Search Results
Results 451 - 500 of 1703
< 5 6 7 8 9 10 11 12 13 14 15 >
Meng Guoyu - - 2003
Many bacteria and about 40,000 plant species form primary carbohydrate reserves based on fructan; these polymers of beta-D-fructofuranose are thought to confer tolerance to drought and frost in plants. Microbial fructan, the beta(2,6)-linked levan, is synthesized directly from sucrose by levansucrase, which is able to catalyze both sucrose hydrolysis and ...
Ferraretto Anita - - 2003
Casein phosphopeptides beta-CN(1-25)4P and alpha(s1)-CN(59-79)5P, from beta- and alpha(s1)-casein, respectively, both carrying the characteristic 'acidic motif' Ser(P)-Ser(P)-Ser(P)-Glu-Glu, were chemically synthesized and administered to HT-29 cells differentiated in culture, which are a used model of intestinal epithelium for absorption studies. Both casein phosphopeptides caused an increase of [Ca(2+)](i) due to influx ...
Braca Alessandra - - 2003
Six new pyrrolizidine alkaloids, a new carboxylic acid, a new phenolic and a new oleanane glycoside, together with the known compounds 7,7'-bis-(4-hydroxy-3,5-dimethoxyphenyl)-8,8'-dihydroxymethyltetrahydrofuran 4'-O-beta-D-glucopyranoside, rosmarinic acid, caffeic acid, tormentic acid 28-O-beta- D-glucopyranoside, euscaphic acid 28-O-beta-D-glucopyranoside, euscaphic acid, and allantoin were isolated from Anchusa strigosa roots. Their structures were established by high ...
Caliceti Paolo - - 2003
beta-Cyclodextrin-poly(ethylene glycol)-folic acid conjugate (CD-PEG-FA) was synthesized according to a two-step procedure: (1). synthesis of CD-PEG-NH(2) by reaction of monotosyl-activated beta-cyclodextrin with excess of 700 Da diamino-PEG; (2). synthesis of CD-PEG-FA by reaction of CD-PEG-NH(2) with succinimidyl ester-activated folic acid. The CD-PEG-NH(2) intermediate was purified by precipitation in acetone, and ...
Sasaki Kenji - - 2003
6-Sulfo-D-GlcNAc with a molecular geometry close to that of N-acetylneuraminic acid (Neu5Ac) was hypothesized to serve as a simple Neu5Ac mimic possessing high potential in biochemical and medicinal applications. The hypothesis was evidenced with a neuraminidase inhibition assay using p-nitrophenyl (pNP) 3-, 4-, and 6-sulfo-beta-D-GlcNAc (4, 5 and 2a) and ...
McNally David J - - 2003
Extraction of cucumber leaf tissue expressing induced resistance against powdery mildew fungi revealed the presence of two new major C-glycosyl flavonoid products: vitexin-6-(4-hydroxy-1-ethylbenzene) (cucumerin A, 1) and isovitexin-8-(4-hydroxy-1-ethylbenzene) (cucumerin B, 2). In addition, the known C-glycosyl flavonoids apigenin-8-C-beta-D-glucopyranoside (vitexin, 3), apigenin-6-C-beta-D-glucopyranoside (isovitexin, 4), luteolin-8-C-beta-D-glucopyranoside (orientin, 5), and luteolin-6-C-beta-D-glucopyranoside (isoorientin, 6), ...
Zhao Jing - - 2003
Two pairs of new geometrically isomeric triterpenoid saponins were isolated from the seeds of Aesculus chinensis and characterized as 28-acetyl-21-tigloylprotoaescigenin 3-O-[beta-D-xylopyranosyl (1 --> 2)] [beta-D-glucopyranosyl (1 --> 4)] [beta-D-glucopyranosiduronic acid (isoescin IIa, 1) and 28-acetyl-21-angeloylprotoaescigenin 3-O-[-beta-D-xylopyranosyl (1 --> 2)] [beta-D-glucopyranosyl (1 --> 4)] beta-D-glucopyranosiduronic acid (isoescin IIb, 2); 28-acetyl-21-tigloylbarringtogenol C ...
