Vasorelaxant effects of extracts of the stem bark of Terminalia superba Engler & Diels (Combretaceae).
OBJECTIVE
The stem bark of Terminalia superba (Combretaceae) (TS) is used in traditional Cameroonian medicine as antihypertensive remedy. In the present study, we investigated the vasorelaxant properties of different extracts of TS and their underlying mechanisms.


METHODS
Activities of aqueous (AQU), methanolic (MET), methylene chloride (MC), and methylene chloride-methanol (MCM) extracts of TS were evaluated on isolated rat aortic rings precontracted with phenylephrine (PE) or high KCl.


RESULTS
All extracts induced a vasodilating effect both on KCl- and PE-induced contractions. The effects of MC and MCM extracts were greater than those of AQU or MET extracts (P<0.05). MC had an endothelium-independent effect and reduced Ca(++)-induced contraction following PE or KCl challenge (P<0.05). After incubation with verapamil, MC induced a relaxation in rings precontracted by PE (P<0.001). By contrast, the effect of MCM was endothelium-dependent and decreased by the nitric oxide synthase inhibitor N(W)-nitro-L-arginine methyl ester (P<0.05).


CONCLUSIONS
These data demonstrate that the MC extract exhibits vasorelaxant effects that are partly due to inhibition of extracellular Ca(++) influx and/or inhibition of intracellular Ca(++) release in vascular smooth muscle cells. By contrast, the effect of the MCM extract was found to be endothelium- and nitric oxide dependent.
Tom
Esther Ngo Lemba
EN
EA 4267 Sciences Séparatives, Biologiques et Pharmaceutiques, UFR des Sciences Médicales et Pharmaceutiques, 25030 Besançon, France.
Girard
Corinne
C
Dimo
Théophile
T
Mbafor
Joseph Tanyi
JT
Berthelot
Alain
A
Demougeot
Céline
C
D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000502:physiology; D024301:Plant Bark; D010936:Plant Extracts / Q000302:isolation & purification / Q000494:pharmacology*; D018547:Plant Stems; D051381:Rats; D017208:Rats, Wistar; D029766:Terminalia; D014664:Vasodilation / Q000187:drug effects* / Q000502:physiology; D014665:Vasodilator Agents / Q000302:isolation & purification / Q000494:pharmacology*
D010936:Plant Extracts; D014665:Vasodilator Agents