For those interested in food source anti-oxidants, the acai fruit has a very high load of anthocyanins, the high anti-oxidant content purple pigments present in purple/red/blue fruits and vegetables. Some earlier, and maybe current, juice/smoothie-type products contained a little acai and a lot of filler, but the solid frozen products such as Sambazon (a big seller at Whole Foods Market) have high acai content. Sambazon, and probably others, have one that is only organic acai and another that contains guarana (which contains some caffeine). I prefer Sambazon's pure acai product. Three of the many acai product Web sites are:

http://www.sambazon.com/

http://www.zolaacai.com/

http://www.amazonthunder.com/

There's also the privately-sold-only product Monavie, which has acai and also wolfberry, cranberry, blueberry and a combination of other natural beneficial juices in it. Not being a fan of MLM's, I have repeatedly turned down invitations to sell this product. It's a bit too slick for me, but seems to have a lot of components that I really like. It comes in a wine sized bottle, recommends you drink 1 oz. daily, and tastes good.

Just thought I'd throw that in the mix for consideration.
Kathe