Chiral nanostructure in polymers under different deposition conditions observed using atomic force microscopy of monolayers: poly(phenylacetylene)s as a case study.

Dynamic poly(phenylacetylene)s (PPAs) adopt helical structures with different elongation or helical senses depending on the types of pendants. Hence, a good knowledge of the parameters that define their structures becomes a key factor in the understanding of their properties and functions. Herein, the techniques used for the study of the secondary structure of PPAs using atomic-force microscopy (AFM) are presented, with special attention directed towards the methods used for the preparation of monolayers, and their consequences in the quality of the AFM images. Thus, monolayers formed by drop casting, spin coating followed by crystallization or annealing, Langmuir-Blodgett and Langmuir-Schaefer methods, onto highly oriented pyrolytic graphite (HOPG) or mica, are described, together with the AFM images and the resulting helical structure obtained for different PPAs. Furthermore, some conclusions are drawn both on the adequacy of the different techniques for the formation of monolayers and on the solid supports utilized to elucidate the secondary structure of different PPAs.

Helical sense selective domains and enantiomeric superhelices generated by Langmuir-Schaefer deposition of an axially racemic chiral helical polymer.

The chiral polymer poly-(R)-1 behaves in solution, despite its chiral pendants, as a dynamic axially racemic (i.e., 1 : 1) mixture of left- and right-handed helices, but its deposition on graphite by a Langmuir-Schaefer (LS) technique leads to a helical sense-selective packing that forms separate enantiomeric domains of left- and right-handed helical chains observed by high resolution atomic force microscopy (AFM). The polymer structure within these domains is very uniform, seldom altered by the presence of reversals, grouped always in contiguous pairs maintaining a single helical sense along the polymer chain. The LS deposition technique has been shown to be crucial to obtain good quality monolayers from poly-(R)-1 and other poly(phenylacetylene)s (PPAs: poly-2, poly-3 and poly-4) with short pendants, where spin coating, drop casting and Langmuir-Blodgett (LB) failed, and suggests that this technique could be the method of choice for the preparation of 2D monolayers for high resolution AFM studies of PPAs with short pendants. Key helical parameters (i.e., sense, pitch, packing angle) are easily measured in this way.

An aquaporin 4 antisense oligonucleotide loaded, brain targeted nanoparticulate system design.

Aquaporins (AQPs), members of the water-channel protein family, are highly expressed in brain tissue especially in astrocytic end-feet. They are important players for water hemostasis during development of cytotoxic as well as vasogenic edema. Increased expression of AQPs is important in pathophysiology of neurological diseases such as neuroinflammation and ischemia. Unfortunately, there are a few pharmacological inhibitors of AQP4 with several side effects limiting their translation as a drug for use in clinical conditions. Another therapeutic approach is using antisense oligonucleotides (ASOs) to block AQP4 activity. These are short, synthetic, modified nucleic acids that bind RNA to modulate its function. However, they cannot pass the blood brain barrier (BBB). To overcome this obstacle we designed a nanoparticulate system made up of chitosan nanoparticles surface modified with PEG and conjugated with monoclonal anti transferrin receptor-1 antibody via streptavidin-biotin binding. The nanocarrier system could be targeted to the transferrin receptor-1 at the brain endothelial capillaries through monoclonal antibodies. It is hypothesized that the nanoparticles could pass the BBB via receptor mediated transcytosis and reach brain parenchyma. Particle size, zeta potential, loading capacity and release profiles of nanoparticles were investigated. It was observed that all types of chitosau (CS) nanoparticles had positive zeta potential values and nanoparticle particle size distribution varied between 100 and 800 nm. The association efficiency of ASOs into the nanoparticles was between 80-97% and the release profiles of the nanoparticles exhibited an initial burst effect followed by a controlled release. The results showed that the designed chitosan based nanocarriers could be a promising carrier system to transport nucleic acid based drugs to brain parenchyma.

Preparation and evaluation of alpha-phenyl-n-tert-butyl nitrone (PBN)-encapsulated chitosan and PEGylated chitosan nanoparticles.

