Synthesis, characterisation and cytotoxicity of chloro derivatives of prenylnaphthohydroquinone

From the Diels-Alder adduct between alpha-myrcene and 2-chloro-1,4-benzoquinone, a family of chloro derivatives of prenylnaphthohydroquinone have been synthesised and evaluated for their cytotoxicity against 14 neoplastic cell lines.     

Fluorescent glucagon derivatives. I. Synthesis and characterisation of fluorescent glucagon derivatives

The synthesis of monofluorescein, monorhodamine, and mono-4-nitrobenz-2-oxa-1,3-diazole (NBD) derivatives of glucagon is reported. The fluorescent groups were introduced by converting tryptophan-25 to 2-thioltryptophan using thiol-specific fluorescent reagents. All derivatives retained the ability to activate adenylate cyclase when compared to glucagon and thus were considered full agonists. IC50 values of 6.8.10(-9), 1.7.10(-8), 1.8.10(-8) and 5.4.10(-9) M were measured in rat liver membranes for NBD-, fluorescein-, rhodamine-Trp25-glucagon and native glucagon, respectively. From the IC50 values Kd values of 2.16.10(-9), 4.10(-9), 2.10(-9) and 1.72.10(-9) M were calculated for the binding of NBD-, fluorescein-, rhodamine-Trp25-glucagon and native glucagon, respectively. The highest quantum yield (0.18) of the monomer derivatives was obtained with fluorescein-Trp25-glucagon in phosphate-buffered saline (pH 7.4). Difluorescein-glucagon was also prepared by reacting the amino groups of histidine-1 and lysine-12 with fluorescein isothiocyanate and dimer derivatives were prepared using fluorescein-labelled 2-thiolTrp25-glucagon. Difluorescein-glucagon bound only weakly to glucagon receptors and displayed antagonist properties. The dimer derivative formed from two difluorescein-2-thiolTrp25-glucagon molecules had similar poor binding qualities, whereas the dimer formed from difluorescein-2-thiolTrp25-glucagon and 2-thiolTrp25-glucagon exhibited, at low concentrations, properties similar to monofluorescein-glucagon. Both dimer derivatives were only sparingly soluble in aqueous medium. Specific binding of fluorescein-Trp25-glucagon and difluorescein-glucagon to rat hepatocytes was followed using flow cytometry.     

Synthesis and rheological properties of hydrogels based on amphiphilic alginate-amide derivatives

New amphiphilic derivatives of sodium alginate were prepared by covalent attachment of dodecylamine onto the polysaccharide via amide linkages at different substitution ratios, using 2-chloro-1-methylpyridinium iodide (CMPI) as coupling reagent. The aim was to limit the progressive loss of associative behaviour which occurs in the case of previously described dodecyl ester alginate derivatives due to hydrolysis of ester bonds. A series of hydrogels was obtained which differed by the amount of attached dodecyl tails. The stability and viscoelastic properties were evaluated and compared to those of hydrogels obtained with alginate esters. The observed differences were discussed in relation to the synthesis procedures. The advantages of amide links are underlined, especially with regard to long-term stability of hydrogels.     

Synthesis and characterisation of celastrol derivatives as potential anticancer agents

In the present study, three series of novel celastrol derivatives were designed and synthesised by modifying the carboxylic acid at the 20th position with amino acid, amine, and triazole derivatives. All the synthesised compounds were screened for their anticancer activities using MTT assay against AGS, MGC-803, SGC-7901, HCT-116, A549, HeLa, BEL-7402, and HepG-2 cell lines. Most of the synthesised compounds exhibited potent antiproliferative effects. The most promising compound 3-Hydroxy-9β,13α-dimethyl-2-oxo-24,25,26-trinoroleana-1(10),3,5,7-tetraen-29-oic amide, N-(R)-methyl-3-(1H-indol-2-yl)propanoate (11) showed considerable high anticancer activity against AGS cell lines, with an IC₅₀ value of 0.44?μM, and considerably higher activities against HCT-116, BEL-7402, and HepG-2 cell lines, with IC₅₀ values of 0.78, 0.63, and 0.76?μM, respectively. The results of apoptosis tests and molecular docking study of compound 11 binding to Caspase-3 revealed that its mechanism of action with antiproliferative was possibly involved in inducing apoptosis by inducing the activation of caspase-3.     

