Cécile Danel

Study of the complexation of risperidone and 9-hydroxyrisperidone with cyclodextrin hosts using affinity capillary electrophoresis and 1H NMR spectroscopy

The complexation of risperidone (Risp) and 9-hydroxyrisperidone (9-OH-Risp), atypical antipsychotics, with seven cyclodextrins (CDs) of pharmaceutical interest (native and hydroxypropylated (HP) alpha-, beta-, gamma-CDs and methyl (Me)-beta-CD) was studied by affinity capillary electrophoresis (ACE) and nuclear magnetic resonance spectroscopy (NMR) for acidic pH 2.5 and physiological pH 7.4. The 1:1 stoichiometry of the complexes was established by (1)H NMR spectroscopy using the continuous variation method developed by Job. The apparent binding constants of the 14 complexes at both pH were determined by ACE through the linear Scotts plots. The NMR spectroscopy investigation of the binding constants was achieved for the two CDs allowing the highest complexation: the beta-CD and Me-beta-CD. Both ACE and NMR spectroscopy studies provide similar conclusions by considering the influence of the 9-hydroxylation, the influence of the CD substitution and the influence of the pH. Moreover, the NMR spectroscopy results have allowed to suppose a pH-dependent inclusion mechanism. A thermodynamic study was then performed by ACE at both pH for the Risp.Me-beta-CD and 9-OH-Risp.Me-beta-CD complexes: the opposite signs of the entropic change (DeltaS degrees <0 at pH 2.5 and DeltaS degrees >0 at pH 7.4) confirms the influence of the pH on the complexation mechanism and the possible difference in the depth of the analyte inclusion in the hydrophobic cavity of the CD. Last, the two-dimensional ROESY (rotating-frame Overhauser spectroscopy) ((1)H-(1)H) and HOESY (heteronuclear Overhauser effect spectroscopy) ((19)F-(1)H) experiments have proved the inclusion of the aromatic part of the Risp and 9-OH-Risp in the hydrophobic CD cavity and lead us to propose a model of complexation.

P-glycoprotein and cytochrome P450 3A4 involvement in risperidone transport using an in vitro Caco-2/TC7 model and an in vivo model.

The possible involvement of P-glycoprotein (P-gp) and cytochrome P450 (CYP) 3A4 in risperidone transport was investigated using in vitro and in vivo models. Firstly, uptake studies were performed on a Caco-2/TC7 cell monolayer; the effects of 1 microg ml(-1) risperidone on apparent permeability were determined for secretory and absorptive directions, in the presence or absence of various P-gp and CYP3A4 inhibitors (verapamil, ketoconazole, erythromycin), and of an associated multidrug-resistant protein inhibitor (indomethacin). Secondly, on a conscious rat model, risperidone pharmacokinetic parameters, notably absorption parameters, were determined using compartmental and deconvolution methods. Three groups of seven rats received respectively an IV risperidone dose, an oral risperidone dose (PO group) and the same oral risperidone dose after verapamil administration (POV group). No formation of 9-hydroxyrisperidone was observed on Caco-2 cells after risperidone administration; there was no evidence that intestinal CYP3A4 is involved in risperidone metabolising. Risperidone secretory permeation was higher than absorptive permeation. Verapamil increased risperidone absorption permeation and decreased its secretory permeation. Indomethacin did not modify these permeation values. In rats, verapamil led to an increase in both risperidone and 9-hydroxyrisperidone plasmatic concentrations. The fraction absorbed in the verapamil group was 3.18 times higher than in the oral group (65.9% and 20.7% for POV group and PO group). The absorption rate constant was lower in the verapamil group. Our results indicate that P-gp decreases the intestinal absorption of risperidone and that intestinal CYP3A4 is not involved in risperidone metabolism.

Oxygenated lanostane-type triterpenes profiling in laccate Ganoderma chemotaxonomy

Oxygenated lanostane-type triterpenes (OLTT), including ganoderic acids and lucidenic acids produced by fungi of the genus Ganoderma (Polyporales), are abundantly documented for their potential pharmacological value. In order to test the correlation between species identity and OLTT composition, methanolic extracts of seven laccate Ganoderma species were analyzed by liquid chromatography coupled to mass spectrometry. OLTT profiles of each species were compared to a phylogenetic reconstruction of Ganoderma based on ITS rDNA sequences. The results suggest a high specificity in OLTT composition in one of the phylogenetic lineages of Ganoderma that encompasses tropical species, when no OLTT compound was detected in other lineages (including the European G. lucidum and the Asian G. sinense). Within the OLTT-positive lineage, G. sichuanense, G. martinicense, and G. tuberculosum (Asian-tropicum clade) were characterized by a specific composition in ganoderic acids and G. curtisii by a variety of lucidenic acids. An unidentified OLTT was found in G. resinaceum, also equivocally positioned in phylogenetic analyses. These results confirm OLTT as a suitable taxonomic marker in a lineage of pharmacologically and economically valuable species. Correlations with phylogeny, and development of OLTT composition as a fingerprint tool for quality control, could be an issue to address next, based on a more complete species sampling.