1-Acetyl- $eta$ -carboline (I), 4,8-dimethoxy-1-ethyl- $eta$ -carboline (II), and three new alkaloids, 4,8-dimethoxy-1-(2-methoxyethyl)- $eta$ -carboline (III), $eta$ -carbolin-1-yl 4,8-dimethoxy- $eta$ -carbolin-1-yl-ethyl ketone (IV) and 3-methylcanthin-2,6-dione (V), were isolated from the root of Picrasma quassioides BENNET (Simaroubaceae). The structures were elucidated on the basis of spectroscopic studies and chemical evidence.