Structural determination of 'cord factor' from a Corynebacterium diphtheriae strain by a combination of mass spectral ionization methods: field desorption cesium cationization and electron impact mass spectrometry studies

Abstract

The composition and structure of a preparation of 'cord factor' (di-beta-hydroxy acyl trehaloses) from Corynebacterium diphtheriae have been determined by a combination mass spectral ionization methods. The methods were tested by means of synthetic 6,6'-dicorynomycolate of alpha-D-trehalose prior to their use on natural products. The determination of the molecular weight of the components and the estimation of their relative abundance in the natural mixture were made by field desorption mass spectrometry and cationization by means of cesium iodide. At least 22 molecular species differing from the chain length and the unsaturation degree were detected (carbon numbers C76 to C66). The position of acylation and the nature of the acyl chains were obtained from the electron impact mass spectra of the trimethylsilyl derivatives. The trehalose molecular was found to be esterified by a complex mixture of corynomycolic acids (3-hydroxy 2-alkyl fatty acids) which were present as saturated, mono-unsaturated and di-unsaturated homologues (carbon numbers C32 to C24). The 6 and 6' sites of acylation were the only detectable ones.