<jats:p>Two pyridine alkaloids were isolated from the derubberized resin of the hybrid Parthenium argentatum x P. tomentosa. These alkaloids are (±)-N-[4-(1-aminoethyl) phenyl]-4-[3-methylbutenylidine]- 1, 4-dihydropyridine (guayulamine A) and (±)-N-[4-(1-aminoethyl) phenyl]-4- [4-methylpentenylidine]-1, 4-dihydropyridine (guayulamine B). The structures were established by one- and two-dimensional NMR spectroscopy and mass spectrometry