[Oxidation in liposomes from egg phosphatidylcholine loaded with L-3,4-dihydroxyphenylalanine (DOPA) and dopamine:...

Oxidation of egg phosphatidylcholine and catechols (L-3,4-dihydroxyphenylalanine or dopamine) in liposome dispersions was studied. These catechols, encapsulated in liposomes, were shown to decrease the rate of phosphatidylcholine oxidation by factors of 4.9 and 2.6, respectively, at storage in darkness at 4 degrees C. After 40 min of Fe(II)-ascorbate-induced oxidation, the level of malonaldehyde in such liposomes remained constant, while in the empty liposomes, it increased 3,4-fold. Egg phosphatidylcholine protected catechols encapsulated into liposomes from oxidation, and the rate of this oxidation was shown to be substantially lower than that in micellar solutions under the same conditions. Evidently, this can be due to the barrier function of a lipid bilayer.