A new alkaloid, 6-hydroxy-β-carboline-1-carboxylic acid (1), together with six known alkaloids, including β-carboline-1-carboxylic acid (2), β-carboline-1-propanoic acid (3), 1-methoxycarbonyl-β-carboline (4), 3-methylcanthin-5,6-dione (5), 5-hydroxy-4-methoxycanthin-6-one (6), and 4,5-dimethoxycanthin-6-one (7), were isolated from the stem of Picrasma quassioides. Their structures were elucidated on the basis of spectroscopic data. Compounds 1-7 were screened for their cytotoxic activities against five cancer cell lines such as CT26.WT, K-562, SGC-7901, Hep G2, and A-549. Among the seven alkaloids tested, only compound 2 exhibited moderate inhibitory activities against K-562 and SGC-7901 cell lines. © 2014 Springer Science+Business Media.