Khellin is found in Egypt, the Middle East, and areas surrounding the Mediterranean. It is a major constituent of the plant Ammi Visnaga, existing between 0.3 and 1.2% in the leaves and seeds. Bishop's Weed is a name given to several species of plants; however, only Ammi Visnaga contains khellin. Khellin is rarely found in its pure form; instead it is found in Ammi Visnaga or "Khella" extract. As a result, many healing properties have been attributed to Khellin that are actually due to other constituents in the extract. Ammi Visnaga preparations are commercially available and very common; however, the amount of Khellin and other ingredients varies greatly between brands and even batches of the same brand. The extract is commonly found as a tea or in a pill form.
Medical use
Therapeutic use is often not recommended, as the risks often outweigh the benefits. Regardless of this recommendation, Ammi Visnaga is still often used in the Middle East, Egypt, and surrounding areas. Unwanted side effects include dizziness, reversible cholestatic jaundice, pseudoallergic reaction, and elevated levels of liver enzymes.
Vitiligo
Vitiligo is a disease which causes loss of pigmentation in portions of skin. When khellin is applied topically in combination with UVA light, it is able to stimulate melanocytes in hair follicles for successful treatment of vitiligo. One such method is blister roof transplantation; in which, blisters are formed on an unaffected area and are then grafted onto a vitiligo affected area. When khellin is applied topically and treated with UV light, pigmentation returns to treated areas. When taken systemically, khellin induces elevated liver enzyme levels and broad photosensitivity; however, topical application reduces these side effects. Psoralens are commonly used for vitiligo treatment, but have higher phototoxic and DNA mutagenic effects. While Khellin treatment in conjunction with UV therapy is successful, accelerated photoaging and increased risk of skin cancer is another concern.
Kidney stones
When ammi visnaga extract is taken daily, as a tea or as a pill, calcium oxalatekidney stone formation is inhibited, making it a good treatment for hyperoxaluria. Khellin was thought to slow or prevent calcium oxalate nucleation, preventing stones from forming. However, studies have shown that khellin is not the active ingredient in Ammi Visnaga extract. Upon studying calcium oxalate nucleation, ammi visnaga extract as a whole was shown to prolong nucleation time as well as change stone conformation, while khellin alone had no effect. Khellin has also been used to treat renal colic, which is due mostly to schistosomiasis infections and stone formation. The plant mixture had diuretic properties that were seen to relieve renal colic by relaxing the ureter and acting as a diuretic.
Other
Intramuscular injections of khellin can also be used to treat asthma. Khellin acts as a bronchodilator; however, the common side effects including nausea present difficulties. Khellin has been used to relieve the pain associated with angina pectoris by acting as a selective coronary vasodilator. This can be done either orally or intramuscularly; however nausea is a major side effect regardless of how the medication is taken.
