N-Valproyl-L-Tryptophan for CNS-Targeting: Synthesis, Characterization and Efficacy In Vitro Studies of a New Potential Antiepileptic Drug

Viviana      De Caro; Giulia      Giandalia; Maria      Gabriella Siragusa; Liliana      Lamartina; Simonetta      Friscia; Pierangelo      Sardo; Fabio      Carletti; Valerio      Rizzo; Giuseppe      Ferraro; Libero      Italo Giannola

Abstract

A new aminoacidic derivative of valproic acid (VPA) has been synthesized and characterized by analytical and spectral data. The rationale for the preparation of such potential antiepileptic agent is based on the observation that chemical combination of the anticonvulsant pharmacophore, VPA with essential aminoacids could afford more effective and less toxic actives. The synthesis, characterization, physico-chemical parameters functional for crossing Blood Brain Barrier of N-valproyl-L-tryptophan (4) are reported. The Log D pH7.4 (0.3) indicates that (4) is adequate to cross biological membranes. Its chemical and enzymatic stability were assessed. The experiments indicate high stability of compound (4) at pH conditions of physiological fluids. Moreover, both in plasma and in cerebral enzymatic environments compound (4) doesnt undergo cleavage after 24 h.

The anticonvulsant activity of the new compound was assessed against epileptic burst discharges evoked in vitro in rat hippocampal slices (Seizure like events - SLEs) and compared with that of the widely used VPA. Compound (4), even at the lower tested concentration, when compared to VPA, showed an improved protective effect against hippocampal seizures. The collected data suggest that compound (4) could be considered a very valuable candidate for subsequent in vivo evaluation as new potential antiepileptic drug.

Keywords: Aminoacidic derivative, antiepileptic drug, CNS-targeting, enzymatic stability, seizure like events model, valproic acid, anticonvulsant pharmacophore, Blood Brain Bar-rier, biological membranes, physiological fluids, anticonvulsant activity, hippocampal sei-zures, Epilepsy, lacosamide, retigabine, rufinamide, talampanel, myoclonic, generalized tonic-clonic seizures, partial sei-zures, pharma-cokinetic, hepatotoxicity, teratogenicity, metabolite, CNS-active compounds, pharmacodynamic, central nervous system, Structure, –, activity relation-ship, physicochemical properties, bioavailability, lipophilicity, water partition coefficient, lipid-mediated free diffusion, valproyl-L-tryptophan, Triethylamine (TEA), 4-Dimethylaminopyridine, N, N'-dicyclohexylcarbodiimide, thin layer chromatography, IR spectra, UV spectra, HPLC analyses, NMR spectra, Electrospray ionization-mass (ESI-MS) spectrometry, crystallization, shake-flask technique, distribution coefficient, UV spectrophotometer analysis, Human Plasma, Phosphate Buffer Solution, chloroform, isotonic phosphate buffer, halothane, entorhinal cortex, hip-pocampus, oscilloscope, Transistor-Transistor Logic pulses, paroxysmal bursting rate, Statistical Analysis, neuron, absorption peaks, cerebral enzymes, Electrophysiological Studies, chiral integrity, toxic residuals, MS spectrum, McLafferty rearrangement, 2D spectrum, HMBC spectrum, parenteral route, GABA, glycine, taurine