A new alkaloid, severidinine, with mp 145-147°C [α]D -50.2°, C19H45NO6, has been isolated from the epigeal part of Koralkowia sewerzowii Regel. On the basis of the IR, PMR, and mass spectra of severidinine and its transformation products, and also passage to the known alkaloids severidine, the structure of 3α-acetylseveridine has been established for severidinine. © 1984 Plenum Publishing Corporation.