Bitter orange (Citrus aurantium) is an aromatic variety of citrus. As the name implies, the tree produces highly bitter and tart fruits. Still, bitter oranges have been used in food and medicine since way back. Native to southeastern Asia, the fruits have likely been introduced into Europe around the 10th century by traders. Spanish and Portuguese settlers brought them to North America within the 16th century. Nowadays, the citrus tree is grown broadly in many parts of the world for its use in food, herbal medicine, perfume, and cosmetics.
Orange marmalade and Bigarade sauce are made from the cooked fruits. The dried orange peels are traditionally used for stimulating the appetite as well as for treating gastric-juice deficiency. In combination with other herbs, Chinese Traditional Medicine has been used bitter orange peel for indigestion, nausea, and constipation since thousands of years.
Many varieties of Citrus aurantium trees are cultivated for their three kinds of essential oils. The very expensive neroli oil is distilled from its flowers. Petitgrain oil is extracted from its leaves and young shoots. Both can be found in perfumes or cosmetics but are also used in aromatherapy. The popular bitter orange oil is made from the fruit peel. It contains flavonoids, a group of plant metabolites which are anti-inflammatory, antibacterial and antifungal. These properties, combined with its pleasant fragrance, explain its long-standing use in aromatherapy, as antiseptic, and as relaxing oil. In foods, bitter orange oil is widely used as flavoring.
Although historically used to stimulate appetite, Citrus aurantium can be frequently found in modern weight-loss supplements due to its active compound synephrine. This compound is structurally similar to the stimulant ephedrine, which is known to promote weight loss. However, they have different pharmacologic properties, meaning the two components act differently. The use of the ephedrine-containing herb ephedra in dietary supplements was banned by the U.S. Food and Drug Administration in 2004. By causing high blood pressure, the use of ephedra is linked to cases of heart attack and stroke. Therefore, bitter orange extract is used as a common substitute in “ephedra-free” dietary supplements.
All citrus trees belong to the genus Citrus in the citrus family, also known as rue family (Rutaceae). There are three types of oranges: sweet oranges, bitter or sour oranges, and mandarins. Mandarins, often called mandarin oranges, are not really oranges but an ancient parental of orange. The sour orange (Citrus aurantium) and the sweet orange (Citrus sinensis) are very distinct botanical species. Bitter (“sour”) orange refers to C. aurantium and is a hybrid between pomelo (Citrus maxima) and pure mandarin (Citrus reticulata).
Native to southeast Asia, various varieties of the sour orange are nowadays found in different parts of the world. A prominent subspecies is the Bergamot orange, C. aurantium,subsp.bergamia, being the star flavor of Earl Grey tea. Medicinal preparations are mostly made from Citrus aurantium subsp. aurantium, also called C. aurantium subsp. amara. This plant is way better known by its common names such as bitter or sour orange, Seville orange, Bigarade orange, and marmalade orange.
What does the plant look like?
The height of the evergreen tree ranges from 2 to 9 meters. It is more erect and has a more compact crown than the sweet orange. Its leaves are long, leathery, and dark green. The flowers are highly fragrant and have 5 to 8 white petals. From April to June, they grow singly or in small clusters in the leaf axils. The fruit has a thick, dimpled skin that turns to bright reddish orange when ripe. When fully grown, the center of the fruit becomes hollow. The pulp of the fruit is bitter and holds less orange juice than sweet oranges. The sour orange tree can stand several degrees of frost for short periods and is very resistant to plant diseases compared with other citrus trees.
Where the name comes from?
Bitter or sour oranges live up to their name as one of the most tart and pungent citrus fruits. The word “orange” is thought to come from a transliteration of the Sanskrit word “nāraṅga”, which originates from the Tamil words “naru”, meaning fragrant, and “ārañcu”.
How or what it is used for
The fruit peel is a traditional digestive aid and appetite stimulant. It also is a good source of antioxidants and is thought to tone and protect blood vessels. Its oil is used in aromatherapy to help with nervousness and anxiety. It can be added to a diffuser, a hot bath or a few drops can be placed on the pulse points. Due to its antiseptic actions, Seville orange oil is also used topically to treat fungal skin diseases and is a popular ingredient in skin cosmetics.
