Effects of triterpenoid glycosides of the dammaran series and their aglycons on phase transitions of dipalmitoylphosphatidylcholine.

The effects of triterpenoid glycosides from Korean red ginseng Panax C.A. Meyer and their aglycons on the phase transitions of model DPPC membranes were studied by microcalorimetry. Glycosides Rb1, Rg1, 20(S) protopanaxadiol only slightly interacted with the DPPC gel phase and caused no formation of new phases. At concentrations close to equimolar values, the glycosides slightly disturbed the packing of lipids and induced the formation of the second phases with more dense lipid packing but smaller sizes of the cooperative domains as compared with pure lipid. Cholesterol (3%) produced no effect on the DPPC interaction with Rb1, Rg1 and panaxatriol but affected the DPPC interaction with panaxadiol. At equimolar panaxadiol/DPPC ratio and in the presence of 3% cholesterol, panaxadiol completely eliminated the main transition.