Complexation of cyclic dodecadepsipeptide, Cereulide with ammonium salts

Cereulide is a principal toxin causing emetic syndrome which is produced by Bacillus cereus and has been known as potassium selective ionophore. This paper deals with its complexation with inorganic and organic ammonium ions to assign the higher structures similar to the complex with potassium ion by means of NMR and ESI-MS spectroscopy. Of particular interest, the detectable ions are not only at m/z 1191.8 as K(+) complex but also (or sometimes exclusively) at m/z 1170.8 as NH(4)(+) complex in its LC-MS analyses depending upon the conditions. This difference is due to the sample preparation and measurement condition.