Today, Citrus aurantium extract and its primary constituent synephrine are widely used for weight loss and weight management, sports performance, appetite control, energy, and mental focus. Questions have been raised about the safety of this main constituent because it has some structural similarity to a banned stimulant.
Medicinal Properties of Bitter Orange
Depending on the dosage form and quantity, bitter orange peel, also known as Aurantii pericarpium, and its essential oil show a large variety of medicinal activities such as
C. aurantium has a complex chemical makeup, though it is perhaps most known for the volatile oil in the peel. It is the familiar oily residue that appears after peeling citrus fruit. Besides containing volatile oil, the most important active constituents in the peel are the alkaloids synephrine, octopamine, N-methyltyramine, tyramine and hordenine. Further, the fruit and its skin are rich in vitamin C, flavonoids, and carotenoids. The fruit and juice also contain coumarins such as bergapten which sensitizes the skin to sunlight.
Para-synephrine, often referred to as simply synephrine is the primary active constituent that comprises approximately 90% of total protoalkaloids. It has thermogenic, meaning heat producing, properties. Uncertainty and some confusion have existed concerning its safety. The type of chemical substance found in bitter orange peel is the para-form, not the meta-form, which was often stated incorrectly in some of the published literature. Meta-synephrine, also called phenylephrine, is the active ingredient in the product Neo-Synephrine. This form exhibits cardiovascular effects but is a synthetic and not a constituent of bitter orange.
Taking bitter orange with monoamine oxidase inhibitors (MAOIs) may increase the concentration of the drug and cause serious side effects. Taking bitter orange along with midazolam might increase the effects and side effects of midazolam. Because of potentially additive effects, synephrine use should be avoided in patients with severe hypertension, tachyarrhythmia, hyperthyroidism, or narrow-angle glaucoma.
Children as well as pregnant and breast-feeding women should avoid bitter orange products since information regarding safety and efficacy is lacking. Applied to the skin, the peel or oil is known to potentially cause photosensitization, particularly in fair-skinned people.
It is good to keep in mind that many people consume p-synephrine daily in the forms of citrus juices and foods with no known or apparent adverse effects. However, you should always check with your doctor first before starting any new health product.
Pascoe Canada does not offer health or medical advice as we are not a healthcare practitioner. Please speak with your healthcare practitioner before beginning any program related to nutrition, diet, exercise, fitness, medical, and/or wellness. All content published by Pascoe Canada is developed through collaborating with licensed medical professionals and contributors. This includes text, graphics, images, and other material on the website, newsletter, and products (“Content”). This content is for informational purposes only and does not constitute medical advice. The content does not substitute professional medical advice, diagnosis, or treatment. Please always do your own research on whether this is for you along with your healthcare practitioner advice. Always consult your healthcare practitioner prior to use specific herbs because you might have underlined conditions needs professional care. The content is general in nature and are subject to change. It is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects.
The Tamil word “ārañcu” translates to “6 and 5”, implying 11 since the fruit typically has 11 individual pieces inside. The Sanskrit word “nāraṅga” reached European languages through Persian (nārang) and Arabic (nāranj) and has been modified in various degrees. In some languages, the orange fruits are known as “Chinese apple”, such as the Dutch “Sinaasappel” or the Danish and Norwegian “appelsin”.
The Citrus aurantium fruit has a leathery skin with many oil glands. Both the peel and its essential oil are considered as generally safe by the FDA (GRAS status) and used frequently in foods and herbal medicine.
Bitter orange has a long-standing use in complementary medicine for the treatment of digestive problems like flatulence, dyspepsia, constipation, sluggish digestion, appetite loss, intestinal gas as well as nausea. In Traditional Chinese Medicine, zhi qiao is prepared from the mature but still green fruit peel and zhi shi is prepared from the immature fruit. Both medicinal materials are added to multiple ingredient formulas to treat indigestion, abdominal distension, and other digestive issues.
In modern herbal medicine, orange peel is traditionally used as a medicine for stimulating the appetite, as well as for treating gastric-juice deficiency and to aid digestion. It is also often contained in digestive tonics or bitters along with other herbs such as gentian or juniper. These bitter herbs are thought to stimulate digestive function by increasing saliva production and promoting both stomach acid and digestive enzyme production. Orange peel is also listed by the German Commission E for treating loss of appetite and poor digestion due to hypoacidity.
