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.