The alkaloid magnoflorine 1, has been isolated for the first time from Croton xalapensis (Euphorbiaceae), in addition two phenylpropenols derivates, 3,4-dimethoxy-(E)-cinnamyl alcohol 2 and 3,4-dimethoxy-5-hydroxy-(E)-cinnamyl alcohol 3, 3,4,5-trimethoxycinnamic acid 4, gallic acid 5, methyl gallate 6 and 3,4-dihydroxybenzoic acid 7 have been also found; these compounds were identified by spectroscopic analysis particularly, 2D NMR and ESI-MS/MS techniques. The high concentration of magnoflorine, calculated with quantitative HPLC, of the aqueous extract, probably contributes to the remarkable medicinal properties of this plant. In addition this is the first phytochemical study on Croton xalapensis to be reported.