Asparagamine A, a new polycyclic alkaloid isolated from the roots of Asparagus racemosus Willd. (Liliaceae), has been elucidated by spectroscopic, chemical and single-crystal X-ray analyses. This novel polycyclic pyrrolizidine derivative is both the first alkaloid to be isolated from this genus and also the first pyrrolizidine derivative with carbon substituents at C-5 and C-8. The compound showed anti-oxytocin activity in vitro in a dose of 10⁻⁷–10⁻⁶ mg mL⁻¹.