[Study on the Effects of Ginsenoside Rb1 on DPPC Bilayers by Using Thermo-Raman Spectrum and DSC]

The research on the interactions between Ginsenosides and biomembranes plays a crucial role in thorough understanding the pharmacological activity and biologyical effect of Chinese medicine Panax ginseng. With the bilayer structure, DPPC often serves as an simulation model of the cell membrane to study the role of drug molecules and cell membranes. Ginsenoside Rb1, one of the most important components of Panaxginseng, playing the significant roles of pharmacological effects and biological properties. Raman and differential scanning calorimetry (DSC) are respectively a powerful tool for discussing the molecular interaction, and a kind of general technology by which researching the bilayer monomer structures and its interactions with drug molecules. However, rarely research reports on the interactions between drug molecules and biomembranes by means of both technologies above. In this paper, the influence of ginsenoside monomer Rb1 on DPPC membrane bilayers was investigated by thermo-Raman and DSC. In Raman spectra, the changes of DPPC molecule have been observed before and after interacted with ginsenoside Rb1, the data analysis indicates three aspects: the O-C-C-N+ polar head group skeleton, C-C stretching vibration area, and the C-H bond stretching vibrarion in terminated methyl group of alkyl chains. The results showed that ginsenoside Rb1 molecule with certain concentration has not changed the gauche conformation of the polar head backbone group in DPPC bilayers, the order of the internal molecular chain and the lateral chain-chain packing have been decreased as the temperature increased, the lateral disposed disorder has been increased. The changes of some thermodynamic constants obtained by DSC experiment such as phase transition temperature (Tm), the temperature at which the transition is half completed (ΔT1/2), and the transition enthalpy normalized per mol of DPPC (AH) have been showed further results of the thermo Raman experiments, with increasing the concentration of ginsenoside Rb1, the pre-transition temperature of DPPC bilayers dropped immediately with small amount of the Rb1 drug when the containtion was only 5 mol% and the whole system has been destructed at the same time, the main phase transition peak showed as a new little shoulder seam, however, both pre- and main transition peak disappeared completely until the drug concentration increased to 20 mol%, the phase transition temperature of DPPC has been reduced significantly, and the fluidity of bilayers has been increased. Both experiments indicated that the strong effects of ginsenoside Rb1 on DPPC.