Bronchodilation, khellin

Many 1,2,3,5-benzenetetrol derivatives are used mediciaaHy. For example, khellin [82-02-0] (65), which is a naturally occurring benzopyranone, is used as a coronary vasodilator and bronchodilator (233). Derivatives of khellin are effective local anesthetics and antiarrythmics (234). Similarly, amine derivatives (68) that are prepared from khellinone oxime (66) exhibit hypnotic, sedative, anticonvulsant, antiinflammatory, cardiac analeptic, diuretic, and antiulcerous activity (235) (see Analgesics, antipyretics, and antiinflammatory agents). 

Five years later, a small British pharmaceutical company, called Benger Laboratories, initiated a program to synthesize khellin analogs as potential bronchodilators for treating asthma, and had prepared a series of compounds that relaxed guinea pig bronchial... 

The discovery that a Middle Eastern herb, Ammi visnaga (Khella, Bishop s weed), had mild bronchodilation effects led to the isolation of a benzopyrene (a chromone), khellin. Khellin had only weak bronchodilator effects, so synthetic analogues were prepared in an attempt to enhance the bronchodilation. All analogues... 

Although the discovery of these antiallergic compounds was a development of a study of the antispasmodic and especially the bronchodilator action of khellin, these chromones do not have a direct effect on smooth muscle and their therapeutic mode of action is of a different kind from that of khellin. They do not usually possess antihistaminic activity neither do they antagonise the actions of other spasmogens which may be associated... 

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