From the bulbs of Zephyranthes robusta Baker (Amaryllidaceae), seven known compounds, belonging to four structural types of Amaryllidaceae alkaloids, were identified and quantified by GC-MS. The alkaloid extract from the bulbs showed promising acetylcholinesterase and butyrylcholinesterase inhibitory activities against HuAChE (IC50 = 35.9 +/- 3.5 microg/mL) and HuBuChE (IC50 = 190.9 +/- 8.2 microg/mL).