Taskova Rilka - - 2003
Two flavonoid aglycons, eight flavonoid glycosides, chlorogenic acid and syringin were isolated from aerial parts of Carthamus lanatus. Isorhamnetin 3-O-beta-D-glucoside and chlorogenic acid were found for the first time in the genus Carthamus and respectively, quercimeritrin, astragalin, kaempferol 3-O-beta-D-sophoroside and syringin in the species. The ethyl acetate fraction of the ...
Langenhan Joseph M - - 2003
We report the synthesis of syn-alpha,beta-dialkyl beta-amino acid derivatives suitably protected for solid-phase synthesis that give rise to residues containing positively charged lysine-like side chains. These amino acids, as well as syn-alpha,beta-dialkyl beta-amino acids that contain diverse hydrophobic side chains, are prepared in good de and ee. The key step ...
Zheng Qunxiong - - 2003
Four eudesmane glucosides, alatosides A-D (1-4), and one megastigmane glucoside, alatoside E (5), were isolated from the BuOH fraction of Laggera alata along with six known compounds. Structures of the new compounds were elucidated by a combination of chemical and spectroscopic methods. Alatosides A-E were characterized as: 1alpha-O-(beta-D-glucopyranosyloxyl)-7-epi-eudesma-11-en-2beta,4alpha-diol (1), 2beta-O-(beta-D-glucopyranosyloxyl)-eudesma-4alpha-hydroxyl-11(13)-en-12-oic-acid ...
Koul Summon - - 2003
Three new triterpenoids, designated as acinospesigenin-A (1), -B (2), and -C (3), isolated from the berries of Phytolacca acinosa, have been characterized as 3 beta-acetoxy-11 alpha,23-dihydroxytaraxer-14-en-28-oic acid, olean-12-en-23-al-2 beta,3 beta-dihydroxy-30-methoxycarbonyl-28-oic acid and olean-12-en-23-al-2 beta,3 beta,11 alpha-trihydroxy-30-methoxycarbonyl-28-oic acid, respectively. The compounds have shown antiedemic activity (LD(50) 10-15 mg/kg mass) in albino ...
Zerbinati Orfeo - - 2003
Five noncommercial and four commercially available cyclodextrin (CD) derivatives were tested as chiral auxiliaries for the capillary electrophoretic (CE) resolution of racemic 1,1'-bi-(2-naphthol) (BN), 1,1'-binaphthyl-2,2'-diyl hydrogenphosphate (BNHP), and 1,1'-binaphthyl-2,2'-diamine (BNA) at pH 4.0, 6.5, and 8.6. The noncommercial CDs were ethyloxycarbonyl-gamma-CD (ethylcarbonate-gamma-CD), dimethylamino ethyloxycarbonyl-beta-CD, a mercaptosuccinic acid derivative of beta-CD, ...
González-Quevedo A - - 2003
A chronic methanol (MeOH) intoxication scheme (2 g/kg/day ip for 2 weeks) was carried out in Sprague-Dawley rats, previously depleted of folates with methotrexate (MTX). beta-Alanine (beta-Ala), 5%, was also administered to some animals in the drinking water. Amino acids were determined in plasma, retina, optic nerve, hippocampus and posterior ...
Hafez Ahmed M - - 2003
A catalytic asymmetric procedure for the preparation of beta-amino acids (specifically beta-substituted aspartic acid derivatives) is reported. The cinchona alkaloid catalyst benzoylquinine (BQ) mediates up to five distinct steps of a reaction pathway, all in one reaction vessel. The products of this reaction, highly optically enriched beta-substituted aspartic acid derivatives, ...
Luisi Renzo - - 2003
[reaction: see text] The stereoselective synthesis of novel alpha-epoxy-beta-amino acids is described by a route that combines the chemistry of oxazolinyloxiranyllithiums with that of nitrones. The intermediate trioxadiazadispiro[2.0.4.3]undecanes 4 have been isolated and converted by hydrolysis into epoxy-5-isoxazolidinones 5 which can be transformed into the alpha-epoxy-beta-amino acids 8 by N-O ...
De Keukeleire Jelle - - 2003
Important secondary metabolites, present in hops (Humulus lupulus L.), include alpha-acids and beta-acids, which are essential for the brewing of beer, as well as the prenylated chalcones, desmethylxanthohumol, and xanthohumol, which exhibit interesting bioactive properties. Their formation and accumulation in five selected hop varieties, Wye Challenger, Wye Target, Golding, Admiral, ...
