The aqueous calyx extract of Hibiscus Sabdariffa (HS) has a folk
reputation as an antihypertensive agent. On account of its antioxidant
properties and probably high K+ concentration, we hypothesized that HS
may attenuate the development of salt-induced hypertension.
Sprague-Dawley rats (n=8 each) were treated for 12 weeks as follows:
control (normal diet + water), salt-loaded (8% salt diet + water), HS
(normal diet + 6mg/ml HS), salt+HS (8% salt diet + 6mg/ml HS) and
furosemide (normal diet+ 0.25mg/Kg furosemide). Their blood pressure
and heart rates were measured and responses to noradrenalin and
acetylcholine (0.01mg/kg respectively) were estimated. The cationic
concentration of 6mg/ml HS was determined. The Na+ and K+
concentrations of 6mg/ml HS were 3.6 and 840mmol/l respectively. The
mean arterial pressure (MAP±SEM; mmHg) of salt loaded rats
(184.6±29.8) was significantly higher than control
(113.2±3.0; P<0.05), HS (90.0±7.4; P<0.001) salt+HS
(119.4±8.9; P<0.05) and furosemide (94.9±11.5; P<0.01).
The MAP of salt+HS and control rats did not differ significantly and
the effect of HS was comparable to furosemide. The pressor response to
noradrenalin or vasodilator response to acetylcholine remained similar
in all groups. These results suggest that HS attenuated the development
of salt-induced hypertension and this attenuation may be associated
with its high K+ content or high potassium: sodium ratio and not with
altered pressor/depressor response to noradrenalin or acetylcholine.
Also the effects of HS and furosemide on blood pressure are comparable
