Identification of D-cysteamide in European flat oyster [Ostrea edulis]

An unknown substance co-eluted with taurine on an amino acid autoanalyzer was found in the aqueous ethanol extract of the oyster Ostrea edulis. The compound was extracted from 100 g of soft parts from 13 specimens, isolated using Dowex 50 (H+ form) and Amberlite CG 400 (OH super(-) form) columns, and crystallized from hot 50% aqueous ethanol. The yield was 16 mg as colorless needles. Its chemical and stereochemical structure was determined to be D-cysteamide [(S)-2-amino-3-sulfopropanamide] by FAB mass, super(1)H and super(13)C NMR, IR, and CD spectra and elemental analysis. In order to confirm the assigned structure, L-cysteamide was synthesized from L-cysteine methyl ester hydrochloride in a crystalline form. The synthetic compound was identical with a natural one in mobilities on the amino acid autoanalyzer and TLC and in FAB mass, super(1)H and super(13)C NMR spectra but showed a reverse Cotton effect in the CD spectrum.