Hydrastine, an isoquinoline alkaloid discovered in 1851, is one of the active components of the phytomedicine goldenseal (Hydrastis canadensis). Hydrastine is a mixture of four stereoisomers (two racemates). Hydrastine has convulsant, cardiac depressant, and uterine and intestinal stimulant actions. Hydrastine increases the non-adrenergic Inhibitory postsynaptic potential of smooth muscle cells of the guinea pig intestine. Recently, research has focussed on the hydrastine isomers with (-​)​-​β-​hydrastine demonstrating antiproliferative activity by inhibiting PAK4 kinase activity in human lung adenocarcinoma cells.