Anti-Malarial Activities of Aqueous Leaf Extract of Pterocarpus Santalinoides on Albino Mice

Abstract

This study was designed to evaluate the effects of aqueous leaf extract of Pterocarpus santalinoides “uturukpa” on albino mice experimentally infected with Plasmodium berghei. Randomized complete block design, divided into 12 groups replicated three times with 18 mice in each group was used in this study. This involved two experimental models; curative test (established infection) and suppressive test. The plant crude extract was screened for its phytochemical composition. Twelve (12) albino mice were used for acute toxicity test. A total of two hundred and sixteen (216) experimental animals were used for this study; 108 for curative test and 108 for suppressive test. The doses of P. santalinoides used for the study were 400 mg, 800 mg and 1,600 mg aqueous extract. Leonart (400 mg) was used as standard drug. The albino mice were not treated until parasitaemia was established on the 4th day after the animals were infected for curative model. For suppressive test, the mice were infected and treatments were given immediately after inoculation. The live body weight and temperature of the experimental mice were determined using weighing balance and thermometer respectively. Blood samples from each of the experimental groups were collected using ethylene diamine tetra acetic acid (EDTA) bottles for storage. The packed cell volume (PCV) and haemoglobin count (HB) were determined using haematocrit capillary tube method and Sahli haemaglobinometre respectively while red blood cell count (RBC) and white blood cell count (WBC) were determined using haemocytometre (counting chamber) method. Blood differential counts were also determined. Serum levels of aspartate transaminase (AST), alanine transaminase (ALT), alkaline phosphatase (ALP), total bilirubin (TB), creatinine, urea and lactate dehydrogenase were determined using standard biochemical methods. Statistical analyses of the results were done using student’s t-test and one-way analysis of variance. Means with differences of p values at p < 0.05 were considered significant. The phytochemical results revealed the presence of alkaloids, tannins, saponins, terpenoids, flavonoids and phenols. Behavioural changes were observed at the different higher doses. There was no record of mortality. The extracts at 400, 800 and 1,600 mg/kg body weight/day reduced (p < 0.05) parasitaemia to 29.47 ± 4.08, 21.90 ± 1.27 and 18.23 ± 0.61 in the curative test as against 46.20 ± 3.36, 50.20 ± 3.75 and 36.47 ± 3.09 for parasitaemia level in 4 days post inoculation. This is in line with the result observed in the standard control. No parasitaemia was recorded in normal control group. Among the extract treated groups, the parasite load decreased significantly (p < 0.05) with increase in extract dose. The parasitaemia level in suppressive group showed no specific pattern of variation with increasing concentration of P. santalinoides extract and duration respectively. Observed result of the initial and final live body weights in the two models were not significantly (p > 0.05) different. There was a duration-dependent decrease (p > 0.05) in body weight in curative groups. The curative test showed a significant (p < 0.05) decrease in temperature in the groups that received 400 and 800 mg/kg of the extract and the standard drug respectively, while the decrease (p < 0.05) was only observed in the group given 1,600 mg/kg body weight of the extract in suppressive test. In the curative group, there was a significant (p < 0.05) reduction and increase in the mean values of the PCV, WBCs and Hb estimations at post infection and post treatment levels respectively. There was no significant (p > 0.05) differences in their differential counts. There was no significant (p > 0.05) effect of the extract on the haematological parameters studied in the suppressive test. There was a significant (p < 0.05) increase at post infection and gradual decrease at post inoculation in biochemical parameters studied in curative test, while in suppressive group, there was significant (p < 0.05) increase in the biochemical parameters, except with the ALT with a (p < 0.05) decrease record. The present study shows that the aqueous extract of P. santalinoides possess antimalarial activity as observed from its ability to suppress P. berghei infection in extract treated groups of albino mice without adverse effect on the haematological and biochemical parameters determined. Thus, the findings lend pharmacological support to the folkloric use of the plant in the treatment of malaria. Further investigations to identify the exact active ingredients responsible for the antimalarial activities of P. santalinoides are recommended.