Antimalarial Activity of Extracts and Partially Purified Fractions of Alstonia boonei De Wild

Abstract

Alstonia boonei De wild is famed for several bioactive properties; this study measures its in vivo antimalarial potentials as well as phytochemical, nutritional and antioxidant properties. Variants of its stem bark extract were screened for phytochemical, nutritional and antioxidant properties using established procedures. In vivo antimalarial properties of extracts and fractions were determined against Plasmodium berghei NK65 infection in mice using chemo-suppressive, prophylactic, curative and mean survival time (MST) bioassays. Alkaloids, saponins, cardiac glycosides, tannins, flavonoids and phenolics were present in almost all extracts. The plant contained nitrogen free extract (NFE), crude fat, crude protein, moisture, crude ash and crude fibre in reasonable amounts. Extracts demonstrated antioxidant activity against DPPH and ferrous ion radicals. The aqueous and ethanol extracts were more active, decreased parasitaemia and increased MST relative to infected untreated control in the chemo-suppressive and prophylactic bioassays. Solvent-solvent partitioning of the hydro-ethanol extract yielded petroleum ether, dichloromethane-DCM, basified-DCM (BDCM), acidified-DCM (ADCM) and aqueous fractions. BDCM had the highest suppressive activity (70.91% suppression; MST: 16.50 ± 1.19), while the crude extract had the highest prophylactic (64.51% suppression; MST: 16.00 ± 1.22) and curative activities (69.80% suppression; MST: 16.80 ± 0.58). Alstonia boonei De wild possesses antimalarial properties likely associated with its phyto-nutritional composition.