A new alkaloid, amarastelline A (1), consisting of a canthin and a carboline unit, was isolated from the bark of Quassia amara. Compound 1 is strongly fluorescent under UV light (365 nm) in a variety of solvents and stains the cell cytoplasm region of living cervical cancer HeLa cells. © 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.