The bittersweet rind of the Mangosteen is not edible. To get past this, you can use the palms of your hands to crush the rind, which is quite brittle, and reach the white fleshy fruit inside. You can also try twisting the Mangosteen rind firmly until it gives way.
Once the rind is taken away, you can see that the inside of Mangosteen fruit consists of wedged segments. The largest wedge is most likely to contain a seed, while the smaller ones lack one.
Mangosteen is very sweet and should be eaten as soon as it is opened. Mangosteen juice is also very popular. Mangosteen drink is marketed by XanGo, a company based in Utah (should have known) and only available since 2002. It has many health benefits!