Andrea Latrofa

2-Phenyl-imidazo(1,2-a)pyridine Compounds Containing Hydrophilic Groups as Potent and Selective Ligands for Peripheral Benzodiazepine Receptors: Synthesis, Binding Affinity and Electrophysiological Studies

A series of imidazopyridine acetamides were synthesized to evaluate the effects of structural changes at both central (CBRs) and peripheral benzodiazepine receptors (PBRs). These changes include the introduction of polar substituents or ionizable functional groups at the 2- and 8-position of the imidazopyridine skeleton. The results suggest that substituents endowed with hydrogen bonding acceptor and/or donor properties in the para position of the phenyl ring lead to high affinity for PBR. In electrophysiological studies, it was found that compounds 9, 12, 13, and 28 markedly enhanced GABA-evoked Cl (-) currents in Xenopus oocytes expressing alpha 1beta 2gamma 2 GABA A receptors. The capability of flumazenil to reduce the stimulatory effect exerted by compound 9 supports the conclusion that the modulatory effects of the examined compounds occur involving the CBR. The ability of compound 16 to increase GABA A receptor-mediated miniature inhibitory postsynaptic currents in CA1 pyramidal neurons is indicative of its ability to stimulate the local synthesis and secretion of neurosteroids.

Dissolution properties and anticonvulsant activity of phenytoin-polyethylene glycol 6000 and -polyvinylpyrrolidone K-30 solid dispersions

Solid dispersions of phenytoin in polyethylene glycol 6000 and polyvinylpyrrolidone K-30 with different drug-to-carrier ratios were prepared by the solvent method with the aim of increasing dissolution rate and bioavailability of the drug. These new formulations were characterized in the solid state by FT-IR spectroscopy, X-ray powder diffraction, and differential scanning calorimetry. Drug solubility and dissolution rate are improved by these formulations, particularly with SDPEG 1/20 and SDPVP 1/20 systems. Storage was found to influence the stability of the solid dispersions. By maximal electroshock test, it was found that the intraperitoneal administration in mice of the SDPEG 1/20 and SDPVP 1/20 systems exhibited anticonvulsant activity similar to diphenylhydantoin sodium salt.

Physicochemical characterization and in vivo properties of Zolpidem in solid dispersions with polyethylene glycol 4000 and 6000.

Solid dispersions and physical mixtures of Zolpidem in polyethylene glycol 4000 (PEG 4000) and 6000 (PEG 6000) were prepared with the aim to increase its aqueous solubility. These PEG based formulations of the drug were characterized in solid state by FT-IR spectroscopy, X-ray powder diffraction, and differential scanning calorimetry. By these physical determinations no drug-polymer interactions were evidenced. Both solubility and dissolution rate of the drug in these formulations were increased. Each individual dissolution profile of PEG based formulation fitted Baker-Lonsdale and first order kinetic models. Finally, significant differences in ataxic induction time were observed between Zolpidem orally administered as suspension of drug alone and as solid dispersion or physical mixture. These formulations, indeed, showed almost two- to three-fold longer ataxic induction times suggesting that, in the presence of PEG, the intestinal membrane permeability is probably the rate-limiting factor of the absorption process.

Depletion of cortical allopregnanolone potentiates stress-induced increase in cortical dopamine output

In freely moving rats finasteride markedly reduced the cortical content of allopregnanolone. This treatment significantly prolonged the increase in the extracellular concentration of dopamine in the prefrontal cortex induced by foot shock. Moreover, finasteride enhanced both maximal increase of dopamine and its duration elicited by a single injection of the anxiogenic drug FG 7142. These results suggest that endogenous allopregnanolone may modulate the excitatory response of cortical dopaminergic neurons to stressful and anxiogenic stimuli.

