Mangosteen is a tropical fruit that has been enjoyed for centuries in Asia. It is an ancient fruit that is rich in nutrients and flavor. Mangosteen is a natural antioxidant that may help with immune system function and digestive health. Mangosteen is a fruit that is best enjoyed fresh and raw, as it has a delicate flavor that is not the best for cooking. Mangosteen is available in most grocery stores, and can be found in the produce section.