The metabolism of 2,3,10,11-oxygenated protoberberine alkaloids was studied in cell cultures of Corydalis species. Without prior isolation, the structures of the metabolites were determined by LC-MS and LC-NMR analyses. Tetrahydropseudocoptisine α-N-metho salt, pseudoprotopine, and pseudomuramine were identified for the first time, and preliminary evidence for metabolic pathways to the formation of these alkaloids were obtained. © 2003 Elsevier Ltd. All rights reserved.