Catharoseumine (1), a new monoterpenoid indole alkaloid possessing a unique peroxy bridge moiety, was isolated from the whole plants of Catharanthus roseus. Its structure was elucidated on the basis of NMR, IR, UV, and high-resolution mass spectrometric data, and its absolute configuration was determined by ECD and chemical methods. Catharoseumine (1) exhibited cytotoxicity against HL-60 cell line with IC50 value of 6.28 mu M and potential inhibition against Plasmodium falciparum falcipain-2 (IC50= 4.06 mu M). A plausible biogenetic pathway of 1 was also proposed. (C) 2012 Elsevier Ltd. All rights reserved.