Nutritional aspects of β-carotene and resveratrol antioxidant synergism in giant unilamellar vesicles.

Giant unilamellar vesicles of soy phosphatidylcholine are found to undergo budding when sensitized with chlorophyll a ([phosphatidylcholine] : [chlorophyll a] = 1500 : 1) under light irradiation (400-440 nm, 16 mW mm(-2)). 'Entropy' as a dimensionless image heterogeneity measurement is found to increase linearly with time during an initial budding process. For β-carotene addition ([phosphatidylcholine] : [β-carotene] = 500 : 1), a lag phase of 23 s is observed, followed by a budding process at an initial rate lowered by a factor of 3.8, whereas resveratrol ([phosphatidylcholine] : [resveratrol] = 500 : 1) has little if any protective effect against budding. However, resveratrol, when combined with β-carotene, is found to further reduce the initial budding rate by a total factor of 4.7, exhibiting synergistic antioxidation effects. It is also interesting that β-carotene alone determines the lag phase for the initiation of budding, while resveratrol supports β-carotene in reducing the rate of the budding process following the lag phase; however, it alone has no observable effect on the lag phase. Resveratrol is suggested to regenerate β-carotene following its sacrificial protection of unsaturated lipids from oxidative stress, modeling the synergistic effects in cell membranes by combinations of dietary antioxidants.