Exploitation of the enantioselectivity space of coated amylose tris(3,5-dimethylphenylcarbamate) in mixtures of 2-propanol and acetonitrile.

Chiral stationary phases (CSPs) with coated amylose tris(3,5-dimethylphenylcarbamate) (ADMPC) selector have long been recognized for their excellent chiral recognition ability in liquid chromatography. The conformational versatility behind this feature is the source of their known hysteretic behavior, which has been previously observed in polar organic (PO) mode eluents containing 2-propanol (IPA). Mixtures of IPA and acetonitrile (MeCN), a typical PO mode eluent system, have not been examined in this aspect yet, even though hysteresis is promising for finding unique unexplored enantioselectivities. Not only was the hysteresis detectable on ADMPC using mixtures of IPA and MeCN, but it was the typical behavior in a diverse set of test compounds. The difference in the retention time of the same analyte under conditions which only differed in the eluent history on the column can go up to 20-fold. The assumed hindered conformational changes of the selector were reflected in retention drift at certain eluent compositions. On the two sides of the transitions, distinct, useful states of the selector were detected. A series of IPA - MeCN compositions with defined pretreatment was selected and recommended as an extension of the preliminary, first choice method screening set that used only alcohols. The incorporation of a solvent possessing substantially different characteristics enhances the potential in practical applications, while keeping the technical simplicity. Stability and robustness of the additional states of the CSP were characterized. The examined columns of different brands shared the observed behavior. Kinetic stability of a column state is adequate for successful application. The evaluated states of ADMPC provide multiple enantiorecognition potential by using mixtures of IPA and MeCN also considering the pretreatment of the column. Unprecedented double and triple elution order reversals along the composition range supported the versatility of the available states. Our findings further enhance the usefulness of ADMPC-containing CSPs. We provide instructions for the application of the widespread chiral selector in common eluent mixtures to avoid pitfalls regarding reproducibility and robustness.

A novel stability-indicating HPLC method for the determination of enantiomeric purity of eluxadoline drug: Amylose tris(3,5-dichlorophenyl carbamate) stationary phase.

A simple and sensitive stability-indicating chiral HPLC method has been developed and validated per International Conference on Harmonization guidelines for the determination of enantiomeric purity of eluxadoline (Exdl). The impact of different mobile phase compositions and chiral stationary phases on the separation of Exdl enantiomer along with process- and degradation-related impurities has been studied. Homogeneity of Exdl and stable results of Exdl enantiomer in all degraded samples reveal the fact that the proposed method was specific (stability indicating). Amylose tris(3,5-dichlorophenyl carbamate) stationary phase column Chiralpak IE-3 (150 × 4.6 mm, 3 µm) provided better resolution with polar organic solvents than cellulose derivative, crown ether, and zwitterion stationary phases and nonpolar solvents. The mobile phase consisted of acetonitrile, tetrahydrofuran, methanol, butylamine, and acetic acid in the ratio of 500:500:20:2:1.5 (v/v/v/v/v). Isocratic elution was performed at a flow rate of 1.0 mL/min, column temperature of 35°C, injection volume of 10 µL, and UV detection of 240 nm. The United States Pharmacopeia (USP) resolution of the Exdl enantiomer was found to be more than 4.0 within a 65-min run time. Exdl enantiomer detector response linearity over the concentration range of 0.859-4.524 µg/mL was found to be R2  = 0.9985. The limit of detection, limit of quantification, and average percentage recovery values were established as 0.283 µg/mL, 0.859 µg/mL, and 96.0, respectively.

Effect of 2-propanol content on solute retention mechanisms determined using amylose tris(3,5-dimethylphenylcarbamate) chiral stationary phase under normal- and reversed-phase conditions.

