Synthesis, characterization, cytotoxicity and antibacterial studies of chitosan, O-carboxymethyl and N,O-carboxymethyl chitosan nanoparticles

Chitosan (CS) is a naturally occurring biopolymer. It has important biological properties such as biocompatibility, antifungal and antibacterial activity, wound healing ability, anticancerous property, anticholesteremic properties, and immunoenhancing effect. Recently, CS nanoparticles have been used for biomedical applications. However, due to the limited solubility of CS in water its water-soluble derivatives are preferred for the above said applications. In this work, the nanoparticles of CS and its water-soluble derivatives such as O-carboxymethyl chitosan (O-CMC) and N,O-carboxymethyl chitosan (N,O-CMC) was synthesized and characterized. In addition, cytotoxicity and antibacterial activity of the prepared nanoparticles was also evaluated for biomedical applications.     

Characterization of a lignin-specific O-Methyltransferase in aspen wood

O-Methyltransferases were extracted from the differentiating xylem of 10-yr-old Populus euramericana. The enzymes were partially purified by ammonium sulfate precipitation, and column chromatography on DEAE-cellulose, Sephadex G200 and hydroxyapatite. The enzymes were resolved into two peaks by DEAE-cellulose chromatography, and the MWs of the respective enzymes were estimated to be 72 000 and 75 000 by gel filtration chromatography. The enzyme corresponding to the latter peak was unstable and thus only the former peak enzyme was characterized completely. Magnesium ions had no effect, EDTA moderately stimulated and heavy metals and SH group inhibitors strongly inhibited enzyme activity. K_mm values for caffeate and 5-hydroxyferulate were estimated to be 3.8 x 10⁻⁴ and 3.1 x 10⁻⁴ M, respectively. The ratio of V_max/K_m for 5-hydroxyferulate was 5.4 times greater than that for caffeate. The enzyme(s) catalysing the formation of ferulate from caffeate and of sinapate from 5-hydroxyferulate were not separated during the purification or by the disc electrophoresis using polyacrylamide gel. Quercetin, cyanin and catechin were not methylated by the enzyme preparation. The O-methyltransferase of aspen wood, where the phenolic metabolism is almost exclusively directed to lignin biosynthesis, catalyses the methylation of both guaiacyl and syringyl lignin precursors, with preferential utilization of the latter substrate. These findings lead to the conclusion that the enzyme is a typical angiosperm-type O-methyltransferase related to guaiacyl and syringyl lignin biosynthesis in aspen wood.     

Reduction of negative alliesthesia for sweet gustatory stimuli by cyproheptadine, a serotonin antagonist

Cyproheptadine (CH) is a serotonin antagonist that increases food intake and body weight. In order to elucidate its mechanism of action on the control of food intake, hunger ratings, pleasure-displeasure to sweet gustatory stimuli and negative alliesthesia induced by a 50 g glucose load were compared in 14 healthy subjects after they had received a placebo or 16 mg of CH. Cyproheptadine did not affect the hunger rating, nor the affective rating in fasted subjects, but it reduced significantly the negative alimentary alliesthesia induced by the glucose load. It was concluded that CH increases food intake more by reducing satiation than by increasing hunger. This is in line with the anti-serotoninergic properties of CH, and the action of serotonin on the control of food intake.     

O-Carboxymethylchitosan-based novel gatifloxacin delivery system

The increase in the treatment efficacy due to the enhanced permeability and retention properties and the decrease in the minimum inhibitory concentration (MIC) are the vital challenges related to the administration of the antibiotic drugs. In the present paper, we describe a novel delivery system of gatifloxacin (GFLX) from O-carboxymethylchitosan (OCMCS). GFLX is a fourth-generation fluoroguinolone, which has shown promise with excellent activity against both Gram-positive cocci and Gram-negative bacteria both in vitro and in vivo. OCMCS is a biocompatible amphiphilic derivative of chitosan. GFLX could be entrapped into OCMCS by the interaction between OCMCS and GFLX, which was characterized by fluorescence spectrum, transmission electron microscope, and dynamic light scattering techniques. The release behaviors of GFLX from this proposed delivery system in phosphate-buffered saline (PBS) solution at 37 °C were studied by fluorescence spectroscopy. The MIC of OCMCS formulation was evaluated. The results demonstrate that the release of GFLX from OCMCS formulation is slower than that from GFLX solution. In vitro bacteria antiproliferative activity assay confirms that the MIC of OCMCS formulation against Gram-negative bacteria is fourfold lower than the system without OCMCS. However, it seems that OCMCS has insignificant effect against Gram-positive bacteria. These results suggest that OCMCS matrix has obvious “transmission effect” on Gram-negative bacteria.     

