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.