TANDEM MASS-SPECTROMETRY AND NUCLEAR-MAGNETIC-RESONANCE SPECTROSCOPY STUDIES OF CANDIDA-BOMBICOLA SOPHOROLIPIDS AND PRODUCT FORMED ON HYDROLYSIS BY CUTINASE

Natural mixtures of sophorolipids produced by the yeast Candida bombicola have been analyzed by fast atom bombardment (FAB)-MS and collision-induced dissociation (CID)-MS. Some pure components have been analysed by two-dimensional NMR spectroscopy. The presence of acidic, lactonic, and O-acetylated forms and the position of double bonds in the fatty acid part of these glycolipids can be easily inferred from positive and negative ion FAB-mass spectra. Details about position of O-acetylation can be obtained from CID mass spectra of [M + H](+) and [M - H](-) ions and from the NMR spectra, Differences in CID fragmentation between protonated and sodiated molecular ions are discussed in detail, Enzymatic hydrolysis of 6',6''-di-O-acetyl sophorolipid lactone by cutinase from Fusarium solani results specifically in the removal of the 6'-O-acetyl group, whereas the 6''-O-acetyl and lactone group are resistant. This specificity is explained from a three-dimensional model of the sophorolipid generated on the basis of the short H-1, H-1 distances as inferred from the NMR (ROESY) spectra. (C) 1995 Academic Press, Inc.