The electrostatic interactions between chiral solutes and polysaccharide (PS)-based chiral selectors are the key to achieving chiral recognition; however, PS-based sorbents, derivatized of phenyl moieties, can exhibit considerably non-polar characteristics, and they are also useful for the separation of enantiomers in the reversed-phase mode. In this study, an immobilized amylose 3,5-dimethylphenylcarbamate-based sorbent was used to investigate the balance between electrostatic interactions and solvophobic interactions, with complementary effects on solute retention behavior when the isopropanol (IPA) concentration was altered. It was proposed that in both normal- and reversed-phase modes, information on the retention mechanisms could be obtained by observing the curvature of the logarithm of the retention factor versus the logarithm of the IPA concentration, and the slope values of the curves were related to the number of displaced IPA molecules upon solute adsorption. Using the proposed model and the two-site adsorption model, the retention behaviors of pantolactone (PL) enantiomers in both normal- and reversed-phase modes were investigated. The PL-sorbent interactions were classified into four types: electrostatic/enantioselective, electrostatic/nonselective, solvophobic/enantioselective, and solvophobic/nonselective. At IPA concentrations below 50 vol.% in n-hexane, the retention behaviors of PL were dominated by electrostatic/enantioselective sites, whereas at IPA concentrations beyond 50 vol.%, the solvophobic interactions of PL-sorbent were strengthened and mostly nonselective. By contrast, in the reversed-phase mode, a reverse in the enantiomeric elution order of PL was observed at 10 vol.% IPA, and considerably different enantioselectivity behaviors were found below and above 20 vol.%, indicating an abrupt change in the sorbent molecular environment. At IPA concentrations beyond 40 vol.%, the presence of PL-sorbent electrostatic interactions enhanced chiral recognition.

Chiral separation of several pesticides on an immobilized amylose tris(3-chloro-5-methylphenylcarbamate) column under polar-organic conditions. Influence of mobile phase and temperature on enantioselectivity.

In this work, the use of different solvents and temperatures was explored, aiming to evaluate their influence on the enantioseparation of pesticides by HPLC in polar-organic conditions, employing a column containing immobilized amylose tris(3-chloro-5-methylphenyl-carbamate). The chiral separation of seventeen different pesticides widely used as herbicides, fungicides, insecticides and precursors were studied. The mobile phases included methanol, ethanol, iso-propanol, n-propanol and acetonitrile; either pure or containing additives such as diethylamine, trifluoroacetic acid, formic acid, acetic acid or mixtures thereof. We studied the influence of these eluents on chiral separation of those pesticides in terms of retention factor, enantioselectivity, enantioresolution and peak symmetry. Regarding temperature influence, evaluated within the range 5 - 40 °C, nearly all the compounds decreased their retention and selectivity factors with the increase in temperature, although the effect was dependent on the mobile phase solvent. Moreover, estimation of thermodynamic parameters was performed based on linear van´t Hoff plots.

Comparison of dimethylated and methylchlorinated amylose stationary phases, coated and covalently immobilized on silica, for the separation of some chiral compounds in supercritical fluid chromatography.

The chromatographic properties of a new coated amylose tris(3-chloro-5-methylphenylcarbamate) were evaluated in supercritical fluid chromatography for the separation of enantiomers of chiral 1-aryl-5-aryl-pyrrolidin-2-one derivatives, potential anticancer agents, and some commercial drugs. The mobile phase consisted of CO2-modifier mixtures with 30% of either methanol or ethanol, the flow rate was 3 mL/min. The column oven temperature was 40 °C and the outlet pressure was 15 MPa, in order to limit the compressibility of the CO2, thus limiting density variation along the column. The obtained results were then compared to those observed toward 3 other stationary phases: the coated amylose tris(3,5-dimethylphenylcarbamate), the immobilized amylose tris(3,5-dimethylphenylcarbamate) and the coated amylose tris(5-chloro-2-methylphenylcarbamate). It was shown that the new coated amylose tris(3-chloro-5-methylphenylcarbamate) was the most retentive column whatever the studied compounds, particularly for thalidomide and omeprazole with retention factors up to 73.3 and 29.5for the second enantiomer, respectively. Concerning the enantioselectivity, even most of the compounds are separated on all the four columns, the coated amylose tris(3-chloro-5-methylphenylcarbamate) allows the best resolution for most of the ten studied analytes (except omeprazole for which the resolution values are equal to 7.8 and 9.7 on the coated amylose tris(3-chloro-5-methylphenylcarbamate) and amylose tris(3,5-dimethylphenylcarbamate), respectively). Acting in complementary ways, the two chlorinated stationary phases permitted the complete separation of enantiomers of nine compounds out of the ten.

