Therapeutic effects of various solvent fractions of alstonia boonei (apocynaceae) stem bark on Plasmodium berghei-induced malaria

Abstract

Malaria , t h e most importan t parasiti c diseas e afflicting man is the leading caus e of mortality and morbidity in the world. Chemotherapy remains the mainstay for the treatment and preveitio n of the disease in the absenc e of an effective vaccine. The incidenc e of resistanc e of malari a parasite s to chemotherap y is increasing and complicated. This study w a s therefor e undertaken in order to evaluate the therapeutic effects of fractions of the stem bark of /\. boonei on P. berghei-induced malaria using chloroquine as control. Different doses (200mg/kg and 400mg/k g body weight) of methanolic extract (ME) , n-hexan e (HF) , chlorofor m (CF), ethylacetate(EF) and aqueous (AF) fractions of the stem bark of A. boonei wer e administered orally to albino mice. Five milligrammes chloroquine base per kilogramme body weight (5mg/kg bw) wa s used as positive control whil e the negative control mice received only the vehicle (5% v/v tween 80). The results obtained showe d that the 400mg/k g bw dose w a s mor e effectiv e wit h respec t to the parasit e clearanc e than the 200mg/k g bw dose. The 400mg/ kg bw dos e of M E gav e 68.1 % percent parasite clearance . T h e C F gav e the highest clearanc e of 98.8% at 40()mg/kg bw afte r 7 days treatment while chloroquin e at 5mg/k g bw gav e 100% parasite clearance. T h e orde r of increasing potency of the fractions (parasite clearance ) wa s ( EF 50.0%< A F 60.3% < H F 63.1 %, < CF 98.4%) indicating that the active principle in the stem bark wa s highest in the CF. Percentage parasitemia following exposure to these fractions also decreased in all groups in the same order and wa s only significant (p<0.05) in CF (0.11%) compared to the untreated control group. The M E of A.boonei also caused increase in P CV by 15.5%. Purification enhanced P CV value as the HF and CF fractions gave 19.0% and 24.5% increases, respectively.