Platisidines A-C, N-Methylpyridinium Alkaloids from an Okinawan Marine Sponge of Plakortis Species

Three new N-methyl pyridinium alkaloids, platisidines A-C (1-3), were isolated from an Okinawan marine sponge of the genus Plakortis, and the structures were elucidated from spectroscopic data. The structures of platisidines A-C (1-3) were elucidated to be N-methyl nicotinic acid derivatives with a n-hexadecanoyl chain. Platisidines A-C (1-3) showed inhibitory activity against acetylcholinesterase.