Possible mechanisms of action of the hypotensive effect of Annona muricata (soursop) in normotensive Sprague-Dawley rats

Pharm Biol. 2012 Nov;50(11):1436-41. doi: 10.3109/13880209.2012.684690. Epub 2012 Sep 11.


Context: Annona muricata Linn (Annonaceae) (soursop) is a food plant reported to have antihypertensive properties.

Objective: We investigated the blood pressure reducing effect of its aqueous leaf extract and the possible mechanisms that may be responsible.

Methods: Intravenous administration of an aqueous leaf extract (9.17-48.5 mg/kg) of A. muricata on the mean arterial pressure and heart rate were recorded invasively on anaesthetized, normotensive Sprague-Dawley rats. Contractile responses of rat aortic rings to the extract (0.5-4.0 mg/mL) were studied using standard organ bath techniques.

Results: A. muricata (9.17-48.5 mg/kg) caused significant (p < 0.05) dose-dependent reduction in blood pressure without affecting the heart rates. The hypotensive effects were unaffected by atropine (2 mg/kg), mepyramine (5 mg/kg), propranolol (1 mg/kg) and L-NAME (5 mg/kg). A. muricata leaf aqueous extract significantly (p < 0.05) relaxed phenylephrine (10(-9)-10(-4) M) and 80 mM KCl induced contractions in endothelium intact and denuded aortic rings; and caused a significant (p < 0.05) rightward shift of the Ca(2+) dose response curves in Ca(2+)-free Kreb's solution containing 0.1 mM EGTA.

Conclusions: The hypotensive effects of A. muricata are not mediated through muscarinic, histaminergic, adrenergic and nitric oxide pathways, but through peripheral mechanisms involving antagonism of Ca(2+).

MeSH terms

  • Animals
  • Annona / chemistry*
  • Antihypertensive Agents / administration & dosage
  • Antihypertensive Agents / isolation & purification
  • Antihypertensive Agents / pharmacology*
  • Aorta, Thoracic / drug effects
  • Aorta, Thoracic / metabolism
  • Blood Pressure / drug effects*
  • Calcium / metabolism
  • Dose-Response Relationship, Drug
  • Endothelium, Vascular / metabolism
  • Heart Rate / drug effects*
  • Male
  • Muscle Contraction / drug effects
  • Plant Leaves
  • Rats
  • Rats, Sprague-Dawley


  • Antihypertensive Agents
  • Calcium