Characterization of chemical profiles of pH-sensitive cleavable D-gluconhydroximo-1, 5-lactam hydrolysates by LC-MS: A potential agent for promoting tumor-targeted drug delivery.

Currently, controllable linker cleavage at the target site will facilitate the clinical treatment of cancer. Dual-functional prodrugs in combination of carbohydrate as targeting group and pH-sensitive cleavable linker are desired in clinical development. Here, a qualified structure of N-phenylcarbamate-d-gluconhydroximo-1,5-lactam was employed and proved to be a potential candidate prodrug in the drug design. To proof this concept, the possible mechanism of Beckmann rearrangement and the degraded products were confirmed by HPLC and LC-MS under the acid condition mimic lysosome. Hence, the strategy of d-gluconhydroximo-1,5-lactam as a prodrug carrier fabricated with interested drugs will provide a great potential approach for chemotherapy.

Impact of Pesticide Type and Emulsion Fat Content on the Bioaccessibility of Pesticides in Natural Products.

There is interest in incorporating nanoemulsions into certain foods and beverages, including dips, dressings, drinks, spreads, and sauces, due to their potentially beneficial attributes. In particular, excipient nanoemulsions can enhance the bioavailability of nutraceuticals in fruit- and vegetable-containing products consumed with them. There is, however, potential for them to also raise the bioavailability of undesirable substances found in these products, such as pesticides. In this research, we studied the impact of excipient nanoemulsions on the bioaccessibility of pesticide-treated tomatoes. We hypothesized that the propensity for nanoemulsions to raise pesticide bioaccessibility would depend on the polarity of the pesticide molecules. Bendiocarb, parathion, and chlorpyrifos were therefore selected because they have Log P values of 1.7, 3.8, and 5.3, respectively. Nanoemulsions with different oil contents (0%, 4%, and 8%) were fabricated to study their impact on pesticide uptake. In the absence of oil, the bioaccessibility increased with increasing pesticide polarity (decreasing Log P): bendiocarb (92.9%) > parathion (16.4%) > chlorpyrifos (2.8%). Bendiocarb bioaccessibility did not depend on the oil content of the nanoemulsions, which was attributed to its relatively high water-solubility. Conversely, the bioaccessibility of the more hydrophobic pesticides (parathion and chlorpyrifos) increased with increasing oil content. For instance, for chlorpyrifos, the bioaccessibility was 2.8%, 47.0%, and 70.7% at 0%, 4%, and 8% oil content, respectively. Our findings have repercussions for the utilization of nanoemulsions as excipient foods in products that may have high levels of undesirable non-polar substances, such as pesticides.

Hysteresis of retention and enantioselectivity on amylose tris(3,5-dimethylphenylcarbamate) chiral stationary phases in mixtures of 2-propanol and methanol.

Seemingly identical chromatographic conditions result in drastically different enantioseparations on amylose tris(3,5-dimethylphenylcarbamate) (ADMPC) columns in mixtures of 2-propanol and methanol. Selectivities of structurally diverse enantiomer pairs depend on the direction from which the composition of the eluent is approached. An alteration in the structure of the chiral stationary phase (CSP) is the only realistic reason behind the dissimilar selectivities in the same eluent. History-dependent retention and recognition mechanisms are indicated by van't Hoff plots and even by a reversal of the enantiomer elution order. The most notable observation is the easy access to markedly different states of the CSP in the same solvent mixture by a short pretreatment with 2-propanol in one case and with methanol in the other, while the transition between the two states is hindered enough to ensure long-term stability for both. Repeatability strongly depends on the composition of the eluent and it is key to utilization and also to rationalization of the phenomenon. From a theoretical point of view, this so-called hysteretic behavior poses another challenge to consider when modeling chiral interactions.