Lynch Christopher L - - 2003
[reaction: see text] A novel approach to alpha,alpha-disubstituted-beta-amino acids (beta(2,2)-amino acids) was employed in the synthesis of a series of 3-(pyrrolidin-1-yl)propionic acids possessing high affinity for the CCR5 receptor and potent anti-HIV activity. The rat pharmacokinetics for these new analogues featured higher bioavailabilities and lower rates of clearance as compared ...
André C - - 2003
The retention mechanism for a series of D,L-dansyl amino acids in high-performance liquid chromatography is investigated using a teicoplanin stationary phase and hydroxypropyl-beta-cyclodextrin (HP-beta-CD) as the mobile phase additive (0-16mM). A theoretical treatment is developed to determine the HP-beta-CD influence on the equilibrium between the teicoplanin phase and the aqueous ...
Plhácková K - - 2003
A bacterial strain producing a beta-lactam antibiotic acylase, able to hydrolyze ampicillin to 6-aminopenicillanic acid more efficiently than penicillin G, was isolated from soil and characterized. The isolate was identified as Achromobacter sp. using the phenotypic characteristics, composition of cellular fatty acids and 16S rRNA gene sequence. The enzyme synthesis ...
Okuyama Ryo - - 2003
Prolonged exposure to free fatty acids induces beta-cell cytotoxicity. We investigated whether this fatty-acid-induced cytotoxicity is affected by high glucose levels. In clonal beta-cell HIT-T15, palmitate-induced cytotoxicity was potentiated depending on elevated glucose concentrations due to increased apoptosis without cytotoxic effects of high glucose per se. This palmitate cytotoxicity was ...
Choudhury Mukherjee Indrani - - 2003
The trisaccharide, 3-aminopropyl 5-acetamido-3,5-dideoxy-D-glycero-alpha-D-galacto-2-nonulopyranosylonic acid-(2-->3)-beta-D-galactopyranosyl-(1-->4)-2-acetamido-2-deoxy-beta-D-glucopyranoside has been synthesized chemoenzymatically for the first time. First, the acceptor, 3-aminopropyl beta-D-galactopyranosyl-(1-->4)-2-acetamido-2-deoxy-beta-D-glucopyranoside was synthesized in a conventional chemical manner, and then it was coupled with CMP-sialic acid using alpha-(2-->3)-(N)-sialyltransferase to afford the desired trisaccharide by an enzymatically stereocontrolled manner.
Sharma Anil K - - 2003
[reaction: see text] A variety of beta-amino-gamma-keto acids were prepared in four steps from commercially available l-homoserine. The reaction sequence is highlighted by a Ni-catalyzed Grignard addition to a N-protected derivative of l-homoserine. One of the beta-amino-gamma-keto acids was then used to create a beta-peptide trimer composed solely of beta-amino-gamma-keto ...
Minter Aaron R - - 2003
We have demonstrated that the high yields and selectivities of 1,3-dipolar cycloadditions can be translated into facile stereoselective syntheses of a diverse array of beta-amino acids, key components of bioactive natural products, beta-lactams, and peptidomimetics. Simply by selecting different combinations of three readily available starting materials (an oxime, a chiral ...
Melek F R - - 2003
Nine triterpenoid saponins were isolated from the leaves and stems of Schefflera arboricola. The saponins were characterised, on the basis of chemical and spectral evidence, as 3-O-[alpha-L-rhamnopyranosyl-(1-->4)-beta-D-glucuronopyranosyl] oleanolic acid, 3-O-[alpha-L-rhamnopyranosyl-(1-->4)-beta-D-glucuronopyranosyl] echinocystic acid, 3-O-[beta-D-apiofuranosyl-(1-->4)-beta-D-glucuronopyranosyl] oleanolic acid 28-O-beta-D-glucopyranosyl ester, 3-O-alpha-L-ramnopyranosyl-(1-->4)-[alpha-L-arabinopyranosyl-(1-->2)-] beta-D-glucuronopyranosyl oleanolic acid, 3-O-alpha-L-rhamnopyranosyl-(1-->4)-[alpha-L-arabinopyranosyl-(1-->2)-] beta-D-glucuronopyranosyl oleanolic acid 28-O-beta-D-glucopyranosyl ester, 3-O-alpha-L-rhamnopyranosyl-(1-->4)-[beta-D-galactopyranosyl-(1-->2)-] beta-D-glucuronopyranosyl oleanolic ...