Cell proliferation and cell sheet detachment from the positively and negatively charged nanocomposite hydrogels

The charged nanocomposite hydrogels (NC gels) were synthesized by copolymerization of positively or negatively chargeable monomer with N‐isopropylacrylamide (NIPAm) in the aqueous suspension of hectorite clay. The ionic NC gels preserved the thermo‐responsibility with the phase‐transition temperature below 37°C. The L929 cell proliferation was sensitive to charge polarity and charge density. As compared to the PNIPAm NC gel, the cationic NC gels with <5 mol % of 2‐(dimethylamino)ethyl methacrylate (DMAEMA) showed improved cell proliferation, whereas the cells grew slowly on the gels with negatively charged 2‐acrylamido‐2‐methylpropane sulfonic acid (AMPSNa). By lowering temperature, rapid cell sheet detachment was observed from the surface of ionic NC gels with 1 mol % of ionizable monomers. However, lager amount of AMPSNa or DMAEMA did not support rapid cell sheet detachment, probably owing to the adverse swelling effects and/or enhanced electrostatic attraction. © 2013 Wiley Periodicals, Inc. Biopolymers 101: 58–65, 2014.     

Iodophenyl tagged sphingosine derivatives: Synthesis and preliminary biological evaluation

A facile synthesis of six 4-iodophenyl tagged sphingosine (SP) derivatives bearing alkyl chain lengths from 6 to 13 is described. The key steps for the assembly of these molecules, 5a–f, are Suzuki–Miyaura cross-coupling and cross-metathesis reactions. The feasibility of radiolabeling was demonstrated by synthesizing two ¹²⁵I labeled compounds, [¹²⁵I]5c and [¹²⁵I]5e. In vitro enzyme assays indicated that the molecules, 5c–e, are potent inhibitors. Thus, they deserve further evaluation as potential radioactive probes for tumor imaging.     

Synthesis and preliminary cytotoxicity of nitrogen mustard derivatives of distamycin A

Distamycin and nitrogen mustard conjugates, in which the nitrogen mustard unit was coupled to the C-terminus of the pyrrole, were synthesized. The switching of the nitrogen mustard unit from the N-terminus to the C-terminus did not compromise the compound's cytotoxicity. Compound 3, bearing three pyrrole units, was highly toxic to human K562 leukemia cells in vitro with an IC(50) value of 0.03 microM. Addition of a trans double bond to the molecule had little effects on cytotoxicity.     

Purification and preliminary characterisation of a thiamine-binding protein from spruce seeds

A thiamine-binding protein was isolated from spruce seeds (Picea abies L.), Karst.) in a nearly homogeneous form using a combination of ammonium sulphate fractionation, DEAE-cellulose ion-exchange chromatography, high performance gel filtration on TSK G3000SW column and fast protein ion-exchange chromatography with MonoQ column. SDS-polyacrylamide gel electrophoresis revealed the basic subunit of 23 kDa. However, the native protein was an oligomer with a molecular mass of about 130 kDa as estimated by gel filtration on analytical Superdex-200 column. The estimated isoelectric point was about 5.1. Thiamine was bound with a capacity of 8.5 nmol per mg protein, suggesting a simple 1:1 molar stoichiometry of thiamine-protein interaction. The dissociation constant of the complex was 8 μM in 0.05 M phosphate buffer at optimal pH 8.6. Several thiamine analogues were also bound to this protein but always with a lower affinity than thiamine. From this chemical probing, the binding site on the spruce protein seems to fit the model, previously deduced for the purified buckwheat-seed protein and generalised in a study of seed extracts of species sampled from major classes of Spermatophyta.     

Synthesis and preliminary cytotoxicity study of glucuronide derivatives of CC-1065 analogues

Glucuronide derivatives of CBI-bearing CC-1065 analogues have been synthesized, and their cytotoxicities tested against U937 leukemia cells. The new compounds show potent antitumor activity in vitro. Compounds 1 and 2, and their corresponding glucuronides 3 and 4 have IC(50) values of 0.6, 0.1, 1.4 and 0.6 nM, respectively. Glucuronide 3 is approximately 2-fold less toxic than its hydroxyl counterpart 1, and glucuronide 4 is approximately 6-fold less toxic than its hydroxyl counterpart 2. Glucuronides 3 and 4 may have limited use in the ADEPT approach. However, they may be used as antitumor agents in a conventional way.     

Synthesis and characterisation of (Z)-styrylbenzene derivatives as potential selective anticancer agents

To identify anticancer agents with high potency and low toxicity, a series of (Z)-styrylbenzene derivatives were synthesised and evaluated for anticancer activities using a panel of nine cancer cell lines and two noncancerous cell lines. Most derivatives exhibited significant anti-proliferative activities against five cancer cell lines, including MGC-803 and BEL-7402. (Z)-3-(p-Tolyl)-2-(3,4,5-trimethoxyphenyl)acrylonitrile (6h) showed a strong inhibitory effect on MGC-803 cells (IC₅₀?50?50 value of 6h in L-02 cells was 10,000-fold higher than in MGC-803 cells. Compound 6h inhibited proliferation of BEL-7402 cells by arresting at the G2/M phase through up-regulation of cyclin B1 expression, down-regulation of cyclin A and D1 expression, and induction of apoptosis. In addition, 6h inhibited the migration of BEL-7402 cells and the formation of cell colonies.     

