Ungeremine is a betaine-type alkaloid that has been found in C. zeylanicum and has diverse biological activities. It is an inhibitor of acetylcholinesterase (AChE; IC50 = 0.35 µM).Ungeremine acts as a topoisomerase poison, inducing double-strand breaks in DNA by stabilizing the linkage between topoisomerase IIβ and DNA. It inhibits the relaxation of supercoiled DNA by human topoisomerase I and -IIα and E. coli topoisomerase I and -IV (IC50s = 6.1, 25.8, 15, and 7.3 µM, respectively). Ungeremine inhibits the growth of HL-60, MOLT-4, K562, U937, and LXFL 529L cells (IC50s = 1.3, 0.7, 0.8, 2.5, and 1.2 µM, respectively). It is cytotoxic to a variety of drug-sensitive and -resistant cancer cells (IC50s = 4.89-6.45 and 3.67-75.24 µM, respectively) and induces ferroptosis, necroptosis, apoptosis, and autophagy in CCRF-CEM leukemia cells. Ungeremine (60 mg/kg twice per week) also reduces tumor growth in a GXF251L mouse xenograft model.