Heard on the news last night that a woman in CA felt better after eating mandarins. She paid USDA (that's what they said!) to do a study & they found mandarins have 7 times amount of antioxidants than any other citrus. There is suddenly a big demand for mandarins.

It depends upon the type of antioxidant chemical measured. There are many groups of antioxidant chemicals. Vitamin C is considered anti-oxidant, as well as limonine , which are also present in citruses, and so citruses would rank better than other fruits.

And if the basis of measure is based on Flavonoids or polyphenols, or anthocyanin compounds, mandarins would rank dead last compared to blueberries or grapes.

I'm sure there was more said, but this is only the parts I caught as I ran in from another room. Wish I heard more of it.
I don't think anything can top concord grapes.

Pomegranates. - Millet