Mechanisms of relaxant action of S-petasin and S-isopetasin, sesquiterpenes of Petasites formosanus, in isolated guinea pig trachea

Planta Med. 2001 Apr;67(3):224-9. doi: 10.1055/s-2001-11991.


We investigated the mechanisms of action of S-petasin and S-isopetasin, from Petasites formosanus Kitamura which is used as a folk medicine for treating hypertension, tumors, and asthma in Taiwan. The tension changes of tracheal segments were isometrically recorded on a polygraph. S-Petasin and S-isopetasin non-competitively inhibited cumulative histamine-, and carbachol-induced contractions with an exception that S-isopetasin produced a parallel, rightward shift of the concentration-response curve of carbachol in a competitive manner. S-Petasin also non-competitively inhibited cumulative Ca(2+)-induced contractions in depolarized (K+, 60 mM; histamine, 100 microM; or carbachol, 10 microM) guinea-pig tracheas. S-Isopetasin did in depolarized (K+, 60 mM) trachea too. The nifedipine (10 microM)-remaining tension of carbachol (0.2 microM)-induced precontraction was further relaxed by S-petasin or S-isopetasin, suggesting that no matter whether either blocked VDCCs or not, S-petasin or S-isopetasin may have other mechanisms of relaxant action. The relaxant effect of S-petasin or S-isopetasin was unaffected by the presence of propranolol (1 microM), 2',5'-dideoxyadenosine (10 microM), methylene blue (25 microM), glibenclamide (10 microM), N omega-nitro-L-arginine (20 microM), or alpha-chymotrypsin (1 U/ml). However, S-petasin (100-300 microM), but not S-isopetasin, significantly inhibited cAMP-, but not cGMP-dependent PDE activity of the trachealis. The above results reveal that the mechanisms of relaxant action of S-petasin and S-isopetasin may be primarily due to its non-specific antispasmodic and antimuscarinic effects, respectively.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Asteraceae / chemistry*
  • Calcium / metabolism
  • Guinea Pigs
  • In Vitro Techniques
  • Male
  • Muscle Relaxation / drug effects*
  • Neuromuscular Depolarizing Agents / pharmacology
  • Phosphoric Diester Hydrolases / metabolism
  • Plants, Medicinal / chemistry
  • Sesquiterpenes / chemistry
  • Sesquiterpenes / isolation & purification*
  • Sesquiterpenes / pharmacology*
  • Stereoisomerism
  • Trachea / drug effects
  • Trachea / physiology


  • Neuromuscular Depolarizing Agents
  • Sesquiterpenes
  • petasin
  • isopetasin
  • Phosphoric Diester Hydrolases
  • Calcium