Isolation of an Unusual 2-Aminoimidazolium Salt of Steroid Trisulfate from a Marine Sponge Topsentia sp.

An unusual salt comprised of three 2-aminoimidazolium cations and halistanol sulfate anion was isolated from a marine sponge Topsentia sp. along with known halistanol trisodium salt. Their structures were determined by spectroscopic methods. The number of 2-aminoimidazoliumions in the molecule was estimated from the signal intensity in the 1H NMR spectrum, and that of sodium ions was from the atomic absorption spectrometry. This is the first report of a unique salt consisted of 2-aminoimidazolium cations in natural source. Both halistanol sulfate salts showed antimicrobial activities against Flavobacterium marinotypicum and Mortierella ramaniana at 10 μg/disk.