Active components are obtained from the fruit and seeds of Ammi visnaga, a member of the carrot family that is native to Egypt and other Middle Eastern areas.
Khella contains furanochromones, khellin, visnagin, khellol, and pyranocoumarins. Other compounds include flavonoids (quercetin, kaemperot isorhamnetin), essential oils (camphor, terpineol, terpinen, linalool oxides), fixed oils, psoralens (methoxypsoralen), and protein.
Actions: Khellin and visnagin act as spasmolytic and vasodilatory agents on the muscles of the bronchi, GI tract, biliary tract, urogenital system, and coronary arteries, similar in action to calcium channel blockers.
When linked with an oxygen atom, khella forms a new compound called cromolyn sodium, formulations of which are used in the preventive treatment of asthma in children as well as for allergic reactions, bronchospasm, and hay fever.
The photobiological activity of khellin and visnagin against yeasts, bacteria, viruses, and fungi is being studied. In ultraviolet light, these compounds appear to affect cell division and alter DNA. Although still preliminary, research has shown antimutagenicity and antimicrobial activity in plant populations . Furochromones from khella have shown anticonvulsant activity equivalent or superior to that of phenobarbital .
Khella is claimed to be effective in treating biliary tract colic, spasmotic conditions of the GI tract, and dysmenorrhea. Traditionally, it has been used with hawthorn extracts to treat anginal symptoms. Early research appeared to yield impressive results in relieving anginal symptoms but later studies have indicated that higher dosages of khella produce intolerable adverse reactions.
Khella may help to prevent asthma attacks but does not relieve an ongoing episode. It has been used to prevent bronchial asthma attacks and allergic reactions and has been used I.V. to treat anaphylaxis . Extracts ofkhella have been used to treat psoriasis, and topical khellin with ultraviolet light irradiation has shown efficacy in treating vitiligo . Topically applied khellin increases the carcinogenic effects of both ultraviolet light and sunlight .
Some components of khella may act favorably on total cholesterol levels, protein levels, and atherosclerotic changes in blood vessels, as evidenced by a study in which oral khella increased HDL levels without affecting total cholesterol or triglyceride levels .
Skin: allergic reactions (itching), weak phototoxic activity, skin cancers (with topical use in patients predisposed to skin cancer). With prolonged use or overdose
headache, insomnia, vertigo.
anorexia, constipation, elevated liver function test results, nausea, vomiting.
Antiarrhythmics: Khella may interfere with antiarrhythmic therapy.
Avoid administration with khella.
Anticoagulants: May have additive effect. Avoid administration with khella.
Calcium channel blockers, other antihypertensives: May potentiate hypotensive effects. Avoid administration with khella.
Contraindications And Precautions:
Avoid using khella in pregnant or breast-feeding patients; effects are unknown. Use cautiously in patients with hepatic disease.
Khella appears to be a strong vasodilator, exerting activity similar to that of calcium channel blockers. It may be valuable in preventing bronchial and allergic reactions and is being studied for other disorders. Until adequate human clinical trials are conducted, khella should not be used without the supervision of a health care provider.