| Abstract: | The effect of propylgallate (PrG, an antioxidant) on the thermotropic behavior of dipalmitoylphosphatidylcholine (DPPC) was studied by means of differential scanning calorimetry. A DPPC/PrG mixture displayed distinctive thermotropic behavior that was significantly different from that of a DPPC/cholesterol or DPPC/vitamin E mixture. Although the enthalpy of the phase transition (delta H) for DPPC decreased at a low concentration of the PrG and the transition peak became broadened, delta H increased again and the peak became sharper on the addition of more PrG. The same was observed for DPPC/methylgallate and DPPC/ethylgallate mixtures, but not for a DPPC/butylgallate mixture. On the other hand, the transition temperature (Tm) of the DPPC/gallate derivative mixtures decreased with an increase in the chain length of the acyl moiety of the gallate derivatives. The pre-transition and subtransition of the DPPC/PrG mixture were eliminated on the addition of a PrG, and Tm of the DPPC/PrG mixture approached about 26 degrees C. These results suggested that the chain length of the acyl moiety must be C1 to C3 for the unique effect of the gallate derivatives described above, and that DPPC forms a complex with PrG as a pure component. |
