1. Antihypertensive activity of 80% methanol seed extract of
Calpurnia aurea (Ait.) Benth.subsp. aurea (Fabaceae) is
mediated through calcium antagonism induced vasodilation
ABSTRACT
Being the most important modifiable risk factor for stroke, renal, vascular and heart diseases;
hypertension is still one of the leading causes of disability, morbidity and mortality among the
populace worldwide. Consequently, the continued search for alternative antihypertensive agents
of natural origin, with fewer side effects but greater effectiveness, necessitated evaluation of
Calpurnia aurea for possible antihypertensive potential. In this study, the antihypertensive
property of hydro-alcoholic seed extract of Calpurnia aurea was assessed using in vivo and ex
vivo techniques. The in vivo antihypertensive efficacy of the crude extracts was evaluated in
normotensive and 2K1C rat model of hypertension. The crude extract caused a significant fall in
systolic blood pressure (SBP), diastolic blood pressure (DBP)and mean arterial blood pressure
(MABP) at the doses of 15, 30 and 45 mg/kg in normotensive anaesthetized rats (p < 0.05, p <
0.01, p< 0.001).The effect on DBP was greater than SBP. In the same manner with the
normotensive study, the BP fell dose-dependently and significantly in renal hypertensive rats,
induced by renal ischemia. The extract produced 15.4% (p< 0.05), 26.9% (p< 0.01), 33.2% (p
<0.01) reduction in SBP at the respective doses of 15, 30 and 45 mg/kg. Similar to the
normotensive result, higher DBP effect was observed; 15.1% (p< 0.05), 30.2% (p< 0.01), 36.1%
(p <0.01) fall from the control value at the above mentioned doses. Regarding MABP; 15.2%
(p< 0.05), 28.8% (p <0.01) and 34.9% (p <0.01) reduction was noted with 15 mg/kg, 30 mg/kg
and 45 mg/kg doses of the extract, respectively. The extract also caused a dose-dependent
relaxation of guinea pig aorta precontracted with KCl (80mM),at a concentration of 5–250
mg/mL, with a maximum relaxation of 92.1±0.72% (p < 0.001) achieved at 250 mg/mL
concentration. The relaxation mechanism was found to be independent of the endothelium
system, muscarinic receptors, histamine receptors, ATP dependent K+ channels, cyclooxygenase
enzymes and cGMP/NO pathway. The relaxation may be correlated with the effect on calcium
ion channels, as it shifted the Ca2+ dose response curve (p< 0.05, p< 0.01 and p< 0.001) to the

2. right with suppression of the maximum effect by 37.4% (p < 0.001). In conclusion, the findings
suggest that the extract had a promising antihypertensive effect most likely caused by dilation of
the blood vessels through Ca++
channel blockade, a confirmation for the folkloric use of the
plant.