The Chemical Composition of the Indigoid Dyes Derived From the Hypobtanchial Glandular Secretions of Murex Molluscs

The composition of the indigoid dyes and their precursors derived from the hypobranchial glandular secretions of Murex trunculus and Murex brandaris have been determined by high-resolution mass spectrometry. M trunculus secretions yielded three dyes: 6,6′-dibromoindigotin (DBI; C.I. 75800), indigotin (C.I. Natural Blue 1; C.I. 75780) and 6-bromoindigotin (MBI), the latter reported here for the first time. M branaris yielded solely DBI and its precursor the 6-bromo-2-methylthioindoxyl (tyrindoxyl); no methylsulphone precursor was observed, although reported by earlier investigators. Moreover, exposure to light was found to be critical for the formation of the greenish-coloured intermediate 2,2′-bis-substituted 6,6′-dibromo-2,2′-di-indoxyl, not only for the latter’s decomposition to DBI. Also includes correspondence from J Wouters and A Verhecken