Lycosquarrines SU, new Lycopodium alkaloids isolated from Phlegmariurus squarrosus

Three new Lycopodium alkaloids (LAs), lycosquarrines SU (1-3), along with nine known congeners (4-12), were isolated from the aerial parts of Phlegmariurus squarrosus. Their structures and absolute configurations were determined by HRESIMS, 1D and 2D NMR spectroscopy, and ECD calculations. Lycosquarrine S (1) was identified as 12-epi-lycoverticine, lycosquarrine T (2) as 8-epi-miyoshianine C, and lycosquarrine U (3) as 5-epi-N-methyllycoposquarrosamine A. HPLC-DAD analysis of the alkaloid-rich extract confirmed the presence of 1, further demonstrating the chemical diversity of this species. The alkaloid-rich extract showed potent acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) inhibitory activities and moderate inhibition of nitric oxide (NO) production in LPS-stimulated RAW 264.7 macrophages. However, none of the isolated alkaloids exhibited significant activity individually, suggesting that the bioactive constituents of the extract remain unidentified. These findings expand the known structural diversity of Lycopodium alkaloids from Ph. squarrosus and contribute to the phytochemical knowledge of this species.