Blurring the Boundary between Bio- and Geohopanoids: Plakohopanoid, a C32-Biohopanoid Ester from Plakortis cf. lita

Plakohopanoid, a new type of hopanoid derivative composed of a C32 hopanoid acid ester linked to a mannosylmyo- inositol, was isolated from the sponge Plakortis cf. lita as its peracetyl derivative. Its structure was determined by a combination of spectroscopic analysis and microscale chemical degradation. Even though plakohopanoid was isolated from a sponge, its component parts are clearly of bacterial origin, and its bacterial biosynthesis is very likely. Until now, C32 hopanoic acids have been considered to be geohopanoids, i.e., diagenetic products that are formed through abiotic degradation of the biohopanoids present in bacteria. The presence of plakohopanoid in a marine living organism shows that there is a biosynthetic pathway to C32 hopanoic acids, and these substances should therefore no longer with certainty be considered to be geohopanoids.