Lycodine-Type Lycopodium Alkaloids from the Whole Plants of Huperzia serrata.

Three new lycodine-type Lycopodium alkaloids, namely 1-methyllycodine (1), 8alpha-hydroxy-15,16-dehydro-des-N-methyl-alpha-obscurine (2), N-methyl-16-hydroxyhuperzine B (3), and one new natural lycodine-type Lycopodium alkaloid, N-methylhuperzine A (4), along with 11 known analogues (5-15), were isolated from the whole plants of club moss Huperzia serrata. The structures of 1-4 were elucidated on the basis of NMR spectroscopic and mass spectrometry data. Among them, compound 1 was the first lycodine-type alkaloid possessing a methyl group at C-1. In addition, the structure of 5 was confirmed by the single-crystal X-ray crystallography data and its 13C NMR was reported for the first time in current study. Compounds 1-5 were tested their BACE1 inhibitory activity.