The alpine violet, Viola biflora, is a rich source of cyclotides with potent cytotoxicity

Violaceae plants are particularly rich in cyclotides, a family of cyclic and cystine knotted plant proteins. In this work, 11 cyclotides were identified by combining MS/MS sequencing and screening of a cDNA library from Viola biflora L., and three out of four highly abundant cyclotides showed potent cytotoxic activity.