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.