In Vitro Antiplasmodial Activity, Cytotoxicity, Antioxidant Action and GC-FID Analysis of Allanblackia Floribunda Extracts

Abstract Background: Malaria is a disease that is caused by Plasmodium parasite that has resulted in death of so many persons in the world especially children below 5 years. Plasmodium falciparum is one of the most widespread etiological agent for human malaria and has become increasingly resistant to standard antimalarial drugs. This study was therefore aimed at evaluating the in vitro antiplasmodial efficacy and cytotoxicity of Allanbackia floribunda stem bark, leaf and oil. Methods: Trager and Jensen method was used to culture Plasmodium falciparum and maintained in fresh O + human erythrocytes at 3% hematocrit in complete medium (Roswell Park Memorial Institute-RPMI 1640). Mark III test developed by WHO was used to assess the antiplasmodial activity of the plant’s crude extract and fractions against the ring stage of P. falciparum strains Pf3D7. Cytotoxicity was determined against Vero cell line using microculture tetrazolium (MTT). GC-FID was employed to identify bioactive constituents in the most active fraction. Results: The plant extracts showed varied degrees of inhibition of parasitaemia with IC 50Pf3D7 values ranging between 4.0 to 1000 μg/ mL. The methanol stem bark extract of A. floribunda exhibited very active antiplasmodial activity (IC 50Pf3D7 = 4.3 ± 0.17μg / mL), the leaf extract showed active antiplasmodial activity (IC 50Pf3D7 = 8.0 ± 0.28 μg / mL) while the oil extract was inactive against the parasite (IC 50 > 100 μg / mL). Both the leaf and stem bark extracts were found to be non-cytotoxic in contrast to the standard cytotoxic drug, doxorubicin. The selectivity indices (S.I.) of the extracts against the parasites were 13.32 and 8.18 for the stem bark and leaf, respectively. Among the stem bark fractions, dichloromethane (DCM) had the best inhibition against the P. falciparum parasite (DCM IC 50Pf3D7 of 1.51 μg/ mL) and was closely followed by the hydromethanol (HMet) fraction (HMet IC 50Pf3D7 of 5.0 μg/ mL) while that of ethylacetate (EAct) and hexane (Hxn) fractions were almost similar (IC 50 Pf3D7 of 6 and 6.25 μg/ mL, respectively).GC-FID analysis of the most active fraction, DCM, showed high presence antiplasmodial flavonoids (naringenin, luteolin, kaemferor and myricetin) and terpenes (α-pinene and β-caryophyllene) which may have been responsible for the excellent antiplasmodial action of the most active fraction. Conclusion: This investigation confirmed that A. floribunda stem bark has potent activity against P. falciparum and it is relatively safe to normal cell. The antiplasmodial action is credited to the presence of bioactive flavonoids and terpenes that may have acted singly or synergistically.