Planta Med 2005; 71(3): 214-218
DOI: 10.1055/s-2005-837819
Original Paper
Pharmacology
© Georg Thieme Verlag KG Stuttgart · New York

Inhibitory Effects of the Essential Oil of Mentha pulegium on the Isolated Rat Myometrium

P. M. G. Soares1 , A. M. S. Assreuy1 , E. P. Souza1 , R. F. Lima1 , T. O. Silva1 , S. R. Fontenele1 , D. N. Criddle1 , 2
  • 1Laboratório de Farmacologia dos Canais Iônicos - LAFACI, Departamento de Ciências Fisiológicas, CCS, Universidade Estadual do Ceará, Fortaleza-CE, Brasil
  • 2MRC Secretory Control Research Group, The Physiological Laboratory, University of Liverpool, Liverpool, UK
Further Information

Publication History

Received: June 24, 2004

Accepted: October 26, 2004

Publication Date:
15 March 2005 (online)

Abstract

The effects of the essential oil of Mentha pulegium L. (EOMP), a plant commonly known as ”pennyroyal” or ”poejo” that is used in folk medicine as an abortifaceant, were assessed on the isolated rat myometrium. Myometrial strips were stimulated with 10 nM oxytocin or 10 μM PGF. EOMP (10 - 300 μg/mL) concentration-dependently and reversibly inhibited the amplitude of oscillatory contractions, being approximately 3-fold more active against contractions stimulated by oxytocin than those by PGF (IC50 values of 45.7 ± 5.6 μg/mL and 160.9 ± 5.9 μg/mL, respectively), although the maximal inhibitory effect occurred at the same concentration (300 μg/mL) in both cases. This action was shared by pulegone (30 - 300 μM), the principal component of the essential oil (IC50 values of 21.8 ± 2.1 μg/mL and 12.7 ± 4.6 μg/mL, respectively). Nifedipine (30 nM - 30 μM) also abolished agonist-stimulated contractions, and was approximately twice and 12 times as potent as EOMP in inhibiting oxytocin- and prostaglandin F (PGF)-stimulated contractions, respectively. In conclusion, our results show that the essential oil of the abortifaceant plant Mentha pulegium exerts an inhibitory effect on the contractile activity of the isolated rat myometrium. This oil shares a common effect with the voltage-dependent calcium channel (VDCC) blocker nifedipine, although ostensibly acting via a different mechanism. It thus appears that EOMP and pulegone do not exert direct toxic effects on the myometrium per se that would cause abortion, and other possibilities such as systemic metabolism of plant constituents may rather underlie the abusive use of Mentha pulegium in popular medicine.

References

Dr. David N Criddle

MRC Secretory Control Research Group

The Physiological Laboratory

University of Liverpool

Crown Street

Liverpool L69 3BX

United Kingdom

Phone: +44-151-794-5355

Fax: +44-151-794-5327

Email: criddle@liv.ac.uk