ANTIPLASMODIAL ACTIVITIES OF STEM BARK AND LEAF OF ALSTONIA BOONEI (DE WILD) AND THE EFFECTS OF MICRONUTRIENTS ON THE PLASMODIAL LOAD

Abstract

The purpose of this study was to evaluate in vivo antiplasmodial effect of methanolic and aqueous extracts of Alstonia boonei leaf and stem bark and the effects of micronutrients on the plasmodial load using positive control (chloroquine phosphate, a standard antimalarial) and negative control (normal saline water). The qualitative and quantitative phytochemical analysis of the extracts was carried out using standard procedures. The oral acute toxicity was evaluated in mice using modified Lorke’s method and the in vivo anti-plasmodial effect against infection was studied using 4-day suppressive test in chloroquine sensitive Plasmodium berghei berghei NK65-infected mice. Results of the phytochemical tests showed relative abundance of tannins, alkaloids, terpenoids, phytates, oxalates and total phenol in the methanolic extracts while it showed the presence of tannin, steroids, phytates, oxalates, total phenols in the aqueous extracts. Quantitative screening of the methanolic extract revealed the presence of tannins (14.75%), alkaloids (8.79%), terpenoids(7.19%), phytates(2.16%), oxalates(6.12%) and total phenol(36.88%) while it revealed tannin(14.14%), steroids(0.92%), phytates(5.35%), oxalates(2.34%) and total phenol(35.35%). The acute toxicity dose was determined and was > 2,000mg/kg per body weight for the methanolic extracts of A. boonsei stembark and > 2500mg/kg per body weight for the methanolic leaf extracts. The suppressive test revealed that methanolic and aqueous leaf extract exerted significant (P< 0.05) dose-dependent reduction against the parasite. The administered dosage of 500mg/kg body weight per day of Alstonia boonei methanolic and aqueous extract caused chemo suppression of 97.80% and 71.42% respectively on day four and chemo suppression of 92.44% and 88.92% at 250mg/kg body weight per day dosage. Similarly, 500mg/kg body weight dosage of methanolic and aqueous stem bark extract caused chemo suppression of 89.59% and 72.89% respectively on day four and chemo suppression 3 of 71.42% and 74.65% on day four at 250mg/kg body weight per dosage. This study revealed that the synergistic use of stem bark and leaf extracts of Alstonia boonei did not give a better suppression of the parasitemia as the 250mg/kg body weight methanolic and aqueous synergistic extract caused chemosuppresion of 81.96% and 77.76% respectively and chemosuppresion of 86.69% and 92.29% at 500mg/kg body weight respectively and these are lower than percentage suppression obtained when leaf extract. Although, all these values were statistically significant (P˂0.05) when compared with the positive control. Also, vitamin C and Calcium cause a chemosuppresion of 20% and 17.08% while Iron and Magnesium caused an increase in the parasitemia by 15.12% and 34% respectively. The hematological and histological parameters of the swiss albino mice revealed significant variation when compared to the control groups. In conclusion, Alstonia boonei contained active antiplasmodial compounds and therefore might be a potential antimalarial drug and Iron and magnesium containing foods should not be taken as it aids parasite proliferation.