Antibronchoconstrictor Effects of Securidaca Longipedunculata (Fresen. ) Root Bark Methanolic Extract in Guinea-pigs

「Summary」This study was designed to examine the antibronchoconstrictor effects of Securidaca tongipedunculata (Fresen.) root bark methanolic extract (MESL) in guinea-pigs. The plant extract relaxed spasmogen-(acetylcholine-, histamine-, serotonin-, and potassium-) induced contractions of the guinea-pig isolated tracheal muscle prepations in a concentrationrelated manner. The plant extract also protected guinea-pigs against histamine aerosol-induced bronchospasm in vivo. Neither the relaxant effects of the plant extract on spasmogen-evoked contractions of the guinea-pig isolated tracheal muscle preparations, nor its protective effects on histamine aerosol-induced bronchospasm in conscious guinea-pigs in vivo was blocked by propranolol, which blocked both the relaxant and protective effects of isoprenaline in the mammalian experimental model used. Although the exact mechanism of the bronchodilator effect of the plant extract remains speculative, it is unlikely that the plant extract stimulates β2-adrenoceptors on the bronchial smooth muscle to produce its bronchodilation. However, it is thought that the antibronchoconstrictor effect of the plant extract is probably largely due to its non-specific spasmolytic activity, through which mechanism it acts to antagonise the post-junctional, spasmogenic and stimulant effects of acetylcholine, histamine, and other spasmogens on the bronchial smooth muscle. Furthermore, since saponins and sapogenins are known to possess non-specific spasmolytic properties against a wide range of spasmogens, it is thought that the bronchodilator activity of the plant extract may be attributed largely to presenegenin, a triterpenoid sapogenin present in the plant extract.