Page 141 - Pharmd general phytochemistry I-Final2024_LEUCTERS

renal colic and urethral spasm (Smooth muscle relaxant). Renal colics are mostly due to
kidney stone formation. Khellin has been suggested to relieve renal colics by relaxing
the ureter and acting as a diuretic.
2. Khellin which is commercially available as tablets and injections is a potent selective
coronary vasodilator and bronchodilator. It is mainly used in angina pectoris.
3. Khellin (as its structure closely resembles that of psoralens) is an efficient drug for the
photochemotherapeutic treatment of vitiligo (three times a week). When khellin is applied
topically in combination with narrow band UVB light (310-315 nm), it is able to stimulate
melanocytes (cells that produce melanin) in hair follicles to restore pigmentation.
However, relapse is common.

Some Synthetic Khellin Analogues:

 Several hundreds of khellin analogues have been prepared since 1950. Semisynthesis
enabled studying structure-activity relationships (SAR). Semisynthesis improved the
potency and selectivity profiles of khellin and reduced its side effects. The most
important clinically useful ones are:

(1) Sodium cromoglycate (cromolyn sodium):

 It entered clinical trials in 1969 and emerged to become a first line prophylactic treatment
for bronchial asthma.

 The essential chemical features required for activity appeared. to be coplanarity of the
chromone nuclei, the flexible dioxyalkyl link and the carboxyl groups in the 2-positions.

 Unlike the natural product prototype khellin, it has no muscle relaxant properties, but is
effective in preventing antigen induced bronchospasms.

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