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Smooth muscle relaxant effect of kaurenoic acid, a diterpene from Copaifera langsdorffii on rat uterus in vitro
Author(s) -
de Alencar Cunha K. M.,
Paiva L. A. F.,
Santos F. A.,
Gramosa N. V.,
Silveira E. R.,
Rao V. S. N.
Publication year - 2003
Publication title -
phytotherapy research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.019
H-Index - 129
eISSN - 1099-1573
pISSN - 0951-418X
DOI - 10.1002/ptr.1133
Subject(s) - acetylcholine , oxytocin , diterpene , contraction (grammar) , calcium , uterine contraction , glibenclamide , chemistry , potassium , calcium channel , pharmacology , biology , biochemistry , uterus , endocrinology , organic chemistry , diabetes mellitus
The effect of kaurenoic acid, a diterpene isolated from the oleo‐resin of the popular medicinal plant Copaifera langsdorfi (Leguminaceae), was analysed on rat uterine muscle responsiveness to various drugs in vitro. Cumulative concentration‐response curves to acetylcholine and oxytocin were obtained before and after incubation of uterine segments with up to 160 µm of kaurenoic acid. The maximal contractile response ( E max ) evoked by these agonists was inhibited by kaurenoic acid in a concentration‐related manner; at 160 µm, kaurenoic acid depressed the E max of oxytocin and acetylcholine by 83% and 91%, respectively. The relaxation caused by kaurenoic acid on oxytocin‐induced contraction was unaffected in the presence of tetraethyl ammonium, a compound that blocks the calcium activated potassium channels. It was partially reversed by glibenclamide (10 ‐5 m), an ATP‐sensitive potassium channel blocker. Also, kaurenoic acid at 160 µm concentration was found to inhibit signicantly the CaCl 2 ‐evoked contractile responses in a medium of high potassium and zero calcium. Furthermore, kaurenoic acid was found to relax the sustained tonic contraction induced by acetylcholine, oxytocin, BaCl 2 and KCl in a concentration‐dependent way. However, KCl‐induced tonic contraction was only weakly inhibited by kaurenoic acid. These data indicate that the diterpene, kaurenoic acid, exerts a uterine relaxant effect acting principally through calcium blockade and in part, by the opening of ATP‐sensitive potassium channels. Copyright © 2003 John Wiley & Sons, Ltd.