Preuplotin, a putative biogenetic precursor of the euplotins, bioactive sesquiterpenoids of the marine ciliated protist Euplotes crassus

Strains of the marine ciliated protist Euplotes crassus typically contain preuplotin {(all-E)-2[6-acetoxy-4-(acetoxymethylene) hex-5-enylidene]-6-methylhept-5-enal}4. This represents the C-12 deprenyl analogue of udoteal, the feeding-deterrent of tropical seaweeds of the genus Udotea. Euplotes crassus typically contains also the O-cyclized form euplotin C 3 which may be thought to descend biogenetically from preuplotin together with euplotins A and B previously isolated from highly-productive strains of this ciliate as likely adjuvant factors of its adaptive radiation.