Alpha-phenyl-n-tert-butyl nitrone (PBN) shows its major effect by scavenging free radicals formed in the ischemia and it has the ability to penetrate through the blood brain barrier easily. The in vivo stability of PBN is very low and when administered systemically, it has a mean plasma half life of about three hours. Therefore, formulations which are able to prolong the plasma residence time of PBN are of major interest, because oxygen radicals are usually continuously formed under pathological conditions. In this study, PBN, a nitrone compound having neuroprotective properties, was encapsulated in chitosan (CS) and chitosan-poly(ethylene glycol) (CS-PEG) nanoparticles for treatment of diseases such as stroke, in which sustained free radical production is reported. The nanoparticles were characterized through particle size determination, zeta potential, encapsulation efficiency, surface morphology determinations and in vitro release studies. The surface morphologies were evaluated by transmission electron microscopy (TEM) and nanoparticles having spherical shapes were characterized. The particle size distribution was between approximately 97 nm and approximately 322 nm; and the zeta potentials varied between approximately 9 mV and approximately 33 mV. Size of the nanoparticle formulations was important for the release of PBN from nanoparticles. The quantitative determination of PBN has been evaluated by a validated analytical HPLC method. The presented chitosan-based nanotechnology opens new perspectives for testing antioxidant activity in vivo.

In vitro efficacy of new antiprotozoals against Philasterides dicentrarchi (Ciliophora, Scuticociliatida).

Philasterides dicentrarchi is a histiophagous ciliate that causes severe losses in turbot and sea bass farming. This study investigated the in vitro efficacy against P. dicentrarchi of 85 newly synthesized compounds and 12 commercial compounds, of which 2 are fluoroquinolones (norfloxacine and lomefloxacine) with known antibacterial activity. Seventeen of the newly synthesized compounds (2 naphthyridines, 2 pyridothienodiazines and 13 pyridothienotriazines) and the fluoroquinolone norfloxacin showed good activity. The most promising compound was the pyridothienotriazine 12k, with activity similar to that of the salicylanilides niclosamide and oxiclozanide (MLC 0.8 mg l(-1) in PBS, 1.5 mg l(-1) in seawater; MLC = minimum 24 h lethal concentration).

Pyrazolopyrimidines: synthesis, effect on histamine release from rat peritoneal mast cells and cytotoxic activity.

A series of 1H-pyrazolo[3,4-d]pyrimidines (3--6) substituted at positions 1 (R(1)=Ph, H, tert-butyl and ribosetribenzoate), 4 (R(2)=chlorine, nitrogen and oxygen nucleophiles), and 6 (dimethylamino) have been synthesized and their effect on the release of histamine from rat peritoneal mast cells measured. After chemical stimulation, (polymer 48/80), several compounds (i.e. 3b, 4a, 4b, 4d, 4g, 5a), produce inhibition two to three times higher (40--60%) than DSCG but this action is lower after preincubation. 4b (R(1)=Ph, R(2)=NHCH(2)Ph; 50--70% inhibition) and 5a (R(1)=H, R(2)=OMe; 50--55% inhibition) are the most active ones in both experiments. With ovoalbumin as stimulus, several pyrazolopyrimidines show inhibition similar to DSCG, the most active compounds being 6a--d (IC(50)=12--16 microM; R(1)=ribosetribenzoate, R(2)=methoxy and amino). Compounds 4e (R(1)=t-butyl, R(2)=OMe) and 4g (R(1)=t-butyl, R(2)=piperidino) are inducers of the release of histamine (60 and 150% increase). Compounds 4b and 4c showed cytotoxic activity (IC(50)=1 microg/mL) to HT-29 human colon cancer cells.

Total synthesis and absolute configuration of minalemine A, a guanidine peptide from the marine tunicate Didemnum rodriguesi.

The total synthesis of the 3S,2S and 3R,2S diastereomers (1a and 1b) of minalemine A and the identification of the natural compound as the 3R,2S isomer is described. The key step in the synthesis is the preparation of the two enantiomers of the beta-amino diacid 3-(N-carboxymethyl)-aminodecanoic acid (Ncma), which were obtained by stereoselective alkylation with allyl bromide of two nonanoic acid imides bearing chiral oxazolidinones as chiral auxiliaries. Natural minalemine A shows identical 1H NMR and very similar 13C NMR spectra compared to the two synthetic diastereomers. Sufficient differences in their chromatographic behavior to allow conclusive identification were not found. However, the corresponding N-2-naphthoyl amides presented quite distinct circular dichroism spectra (CD), and these confirmed the 3R,2S configuration for the natural minalemines and the R configuration for the constituent beta-amino diacid, Ncma.

Triterpene glycosides from the far eastern sea cucumber Pentamera calcigera II: disulfated glycosides.

Three new triterpene glycosides, calcigerosides D(1) (1), D(2) (2), and E (3), have been isolated from the sea cucumber Pentamera calcigera. Their structures have been deduced from extensive spectral analysis (NMR and MS) and chemical evidence. All the compounds are disulfated pentaosides differing in aglycon structure and position of sulfate group, which were determined by the measurement of NT(1) values in the cases of glycosides 1 and 2. Glycoside 1 is a nonholostane derivative, that is, it lacks an 18(20)-lactone, which is very rare among the sea cucumber glycosides.

