Actually, purple grape juice provides far greater antioxidant effects than orange juice. according to a study published in the journal of medicinal food.
The study states that, people who are looking to promote their cardiovascular health through increased antioxidant consumption might prefer a glass of purple grape juice in the morning to orange juice," says Joe A. Vinson, professor of chemistry at The University of Scranton and lead author of the study. "In our tests, we saw dramatically superior antioxidant performance by the grape juice."
In 1996, research at the USDA showed that total antioxidant capacity of purple grape juice was more than three times that of either orange, grapefruit, tomato or apple juice. In 2000, other research comparing purple grape juice to orange and grapefruit juice found that only the grape juice inhibited platelet activity in humans. Relatively low platelet activity (i.e. greater inhibition) is another indicator of healthy cardiovascular function.