khellin

Khellin has been used as an herbal folk medicine, with use in the Mediterranean dating back to Ancient Egypt, to treat a variety of maladies including: renal colic, kidney stones, coronary disease, bronchial asthma, vitiligo, and psoriasis. It is a major constituent of the plant Visnaga daucoides, also known as Ammi visnaga and as bishop's weed. Once purified, khellin exists as colorless, odorless, bitter-tasting needle-shaped crystals and is classified as a gamma-pyrone, a furanochromone derivative. In the early 20th century, researchers searched for khellin analogs with lower toxicity and better efficacy. A number of drugs were discovered through this research, such as amiodarone and cromolyn sodium, which are used in current medical practice. Efloxate is also mentioned as analog.

==Background== Khellin is found in Egypt, the Middle East, and areas surrounding the Mediterranean. It is a major constituent of the plant Visnaga daucoides, 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 Visnaga daucoides contains khellin. Khellin is rarely found in its pure form; instead it is found in Visnaga daucoides or "khella" extract. As a result, many healing properties have been attributed to khellin that are actually due to other constituents of the extract. Visnaga daucoides 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.