Tanaka Kazuhiko - - 2003
In this study, an aqueous solution consisting of benzoic acid with low background conductivity and beta-cyclodextrin (beta-CD) of hydrophilic nature and the inclusion effect to benzoic acid were used as eluent for the ion-exclusion chromatographic separation of aliphatic carboxylic acids with different pKa values and hydrophobicity on a polymethacrylate-based weakly ...
Mazzio Elizabeth A - - 2003
Elevated production of hydrogen peroxide (H2O2) in the central nervous system has been implicated in the pathogenesis of several neurodegenerative diseases, including Parkinson's disease, ischemic reperfusion, stroke, and Alzheimer's disease. Pyruvic acid has a critical role in energy metabolism and a capability to nonenzymatically decarboxylate H2O2 into H2O. This study ...
Ventura C A - - 2003
Biphenylylacetic acid (BPAA) was linked to the free hydroxyl group of 2,6-di-O-methyl-beta-Cyclodextrin (DM-beta-CyD) through an ester linkage to obtain the site specific release of the drug to the colon. The conjugate at 1:1 mole ratio was separated from the reaction mixture by semipreparative reverse-phase HPLC and characterized by 1H-NMR, 13C-NMR, ...
Sammis Glenn M - - 2003
(Salen)Al-Cl complex 1a catalyzes the asymmetric conjugate addition of hydrogen cyanide to alpha,beta-unsaturated imides in high yields and enantioselectivities. The cyanide adducts can readily be converted into a variety of useful chiral building blocks, including alpha-substituted-beta-amino acids and beta-substituted-gamma-aminobutyric acids. Mechanistic data obtained thus far point to a cooperative bimetallic ...
Batrakov S G - - 2003
The lipids extracted with CHCl(3)/MeOH mixtures from mycelium of the lower filamentous fungus Absidia corymbifera F-295 were found to contain three glycolipids. Based on the IR, 1H and 13C NMR spectra, plasma-desorption ionisation (PDI) mass spectra as well as chemical degradation results, the glycolipids were established to be 1-O-beta-D-glucopyranosyl-2-N-(2'-D-hydroxyhexadecanoyl)-9-methylsphinga-4(E),8(E)-dienine (glucosyl ...
Kuo Yu-Haey - - 2003
The seeds and one to three years old plants of Asian ginseng (Panax ginseng C.A. Meyer) were analyzed for their free amino acid contents. The neuro-excitatory beta-ODAP (beta-N-oxalyl-L-alpha,beta-diaminopropionic acid), suggested to be the cause of the crippling neurolathyrism, was the major component in the seed extract (70% of the total ...
Vranicar L - - 2003
2H-Pyran-2-ones 1 were transformed with various hydrazines into (E)- or (Z)-alpha, beta-didehydro-alpha-amino acid (DDAA) derivatives 4 (and 7) containing a highly substituted pyrazolyl moiety attached at the beta-position. With heterocyclic hydrazines, the products 4 were accompanied also by decarboxylated enamines E-6. In order to separate (E/Z)-mixtures of acids, they were ...
Dufrasne François - - 2003
1R-(-)-myrtenal was tested as a chiral derivatising agent for the determination of the enantiomeric purity of aliphatic primary amines, beta-aminoalcohols, beta-diamines and alpha-amino-acids. Derivatisation procedure consists in mixing one equivalent each of the amine and 1R-(-)-myrtenal directly into the nuclear magnetic resonance (NMR) tube before addition of the appropriate deuterated ...
Shi Hai-Ming - - 2003
Two new triterpenoid saponins, 3beta-O-beta-D-xylopyranosyl (1 --> 3)-alpha-L-rhamnopyranosyl-pyrocincholic acid 28-O-beta-D-glucopyranosyl (1 --> 6)-beta-D-glucopyranosyl ester (1), and 3beta-O-beta-D-xylopyranosyl(l --> 3)-alpha-L-rhamnopyranosyl-cincholic acid 28-O-beta-D-glucopyranosyl ester (2) were isolated from the roots of Adina pilulifera, together with 18 known compounds. The structures of 1 and 2 were determined by spectroscopic methods.