Absolute configuration of 1,n-diols by NMR: the importance of the combined anisotropic effects in bis-arylmethoxyacetates

The absolute configuration of a 1,n-diol can be assigned from the (1)H NMR spectra of its (R)- and (S)-AMAA diesters if the chemical shifts are interpreted as the result of the joint action of the two chiral auxiliaries.

Hemolytic polar steroidal constituents of the starfish Aphelasterias japonica.

A reinvestigation of the polar steroid fraction from the starfish Aphelasterias japonica, collected near the Russian shore of the Sea of Japan, has afforded two new compounds, the disulfated quinovoside aphelasteroside C (1) and the monosulfated polyhydroxysteroid aphelaketotriol (2). Compounds 1 and 2 contain a unique 23-oxo-24-hydroxylated side chain that is unprecedented in marine steroids. The known compounds cheliferoside L1 (3), 3-O-sulfoasterone (4), forbeside E3 (5), and 3-O-sulfothornasterol A (6) were also isolated from this source. Compounds 1-3, 5, and 6 showed hemolytic activity to mouse erythrocytes.

The occurrence of the human glycoconjugate C(2)-alpha-D-mannosylpyranosyl-L-tryptophan in marine ascidians.

[structure: see text] The C-glycoconjugate C(2)-alpha-D-mannosylpyranosyl-L-tryptophan (1), a metabolite known to be generated in humans through a novel posttranslational process, has been isolated from marine ascidians Leptoclinides dubius and Pharyngodictyon cauliflos and its N(alpha)-methyl derivative (2) from Ritterella rete.

The [4+2]] addition of singlet oxygen to thebaine: new access to highly functionalized morphine derivatives via opioid endoperoxides.

The photooxidation of thebaine (3) with a sun lamp affords two main products: hydrodibenzofuran 10 (major) and benzofuran 11 (minor). The latter compound becomes predominant if a Hg lamp is used instead of a sun lamp. The formation of 10 proceeds via an endoperoxide intermediate that undergoes oxidation at the nitrogen atom. Protection of the nitrogen either by protonation or quaternization prevents its oxidation and thus the photooxidation of 3 in acid media constitutes a one-pot procedure for the preparation of 14-hydroxycodeinone 35. Photooxidation of the thebaine ammonium salt 31 allows the isolation in good yields of the corresponding to thebaine endoperoxide 32. The selective protection and reduction of the keto, aldehyde, and olefinic groups of hydrodibenzofuran 10 allowed the preparation of several diol and keto alcohol derivatives. This is the first report on the use of photooxidation to functionalize thebaine at C(6) and C(14) and also the first on the isolation of opioid endoperoxides.

An anti-inflammatory ditriazine inhibiting leukocyte functions and expression of inducible nitric oxide synthase and cyclo-oxygenase-2.

A ditriazine derivative (4,10-dichloropyrido[5,6:4,5]thieno[3,2-d':3, 2-d]-1,2,3-ditriazine (DTD)) inhibited neutrophil functions, including degranulation, superoxide generation, and leukotriene B(4) production, without any effect on 5-lipoxygenase activity. This compound reduced nitric oxide (NO) and prostaglandin E(2) production in mouse peritoneal macrophages stimulated with lipopolysaccharide, whereas no influence on the activity of inducible NO synthase, cyclo-oxygenase-2 or cyclo-oxygenase-1 was observed. DTD significantly reduced mouse paw oedema induced by carrageenan and also markedly reduced NO and prostaglandin E(2) levels in exudates from 24-h zymosan-stimulated mouse air pouch. Western blot analysis showed that DTD reduced the expression of inducible NO synthase and cyclo-oxygenase-2. Our results indicate that DTD exerts anti-inflammatory effects related to the inhibition of neutrophil functions and of NO and prostaglandin E(2) production, which could be due to a decreased expression of inducible NO synthase and cyclo-oxygenase-2.

