The isolation and characterization of a new tetrahydroprotoberberine alkaloid from Corydalis clarkei

The MeOH extract of Corydalis clarkei Prain yielded two tetrahydroprotoberberine alkaloids that bear the unusual 1,2- and 9, 10-tetraoxygenated substitution pattern observed previously only in caseanidine . The alkaloids have been identified as caseanidine (1) and the new alkaloid, clarkeanidine (2). The 1H- and 13C-nmr shifts of both alkaloids have been assigned unambiguously using 2-D nmr. The elucidation of the structure of 2 was achieved by comparison of the 1H- and 13C-nmr spectra of 2 with those of caseanidine coupled with additional spectroscopic evidence.