Isolation and structure determination of a new sesquiterpene lactone from Nauplius aquaticus.

The aerial part of Nauplius aquaticus afforded a new sesquiterpene lactone with a humulanolide skeleton, 6,7,9,10-tetrahydroasteriscunolide (1), in addition to the known asteriscunolides A (2) and D (3). Their structures were established principally by two-dimensional NMR spectroscopy.