Enantioseparation of racecadotril using polysaccharide-type chiral stationary phases in polar organic mode.

Enantioseparation of the antidiarrheal drug, racecadotril, was investigated by liquid chromatography using polysaccharide-type chiral stationary phases in polar organic mode. The enantiodiscrimininating properties of 4 different chiral columns (Chiralpak AD, Chiralcel OD, Chiralpak AS, Chiralcel OJ) with 5 different solvents (methanol, ethanol, 1-propanol, 2-propanol, and acetonitrile) at 5 different temperatures (5-40 °C) were investigated. Apart from Chiralpak AS column the other 3 columns showed significant enantioseparation capabilities. Among the tested mobile phases, alcohol type solvents were superior over acetonitrile, and significant differences in enantioselective performance of the selector were observed depending on the type of alcohol employed. Van't Hoff analysis was used for calculation of thermodynamic parameters which revealed that enantioseparation is mainly enthalpy controlled; however, enthropic control was also observed. Enantiopure standard was used to determine the enantiomer elution order, revealing chiral selector-and mobile-phase dependent reversal of enantiomer elution order. Using the optimized method (Chiralcel OJ stationary phase, thermostated at 10 °C, 100% methanol, flow rate: 0.6 mL/min) baseline separation of racecadotril enantiomers (resolution = 3.00 ± 0.02) was achieved, with the R-enantiomer eluting first. The method was validated according to the ICH guidelines, and its application was tested on capsule and granules containing the racemic mixture of the drug.

Using short-term bioassays to evaluate the endocrine disrupting capacity of the pesticides linuron and fenoxycarb.

Several short-term whole-organism bioassays based on transgenic aquatic models are now under validation by the OECD (Organization for Economic Co-operation and Development) to become standardized test guidelines for the evaluation of the endocrine activity of substances. Evaluation of the endocrine disrupting capacity of pesticides will be a domain of applicability of these future reference tests. The herbicide linuron and the insecticide fenoxycarb are two chemicals commonly used in agricultural practices. While numerous studies indicate that linuron is likely to be an endocrine disruptor, there is little information available on the effect of fenoxycarb on vertebrate endocrine systems. Using whole-organism bioassays based on transgenic Xenopus laevis tadpoles and medaka fry we assessed the potential of fenoxycarb and linuron to disrupt thyroid, androgen and estrogen signaling. In addition we used in silico approach to simulate the affinity of these two pesticides to human hormone receptors. Linuron elicited thyroid hormone-like activity in tadpoles at all concentrations tested and, showed an anti-estrogenic activity in medaka at concentrations 2.5mg/L and higher. Our experiments suggest that, in addition to its previously established anti-androgenic action, linuron exhibits thyroid hormone-like responses, as well as acting at the estrogen receptor level to inhibit estrogen signaling. Fenoxycarb on the other hand, did not cause any changes in thyroid, androgen or estrogen signaling at the concentrations tested.

Evaluation and comparison of three different separation techniques for analysis of retroamide enantiomers and their biological evaluation against h-P2X7 receptor.

