Citrus aurantium L. subsp. aurantium [Fam. Rutaceae]
Aqueous extract of fresh and/or cut and dried bitter orange peel
– Appetite Stimulant
– Digestive Disorders
– Gastric-juice Deficiency
– Gastrointestinal Disorders
– Prevention of abnormal growths (skin, breast, colon, etc.)
The peel of bitter orange, Citrus aurantium L. subsp. aurantium [Fam. Rutaceae], is a leathery exocarp, or skin, containing numerous oil glands. Orange peel tea was traditionally used as a medicine for stimulating the appetite, as well as for treating gastric-juice deficiency and to aid digestion. The German Commission E also lists orange peel for treating poor digestion due to hypo-acidity. Orange peel is often used as a flavour enhancer. Extract of orange peel is among the most popular bitters on the market. New studies on a monoterpene found in orange peel called limonene show that it very effectively prevents individuals from developing abnormal growths on their skin. Limonene also has demonstrated prevention efficacy in preclinical models of breast and colon abnormal growths. The principal dietary sources of d-limonene are the oils of orange, grapefruit, and lemon. A recent case-control study of an Arizona population found that orange peel consumption was not uncommon, with 34.7% of all subjects reporting citrus peel use and that the related protection against abnormal growths of the skin was quite high and very significant. There was no protective effect shown from eating oranges or other citrus fruit pulps – only the peels. Moreover, there was a dose-response relationship between higher citrus peel in the diet and degree of risk lowering. Limonene has chemopreventive activity against rodent mammary, skin, liver, lung and upper stomach abnormal growths. Other monoterpenes from orange peel oil including perillyl alcohol and geraniol, have also been shown to have tremendous activity in combating abnormal growths. Perillyl alcohol has chemopreventive activity against rat liver abnormal growths, and geraniol has in vivo activity against abnormal white blood cells. Perillyl alcohol and d-limonene also have chemotherapeutic activity against rodent mammary and pancreatic abnormal growths and are under evaluation in Phase I clinical trials with humans.
Orange peel contains: Many bitter tasting flavonoid glycosides including neohesperidin and naringin; non-bitter flavonoids, such as hesperidin, rutoside, sinensetin, nobiletin, tangeretin; between 1-2% essential oil with limonene as the main component (>90%), perillyl alcohol and geraniol; pectins; and furanocoumarins. There are also many phenols contained in the peel including polymethoxylated flavones and numerous hydroxycinnamates.
Orange peel can be taken as a tea with the recommended dosage of a cold or moderately hot cup of tea taken several times a day half an hour before meals. An infusion is made using 2-3g (one teaspoonful) of the coarsely cut peel. Boiling water (ca. 150ml) is poured over this and extracted for 10-15 minutes. The tea can also be prepared by soaking the orange peel pieces in cold water for 6-8 hours, with occasional stirring. The daily dose corresponds to 4-6 grams of orange peel. A tincture can also be taken, with the usual dosage of 2-3grams, or the extract at 1-2g.
The furanocoumarins within orange peel can cause photosensitivity in people exposed to high levels of UV, especially in people with fair skin.
Crowell PL. 1999. Prevention and therapy of cancer by dietary monoterpenes. J Nutr. 1999 Mar; 129(3): 775S-778S. Review.
Hakim IA, Harris RB, Ritenbaugh C. 2000. Citrus peel use is associated with reduced risk of squamous cell carcinoma of the skin. Nutr Cancer 2000; 37(2): 161-8.
Hudes GR, Szarka CE, Adams A, Ranganathan S, McCauley RA, Weiner LM, Langer CJ, Litwin S, Yeslow G, Halberr T, Qian M, Gallo JM. 2000. Phase I pharmacokinetic trial of perillyl alcohol (NSC 641066) in patients with refractory solid malignancies. Clin Cancer Res. 2000 Aug; 6 (8): 3071-80.
Manthey JA, Grohmann K. 2001. Phenols in citrus peel byproducts. concentrations of hydroxycinnamates and polymethoxylated flavones in citrus peel molasses. J Agric Food Chem. 2001 Jul; 49(7): 3268-73.
Wichtl M (ed). 1994. Aurantii pericarpium – Bitter-orange peel (English translation by Norman Grainger Bisset). In Herbal Drugs and Phyto-pharmaceuticals. CRC Press, Stuttgart, pp. 94-95.