Synthesis, in vitro and in vivo cytotoxicity, and prediction of the intestinal absorption of substituted 2-ethoxycarbonyl-imidazo[2,1-b]benzothiazoles

The imidazobenzothiazole compounds 3-17 together with the imidazobenzoxazole 18, and the imidazobenzoimidazole 19 were prepared and their cytotoxic activity evaluated at the National Cancer Institute (NCI) for testing against a panel of approximately 60 tumor cell lines. Compounds 5, 7, 8, and 16 exhibited interesting in vitro cytotoxic activity. The most active imidazobenzothiazole derivative 8 was further evaluated as a cytotoxic agent in the hollow fiber assay and showed a score greater than the minimum values for xenograft testing together with a net cell kill. Comparison with the results displayed in the in vivo assay by standard antitumor drugs in clinical use revealed a significant in vivo activity of the benzothiazole compound. COMPARE analyses for compounds 4-19 against the NCIs standard agent database show poor or no correlation, and it might suggest for these compounds a mechanism of action unrelated to that of any known drug. Furthermore, the benzothiazole 8 did not show significant antitumor activity in a panel of two xenotransplanted tumors (i.e. colon and non-small cell lung tumors). By computing the polar surface area of compounds 3-19 with the MAREA computer program it was established that the most active compounds 5, 7, 8, and 16 should experience good intestinal permeability.

Highly water-soluble derivatives of the anesthetic agent propofol: in vitro and in vivo evaluation of cyclic amino acid esters.

Cyclic amino acid esters of propofol were synthesized in an attempt to develop new water-soluble anesthetic agents. Their solubility and stability in aqueous solution, and their ability to release propofol in vitro under physiological conditions were determined. L-Proline (6a) and racemic nipecotic acid (6c) esters were found to be highly soluble in water. Sufficiently stable at physiological pH (half-lives >6 h), the alpha-amino acid esters, 6a and 6b, were found to be quantitatively hydrolyzed in plasma and liver esterase solutions within a few minutes, showing prodrug behavior. The in vitro activity of the esters, determined either by the [(35)S]tert-butylbicyclophosphorothionate ([(35)S]TBPS) binding assay or electrophysiological measurements of the action at cloned human receptors, proved to be a mechanism involving allosteric modulation of GABA(A) receptors. Indeed, L-proline (6a), and racemic pipecolinate (6b) and nipecotate (6c), like propofol, reduced [(35)S]TBPS binding, whereas isonipecotate (6d) showed bicuculline-like behavior, increasing [(35)S]TBPS binding. A nonlinear relation between GABA(A) receptor binding affinity and lipophilicity, as assessed by reversed-phase high-performance liquid chromatography, emerged as a trend. The in vivo anticonvulsant and anesthetic activities of prolinate 6a, intraperitoneally administered in water solution, showed that is a water-soluble propofol prodrug candidate for developing formulations useful for parenteral administration.

Complexation of Zolpidem with 2‐Hydroxypropyl‐β‐, Methyl‐β‐, and 2‐Hydroxypropyl‐γ‐Cyclodextrin: Effect on Aqueous Solubility, Dissolution Rate, and Ataxic Activity in Rat

The effect of some chemically modified cyclodextrins (namely, 2-hydroxy- propyl-b-, methyl-b-, and 2-hydroxypropyl-g-cyclodextrin (HP-b-CD, Me-b-CD, and HP-g-CD, respectively)) on the aqueous solubility and dissolution rate of the hypnotic agent Zolpidem (ZP) was investigated. Solid complexes were prepared by freeze drying and characterized by infrared spectroscopy, X-ray powder diffraction, and differential scanning calorimetry. The solubility and dissolution rate of the drug were significantly improved by complexation with HP-b -CD or Me-b-CD. The structure of the inclusion complex ZP-HP-b -CD in CH 3COOD/D2O was investigated by 1 H and 13 C NMR spec- troscopy, including NOE measurements. These measurements revealing a weak inter- action between the tolyl moiety of the guest molecule and the HP-b-CD cavity. The ataxic activity in rat was also investigated and it was found that ZP-HP-b-CD and ZP-Me-b-CD complexes showed almost 2-fold longer ataxic induction times than con- trols.