The P2X receptors are seven-transmembrane domain G protein-coupled receptors and the 7 subtypes of P2X receptors identified in humans, and named P2X1 to P2X7, are channel receptors whose endogenous ligand is ATP. New antagonists of the P2X7 receptor were developed, since this purinergic receptor was highlighted to be involved in many diseases such as different types of pain, cancer, ischemia, neurodegenerative diseases (including Parkinson's and Alzheimer's diseases) characterized by inflammatory processes. With the aim of evaluate the impact of chirality on the pharmacological activity of a new P2X7R antagonist, a semi-preparative method was developed in supercritical fluid chromatography (SFC). Among four polysaccharide based chiral stationary phases: Chiralcel OD-H and OJ-H and Chiralpak AS-H and AD-H, the last one namely amylose tris (3,5-dimethylphenylcarbamate) with a mobile phase consisted of carbon dioxide-ethanol (80:20, v/v), led to the successful separation of the enantiomers in short run time and with good resolution. Limits of detection and quantification were calculated and were found equal for compound 1, to 1.37 µM and 4.57 µM respectively, for peak 1 and were equal to 1.60 µM and 5.30 µM respectively, for peak 2 at λ=210 nm. Before carrying out the pharmacological evaluation of each enantiomer, two complementary methodologies, e.g. liquid chromatography and capillary electrophoresis were performed in parallel to improve the limits of detection and quantification to assess the enantiomeric purity. HPLC using a Chiralpak AD stationary phase led to four times lower limits of detection and quantification with regard to SFC. In the same time, capillary electrophoresis involving dual cyclodextrins system constituted of a SBE-ß-CD and a MM-ß-CD mixture enhanced the signal-to-noise ratio and led to similar limits of detection and quantification with regard to SFC. No trace of the other enantiomer was found in the isolated one. Biological activities of individual enantiomers were then evaluated and revealed no cytotoxicity against cell lines and a significant difference in terms of their IC50 values with respect to the investigated racemate (6.43 µM): 3.49 µM for the (R)-enantiomer and >10(-4)µM for the (S)-enantiomer, for compound 1, showing that, this antagonist activity is stereospecific.

Immobilized ß-cyclodextrin-based silica vs polymer monoliths for chiral nano liquid chromatographic separation of racemates.

The enantioselectivity of immobilized ß-cyclodextrin phenyl carbamate-based silica monolithic capillary columns was compared to our previously described polymer counterpart. 2,3,6-Tris(phenylcarbamoyl)-ß-cyclodextrin-6-methacrylate was used as a functional monomer for the preparation of ß-cyclodextrin (ß-CD)-based silica and polymer monoliths. The silica monoliths were prepared via the sol-gel technique in fused silica capillary followed by modification of the bare silica monoliths with an anchor group prior to polymerization with ß-CD methacrylate using either 2,2'-azobis(isobutyronitrile) or benzoylperoxide as radical initiators. On the other hand, the polymer monoliths were prepared via the copolymerization of ß-CD methacrylate and ethylene glycol dimethacrylate in different ratios in situ in fused silica capillary. The prepared silica/polymer monoliths were investigated for the chiral separation of different classes of pharmaceuticals namely; α- and ß-blockers, anti-inflammatory drugs, antifungal drugs, dopamine antagonists, norepinephrine-dopamine reuptake inhibitors, catecholamines, sedative hypnotics, diuretics, antihistaminics, anticancer drugs and antiarrhythmic drugs. Baseline separation was achieved for alprenolol, bufuralol, carbuterol, cizolertine, desmethylcizolertine, eticlopride, ifosfamide, 1-indanol, propranolol, tebuconazole, tertatolol and o-methoxymandelic acid under reversed phase conditions using mobile phase composed of methanol and water. The silica-based monoliths showed a comparative enantioselectivity to the polymer monoliths.

Phenylthiocarbamate or N-carbothiophenyl group chemistry in peptide synthesis and bioconjugation.

The design of novel chemoselective and site-specific ligation methods provides new tools for obtaining complex scaffolds, peptidomimetics, and peptide conjugates. The chemistry of the N-phenylthiocarbonyl group has led to several developments in peptide ligation chemistry and peptide bioconjugation during the last 10 years. The aim of this review is to provide an overview of this emerging field.

Enantiomeric separation of amlodipine and its two chiral impurities by nano-liquid chromatography and capillary electrochromatography using a chiral stationary phase based on cellulose tris(4-chloro-3-methylphenylcarbamate).

