Ergot alkaloid from the sea slug Pleurobranchus forskalii.

The sea slug Pleurobranchus forskalii is a carnivorous scavenger that is widely distributed in shallow subtidal areas. Very few investigations of the chemical components of this gastropod have been reported. In this study we performed a comprehensive analysis of an extract of the marine mollusc, P. forskalii, collected off Ishigaki Island, Japan. As a result, an alkaloid was isolated from the chloroform extract. Remarkably, the structure elucidation based on the spectral data revealed that it was an ergot alkaloid peptide, ergosinine. Various ergot alkaloids have previously been isolated mainly from terrestrial higher plants or fungi. This is the first report of the isolation of an ergopeptine from marine life, and thus the known geographical extent of ergot alkaloids now includes both terrestrial and aquatic organisms.