Planta Med 2005; 71(11): 1025-1029
DOI: 10.1055/s-2005-871291
Original Paper
Pharmacology
© Georg Thieme Verlag KG Stuttgart · New York

Mechanism Involved in the Spasmolytic Effect of a Mixture of Two Triterpenes, Cycloartenol and Cycloeucalenol, Isolated from Herissanthia tiubae in the Guinea-Pig Ileum

Ana Yara S. Gomes1 , Maria de Fátima V. Souza1 , Steyner F. Cortes2 , Virgínia S. Lemos3
  • 1Laboratório de Tecnologia Farmacêutica, Universidade Federal da Paraíba, João Pessoa, PB, Brazil
  • 2Departamento de Farmacologia, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
  • 3Departamento de Fisiologia e Biofísica - ICB, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
Further Information

Publication History

Received: December 8, 2004

Accepted: May 27, 2005

Publication Date:
19 August 2005 (online)

Abstract

The smooth muscle relaxant properties of a mixture of the two triterpenoids cycloeuclalenol and cycloartenol (CC) isolated from Herissanthia tiubae (Malvaceae) were studied in several smooth muscle preparations. CC inhibited contractions induced by carbachol, histamine and KCl in the guinea-pig ileum, but no spasmolytic activity was found in guinea-pig trachea or rat aorta. In guinea-pig ileum, concentration-response curves to carbachol and CaCl2 in high K+ were shifted to the right by CC in a concentration-dependent manner with slopes of the Schild plot differing from the unity. IC50 values were 3.4 ± 0.8 × 10-5 M and 8.44 ± 1.87 × 10-5 M for carbachol and CaCl2, respectively. The phorbol ester TPA, which activates protein kinase C (PKC), potentiated contractions induced by submaximal concentrations of carbachol. This potentiation was inhibited by CC. Desensitization of PKC by TPA completely abolished the inhibition produced by CC on carbachol-induced contractions. Together, our results indicate that inhibition of PKC is involved in the spasmolytic effect of CC in the guinea-pig ileum.

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Virgínia S. Lemos

Universidade Federal de Minas Gerais

Instituto de Ciências Biológicas

Departamento de Fisiologia e Biofísica

Av. Antônio Carlos, 6627

31270-901 Belo Horizonte

MG

Brazil

Phone: +55-31-3499-2950

Fax: +55-31-3499-2924

Email: vslemos@mono.icb.ufmg.br

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