LDL oxidation may promote
atherosclerosis. We found that polyenyphosphatidylcholine (PPC), a mixture of polyunsaturated
phospholipids extracted from soybeans, has
antioxidant effects in in vivo models of oxidative stress. To assess whether components of PPC affect the in vitro oxidizability of
LDL, plasma from 15 healthy volunteers was incubated with 10 microM of either dilinoleoyl-, palmitoyl-linoleoyl-, linoleoyl-palmitoyl- or
distearoyl-phosphatidylcholine as well as 10 microM and 1 mM
alpha-tocopherol.
LDL oxidation was initiated with 5 microM Cu(2+)
sulfate and monitored by conjugated diene production, or with 2, 2'-azobis (2-amidinopropane) dihydrochloride, a
free radical generator, and monitored by O(2) consumption. After addition of Cu(2+), the lag phase (indicative of resistance of
LDL to oxidation) was longer (140% of controls; P<0.001) for
LDL incubated with dilinoleoyl-, but not with the other
phosphatidylcholine species. This effect was similar to that of 1 mM
alpha-tocopherol (135%). After addition of 2,2'-azobis (2-amidinopropane) dihydrochloride, the inhibition time (also reflecting the
antioxidant content of
LDL) was prolonged (P<0.001) for
alpha-tocopherol (206%) and dilinoleoyl-(188%), but not for distearoyl-
phosphatidyl-choline. Thus,
dilinoleoyl-phosphatidylcholine (the main component of PPC) protects against
LDL oxidation, a possible mechanism for its reported anti-
atherosclerosis effects.