In this work, a novel polysaccharide-based chiral stationary phase, cellulose tris(4-chloro-3-methylphenylcarbamate), also called Sepapak 4 has been evaluated for the chiral separation of amlodipine (AML) and its two impurities. AML is a powerful vasodilatator drug used for the treatment of hypertension. Capillary columns of 100 µm id packed with the chiral stationary phase were used for both nano-LC and CEC experiments. The optimization of the mobile phase composed of ACN/water, (90:10, v/v) containing 15 mM ammonium borate pH 10.0 in nano-LC allowed the chiral separation of AML and the two impurities, but not in a single run. With the purpose to obtain the separation of the three pairs of enantiomers simultaneously, CEC analyses were performed in the same conditions achieving better enantioresolution and higher separation efficiencies for each compound. To fully resolve the mixture of six enantiomers, parameters such as buffer pH and concentration sample injection have been then investigated. A mixture of ACN/water (90:10, v/v) containing 5 mM ammonium borate buffer pH 9.0 enabled the complete separation of the three couples of enantiomers in less than 30 min. The optimized CEC method was therefore validated and applied to the analysis of pharmaceutical formulation declared to contain only AML racemate.

Potential therapeutic effect of nanobased formulation of rivastigmine on rat model of Alzheimer's disease.

BACKGROUND: To sustain the effect of rivastigmine, a hydrophilic cholinesterase inhibitor, nanobased formulations were prepared. The efficacy of the prepared rivastigmine liposomes (RLs) in comparison to rivastigmine solution (RS) was assessed in an aluminium chloride (AlCl(3))-induced Alzheimer's model. METHODS: Liposomes were prepared by lipid hydration (F1) and heating (F2) methods. Rats were treated with either RS or RLs (1 mg/kg/day) concomitantly with AlCl(3) (50 mg/kg/day). RESULTS: The study showed that the F1 method produced smaller liposomes (67.51 ± 14.2 nm) than F2 (528.7 ± 15.5 nm), but both entrapped the same amount of the drug (92.1% ± 1.4%). After 6 hours, 74.2% ± 1.5% and 60.8% ± 2.3% of rivastigmine were released from F1 and F2, respectively. Both RLs and RS improved the deterioration of spatial memory induced by AlCl(3), with RLs having a superior effect. Further biochemical measurements proved that RS and RLs were able to lower plasma C-reactive protein, homocysteine and asymmetric dimethy-larginine levels. RS significantly attenuated acetylcholinesterase (AChE) activity, whereas Na(+)/K(+)-adenosine triphosphatase (ATPase) activity was enhanced compared to the AlCl(3)-treated animals; however, RLs succeeded in normalization of AChE and Na(+)/K(+) ATPase activities. Gene-expression profile showed that cotreatment with RS to AlCl(3)-treated rats succeeded in exerting significant decreases in BACE1, AChE, and IL1B gene expression. Normalization of the expression of the aforementioned genes was achieved by coadministration of RLs to AlCl(3)-treated rats. The profound therapeutic effect of RLs over RS was evidenced by nearly preventing amyloid plaque formation, as shown in the histopathological examination of rat brain. CONCLUSION: RLs could be a potential drug-delivery system for ameliorating Alzheimer's disease.

Computational analysis of human OGA structure in complex with PUGNAc and NAG-thiazoline derivatives.

The substitution of serine and threonine residues in nucleocytoplasmic proteins with 2-acetamido-2-deoxy-ß-D-glucopyranose (O-GlcNAc) residues is an essential post-translational modification found in many multicellular eukaryotes. O-glycoprotein 2-acetamino-2-deoxy-ß-D-glucopyranosidase (O-GlcNAcase) hydrolyzes O-GlcNAc residues from post-translationally modified serine/threonine residues of nucleocytoplasmic protein. O-GlcNAc has been implicated in several disease states such as cancer, Alzheimer's disease, and type II diabetes. For this paper, a model of the human O-GlcNAcase (hOGA) enzyme based on the X-ray structures of bacterial Clostridium perfringens (CpNagJ) and Bacteroides thetaiotaomicrometer (BtOGA) homologues has been generated through molecular homology modeling. In addition, molecular docking, molecular dynamics (MD) simulations, and Linear Interaction Energy (LIE) were employed to determine the bind for derivatives of two potent inhibitors: O-(2-acetamido-2-deoxy-D-glucopyranosylidene)amino-N-phenylcarbamate (PUGNAc) and 1,2-dideoxy-2'-methyl-R-D-glucopyranoso-[2,1-d]-Δ2'-thiazoline (NAG-thiazoline), with hOGA. The results show that the binding free energy calculations using the Linear Interaction Energy (LIE) are correlated with inhibition constant values. Therefore, the model of the human O-GlcNAcase (hOGA) obtained here may be used as a target for rational design of new inhibitors.

