PH_I_L: Pharmaceutical Sciences I. Lectures
Eszter Kalydi1, Dóra Ujj2, Erzsébet Varga2, Milo Malanga2, Szabolcs Béni1, Gábor Benkovics2
1Department of Pharmacognosy, Semmelweis University, Budapest
2CycloLab, Cyclodextrin R&D Ltd, Budapest
Cyclodextrins (CDs) are cyclic oligosaccharides, consisting of six (αCD), seven (βCD) or eight (γCD) α-D-glucopyranose units. Owing to their hydrophilic surface and a lipophilic cavity, CDs are able to form inclusion complexes with lipophilic compounds. Due to the moderate aqueous solubility of native CDs, wide range of synthetically modified derivatives are prepared and used for various purposes. Beyond their inclusion complex forming ability, their intrinsic chirality makes CDs an excellent choice as chiral resolving agents in capillary electrophoresis (CE). Sugammadex is a specially designed γCD derivative used as an antidote in the clinical practice, however its analytical applicability has not been explored yet.
We aimed to synthesize two new sugammadex-analogues, sualphadex and subetadex differing only in their cavity size. Bearing multiple carboxyl moieties, their protonation state determines their interactions with basic compounds, also influencing their inclusion complex formations. Therefore, the characterization of the acid-base properties of these compounds were also intended using NMR spectroscopy. Our third goal was to explore their applicability as chiral selectors in CE.
The new analogues were synthetized according to Cyclolab Ltd.’s know how. The structures were confirmed by 1H- and 2D NMR and ESI-MS techniques. To determine the pKa values, NMR-pH titration method was used, while the pKa values were calculated using the HypNMR software. CE experiments were performed at pH 7.0, pH 5.0 and pH 2.5 using selected cathinone racemates as test analytes.
The structural identification results supported the single isomeric nature of all compounds, substituted with carboxyethylthio sidechains. Their acid-base properties showed no significant variation, the complete protonation is reached below pH 3, while full disassociation was found above pH 7 in each cases. Accordingly, pH-dependent chiral resolving ability was observed during the CE experiments.
Conclusions: A homologous series of three multianionic CDs were prepared exhibiting similar protonation behavior. Consequently, their divergent interactions with host racemates is only driven by their cavity sizes. For the resolution of the studied cathinones, subetadex turned out to be the most efficient selector, as almost all the 20 selected drugs were successfully resolved.
Semmelweis University, Doctoral School of Pharmaceutical Sciences