Citrus aurantium is the Latin name for a fruit called Seville orange, or bitter orange. The juice, peel, and essential oil have all been used medicinally. Traditionally uses include digestive problems, epilepsy, fatigue, insomnia, infections, respiratory problems, skin problems, and many other uses. As a flavoring, essence of bitter orange is found in the drinks Triple Sec and Cointreau.

Citrus aurantium juice and peel contain the stimulant chemical synephrine as well as related stimulants such as octopamine, tyramine, N-methyltyramine, and hordeline. On this basis, Citrus aurantium has been widely marketed as a weight-loss product. However, there is no reliable evidence thatCitrus aurantium is effective, and considerable reason to worry that it may cause harm (see Safety Issues). The reassuring statement made by some manufacturers thatCitrus aurantium offers the “benefits of ephedra without the risks” is not supported by scientific evidence.

The only published double-blind, placebo-controlled trial on Citrus aurantium juice did not test the herb alone, but rather evaluated a combination product that also contained caffeine and St. John's wort.1 While the results were somewhat positive, overall the study was too preliminary to reach reliable conclusions. An even less reliable study evaluated the synephrine constituent of Citrus aurantiumand found possible “fat burning” actions.2 In view of the weakness of the evidence in favor of Citrus aurantium, and the considerable evidence that it presents health risks, we recommend against using it for weight loss.

Other evidence, far too weak to rely upon at all, hints that synephrine-rich Citrus aurantium extracts might have antidepressant effects.3,4

Besides synephrine and other stimulants, whole Citrus aurantium peel contains including citral, limonene, and several citrus bioflavonoids, including hesperidin, neohesperidin, naringin, and rutin. Weak evidence hints that these substances might havecancer-preventive5,6and antiviral actions.7

The essential oil of Citrus aurantiumcontains linalool and the fragrant substance limonene and might have antianxiety and sedative effects.8 However, neither of these proposed uses has more than extremely preliminary supporting evidence.