Maedler Kathrin - - 2003
Glucotoxicity and lipotoxicity contribute to the impaired beta-cell function observed in type 2 diabetes. Here we examine the effect of saturated and monounsaturated fatty acids at different glucose concentrations on human beta-cell turnover and secretory function. Exposure of cultured human islets to saturated fatty acid and/or to an elevated glucose ...
Lee Hee-Seung - - 2003
We report a practical and scalable synthetic route for the preparation of alpha-substituted beta-amino acids (beta(2)-amino acids). Michael addition of a chiral hydroxylamine, derived from alpha-methylbenzylamine, to an alpha-alkylacrylate followed by cyclization gives a diastereomeric mixture of alpha-substituted isoxazolidinones. These diastereomers are separable by column chromatography. Subsequent hydrogenation of the ...
Hu Hui-Yu - - 2003
A thermostable N-carbamoyl- l-amino acid amidohydrolase ( l-N-carbamoylase) gene composed of an 1,230-bp ORF encoding a 44.3-kDa protein was cloned from the thermophile Bacillus kaustophilus CCRC11223. This l-N-carbamoylase contained six cysteine residues that form three disulfide bridges. The purified l-N-carbamoylase was stringently l-specific and exhibited high activity in the hydrolysis ...
Mittendorf Joachim - - 2003
A series of novel beta-amino acids has been synthesized and tested for their in vitro antifungal activity against Candida albicans. A steep SAR was observed. beta-Amino acid 21 (BAY 10-8888/PLD-118) revealed the most favourable activity-tolerability profile and was selected for clinical studies as a novel antifungal for the oral treatment ...
Atkinson Samantha D M - - 2003
Infrared and Raman microspectroscopy have been used to follow the photodimerisation reactions of single crystals, the alpha- and beta-forms of trans-cinnamic acid. This approach allows the starting materials and products-alpha-truxillic acid that has Ci symmetry and beta-truxinic acid, which has Cs symmetry-to be identified. It also allows the topotactic nature ...
Dell'Agli Mario - - 2003
To investigate the mechanism of action of two antiplasmodial compounds, ellagic acid and 3,4,5-trimethoxyphenyl (6'-O-galloyl)-beta-D-glucopyranoside (TMPGG), we studied in vitro two metabolic reactions of intraerythrocytic parasites: the activity of recombinant plasmepsin II, one of the haemoglobin proteases, and the detoxification of haematin into beta-haematin. Both compounds inhibited plasmepsin II activity, ...
Nørbaek R - - 2003
From the leaves of barley, Hordeum vulgare, one new flavone C-glucoside and three known flavone glucosides were isolated and characterized by (1)H and (13)C NMR and MALDI-TOF-MS. The novel flavone C-glucoside was isovitexin 7-O-beta-[6' "-O-(E)-p-coumaroyl]glucoside (6' "-coumaroylsaponarin), and the known compounds were isovitexin 7-O-beta-[6' "-O-(E)-feruloyl]glucoside, isoorientin 7-O-beta-[6' "-O-(E)-feruloyl]glucoside, and tricin ...
Roeber Dana - - 2003
Acid beta-glucocerebrosidase (N-acylsphingosyl-1-O-beta-D-glucoside:glucohydrolase) is a lysosomal glycoprotein that catalyzes the hydrolysis of the glycolipid glucocerebroside to glucose and ceramide. Inadequate levels of this enzyme underly the pathophysiology of Gaucher's disease. Cerezyme (Genzyme Corporation, Cambridge, MA, USA) is a partially deglycosylated form of recombinant human acid beta-glucocerebrosidase that is used in ...
Careri Maria - - 2003
A reinvestigation of the equilibria of (S)-alpha-alaninehydroxamic acid (alpha-Alaha) and (R)-aspartic-beta-hydroxamic acid (Asp-beta-ha) with copper(II) was performed in aqueous solution in order to clarify some contradictory literature reports regarding the stoichiometry of the polynuclear complexes formed. beta-Alaninehydroxamic acid (beta-Alaha, HL), for which the formation of a planar 12-metallacrown-4, [Cu(5)L(4)H(-4)](2+), was ...
