Herbacetin is a natural product that acts as a selective inhibitor of ornithine decarboxylase (ODC).¹ It inhibits recombinant and HCT116 and HT29 colon cancer cell-derived ODC in a dose-dependent manner while having no effect on 13 tested kinases or S-adenosylmethionine decarboxylase in vitro. Herbacetin suppresses anchorage-independent growth, activation of activator protein-1 (AP-1), a MAP kinase transcription factor, and phosphorylation of ERK1/2 and p90RSK in vitro. It suppresses HCT116 xenograft tumor growth in mice without significant body weight loss when administered i.p. or orally. Herbacetin also inhibits acetylcholinesterase (AChE; IC50 = 1.37 μM) in vitro.²