By using ultrafiltration membrane with a certain porosity, it is possible to achieve selective fractionation of dimeric and monomeric alkaloids at the molecular weight level. With porosity of the membrane 100-150A° and filtration of alcohol extracts of Vinca rosea L. obtained from the aerial part of the plant, selective fractionation was achieved within the molecular masses from M+ 168 to M+ 426. In the fraction of minor alkaloids, a norharman (M+ 168), dihydrositsirikin (M+ 356) and vindorosine (M+ 426) were identified by the method of LC-MS/MS and GC/MS. The fraction of the minor alkaloids showed strong cytotoxic activity against the DLD-1 and WS-1 cell lines (Resazurin test), and according to the Hoechst test, to the cells of all A-549, DLD-1 and WS-1 lines.