Synthesis and preliminary pharmacological characterisation of a new class of nitrogen-containing bisphosphonates (N-BPs)

A new series of bisphosphonates bearing either the nitrogen-containing NO-donor furoxan (1,2,5-oxadiazole 2-oxide) system or the related furazan (1,2,5-oxadiazole) in lateral chain has been developed. pK_a values and affinity for hydroxyapatite were determined for all the compounds. The products were able to inhibit osteoclastogenesis on RAW 246.7 cells at 10 μM concentration. The most active compounds were further assayed on human PBMC cells and on rat microsomes. Unlike most nitrogen-containing bisphosphonates which target farnesyl pyrophosphate synthase, experimental and theoretical investigations suggest that the activity of our derivatives may be related to different mechanisms. The furoxan derivatives were also tested for their ability to relax rat aorta strips in view of their potential NO-dependent vasodilator properties.     

Synthesis and biological characterisation of ester and amide derivatives of fusidic acid as antiplasmodial agents

A series of novel fusidic acid (FA) derivatives was synthesized by replacing the carboxylic acid group with various ester and amide groups and evaluated in vitro for their antiplasmodial activity against the chloroquine-sensitive NF54 and multidrug-resistant K1 strains of the malarial parasite Plasmodium falciparum. Most of these derivatives showed a 4–49 and 5–17-fold increase in activity against NF54 and KI strains, respectively, as compared to FA and had a good selectivity index. These derivatives are stable over the incubation period and do not appear to be prodrugs of fusidic acid.     

Production of scleroglucan from Sclerotium rolfsii MTCC 2156

Scleroglucan, a neutral homopolysaccaride consisting of a linear chain of beta-D-(1-3)-glucopyranosyl and beta-D-(1-6)-glucopyranosyl groups, was produced by pure culture fermentation from Sclerotium rolfsii MTCC 2156 by submerged culture. Fermentation process was optimized in two steps. In the first step, one-factor-at-a-time method was used to investigate the effects of medium constituents such as carbon and nitrogen sources. In the second step, concentration of medium components was optimized using an L16-orthogonal array method. In all, 10 different carbon sources and eight different nitrogen sources were evaluated. Maximum yield of 16.58 g/l was obtained in a medium containing sucrose as a carbon source and sodium nitrate and yeast extract as nitrogen source.     

Synthesis and partial characterization of hydrogels obtained via glutaraldehyde crosslinking of acetylated chitosan and of hyaluronan derivatives

Hydrophilic networks based on functionalized hyaluronic acid and on partially acetylated chitosan, respectively, have been obtained. In the case of hyaluronic acid (HA), primary amino functionalities have been introduced along the polysaccharide chains. The ensuing derivatives, i.e., HA-lysine (HA-K), HA-diamino pentane (HA-DAP), and HA-glycine-lysine (HA-GK), have been characterized by high field NMR spectroscopy. NMR 2D-DOSY experiments have allowed us to optimize the purification procedure. Chitosan was made soluble in water by partial acetylation. Cross-linking reactions have been performed using glutaraldehyde. The obtained networks have been qualitatively characterized by means of (13)C CP-MAS NMR technique. The hydrogels have been characterized also in terms of water uptake.     

Synthesis and characterization of chitosan-based hydrogels

Biocompatible hydrogels based on water-soluble chitosan–ethylene glycol acrylate methacrylate (CS–EGAMA) and polyethylene glycol diamethacrylate (PEGDMA) were synthesized by photopolymerization. Characterization of morphology, weight loss, water state of hydrogel, pH-sensitivity and cytotoxicity were investigated by scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), X-ray diffraction (XRD), differential scanning calorimetry (DSC), Fourier transform infrared (FTIR), swelling test and methylthiazolydiphenyl-tetrazolium bromide (MTT) assay. The results indicated that the hydrogels were sensitive to pH of the medium, no cytotoxicity for L929 and SW1353, satisfactory for the composite to be used in bioapplications.     

