Do you mean acai for weight loss? It's a big scam, unfortunately. Acai has no effect on weight loss, and it's just a marketing gimmick used by a few companies to try to sell the product.
The only connection with Opra would be the day a doctor mentioned them for their high antioxidant content. They have never been promoted otherwise on Oprah.
Acai is loaded with antioxidants, which may help protect against cancer and other diseases. As far as I know, there's no evidence that acai works any better than blueberries, pomegranates, and similar foods high in antioxidants. If interested, look for freeze-dried, fresh or frozen acai products at your local health food store. Many of the acai pills out there are processed in a way that destroys most of the antioxidants. You can buy chilled beverages and acai pulp that are yummy
But make sure to count the calories, because they aren't going to help you lose weight