New 9-thiocyanatopupukeanane sesquiterpenes from the nudibranch Phyllidia varicosa and its sponge-prey Axinyssa aculeata

Two new 9-thiocyanatopupukeanane sesquiterpene isomers were isolated as major metabolites from the MeOH extract of the sponge Axinyssa aculeata and from its nudibranch predator Phyllidia varicosa. The presence of the sesquiterpenes was monitored by GC-MS, and the structures were confirmed by both 1D and 2D NMR spectroscopy. The isolated sesquiterpenes were found to be toxic toward brine shrimp at LC50 of 5 ppm. At a dose level of 20 mug, they were found to be weakly and moderately active against B. subtilis and C. albicans, respectively.