Essential bitter orange oil has scientifically proven anti-bacterial and anti-fungal properties. Due to these germ-killing actions, it is effective for skin fungal infections like ringworm and athlete’s foot. The diluted oil is also used to treat pimples and acne. In aromatherapy, the uplifting but also calming oil is used to ease stress and anxiety. A 2018 review of clinical studies conducted with Citrus aurantium or Citrus sinensis on people with anxiety confirmed that inhalation or oral administration of C. aurantium can exert beneficial effects on anxiety. Additionally, its use as an alternative treatment for insomnia, anxiety and epilepsy was confirmed in mice.
Some of the plants more recent applications are as sources of antioxidants and chemical exfoliants in specialized cosmetics. In dietary supplements, extracts are used for weight loss, body building, and improving athletic performance. These bitter orange supplements often contain high amounts of synephrine which increases body heat through metabolic stimulation. Other uses for extracts are nasal congestion, allergic rhinitis, and chronic fatigue syndrome.
The para-form exerts metabolic enhancement without acting as a central nervous system or cardiovascular stimulant at commonly used doses. Clinical studies have demonstrated that para-synephrine does not increase heart rate or blood pressure even at oral doses up to 100 mg. Also, it is naturally found in juices of numerous popular citrus varieties and thus more widespread in the conventional food supply than many people probably recognize.
Another substance with thermogenic effects is hordenine. It is known as a stimulant and was originally derived from the sour orange plant. Today, hordenine weight loss and pre-workout supplements are sold online to increase energy and metabolism even though there is not a lot of research backing it. Another popular substance used for weight loss is L-carnitine. This amino acid also has thermogenic function and can be naturally found in meat and dairy products.
The bitter tasting flavonoid glycosides neohesperidin and naringin in the orange skin are the reason for its characteristic bitterness and traditional use as digestive aid and appetite stimulant. Our body contains tons of receptors for bitter compounds in not only the mouth and tongue, but the stomach, gut, liver, and pancreas. This is mostly for protective reasons, as most dangerous and poisonous things are highly bitter tasting. Still, the stimulation of these bitter receptors promotes healthy digestion by increasing digestive secretions. Also, the flow of bile flow from the stomach, pancreas, liver, and gallbladder is initiated. This digestive cascade results in better digestion and relieves digestive discomforts.
Bitter substances only stimulate the appetite if there is no healthy appetite, for instance as a result of illness or a weak condition. In these cases, one is often not hungry and does not want to eat anything, even though the body needs to be supplied with important nutrients to recover. In case we are “well fed”, feelings of hunger are not additionally fueled, but rather regulated. Especially in low doses, bitter substances may even slow down cravings for sweets. This means, if someone already has a healthy appetite, there is no need to worry about sudden constant appetite or even cravings. For those who suffer from loss of appetite due to illness, bitter substances can bring new appetite and thus strengthening.
Bitter orange extract is often used in “ephedra-free” products since the FDA ban of ephedra for serious side effects on the heart. These side effects of ephedra containing products included increase in blood pressure and heart rate. Back in 2004, reports of serious adverse reactions triggered public concern also to products containing Citrus aurantium. However, subsequent investigations revealed that many reports were duplicates or very incomplete. Also, most of the reports were incorrectly linked. They involved either ephedrine-containing products without a bitter orange ingredient or products that also contained caffeine. Only one report involved a product with bitter orange as the only medicinal ingredient.
In 2010, a Consumer Reports article listed bitter orange extract as one of its “Dirty Dozen” ingredients with questionable safety. Still, numerous clinical studies have been conducted on the plant's safety. In 2017, a review of 30 human studies concluded that Citrus aurantium extract and p-synephrine are safe for use in dietary supplements and foods at the commonly used doses. Health Canada also states that doses of 1 to 50 mg p-synephrine per day are not likely to cause any adverse health consequences.
Weight loss and bodybuilding products often additionally contain caffeine. There is some evidence that caffeine may potentiate adverse effects of p-synephrine. At high doses caffeine itself can trigger cardiovascular adverse events in some people such as raised blood pressure and increased or irregular heartbeat.