Assignment of the absolute configuration of alpha-chiral carboxylic acids by 1H NMR spectroscopy

The prediction of the absolute configuration of alpha-chiral carboxylic acids from the 1H NMR spectra of their esters with (R)- and (S)-ethyl 2-hydroxy-2-(9-anthryl) acetate [(R)- and (S)-9-AHA, 5] is discussed. Low-temperature NMR experiments, MM, semiempirical, and aromatic shielding effect calculations allowed the identification of the main conformers and showed that, in all esters studied, conformer ap is the most stable. A simple model for the assignment of the absolute configuration from NMR data is presented, and its reliability is corroborated with acids 6-31 of known absolute configuration. In addition to 5, other auxiliary reagents with open (32-38) and cyclic (39-42) structures have also been studied. trans-(+)- and (-)-2-phenyl-1-cyclohexanol (41) was found to be particularly efficient and produced delta delta RS values similar to those of 5.

Effects of some isoxazolpyrimidine derivatives on nitric oxide and eicosanoid biosynthesis.

The inhibitory effect of some isoxazolpyrimidine derivatives on iNOS and COX-2 endotoxin induction in mouse peritoneal macrophages has been studied. Three of these compounds inhibited nitrite and PGE2 accumulation in a concentration dependent-manner at microM range. None of these active compounds affected iNOS, COX-2, COX-1 or PLA2 activities, although some reduced iNOS or COX-2 expression. Besides, no effect was observed on human neutrophil inflammatory responses (LTB4 biosynthesis and superoxide or elastase release). Active compounds were assayed by oral administration in the mouse air pouch model, where they inhibited nitrite accumulation without affecting PGE2 levels or leukocyte migration.

Triterpene glycosides from the Far-Eastern sea cucumber Pentamera calcigera. 1. Monosulfated glycosides and cytotoxicity of their unsulfated derivatives.

Three new monosulfated triterpene glycosides, calcigerosides B (2), C(1) (3), and C(2) (4), along with the known cucumarioside G(2) (1), have been isolated from the sea cucumber Pentamera calcigera. Their structures have been deduced from extensive spectral analysis (NMR and MS) and chemical evidence. Compounds 2-4 present a novel pentasacharide chain never reported before in sea cucumber triterpene glycosides. The desulfated derivatives of calcigerosides B, C(1), and C(2) (5, 7, and 9, respectively) showed moderate cytotoxicity (IC(50) = 5 microg/mL) against a selection of four human and mouse tumor cell lines.

Synthesis and pharmacological evaluation of some 8-cyanopyrido[3', 2':4,5]thieno[3,2-d]triazine derivatives as inhibitors of nitric oxide and eicosanoid biosynthesis.

A series of 8-cyanopyrido[3',2':4,5]thieno[3,2-d]-1,2,3-triazines, substituted at C-4 and C-7, were synthesized and evaluated as nitric oxide and prostaglandin E(2) inhibitors in murine peritoneal macrophages stimulated with bacterial endotoxin. Several compounds exhibited considerable activity, compounds 10 and 13 being the most interesting ones with IC(50) values of 11.2 and 3.4 microM on nitrites and 0.9 and 0.6 microM on prostaglandin E(2) production, respectively. None of the examples of pyridothienotriazines that were active at 10 microM showed any effect on inducible nitric oxide synthase, cyclooxygenase-2, and cyclooxygenase-1 enzymes, suggesting that they act by modifiying the level of expression of these inducible enzymes.

Synthesis and antiallergic activity of pyridothienopyrimidines.

The synthesis of a series of pyridothienopyrimidines and their evaluation as inhibitors or inducers of the release of histamine from rat mast cells is reported. The activity was measured after immunological stimulation with ovoalbumin and chemical stimulation with polymer 48/80 and the drugs adryamicin and vinorelbine. The experiments were carried out with and without preincubation of the stimulus with the cells before addition of the drug. Several pyridothienopyrimidines show inhibitory IC50 values in the range 2-25 microM, indicating they are up to 100 times more potent than cromoglycate (DSCG) and 10 times greater than Ketotifen. Compound 9l is a potent inhibitor in all the conditions tested and shows IC50 = 9-25 microM. Pyridothienopyrimidines 4l and 9e are very strong inducers of histamine release in the immunological (4l, 170-230%) and chemical (9e, 100-150%) assays, respectively. Compounds 4l and 9i are cytotoxic in vitro (IC50 = 0.1-0.2 microgram/mL) against P-388, A-549, HT-29, and MEL-28 tumor cell lines.

Koreoside A, a new nonholostane triterpene glycoside from the sea cucumber Cucumaria koraiensis.

The new triterpene glycoside koreoside A (1) has been isolated from the sea cucumber Cucumaria koraiensis. Koreoside A (1) is the first glycoside reported from holothurians that presents a delta(7) nonholostane aglycon without a lactone group and with a shortened side chain. Its structure has been elucidated by 13C and 1H NMR as well as FABMS studies.