Nine compounds (1 - 9), ${alpha}$-linolenic acid (1), cis-5,8,11,14,17-elcosapentaenoic acid (2), phytol (3), loliolide (4), uridine (5), thymidine (6), deoxyadenosine (7), adenine (8), and adenosine (9), were isolated from the n-hexane, methylene chloride, ethyl acetate and n-butanol fractions of Capsosiphon fulvescens. The structures of these compounds were elucidated on the basis of spectroscopic evidence. Compounds 1 - 9 exhibited acetylcholinesterase (AChE) inhibitory activities with $IC_{50}$ values ranging from 114.91 to $252.40{mu}M$, whereas 2 - 4 showed butyrylcholinesterase (BChE) inhibitory activities with $IC_{50}$ values ranging from 251.18 to $499.16{mu}M$.