In Vitro and in Vivo Evaluation of the Antimalarial Activities of Kniphofia reflexa Hutchinson ex Codd

In a phytochemical investigation of the rhizomes of Kniphofia reflexa, an endemic plant used to treat relapsing fevers in Kejom, northwestern Cameroon, 12 known (1-12) compounds were obtained following chromatographic methods and purification, together with 3 new derivatives (13-15) prepared by acetylation. One-dimensional and 2-dimensional nuclear magnetic resonance spectroscopic studies together with infrared and ultraviolet spectral analyses in association with data found in the literature were used to determine the structure of the compounds. In the in vitro evaluation of compounds 1-9, 12-14, and the crude extract against Plasmodium falciparum chloroquine-sensitive (D6) and chloroquine-resistant (W2) strains, cassiamin C (1) [IC50 0.57 ± 0.54 (D6); 0.78 ± 0.08 (W2)], and crude extract [IC50 1.06 ± 0.22 (D6); 1.08 ± 0.12 (W2)] were highly active against the parasites. Kniphofiarexine (12) was inactive. However, its derivative, kniphofiarexine B (14), was moderately active. In the in vivo studies, the extract suppressed Plasmodium berghei growth, but did not clear completely the parasites.