Capsofulvesins A-C, cholinesterase inhibitors from Capsosiphon fulvescens

Activity-directed isolation of the n-hexane and dichloromethane fractions of Capsosiphon fulvescens resulted in the identification of four new glycolipids (1-3): (2S)-1-O-(6Z,9Z,12Z,15Z-octadecatetraenoyl)-2-O-(4Z,7Z,10Z,13Z- hexadecatetraenoyl)-3-O-β-D-galactopyranosyl glycerol (1, capsofulvesin A), (2S)-l-O-(9Z,12Z,15Z-octadecatrienoyl)-2-O-(10Z,13Z-hexadecadienoyl)-3-O- β-D-galactopyranosyl glycerol (2, capsofulvesin B), (2S)-1-O-(6Z,9Z,12Z, 15Z-octadecatetraenoyl)-3-O-β-D-galacatopyranosyl glycerol (3, capsofulvesin C). Compounds 1-6 exhibited acetylcholinesterase (AChE) inhibitory activities with IC₅₀ values ranging from 50.90 to 82.83 μM, whereas 2-6 showed butyrylcholinesterase (BChE) inhibitory activities with IC₅₀ values of 114.75-185.55 μM. Although most of the compounds isolated lacked scavenging activity for 1,1-diphenyl- 2-picrylhydrazyl (DPPH) radical and peroxynitrite (ONOO^-), compound 8 showed ONOO^- scavenging activity with an IC₅₀ value of 26.23 μg/mL.