Amphiphilic polyaspartamide copolymer-based micelles for rivastigmine delivery to neuronal cells.

A novel polysorbate-80 (PS(80))-attached amphiphilic copolymer comprising a hydrophilic α,ß-poly(N-2-hydroxyethyl)-D,L-aspartamide (PHEA) backbone and hydrophobic squalenyl-C(17) (Sq(17)) portions was synthesized and characterized; the formation of polymeric micelles was also evaluated. Rivastigmine free-base (Riv), a hydrophobic drug employed to treat Alzheimer's disease, was chosen as model drug to investigate micelle's ability to incorporate hydrophobic molecules and target them to neuronal cells. Micelle formation was studied through analyses including fluorescence spectroscopy and 2D (1)H-NMR NOESY experiments. Finally, the capacity of Riv-loaded micelles, versus free drug, to penetrate mouse neuroblastoma cells (Neuro2a) was evaluated. 2D (1)H-NMR NOESY experiments demonstrated that the PHEA-EDA-Sq(17)-PS(80) copolymer self-assembles into micelle structures in water, with a micelle core formed by hydrophobic interaction between Sq(17) alkyl chains. Fluorescence probe studies revealed the CAC of PHEA-EDA-Sq(17)-PS(80) micelles, which was 0.25 mg mL(-1). The micelles obtained had a nanometric hydrodynamic diameter with narrow size distribution and negative surface charge. The PHEA-EDA-Sq(17)-PS(80) micelles incorporated a large amount of Riv, and the system maintained the stability of Riv after incubation in human plasma. An in vitro biological assay evidenced no cytotoxic effects of either empty or loaded micelles on the neuronal cell lines tested. Moreover, the micelles are internalized by neuroblastoma cell lines with drug uptake depending on the micelles concentration.

Evaluation of new cellulose-based chiral stationary phases Sepapak-2 and Sepapak-4 for the enantiomeric separation of pesticides by nano liquid chromatography and capillary electrochromatography.

Two novel polysaccharide-based chiral stationary phases (CSPs), known as Sepapak-2 (cellulose tris(3-chloro-4-methylphenylcarbamate)) and Sepapak-4 (cellulose tris(4-chloro-3-methylphenylcarbamate)), have been evaluated in this work for the chiral separation of a group of 16 pesticides including herbicides, insecticides and fungicides. The optimization of the mobile phase employed in nano-liquid chromatography (nano-LC) enabled the chiral separation of seven pesticides on Sepapak-2 and of nine pesticides on Sepapak-4. Due to the fact that Sepapak-4 gave better results, this column was selected to compare nano-LC and capillary electrochromatography (CEC) under the same conditions that consisted in the use of a 90/9/1 (v/v/v) ACN/H2O/ammonium formate (pH 2.5) background electrolyte (BGE). As expected, both the efficiency and the chiral resolution obtained in CEC experiments were higher than in nano-LC for all the analyzed compounds. The analytical characteristics of the CEC developed methodology were evaluated in terms of linearity, LODs, LOQs, precision, selectivity, and accuracy allowing its application to the quantitation of metalaxyl and its enantiomeric impurity in a commercial fungicide product marketed as enantiomerically pure (metalaxyl-M) and in soil and tap water samples after solid phase extraction (SPE). The determined amount of metalaxyl-M was found to be a 26% above the labeled content and it contained an enantiomeric impurity of a 3.7% of S-metalaxyl was determined.