Xanthone O-glycosides from Polygala tenuifolia

Four xanthone O-glycosides, polygalaxanthones IV–VII were isolated from the roots of Polygala tenuifolia Willd., together with eight known compounds. The structures of the four xanthone O-glycosides were established as 6-O-[α- -rhamnopyranosyl-(1→2)-β- -glucopyranosyl]-1-hydroxy-3,7-dimethoxyxanthone (polygalaxanthone IV), 6-O-[α- -rhamnopyranosyl-(1→2)-β- -glucopyranosyl]-1,3-dihydroxy-7-methoxyxanthone (polygalaxanthone V), 6-O-(β- -glucopyranosyl)-1,2,3,7-tetramethoxyxanthone (polygalaxanthone VI), and 3-O-[α- -rhamnopyranosyl-(1→2)-β- -glucopyranosyl]-1,6-dihydroxy-2,7-dimethoxyxanthone (polygalaxanthone VII), respectively, on the basis of analysis of spectroscopic evidence.     

NeuA O-acetylesterase activity is specific for CMP-activated O-acetyl sialic acid in Streptococcus suis serotype 2

Several bacteria causing meningitis, such as Escherichia coli K1, Streptococcus suis, Neisseria meningitidis, and group B Streptococci (GBS), produce sialic acid (Neu5Ac)-containing capsular polysaccharide (CPS). Biosynthesis of the Neu5Ac-containing CPS requires CMP-Neu5Ac as substrate, which is synthesized by CMP-Neu5Ac synthetase from CTP and Neu5Ac. In E. coli or GBS, the NeuA protein encoded by the neuA gene has been known encoding a bifunctional enzyme that possesses both CMP-Neu5Ac synthetase and O-acetylesterase activity. In this report, we found that the S. suis NeuA (SsNeuA) was also a bifunctional CMP-Neu5Ac synthetase/O-acetylesterase. Biochemical analyses revealed that the SsNeuA strictly de-O-acetylated CMP-O-acetyl-Neu5Ac, whereas the E. coli NeuA (EcNeuA) preferentially de-O-acetylated CMP-O-acetyl-Neu5Ac. E. coli devoid of NeuA O-acetylesterase activity was unable to produce capsule and only CMP-Neu5Ac synthetase activity of the EcNeuA or SsNeuA could not restore its ability to produce capsule. These results suggest that the O-acetylesterase is essential for the synthesis of capsular Neu5Ac in E. coli, probably in S. suis and GBS as well. Our findings are key to understanding the biosynthesis of capsular Neu5Ac in E. coli, S. suis and GBS.     

Electron-impact mass spectrometry of methyl O-methylglucopyranosiduranamides

6-O-Acetyl-2,4-diazido-3-O-benzyl-2,4-dideoxy-β-D-glucopyranosyl chloride and 2,6-diazido-3,4-di-O-benzyl-2,6-dideoxy-β-D-glucopyranosyl chloride are two valuable building units suitable for the synthesis of α-linked disaccharides containing 2,4-diamino-2,4-dideoxy- or 2,6-diamino-2,6-dideoxy-D-glucose as nonreducing moieties. The glycoside synthesis is accomplished stereoselectively under mild conditions in the presence of silver perchlorate. The α-(1→3)-linked disaccharides 2,4-diacetamido-2,4-dideoxy-3-O-(2,4-diacetamido-2,4-dideoxy-α-D-glucopyranosyl)-D-glucopyranose and 2-acetamido-2-deoxy-3-O-(2,6-diacetamido-2,6-dideoxy-α-D-glucopyranosyl)-D-glucopyranose have been prepared.     

