenging activity. Thus, flavonoids could have beneficial effects in diseases such as atherosclerosis in which hypochlorite plays a pathogenic role. [source] NMR spectroscopic characterization of inclusion complexes comprising cyclodextrins and gallated catechins in aqueous solution: cavity size dependencyMAGNETIC RESONANCE IN CHEMISTRY, Issue 4 2009Takashi Ishizu Abstract The structure of inclusion complexes of ,-cyclodextrin (,-CD), (,)-gallocatechin gallate (GCg), and (,)-epigallocatechin gallate (EGCg) in D2O was investigated using several NMR techniques. GCg formed a 1:1 inclusion complex with ,-CD in which the A and C rings of GCg were inserted deep at the head of the A ring into the ,-CD cavity from the wide secondary hydroxyl group side. In the 1:1 inclusion complex with GCg and ,-CD, the GCg moiety maintained a conformation in which the B and B, rings of GCg took both pseudoequatorial positions with respect to the C ring. The structure of the inclusion complex of GCg and ,-CD obtained from NMR experiments supported well that determined from PM6 semiempirical SCF MO calculations. However, 1H NMR experiments suggested that EGCg did not form any inclusion complex with ,-CD in D2O. The marked difference between GCg and EGCg in inclusion behavior toward ,-CD may be explained in terms of the stabilization energy calculated with the PM6 method. Copyright © 2008 John Wiley & Sons, Ltd. [source] Isolation and structure of I-deoxybaccatin VI from the root of taxus chinensis, rehd. var. maireiCHINESE JOURNAL OF CHEMISTRY, Issue 7 2004Hai-Xia Lin Abstract Deoxybaccatin VI (4,,7,,9,,10,,13,-penta-acetoxy-2a-benzoyloxy-5,,20-epoxytax-11-ene) was isolated from the roots of Taxus chinensis, Rehd. var mairei. The structural assignments of the compound were based on their spectral data, including 2D NMR experiments and chemical correlation. The X-ray crystallographic analysis of 1-deoxybaccatin VI provided unambiguous characterization for the structures. In the structure, the six-membered A ring exhibits boat conformation, the eight-membered B ring adopts boat-chair conformation, and the six-membered C ring exhibits a sofa conformation. [source] A comparison of crystallographic and NMR data for thieno[2,3- b:4,5- b,]dipyridine and its monohydroperchlorate saltJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 4 2000Leroy H. Klemm X-ray crystallographic studies of thieno[2,3- b:4,5- b,]dipyridine (1) and its monohydroperchlorate salt (1a) show that 1 is protonated at N1 in ring A and not at N6 in ring C. In each compound individual rings are planar, but there is a small dihedral angle-of-twist between the A and C rings. On going from 1 to 1a the largest changes in bond angles and bond lengths occur in ring A. 1H and l3C nmr spectra of 1 plus the 13C nmr spectrum of 1a are reported. [source] NMR spectroscopic characterization of inclusion complexes comprising cyclodextrins and gallated catechins in aqueous solution: cavity size dependencyMAGNETIC RESONANCE IN CHEMISTRY, Issue 4 2009Takashi Ishizu Abstract The structure of inclusion complexes of ,-cyclodextrin (,-CD), (,)-gallocatechin gallate (GCg), and (,)-epigallocatechin gallate (EGCg) in D2O was investigated using several NMR techniques. GCg formed a 1:1 inclusion complex with ,-CD in which the A and C rings of GCg were inserted deep at the head of the A ring into the ,-CD cavity from the wide secondary hydroxyl group side. In the 1:1 inclusion complex with GCg and ,-CD, the GCg moiety maintained a conformation in which the B and B, rings of GCg took both pseudoequatorial positions with respect to the C ring. The structure of the inclusion complex of GCg and ,-CD obtained from NMR experiments supported well that determined from PM6 semiempirical SCF MO calculations. However, 1H NMR experiments suggested that EGCg did not form any inclusion complex with ,-CD in D2O. The marked difference between GCg and EGCg in inclusion behavior toward ,-CD may be explained in terms of the stabilization energy calculated with the PM6 method. Copyright © 2008 John Wiley & Sons, Ltd. [source] Rat lens aldose reductase inhibitory constituents of Nelumbo nucifera stamensPHYTOTHERAPY RESEARCH, Issue 10 2006Soon Sung Lim Abstract Aldose reductase, the principal enzyme of the polyol pathway, has been shown to play an important role in the complications associated with diabetes. A methanol extract of the stamens of Nelumbo nucifera Gaertn. was shown to exert an inhibitory effect on rat lens aldose reductase (RLAR), and thus was fractionated using several organic solvents, including dichloromethane, ethyl acetate and n -butanol. The ethyl acetate-soluble fraction, which manifested potent RLAR-inhibitory properties, was then purified further via repeated measures of silica gel and Sephadex LH-20 column chromatography. Thirteen flavonoids: kaempferol (1) and seven of its glycosides (2,9), myricetin 3,,5,-dimethylether 3- O - , - d -glucopyranoside (10), quercetin 3- O - , - d -glucopyranoside (11) and two isorhamnetin glycosides (12, 13) were isolated from N. nucifera, as well as four non-flavonoid compounds: adenine (14), myo -inositol (15), arbutin (16) and , -sitosterol glucopyranoside (17). These compounds were all assessed with regard to their RLAR-inhibitory properties. Among the isolated flavonoids, those harboring 3- O - , - l -rhamnopyranosyl-(1,6)- , - d -glucopyranoside groups in their C rings, including kaempferol 3- O - , - l -rhamnopyranosyl-(1,6)- , - d -glucopyranoside (5) and isorhamnetin 3- O - , - l -rhamnopyranosyl-(1,6)- , - d -glucopyranoside (13), were determined to exhibit the highest degree of rat lens aldose reductase inhibitory activity in vitro, evidencing IC50 values (concentration required for a 50% inhibition of enzyme activity) of 5.6 and 9.0 µm, respectively. Copyright © 2006 John Wiley & Sons, Ltd. [source] Structural evidence for a constant c11 ring stoichiometry in the sodium F-ATP synthaseFEBS JOURNAL, Issue 21 2005Thomas Meier The Na+ -dependent F-ATP synthases of Ilyobacter tartaricus and Propionigenium modestum contain membrane-embedded ring-shaped c subunit assemblies with a stoichiometry of 11. Subunit c from either organism was overexpressed in Escherichia coli using a plasmid containing the corresponding gene, extracted from the membrane using detergent and then purified. Subsequent analyses by SDS/PAGE revealed that only a minor portion of the c subunits had assembled into stable rings, while the majority migrated as monomers. The population of rings consisted mainly of c11, but more slowly migrating assemblies were also found, which might reflect other c ring stoichiometries. We show that they consisted of higher aggregates of homogeneous c11 rings and/or assemblies of c11 rings and single c monomers. Atomic force microscopy topographs of c rings reconstituted into lipid bilayers showed that the c ring assemblies had identical diameters and that stoichiometries throughout all rings resolved at high resolution. This finding did not depend on whether the rings were assembled into crystalline or densely packed assemblies. Most of these rings represented completely assembled undecameric complexes. Occasionally, rings lacking a few subunits or hosting additional subunits in their cavity were observed. The latter rings may represent the aggregates between c11 and c1, as observed by SDS/PAGE. Our results are congruent with a stable c11 ring stoichiometry that seems to not be influenced by the expression level of subunit c in the bacteria. [source] | |||||||||||||