Dong He - - 2003
Recognition of five steroid compounds, beta-estradiol, ethynylestradiol, estradiolbenzoate, testosterone and methyltestosterone were studied using a synthesized molecularly imprinted polymer (MIP). When beta-estradiol was used as the template molecule, the polymer was synthesized with methacrylic acid (MAA) as the functional monomer and ethylene glycol dimethacrylate (EGDMA) as the cross linking agent ...
Bernasconi Claude F - - 2003
Acidity constants of six substituted 1-benzyl-1-methoxy-2-nitroethylenes (2-Z with Z = m-NO(2), m-CF(3), m-Cl, H, p-Me, p-MeO) and their respective nitronic acids were determined in 50% DMSO-50% water (v/v) at 20 degrees C. Kinetic data were obtained on the reversible deprotonation of all six 2-Z by OH(-) and piperidine and on ...
Robin J - - 2003
The influence of adipate concentration and dissolved oxygen on production of adipoyl-7-aminodeacetoxycephalosporanic acid (ad-7-ADCA) by a recombinant strain of Penicillium chrysogenum expressing the expandase gene from Streptomyces clavuligerus was studied in glucose-limited continuous cultures. Operating conditions were maintained constant but the adipate and dissolved oxygen concentrations (DOC) were varied separately ...
Ahmed Maruf - - 2003
Beta(3)-adrenoceptor is the predominant beta-adrenoceptor in adipocytes and has drawn much attention during the investigation for anti-obesity and antidiabetes therapeutics. Thirteen new compounds have been evaluated for their potencies and efficacies as beta(3)-adrenoceptor agonists on human beta(3)-adrenoceptor expressed in COS-7 and Chinese hamster ovary (CHO) cells using radioligand binding assay ...
Zhang Zhizhen - - 2003
Assay-guided fractionation of the ethanol extract of the twigs and leaves of Miconia trailii yielded two new flavanone glycosides, matteucinol 7-O-alpha-l-arabinopyranosyl(1-->6)-beta-d-glucopyranoside (miconioside A, 1) and farrerol 7-O-beta-d-apiofuranosyl(1-->6)-beta-d-glucopyranoside (miconioside B, 2), along with the known compounds matteucinol 7-O-beta-d-apiofuranosyl(1-->6)-beta-d-glucopyranoside (3), matteucinol (4), 2alpha,3beta,19alpha-trihydroxyolean-12-ene-24,28-dioic acid (bartogenic acid, 5), 2alpha,3beta,23-trihydroxyolean-12-ene-28-oic acid (arjunolic acid, 6), ...
White W Hunter - - 2003
The amino acid beta-alanine is an intermediate in pantothenic acid (vitamin B(5)) and coenzyme A (CoA) biosynthesis. In contrast to bacteria, yeast derive the beta-alanine required for pantothenic acid production via polyamine metabolism, mediated by the four SPE genes and by the FAD-dependent amine oxidase encoded by FMS1. Because amine ...
Goel M - - 2003
(+/-)-alpha-Hydrastine and (+/-)-beta-hydrastine were isolated from Corydalis longipes; both exhibited considerable efficacy against spore germination of some saprophytic and phytopathogenic fungi. While (+/-)-alpha-hydrastine was effective against most of the fungi, Helminthosporium echinoclova was least affected even at the highest dose (150 ppm). (+/-)-beta-Hydrastine was equally effective against several fungi. Mixture ...
Ido Akira - - 2003
We investigated the effects of an angiotensin-converting enzyme inhibitor (temocapril) and an angiotensin II type 1 receptor blocker (olmesartan) on changes in myocardial sympathetic nervous activity, fatty acid metabolism and myocardial blood flow using 131I-meta-iodobenzylguanidine, 125I-beta-methyl-iodophenyl pentadecanoic acid and 99mTc-tetrofosmin, respectively, in rats with isoproterenol-induced cardiac hypertrophy. Male Sprague-Dawley rats ...
< 5 6 7 8 9 10 11 12 13 14 15 >