Water-soluble salts of aminoacid esters of the anaesthetic agent Propofol

Abstract The glycinates 4 , 5 , acetates 6 , 7 , 10 , propionate 8 , butyrate 9 and carbonate 11 were synthesized and evaluated as potential water-soluble prodrugs of Propofol (2,6-diisopropylphenol) 1 suitable for parenteral administration. The 4–9 · HCl salts were also prepared and some of them (i.e. 4 · HCl and 6 · HCl) were found sufficiently soluble in aqueous solutions. The kinetics of hydrolysis of the esters 4–11 and 4–9 · HCl salts were studied in 0.05 M phosphate buffer pH 7.4, and a number of derivatives ( 4 , 6 , 7 , and corresponding HCl salts) were examined for their stability in human plasma and brain homogenate. Our results indicated that the salts 4 · HCl and 6 · HCl, sufficiently soluble in water, are relatively stable in physiological media. Most of the examined compounds, in particular compound 6 , were found to inhibit the binding of [ 35 S]- tert -butylbicyclophosphorothionate ([ 35 S]TBPS) demonstrating to possess affinity for the Propofol recognition site on GABA A receptors.

Amphiphilic inulin-d-α-tocopherol succinate (INVITE) bioconjugates for biomedical applications

Herein is reported the synthesis and characterization of innovative inulin (INU)-vitamin E succinate (VITE) bioconjugates (INVITE). The obtained amphiphilic INU-based polymers, self-assembling in nanostructures, have been thought as new drug delivery systems (DDS) for the therapy of urinary tract infections (UTI). The synthesis of INVITE bioconjugates was carried out in bulk, without isolation of intermediate products, to reduce the amount of solvents used in the purification steps and to prevent possible VITE oxidation during work up. Six different INVITE conjugates (INVITE 1-6) have been synthesized by varying both the relative amount of VITE with respect to INU repetitive units and the reaction temperature. Afterwards, the ability of the new conjugates to form micelle systems, by applying two different established methods for critical aggregation concentration (CAC) evaluation, has been verified. Both methods produced similar CAC values ranging from 2.5 × 10(-3)mM to 2.4 × 10(-2)mM in agreement with the different degrees of derivatization shown by the INVITE 1-6 conjugates. The mean diameter of prepared INVITE micelles, resulted in the range 24-60 nm. The size of the obtained INVITE micelles did not change as measured at different time points up to 12 days, so confirming their stability upon storage.

Translocator Protein (TSPO) Ligand-Ara-C (Cytarabine) Conjugates as a Strategy To Deliver Antineoplastic Drugs and To Enhance Drug Clinical Potential

The aim of this work was to evaluate TSPO ligand-Ara-C conjugation as an approach for the selective delivery of the antineoplastic agent to brain tumors as well as for overcome P-gp resistance induction observed for the majority of cytotoxic agents, enhancing the drug clinical potential. To this end, the novel N-imidazopyridinacetyl-Ara-C conjugates 3a-c, 10 and 15 have been prepared and evaluated for their cytotoxicity against glioma cell lines. In contrast to that observed for 3a-c and 10, the conjugate 15 resulted stable in both phosphate buffer and physiological medium. In all cases, the release of free Ara-C from hydrolyzed conjugates was checked by HPLC and ESI-MS analysis. Conjugates 10 and 15 displayed very high in vitro TSPO affinity and selectivity, and, hence, they may possess potential for targeted brain delivery. Due to the favorable features displayed by the conjugate 15, it was further evaluated on glioma cell lines, expressing high levels of TSPO, in the presence and in the absence of specific nucleoside transport (NT) inhibitors. In contrast to that observed for the free Ara-C, the presence of NT inhibitors did not reduce the cytotoxic activity of 15. Moreover, conjugate 15, as N(4)-acyl derivative of Ara-C, should be resistant to inactivation by cytidine deaminase, and it may possess enhanced propensity to target brain tumor cells characterized by a reduced expression of NTs. In addition, this conjugate behaves as a clear P-gp modulator and thereby may be useful to reverse MDR. Transport studies across the MDCKII-MDR1 monolayer indicated that conjugate 15 should overcome the BBB by transcellular pathway. All these features may be useful for enhancing the clinical potential of the nucleoside drug Ara-C.