Korsevine and the new alkaloids severine N-oxide and korsemine have been isolated from the combined alkaloids of Korolkowia sewerzowii Regel. On the basis of the results of a study of the IR and NMR spectra of the alkaloids and also of a correlation with korseveriline and korsevine it has been established that base (I) is severine N-oxide and korsemine has the structure of korsevine 3β-D-glucopyranoside. © 1980 Plenum Publishing Corporation.