Galanthamine, Plicamine, and Secoplicamine Alkaloids from Zephyranthes candida and Their Anti-acetylcholinesterase and Anti-inflammatory Activities.

Sixteen new alkaloids belonging to the galanthamine (1-6), plicamine (7-14), and secoplicamine (15 and 16) classes, together with eight known analogues (17-24), were isolated from Zephyranthes candida. The structures of 1-16 were determined by extensive spectroscopic analyses, and the absolute configurations of 1, 2, 7, 8, and 17 were confirmed by single-crystal X-ray diffraction analysis. The orientation of 3-OCH3 in N-methyl-5,6-dihydroplicane (22) was revised. Alkaloids 3, 12-14, and 18-21 exhibited anti-acetylcholinesterase activities with IC50 values ranging from 0.48 to 168.7 μM. Compounds 10-12, 14, and 16 showed in vitro anti-inflammatory activities with IC50 values ranging from 7.50 to 23.55 μM.