Antibacterial scalarane from<i>Doriprismatica stellata</i>nudibranchs (Gastropoda, Nudibranchia), egg ribbons, and their dietary sponge<i>Spongia</i>cf.<i>agaricina</i>(Demospongiae, Dictyoceratida)

Abstract

Investigations on the biochemical relationship between <i>Doriprismatica stellata</i> (Chromodorididae, Doridoidea) nudibranchs, their egg ribbons, and the associated dietary sponge <i>Spongia</i> cf. <i>agaricina</i> (Demospongiae, Porifera) led to the isolation of the structurally new scalarane-type sesterterpene 12-deacetoxy-4-demethyl-11,24-diacetoxy-3,4-methylenedeoxoscalarin, with an unprecedented position of the cyclopropane ring annelated to the ring A. Unlike other scalaranes, which are most often functionalized at C-12 of ring C, it bears two acetoxy groups at C-11 and C-24 instead. The compound was present in all three samples, supporting the dietary relationship between chromodorid nudibranchs of the genus <i>Doriprismatica</i> and scalarane-containing dictyoceratid sponges of the Spongiidae family. The results also indicate that <i>D. stellata</i> passes the scalarane metabolite on to its egg ribbons, most likely for protective purposes. The scalarane showed antibacterial activity against the Gram-positive bacteria <i>Arthrobacter crystallopoietes</i> (DSM 20117) and <i>Bacillus megaterium</i> (DSM 32).