Funny you should post this thread, I had made a long post on the Mangosteen fruit in reply to Jason's friend, then deleted it all since it was off topic and some people don't want to hear about natural remedies, or multi level marketing schemes..
I copied this off the web.
The mangosteen fruit has the highest concentration of Xanthones. There are over 200 xanthones in nature. Each xanthone can have specific effects on the body. What's remarkable about the mangosteen is that there are over 40 xanthones identified in the pericarp, or rind, making it the single most xanthone-rich source in the world