THE INTERACTION OF ABIETIC ACID WITH PHOSPHOLIPID-MEMBRANES

Abietic acid is a major component of the oleoresin synthesized by many conifers and constitutes a major class of environmental toxic compoun ds with potential health hazard to animal, including human, and plant life. Being an amphipathic molecule, the study of the influence of abi etic acid on the structure of membranes would be important to get insi ght into the mechanism of toxic action of the molecule. The interactio n of abietic acid with model membranes of dipalmitoylphosphatidylcholi ne (DPPC) and dielaidoylphosphatidylethanolamine (DEPE) has been studi ed by differential scanning calorimetry and P-31-nuclear magnetic reso nance spectroscopy. It has been found that abietic acid greatly affect s the phase transition of DPPC, shifting the transition temperature to lower values, giving rise to the appearance of two peaks in the therm ogram and to the presence of fluid immiscible phases. In a similar way , the phase transition of DEPE, in the presence of abietic acid, was s hifted to lower temperatures, and two peaks appeared in the thermogram s. The temperature of the lamellar to hexagonal H-II phase transition was also decreased by the presence of abietic acid, but phase immiscib ilities were not detected. The possible implications of these effects on the action of abietic acid on biological membranes are discussed.