Phytochemical examination of Corydalis decumbens has afforded two new morphinandienone alkaloids, namely, (-)-pallidine N-oxide (1) and (-)-salutaridine N-oxide (2), together with one known analogue, (-)-pallidine (3), and three known aporphine alkaloids (4−6). Their structures were elucidated via comprehensive spectroscopic analysis and chemical correlation. This study represents the first isolation of morphinandienone alkaloids from the title plant. All isolates were tested for their activities towards neuronal excitability in primary cultured neocortical neurons. © 2018 Phytochemical Society of Europe