A new β-carboline alkaloid, named picrasidine E (I), was isolated from the wood of Picrasma quassioides BENNET (Simaroubaceae) together with seven known alkaloids, 1-methoxycarbonyl-β-carboline (II), 1-ethoxycarbonyl-β-carboline (III), 1-formyl-β-carboline (IV), 1-hydroxymethyl-β-carboline (V), β-carboline-1-propionic acid (VI), 4, 5-dimethoxy-canthin-6-one (VII), and 5-hydroxy-4-methoxycanthin-6-one (VIII). These structures were elucidated on the basis of spectroscopic and chemical evidence.