Natural Health Labs Mangosteen Rx is not a proprietary formulation, it is however, Pure 100% Mangosteen from the hull (or pericarp) of the fruit. The hull is the most potent part of the fruit that is richest in Xanthones. The results are a better quality of life for a fraction of the cost. In fact, there is a whole family of Xanthones, and the most dynamic of these are found in the amazing Mangosteen Pericarp. While most people know about the antioxidant benefits of Vitamins C and E, far fewer are aware of the incredibly potent antioxidant power of Xanthones.