Pharmacological analysis of the inhibitory effect of jatrophone, a diterpene isolated from Jatropha elliptica, on smooth and cardiac muscles

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Abstract
The present work was conducted to analyse the effect of the diterpene jatrophone on drug and electrically evoked contractions of cardiac and smooth muscle preparations. Pre‐incubation of the isolated rat uterus with jatrophone (1–100 μM), for 20 min caused a decrease in the maximal contractions and a rightward displacement of the dose‐response curves to acetylcholine, bradykinin, and oxytocin. In the isolated longitudinal muscle from guinea‐pig ileum, jatrophone (1.6–12.8 μM) produced a concentration‐dependent inhibitory effect of acetylcholine, bradykinin and histamine‐induced contractions. In this tissue, jatrophone was about 5 to 8‐fold more potent in inhibiting acetylcholine and bradykinin than in uterine muscle. In strips of guinea‐pig ileum, guinea‐pig urinary bladder, rat left atrium electrically stimulated, and dog ureter contractions, jatrophone (1–100 μM) caused a concentration‐dependent inhibitory effect. In preparations electrically stimulated, jatrophone was about 2.5 to 23‐fold less potent compared to those values obtained against agonist‐induced contractions in the guinea‐pig ileum. These results demonstrate that jatrophone exerts direct inhibitory effect on cardiac and smooth muscle preparations and show that its inhibitory potency may vary according to the tissue and/or stimulus employed to induce muscle contractions.