Mass spectrometry-guided isolation of two new dihydrobenzophenanthridine alkaloids from Macleaya cordata

Two new alkaloids 6-hydroxyethyldihydrochelerythrine (1) and 6-hydroxymethyl-7,8-demethylenedihydrochelerythrine (2) together with two analogues named maclekarpine E (3) and 6-hydroxymethyldihydrosanguinarine (4) were detected primarily from the leaves of Macleaya cordata by their characteristic mass spectrometry (MS) and tandem mass spectrometry (MS/MS). And then isolation of four targeted-compounds was performed by column chromatography and preparation HPLC under the guiding of MS. Finally, their structures were determined by spectrum analysis. Alkaloids 3 and 4 were isolated from this plant medicine for the first time.