Orange (peel). The peels of both the sweet orange, Citrus sinensis, and the bitter orange, Citrus aurantium, are commonly used in dietary supplements. The sweet orange peel is a source of vitamin C and contains carotenoids, pectin and numerous bioflavonoids, such as hesperidin. The bitter orange peel contains many of the same flavonoid compounds 1. Both contain nutrients that demonstrate antioxidant activities. Orange peel and extracts made from both the sweet and bitter orange peels are approved for use as food additives by the U.S. Food and Drug Administration (FDA) 2.