Progesterone reduces the effect of the serotonin 1B/1D receptor antagonist, GR 127935, on lordosis behavior

Ovariectomized rats were hormonally primed with 10 μg estradiol benzoate or with estradiol benzoate plus 500 μg progesterone. Rats received a bilateral infusion with 200 ng of the 5-HT_1B/1D receptor antagonist, N-[4-methoxy-3-(4-methyl-1-piperazinyl)phenyl]-2′-methyl-4′-(5-methyl-1,2,4-oxadiazol-3-yl)-1-1′-biphenyl-4-carboxamide hydrochloride (GR 127935), into the ventromedial nucleus of the hypothalamus (VMN), followed by a 5 min restraint or home cage experience. In estrogen-primed females that had experienced minimal handling between ovariectomy and use in the experiment, infusion with the water vehicle transiently inhibited lordosis behavior, and the 5-HT_1B/1D receptor antagonist amplified this inhibition. There were no effects in rats hormonally primed with estrogen and progesterone. Handling for two days before the experiment reduced the effects of the infusions in estrogen-primed rats. However, when a 5 min restraint experience followed infusion with GR 127935, there was a significant decline in lordosis behavior that persisted for 10 to 15 min after the experience. Regardless of the prior experience or type of infusion, the addition of progesterone to the hormonal priming completely prevented the lordosis inhibition. These findings are consistent with prior evidence that progesterone protects against the inhibitory effects of a 5 min restraint experience on lordosis behavior. Moreover, these are the first experiments to demonstrate an inhibitory effect of a selective 5-HT_1B/1D receptor antagonist in the VMN on lordosis behavior of estrogen primed, but not estrogen and progesterone primed, ovariectomized rats.     

Effect of metergoline, a specific serotonin antagonist, on human growth hormone response to arginine and L-dopa.

In seven normal subjects the repeated oral administration of metergoline, a specific antiserotonin agent, has enhanced HGH response to arginine infusion. Following placebo administration, arginine-induced HGH release was slightly but not significantly reduced; similarly, in eight metergoline treated subjects, HGH response to oral L-Dopa was slightly but not significantly reduced. HGH response to i.v. L-Dopa was not modified by the drug. These results suggest that serotonin controls HGH response only in response to arginine, not to L-Dopa.     

SAR development of a selective 5-HT1D antagonist/serotonin reuptake inhibitor lead using rapid parallel synthesis

Incorporation of an SRI (serotonin reuptake inhibitor) pharmacophore into a selective 5-HT(1D) agonist has led to the discovery of a molecule having both 5-HT(1D) antagonist and SRI activity. RPS methodology was used to develop the SAR and identify potential approaches to reduce unwanted adrenergic alpha 1 and dopamine D(2) cross-reactivities.     

Synthesis and antiperoxidant activity of new phenolic O-glycosides

We describe the synthesis of some 3-tert-butyl-4-hydroxyphenyl -glycopyranosides by reaction of tert-butylhydroquinone with β- -pentaacetyl-glucose, β- -pentaacetyl-galactose, 2-acetamido- and 3,4,6-tri-O-acetyl-2-butanamido-2-deoxy-β- -glucopyranosyl chlorides as well as the formation of anomeric 3-tert-butyl-4-hydroxyphenyl 4,6-di-O-acetyl-2,3-dideoxy- -erythro-hex-2-eno-pyranosides by reaction between tert-butylhydroquinone and 3,4,6-tri-O-acetyl- -glucal. All compounds, except 3-tert-butyl-4-hydroxyphenyl α- and β- -glucopyranosides, inhibited lipid peroxidation with a degree of potency comparable to that of tert-butyl hydroxyanisole.     

Effect of an oral serotonin antagonist,ketanserin, on plasma ACTH concentrations in Nelson's syndrome.

A study was performed to see whether ketanserin, a serotonin antagonist, would reduce the raised concentrations of adrenocorticotrophic hormone (ACTH) in patients with Nelson''s syndrome. Six patients who had undergone bilateral adrenalectomy for Cushing''s disease and who had Nelson''s syndrome were given ketanserin 40 mg twice daily and placebo, for at least two months each, in a double blind crossover study. Ketanserin had no effect on ACTH concentrations. In healthy people serotonin seems to have a stimulatory role in the regulation of ACTH secretion, and the effect of ketanserin in reducing the ACTH response to hypoglycaemia suggested that it might prove useful in Nelson''s syndrome. These results show that it is not indicated in these patients.     