Synthesis and preliminary evaluation of pharmacological properties of some piperazine derivatives of xanthone

A series of 9 piperazine derivatives of xanthone were synthesized and evaluated for cardiovascular activity. The following pharmacological experiments were conducted: the binding affinity for adrenoceptors, the influence on the normal electrocardiogram, the effect on the arterial blood pressure and prophylactic antiarrhythmic activity in adrenaline induced model of arrhythmia (rats, iv). Three compounds revealed nanomolar affinity for α₁-adrenoceptor which was correlated with the strongest cardiovascular (antiarrhythmic and hypotensive) activity in animals’ models. The most promising compound was 4-(3-(4-(2-methoxyphenyl)piperazine-1-yl)propoxy)-9H-xanthen-9-one hydrochloride (12) which revealed antiarrhythmic activity with ED₅₀ value of 0.69 mg/kg in adrenaline induced arrhythmia (rats, iv). Other synthesized xanthone derivatives, that is, (R,S)-4-(2-hydroxy-3-(4-(2-methoxyphenyl)piperazine-1-yl)propoxy)-9H-xanthen-9-one hydrochloride (10) and (R,S)-4-(2-acetoxy-3-(4-(2-methoxyphenyl)piperazine-1-yl)propoxy)-9H-xanthen-9-one hydrochloride (11) also acted as potential antiarrhythmics in adrenaline induced model of arrhythmia in rats after intravenous injection (ED₅₀ = 0.88 mg/kg and 0.89 mg/kg, respectively). These values were lower than values obtained for reference drugs such as propranolol and urapidil, but not carvedilol.Results were quite promising and suggested that in the group of xanthone derivatives new potential antiarrhythmics and hypotensives might be found.     

Isolation and preliminary characterisation of DNA-protein complexes from the mitochondria of Saccharomyces cerevisiae

Four independent rat L6 myoblast cell lines have been selected in a single step for resistance to the cytotoxic effects of the lectin concanavalin A (conA). In contrast to parental wild-type myoblast lines, all of the variant clones are unable to undergo normal cellular differentiation to form multinucleated myotubes or biochemical differentiation to produce an increase in the specific activity of the muscle-specific enzyme, creatine phosphokinase (CPK). The correlation between lectin resistance and loss of fusion potential is very tight; clonal variation studies show that there is less than a 2.8×10^?8 chance that the two are not directly related. Membrane preparations from the conA-resistant myoblast lines incorporate significantly less GDP-[¹⁴C]mannose into the lipid intermediates of protein glycosylation than preparations from parental wild-type cells. Also, conversion of mannose label to fucose occurs in myoblasts and this pathway is more active in conA-resistant cells than wild-type cells. Reduced binding of labelled conA to the cell surfaces of variant myoblasts was observed which may result from alterations to membrane glycoprotein receptors. These studies suggest that mannosylated glycoproteins of the cell surface play a role in the development of the myotubes from myoblasts. Lectin-resistant myoblasts should be useful model systems for investigating what appears to be a pleiotropic mutation affecting the myogenesis process through membrane modifications.     

Synthesis and characterisation of polyglucuronan

Several samples of polyglucuronan have been prepared by oxidation of cellulose with nitrogen oxides. Optimisation of the reaction conditions in terms of degree of oxidation and molecular weight of the products was carefully performed.     

Synthesis, characterisation and insulin-mimetic activity of oxovanadium(IV) complexes with amidrazone derivatives

The complexation of VO(2+) ion by ten acetamidrazone and 2-phenylacetamidrazone derivatives (L) was studied. Sixteen novel VO(2+) complexes were synthesised and characterised through the combined application of analytical and spectroscopic (EPR (electron paramagnetic resonance), FT-IR and diffuse reflectance electronic absorption) techniques. Eight are 1:2 species of composition [VOL(2)]SO(4) x xH(2)O and eight are 1:1 species with formula [VOL(SO(4))](n) x xH(2)O. The experimental data suggest a bidentate coordination mode for L with the donor set formed by the imine nitrogen and the carbonyl oxygen. EPR spectra indicate a square-pyramidal geometry for the 1:1 complexes and a penta-coordinated geometry intermediate between the square-pyramid and the trigonal-bipyramid for the 1:2 species. The hyperfine coupling constant along z axis, A(z), of the 1:2 complexes exhibits a marked reduction with respect to the predicted value (approximately 148x10(-4)cm(-1) vs. approximately 170x10(-4)cm(-1)). IR spectroscopic evidence supports the presence of sulphate as a counter-ion in the 1:2, and as a bridging bidentate ligand in the 1:1 complexes. Insulin-mimetic tests on modified fibroblasts, based on a modified MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazoliumbromide) assay, performed on three of the bis-chelated and eight of the mono-chelated derivatives, indicate that they are biologically active. The similar hydro/lipophilicity and the lack of ligand substituents recognizable by cell membrane receptors prevent substantial differentiation in the insulin-mimetic action.