ABSTRACT
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.
Subject(s)
Chromones/chemistry , Ammi/chemistry , Ammi/metabolism , Animals , Anti-Allergic Agents/chemistry , Anti-Allergic Agents/pharmacology , Anti-Allergic Agents/therapeutic use , Asthma/drug therapy , Chromones/history , Chromones/therapeutic use , Guinea Pigs , Histamine/metabolism , Histamine Release , History, 20th Century , Humans , Leukotrienes/metabolism , Lung/drug effects , Lung/metabolism , Seeds/chemistry , Seeds/metabolismABSTRACT
Current drug therapy for asthma is highly effective and has evolved from naturally occurring substances through logical pharmaceutical developments. Pharmacology has played a critical role in asthma drug development and several key experimental observations have been published in this journal. Understanding the pharmacology of effective drug therapies has also taught us much about the underlying mechanisms of asthma. beta(2)-Adrenoceptor agonists are the most effective bronchodilators and evolved from catecholamines from the adrenal medulla, whereas corticosteroids, from the adrenal cortex, are by far the most effective controllers of the underlying inflammatory process in the airways. The current 'gold standard' of asthma therapy is a combination inhaler containing a long-acting beta(2)-agonist with a corticosteroid - an improved form of adrenal gland extract. Cromoglycate, derived from a plant product and theophylline, a dietary methyl xanthine, have also been extensively used in the therapy of asthma, but we still do not understand their molecular mechanisms. Pharmacology has played an important role in improving natural products to make effective long lasting and safe asthma therapies, but has so far been challenged to produce new classes of antiasthma therapy. The only novel class of antiasthma therapy introduced in the last 30 years are leukotriene antagonists, which are less effective than existing treatments. New, more specific, therapies targeted at specific cytokines are less effective than corticosteroids, whereas more effective therapies carry a risk of side effects that may not be acceptable. It seems likely that pharmacology, rather than molecular genetics, will remain the main approach to the further improvement of treatment for asthma.
