Spectroscopic and PM5 semiempirical study of a new lasalocid ester with 2-allyloxyethanol and its complexes with monovalent cations

New Hydrophilic Derivatives of Lasalocid and Their Complexes with Selected Metal Cations

Two new esters of lasalocid, that are more hydrophilic, with glucose (LasGlu) and xylitol (LasX), have been synthesized, and their complexation of monovalent cations has been studied by various spectrometric and spectroscopic methods, such as ESI mass spectrometry, ¹H, ¹³C NMR and FT-IR. Analyses of the results confirmed the synthesis of new esters with good yields. In order to carry out further studies, it was necessary to purify them using "flash" liquid chromatography. It was confirmed that the newly obtained molecules, as well as their complexes with lithium, sodium and potassium cations, were stabilized by a strong system of intramolecular hydrogen bonds. It was found that the hydroxyl groups of esters derived from xylitol and glucose were also involved in the complexation of cations. The results of the PM6 semiempirical calculations permitted determination of the heat of formation (HOF), and visualization of the structure of the new esters and their complexes with the cations studied. All computation results are in agreement with the spectroscopic data.

Fine-tuning of POPC liposomal leakage by the use of beta-cyclodextrin and several hydrophobic guests

The effect of entrapped beta-cyclodextrin (beta-CD) on the stability of multilamellar vesicles (MLVs) of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), prepared by the dehydration-rehydration method, was studied by monitoring the release of 5(6)-carboxyfluorescein encapsulated into the liposomes. Different hydrophobic guests, such as Fullerene C(60), have been incorporated into the POPC bilayer in order to modify the membrane composition. The kinetic results as well as ESI-MS measurements evidenced that the destabilizing activity of beta-CD is due to the formation of beta-CD inclusion complexes and the consequent removal of selected bilayer constituents from the liposomal membrane. Hence, when beta-CD was added to the liposomes in the form of a strong, water-soluble 2:1 beta-CD/C(60) inclusion complex, such a destabilizing effect was not observed. However, the same beta-CD/C(60) inclusion complex does not form as a result of C(60) extraction from the bilayer. This may be attributed either to the overwhelming concentration of POPC with respect to C(60) and/or to the fact that C(60) is largely aggregated in the bilayer. Turbidimetric and fluorimetric determinations of lamellarity and entrapped volume of the studied MLVs provided further evidence of the alteration of the liposomal bilayer as a consequence of the addition of beta-CD and/or the presence of the studied guests.