Chromones.

The chromones are a class of chemical compounds characterised by the presence of the structure 5:6 benz-1:4-pyrone in their chemical make-up. The first chromone in clinical use, khellin, was extracted from the seeds of the plant Ammi visnaga, and had been used for centuries as a diuretic and as a smooth muscle relaxant. Its use in bronchial asthma was reported in 1947. In the 1950s, Benger's Laboratories embarked on a research programme to synthesise and develop modifications of khellin for the treatment of asthma. New compounds were screened using animal models to test the ability of the compound to prevent the anaphylactic release of histamine and SRS-A (leukotrienes) from sensitised guinea pig lung, and a human model to check the ability to reduce the bronchoconstriction induced by inhaled antigen bronchial challenge. For initial screening the human work was undertaken by Dr. R.E.C. Altounyan, who suffered from allergic bronchial asthma and was employed by Benger's Laboratories. After 8 years and more than 600 challenges using over 200 compounds, in 1965 Altounyan arrived at disodium cromoglycate (DSCG), the chromone that met the criteria of providing more than 6 h of protection. DSCG is still used today as a mast cell stabiliser.