Production of alkaloids with both canthin-6-one and β-carboline structure by Ailanthus altissima cell cultures is reported. Besides canthin-6-one (1), l-methoxycanthin-6-one (2), canthin-6-one-3-oxide (7), l-methoxycanthin-6-one-3-oxide (8), 1-hydroxycanthin-6-one(3), 5-hydroxycanthin-6-one (6), β-carboline- 1-propionic-acid (11), and 4-methoxy-p-carboline-1-carboxylic acid methylester (10), three new alkaloids are described. These are 2-hydroxycanthin-6-one (4), 4-hydroxycanthin-6-one (5), and 4,5-dihydrocanthin-6-one (9). © 1986, American Chemical Society. All rights reserved.