EFFECTS OF TRITERPENOID GLYCOSIDES OF THE DAMMARAN SERIES AND THEIR AGLICONS ON PHASE-TRANSITIONS OF DIPALMITOYLPHOSPHATIDYLCHOLANE

The effects of triterpenoid glycosides from Korean red ginseng Panax C .A. Meyer and their aglicons on the phase transitions of model DPPC me mbranes were studied by microcalorimetry. Glycosides R(bl), R(gl) 20(S ) protopanaxadiol only slightly interacted with the DPPC gel phase cau sed no formation of new phases. At concentrations close to equimolar, the glycosides slightly disturbed the package of lipids and reduced th e sizes of cooperative domains. 20(S) Protopanaxadiol interacted with the DPPC gel phase and induced the formation of the second phases with more dense lipid package but smaller sizes of the cooperative domains as compared to pure lipid. Cholesterol (3%) produced no effect on the DPPC interaction with R(bl), R(gl) and panaxatriol but affected the D PPC interaction with panaxadiol. At equimolar panaxadiol/DPPC ratio an d in the presence of 3% of cholesterol, panaxadiol completely eliminat es the main transition.