Preparation and mass-spectral analysis of O-hydroxy-ethyl derivatives of -glucose

Various hydroxyethyl ethers of -glucose have been prepared in good yield by treating -glucose derivatives with 2-bromoethyl tetrahydropyranyl ether in the presence of sodium hydride. The derived O-(hydroxyethyl)--glucitol acetates exhibited characteristic mass-spectral fragments. The furanose and pyranose forms of 1,2-O-ethylene--glucose derived from 2-O-(2-hydroxyethyl)--glucose were identified by mass-spectral analysis.     

Synthesis of an O-sulfo Lewis analog as glycolipid antigen

The title compound containing dihydroceramide as a ligand for CD1d was accomplished using the mannosyl, glucosaminyl, and fucosyl donors, and a sphinganine analogue, as suitable building blocks. The 2-O-unprotected mannosyl donor was coupled effectively with the sphinganine analog to afford the mannnosyl sphinganine derivative. The coupling of the glucosaminyl donor with the mannnosyl sphinganine acceptor required triflic acid as a promoter and the promoter change to silver triflate led to the undesired glycal production. The reduction of azide group using Zn powder was the key process, in which the amount of acetic acid was restricted to avoid the benzoyl migration and N-trichloroacetyl deprotection. The trisaccharide glycolipid was sulfonated at the 3-position of fucose moiety.     

Pyrrolidino-tetrahydroisoquinolines as potent dual H3 antagonist and serotonin transporter inhibitors

A series of novel and potent pyrrolidino-tetrahydroisoquinolines with dual histamine H(3) antagonist/serotonin transporter inhibitor activity is described. A highly regio- and diastereoselective synthesis of the pyrrolidino-tetrahydroisoquinoline core involving acid mediated ring-closure of an acetophenone intermediate followed by reduction with NaCNBH(3) was developed. In vitro and in vivo data are discussed.     

The Lectin from the Crustacean Liocarcinus depurator Recognizes O-acetylsialic Acids

A lectin that recognized sialic acids and agglutinated mouse erythrocytes was purified from hemolymph of the crab Liocarcinus depurator. It consisted of 38-kDa subunits and had a pI about 6.0. The specificity of the lectin was assayed by hemagglutination inhibition. N-acetylneuraminic acid (Neu5Ac) was a good inhibitor and its N-acetyl group at C-5 was critical for lectin-ligand interaction. Substitution of the C-9 hydroxyl on Neu5Ac with an O-acetyl group (9-O-Ac-Neu5Ac) increased the inhibitory potency of this molecule. Furthermore, O-acetyl substitution of all the hydroxyl groups yielded even better inhibitors (2,4,7,8,9-O-Ac-Neu5Ac and its 1-O-methyl ester). Removal of the hydroxyl or O-acetyl group connected to C-2 reduced the potency of these inhibitors. The lectin agglutinated and stimulated human but not mouse lymphocytes. It was also inhibited by Escherichia coli (O111:B4) lipopolysaccharide and agglutinated specific gram-negative bacteria. In vitro labeling with [³⁵S]methionine indicated that the lectin was synthesized in hepatopangreas of L. depurator. Immunofluorescence showed that among hemocytes it localized mainly in the large-granule population.     

Oo mutations in the galactose operon in E. coli

Summary Eleven mutants lacking the three enzymes of galactose fermentation were investigated.Eight of the mutants revert spontaneously to the Gal ⁺ phenotype. These cannot be deletions. Six of these spontaneously reverting mutants do not respond to the mutagens 2-aminopurine, ethyl-methanesulfonate and N-Methyl-N-Nitro-N-nitrosoguanidine. It is concluded that these o ^o mutations cannot be reverted by base substitution.The eleven o ^o mutants are not of the amber or ochre type as shown by their behaviour towards suppressor genes.The possible nature of the mutations is discussed.     

Physiological responses of soybean plants grown in a nitrogen-free or energy limited environment

Soybean (Glycine max [L.] Merr.) seedlings grown in the absence of combined N and in an Ar:O₂ (79:21, volume/volume) atmosphere had greater seedling and nodule mass, threefold higher acetylene reducing activity per gram fresh weight nodules, no observable increase in nitrogenase Fe-protein, and a higher energy charge than did control plants. A sharp fall in acetylene reducing activity and energy charge accompanying stem-girdling was prevented by exogenous succinate, a result consistent with a path from the roots to the nodule other than via the phloem.