Two new alkaloids, oryzadiamines A and B, were isolated from the bran of an Oryza sativa mutant with yellow grains. The structures of oryzadiamines A and B were elucidated with spectroscopic analyses. Oryzadiamines A and B are new natural products possessing unique nitrogen-containing heterocyclic ring systems. Oryzadiamine A may play a significant role in the yellow color of the grain. (C) 2019 The Authors. Published by Elsevier Ltd.