title: Tetra- and Penta-Cyclic Triterpenes Interaction with Lipid Bilayer Membrane: A Structural Comparative Study.
abstract: The effect of tetracyclic (cortisol, prednisolone, and 9-fluorocortisol acetate) and pentacyclic (uvaol and erythrodiol) triterpenes (TTPs) on the fluidity of dipalmitoyl phosphatidyl choline (DPPC) liposome membrane was investigated by differential scanning calorimetry, Raman spectroscopy, and fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene (DPH). Liposomes were prepared in the absence and presence of TTPs at molar ratios DPPC:TTP 100:1, 100:2.5, and 100:10. All the studied TTPs abolished the pre-transition and modified the intensity of the Raman peak at 715 cm(-1) proving the interaction of TTP molecules with the choline head group of phospholipids. An increase in the Raman height intensity ratios of the peaks I 2935/2880, I 2844/2880, and I 1090/1130, giving information about the ratio disorder/order of the alkyl chains, and a decrease of the main transition temperature demonstrated the interaction of TTPs with the alkyl chains. The tetracyclic TTPs produced broadening of the phase transition profile. Besides, a scarcely splitting of the main transition peak was obtained with prednisolone and 9-fluorocortisol acetate. The results of fluorescence depolarization of DPH showed that the studied molecules fluidized the liposomal membrane at 25, 41, and 50 °C. Pentacyclic TTPs, being more hydrophobic than tetracyclic ones, demonstrated higher fluidizing effect than tetracyclic TTPs in the liquid crystalline phase suggesting a deeper incorporation in the lipid bilayer. The presence of a free polar head group at the ring D seems to control the TTP incorporation in the bilayer and consequently its effect on the membrane fluidity.
authors.affiliation: Bioactive Molecules Research Group, Doctoral School of Sciences and Technologies, Faculty of Sciences, Section II, Lebanese University, B.P. 90656, Jdaidet el-Matn, Lebanon.|Laboratoire d'Automatique et de Génie des Procédés (LAGEP), UMR-CNRS 5007, Université Claude Bernard Lyon 1, CPE Lyon, Bat 308G, 43 Boulevard du 11 Novembre 1918, 69622, Villeurbanne Cedex, France.
authors.forename: Rola
authors.initials: R
authors.lastname: Abboud
authors.affiliation: Laboratoire d'Automatique et de Génie des Procédés (LAGEP), UMR-CNRS 5007, Université Claude Bernard Lyon 1, CPE Lyon, Bat 308G, 43 Boulevard du 11 Novembre 1918, 69622, Villeurbanne Cedex, France.
authors.forename: Catherine
authors.initials: C
authors.lastname: Charcosset
authors.affiliation: Bioactive Molecules Research Group, Doctoral School of Sciences and Technologies, Faculty of Sciences, Section II, Lebanese University, B.P. 90656, Jdaidet el-Matn, Lebanon. greigegeorges@yahoo.com.
authors.forename: Hélène
authors.initials: H
authors.lastname: Greige-Gerges
mesh_terms: D002152:Calorimetry, Differential Scanning; D005454:Fluorescence Polarization; D008051:Lipid Bilayers / Q000737:chemistry* / Q000378:metabolism; D008560:Membrane Fluidity; D015394:Molecular Structure; D053978:Pentacyclic Triterpenes / Q000737:chemistry* / Q000378:metabolism; D013059:Spectrum Analysis, Raman; D013329:Structure-Activity Relationship; D014315:Triterpenes / Q000737:chemistry* / Q000378:metabolism
chemical_list: D008051:Lipid Bilayers; D053978:Pentacyclic Triterpenes; D014315:Triterpenes
keywords: DPPC membrane; DSC; Fluidity; Fluorescence polarization; Raman spectroscopy; Triterpenes