Orange (flower). The bitter orange tree, Citrus aurantium, is a flowering, citrus fruit-bearing tree native to tropical Asia. Over the centuries, bitter orange has been highly valued as a food and for its health benefits. The bitter orange peel, flowers and leaves contain flavonoids that have antioxidant activities 1. The flowers of Citrus aurantium are considered generally recognized as safe (GRAS) by the U.S. Food and Drug Administration (FDA) for use as food additives (21CFR182.20) 2.