Mangosteen has been used for hundreds of years in Asia. My advise is the following:
Check out: http://mangosteenmd.com
Check out: http://pubmed.com and type the word xanthones (mangosteen's main biologicaly active molecules) and see for yourself.
Xango is the best and yes it's the first to market. When it comes to health is smart to use the best. When Xango came for the first time, hundreds of imitators also wanted a slice of the pie. Thai go is made by nature's sunshine and nature's sunshine has been around for many years, but like the rest of other companies, when they saw Xango's success they started making imitations including natures sunshine.
Xango works because I've seen the results in my family (Diabetes and Parkinson's desease). My sugestion is "Buy the Best" and you won't regret.