In our continuing phytochemical investigation of biologically active constituents from Simaroubaceae spp., we report here the Occurrence in root barks of Quassia africana Baill. (syn. Simaba africana Baill.) of three alkaloids (canthin-6-one, 4,5-dimethoxycanthin-6-one, β-carboline-1-propionic acid) and quassin, an additional quinoid different from those previously isolated from this plant (1). Their structures were established by spectroscopy and direct comparison with authentic samples.