Background: Newbouldia laevis and Crateva adansonii are popular plants used traditionally in the management of patients with malaria infection in Nigeria. In this study, the acute toxicity and anti-plasmodial effects of the leaf extracts of Newbouldia laevis and Crateva adansonii were investigated in mice.
Methods: The Anti-plasmodial activities of both extracts were investigated individually and combined in mice infected with the chloroquine sensitive ANKA-65 Plasmodium berghei strain. Five groups of four mice each were used in our experiments. The LD50 was determined, using the line equation of the mortality against dose levels plot. 
Results: The extracts of N. laevis and C. adansonii had a safety level of 200 mg/kg (LD50= 471.43 mg/kg) and 600 mg/kg (LD50=3,500 mg/kg), respectively. Each experimental group was infected with P. berghei strain. The percent inhibition of parasitemia induced by the extracts of N. laevis and C. adansonii were 30.14±2.88% and 61.35±1.41%, respectively, compared to the 78.89% achieved for the standard drug (chloroquine). Mice treated with the combined extracts had a parasite inhibition of 24.23±0.86%. Upon the analysis of the extracts, there were tannins, steroids, flavonoids, saponins and alkaloids in both. The quantitative analyses revealed that tannins were the most abundant (261.85±4.76 mg/100 g & 92.71±6.58 mg/100 g) while saponins were the least abundant (15.09±1.13 mg/100 g & 14.08±1.28 mg/100 g) phytochemicals in both extracts.  
Conclusion: The findings support the notion that the traditional use of either plant in the management of malaria in Nigeria appears to be logical.