A synthetic decursin analog with increased in vivo stability suppresses androgen receptor signaling in vitro and in vivo.

Targeting androgen receptor (AR) signaling with agents distinct from current antagonist drugs remains a rational approach to the prevention and treatment of prostate cancer (PCa). Our previous studies have shown that decursin and isomer decursinol angelate (DA), isolated from the Korean medicinal herb Angelica gigas Nakai, interrupt AR signaling and possess anti-PCa activities in vitro. In the LNCaP PCa cell model, these pyranoccoumarin compounds exhibit properties distinct from currently used antagonists (e.g., Casodex). However, both are rapidly de-esterified to decursinol, a partial AR agonist. We report here that a synthetic decursin analog, decursinol phenylthiocarbamate (DPTC), has greater in vivo stability than the parent compounds. DPTC-decursinol conversion was undetectable in mice. Furthermore, in LNCaP cells, DPTC decreased prostate specific antigen (PSA) expression, down-regulated AR abundance and mRNA and inhibited AR nuclear translocation. The effect of DPTC on AR and PSA mRNA and protein abundance was also observed in VCaP cells expressing wild type AR. DPTC inhibited growth of both PCa cell lines through G(1) cell cycle arrest and apoptosis, as did decursin and DA. Furthermore, i.p. administration of DPTC for 3 weeks suppressed the expression of AR target genes probasin and Nkx3.1 in mouse prostate glands. Overall, our data suggest that DPTC represents a prototype lead compound for development of in vivo stable and active novel decursin analogs for the prevention or therapy of PCa.

Synthesis and chromatographic enantioresolution of anti-HIV quinolone derivatives.

The successful enantioseparation of five 6-desfluoroquinolones with three polysaccharide-based stationary phases (namely, the cellulose-based Chiralpak IB and the two amylose-based Chiralpak AD-H and Lux Amylose-2) is herein described. The investigated species differ for the nature of substituents and/or the position of the stereogenic centre on the quinolone scaffold. The effect on the enantioseparation performance exerted by the different morphology of the cellulose-based and amylose-based polymers, was systematically evaluated for all compounds. In this frame, the impact of alternative alcoholic (ethanol, 2-ethoxyethanol, methanol, 2-propanol) and acidic (acetic, methanesulfonic and trifluoroacetic acid) modifiers as well as of a "non-standard" solvent (chloroform), was investigated in normal phase conditions along with the stereo-electronic peculiarities of the selected polymers. While 7-[4-(1,3-benzothiazol-2-yl)-2-methyl-1-piperazinyl]-1-methyl-4-oxo-1,4-dihydro-1,8-naphthyridine-3-carboxylic acid (1) was enantioresolved with conventional normal-phase conditions by means of the largely employed amylose-based Chiralpak AD-H column, the recruitment of a bulky alcohol (2-ethoxyethanol) succeeded in the enantioresolution of 6-amino-1-methyl-7-[2-methyl-4-(2-pyridinyl)-1-piperazinyl]-4-oxo-1,4-dihydro-3-quinolinecarboxylic acid (2) and 6-amino-1-[1-(hydroxymethyl)propyl]-4-oxo-7-(4-pyridin-2-ylpiperazin-1-yl)-1,4-dihydroquinoline-3-carboxylic acid (3) with the same column. The use of the amylose-based Lux Amylose-2 column, carrying both an electro-withdrawing (chlorine) and an electro-donating (methyl) group on the carbamate residue, allowed to get 6-amino-1-methyl-4-oxo-7-[3-(2-pyridinyl)-1-pyrrolidinyl]-1,4-dihydro-3-quinolinecarboxylic acid hydrochloride (4) enanantioresolved, and 6-amino-1-methyl-4-oxo-7-(3-pyridin-2-ylpiperidin-1-yl)-1,4-dihydroquinoline-3-carboxylic acid (5) enantioseparated.