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International audience; Cucurbitacin E (Cuc E), highly oxygenated triterpene from cucurbitaceae ă family, was demonstrated to possess anti-proliferative, ă anti-inflammatory and anti-oxidant activities. Here, we studied the ă effect of Cuc E on the properties of the phospholipid membrane. Large ă unilamellar vesicles, with and without sulforhodamine B (SRB), were ă prepared in the absence and presence of Cuc E. The fluorescence ă increase, resulting from SRB release from vesicles due to inhibition of ă auto-quenching, was used to assess the permeability of liposome at 4 ă degrees and 37 degrees C. At 4 degrees C, blank liposomes and those ă containing Cuc E were stable; while at 37 degrees C Cuc E loaded ă liposomes showed less stability than blank ones. The loading efficiency ă of Cuc E into the vesicles was demonstrated to be 85% by HPLC. Dynamic ă light scattering measurements showed that liposomes embedding Cuc E were ă smaller than those which did not. Multilamellar vesicles were ă manufactured from dipalmitoylphosphatidylcholine in the presence and ă absence of Cuc E (molar ratio 7%). Results obtained by differential ă scanning calorimetry suggest that Cuc E binds mainly at the polar/apolar ă interfacial region of lipid bilayers and may incorporate into the lipid ă bilayer. Cuc E does not produce phase separation and thus might be ă included in liposome formulation. (C) 2013 Elsevier B.V. All rights ă reserved.

The effect of erythrodiol, a natural pentacyclic triterpene to which humans are exposed through nutrients, on the lipid membranes is studied using liposomes as a membrane model. Empty and erythrodiol-loaded liposomes were prepared by the reverse phase evaporation method followed by the extrusion and by the thin film hydration method. Liposomes were characterized in terms of size and zeta potential and were imaged by transmission electron microscopy (TEM) and atomic force microscopy (AFM). The effect of erythrodiol on thermotropic behavior of DPPC bilayers is also examined by differential scanning calorimetry (DSC). The DSC thermograms suggested that erythrodiol interacted with the polar head groups of phospholipids and may produce a disruption of the ordering of the alkyl chains. The diffraction light scattering analysis showed that erythrodiol-loaded liposomes presented a decrease in the vesicle size when compared to blank liposomes. Images obtained by TEM confirmed the formation of unilamellar and spherical liposomes. AFM images showed spherical vesicles and single lipid bilayers. The latter were more abundant in the preparations containing erythrodiol than in the blank ones. Moreover, erythrodiol-loaded liposomes tended to rupture into single lipid bilayers during scanning. The study may provide a better understanding of pentacyclic triterpenes–membrane interaction.

Cucurbitacin E (Cuc E), an oxygenated triterpene molecule, has demonstrated anti-proliferative effect on various cancer cells. Here, we examined the effect of Cuc E on the membrane morphology and properties using differential scanning calorimetry, transmission electron microscopy and atomic force microscopy techniques. Dipalmitoylphosphatidylcholine vesicles were prepared by the thin film hydration method in the absence and presence of Cuc E at molar ratios 100:12 and 100:20. The loading efficiency of Cuc E was found to be higher than 98% upon HPLC analysis. The thermodynamic parameters suggest that Cuc E does not penetrate into the bilayers and interacts with the polar/apolar interface of the lipid membranes. Blank and Cuc E loaded liposomes prepared from a mixture of DPPC/DPPE/DPPG/Cho were imaged by TEM and AFM. Images obtained by TEM revealed unilamellar liposomes for blank and Cuc E loaded liposomes. AFM images showed that the size and the height of Cuc E loaded liposomes were respectively smaller and higher than blank ones. Results suggest that Cuc E produces modifications in the lipid membrane structures.

International audience; Cucurbitacins are a class of natural compounds known for their numerous ă potential pharmacological effects. The purpose of this work was to ă compare the cytotoxicity of three cucurbitacins I, D, E on the ă chondrosarcoma SW 1353 cancer cell line and to investigate their ă biotransformation in man. Cucurbitacins I and D showed a very strong ă cytotoxicity, which was higher than that of cytochalasin D, used as a ă drug reference. Almost 100% of the cells were apoptotic as observed by ă DNA fragmentation (TUNEL assay) after 12 h with cucurbitacins I and D (1 ă mu M) and cucurbitacin E (10 mu M). In terms of IC50 values, ă cucurbitacins I and E presented a higher toxicity compared to that of ă cucurbitacin D (MTT assay). Cucurbitacin E was readily hydrolyzed by ă human hepatic microsomes, leading to cucurbitacin I (K-m 22 mu M, V-max ă 571 nmol/mg proteins/min). On the other hand, the three cucurbitacins ă were hydroxylated at a very low extent, but they were sulfated and ă glucuronidated. In terms of V-max/K-m, the cucurbitacin E was the best ă substrate of UDP-glucuronosyltransferases. This study shows that ă cucurbitacins I, D and E present a potent cytotoxic activity toward the ă chondrosarcoma SW 1353 cell line and are metabolized as sulfate and ă glucuronide conjugates. (C) 2012 Elsevier Ireland Ltd. All rights ă reserved.