Abstract The derivatization of dregamine (1) and tabernaemontanine (2), two epimeric monoterpene indole alkaloids isolated from the methanol extract of the roots of Tabernaemontana elegans, with several hydrazines and hydroxylamine gave rise to ten new derivatives (3-12). Their structures were assigned by spectroscopic methods, including 2D NMR experiments. The compounds were tested for their ability to induce apoptosis in HCT116 colon and HepG2 liver cancer cells. Firstly, the cytotoxicity of all compounds (1-12) was evaluated in both cell lines by the MTS assay. The most active compounds (6, 9, 10) along with 1 and 2 were further investigated for their apoptosis induction capability by Guava ViaCount flow cytometry assays, nuclear morphology evaluation by Hoechst staining, and caspase-3/7 activity assays. Compounds 9 and 10 showed promising apoptosis induction profile, displaying higher activities than 5-fluorouracil, the mainstay in colon cancer treatment. © 2015 Elsevier Ltd.