This study investigated bioactive extracts of Polyalthia debilis (Annonaceae)
with antimicrobial, antimalarial and cytotoxic activities. Extensive chromatographic
isolations provided azafluorenone alkaloids; onychine (1) and 7-methoxyonychine (2)
together with a mixture of β–sitosterol and stigmasterol. The two alkaloids were isolated
from the P. debilis for the first time. Isolated fractions containing a mixture of triterpenoids
(C7, C8 and C9) exhibited the most potent antimicrobial activity against many bacterial
strains with minimum inhibitory concentration of 64 μg/mL. Fractions with antimalarial
and cytotoxic activities were also observed. The findings suggest the potential use of
P. debilis in medicinal applications.
