Abstract
In the present study, Loranthus ferrugineus was evaluated for blood pressure lowering activity using in vitro and in vivo animal experimental approaches. The fresh aerial parts of the plant were dried, pulverized into powder and successively extracted with petroleum ether, chloroform, ethyl acetate, methanol and water using hot extraction methods. Each of the extracts was dried under reduced pressure using rotary evaporator and subsequently freeze-dried. The effects of three different concentrations (0.5, 1 and 2 mg mL(-1) of each extract were examined on isolated rat aortic ring preparations and responses to cumulative doses of noradrenaline (NA) were measured. It was found that the relatively polar methanol extract was the most potent to produce a significant (p < 0.05) dose-dependent inhibition in the maximum response and to shift the dose-response curve of NA to the right which suggests that Loranthus ferrugineus methanolic extract (LFME) contains compound(s) with non-competitive inhibitory activity. In another set of experiments, LFME was found to be the most active in blood pressure lowering activity in anaesthetized normotensive Sprague. Dawley (SD) rat model. Moreover, LFME produced a dose-dependent blood pressure lowering effect. Chemical analysis of LFME showed the presence of significant amounts of polyphenolic and flavoniod constituents. The data suggests that LFME contains some biologically active substances that produce a significant dose-dependent blood pressure lowering effect and vasodilatation is one of the possible mechanisms which may explain its use in the management of hypertension. Furthermore, LFME effects can possibly be attributed to the high polyphenolic contents of this plant.