**3.3 Formalin and tail-flick tests**

The extract at doses of 100 and 200 mg/kg induced significant (p<0.05) reduction in pain response in both phases (aphasic and tonic) of pain induced by formalin in comparison with control (Fig 2).

In all cases ASA, a positive analgesic agent demonstrated significant anti-nociceptive action with a slightly stronger pharmacological intensity than *V. amygdalina* at 200 mg/kg in the late phase. The extract exerted no significant effect on nociception in tail-flick as values

Herbal Medicine in the Treatment of Malaria:

Values are mean count S.E.M. (for n = 5)

N.S., Normal saline

*berghei* in mice.

control (Table 5).

(Fig 5 and 6).

**3.6 Six weeks exposure** 

\*Significantly (p<0.05) different from saline control group

**3.5 Sub-chronic toxicity (14 days exposure)** 

**Clinical observation, Body and organ weight** 

**3.4 Antiplasmodial activity** 

*Vernonia amygdalina*: An Overview of Evidence and Pharmacology 177

The extract caused a significant (P < 0.05) and dose-dependent reduction in mean parasitaemia in mice infected with Plasmodium berghei in comparison to CQ (5 mg/kg). The extract caused a parasitaemia reduction of 52% in 50 mg/kg, 64% and 73% in 100 and 200 mg/kg respectively (Table 2). One animal death was recorded in the 200 mg/kg extract groups throughout the 30 days observation period of the experiment while the remaining mice recovered fully. All mice in the saline group were lost within 15 days of the study.

Table 2. Curative activity of the aqueous extract of *V. amygdalina* and CQ against *Plasmodium* 

No treatment deaths occurred and no treatment related clinical signs were noted during the study. The extract did not exert significant changes on mean body and organ weight, fluid and food intake (Table 3). All animals demonstrated a progressive increase in body weight during the exposure. The organ weights were expressed as a percentage of the body weight (% relative organ weight), rather than as absolute weights, so as to take into consideration differences in the organ weight that may solely be attributable to differences in the body weights of the respective rats. The hematology result showed a significant decrease (p<0.05) in red blood count at the dose of 2000mg/kg compared to control (Table 4). The result of the clinical chemistry parameter showed a dose-dependent increase in direct and total bilirubin, there was also an increase in uric acid at the doses of 500 and 1000mg/kg compared to

At the end of the 43-day-period of drug administration, No overt signs of toxicity were seen in any of the animals during the course of the study. No statistical difference was observed between the body and organ weight of the control group and the assay group in the male rats receiving the three doses, all animals exhibited a gain in body weight. Organ weights (% relative organ weights) were similar to those of the corresponding organs from the control.

obtained correspond with those with saline. However pethidine the reference agent markedly prolonged the tail-flick reaction time in rats (Fig 3)

Fig. 2. Effect of aqueous extract of *V.amygdalina* leaves on formalin test in rats (NT, non treated animals; Va, *V. Amygdalina*; ASA acetyl salicilic acid). All data are presented as means ± S.E.M., n=5. The asterisk (\*) denotes significance (p<0.05) between treated group and NT control

Fig. 3. Effect of aqueous extract of *V.amygdalina* leaves on thermal stimulus-induced tail-flick test in rats (NS, normal saline; Va, *V. Amygdalina*; PH, penthidine hydrochloride). All data are presented as means ± S.E.M., n=5. The asterisk (\*) denotes significance difference (p<0.05).
