Ray Sahelian, M.D. Immune Support Energy Production Active Xanthones Doctor Formulated Dietary Supplement Formulated by Medical Doctor Ray Sahelian, M.D.  Bestselling Author and Nutrition Expert Mangosteen (pericarp) is a fruit grown in Thailand and Myanmar whose rind with an active substance Xanthones, a group of compounds that have antioxidant and other potent physiological properties.Advance Physician Formulas, Inc.