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 bombic ola have been analyzed by fast atom bombardment (FAB)-MS and collision -induced dissociation (CID)-MS. Some pure components have been analyse d by two-dimensional NMR spectroscopy. The presence of acidic, lactoni c, and O-acetylated forms and the position of double bonds in the fatt y acid part of these glycolipids can be easily inferred from positive and negative ion FAB-mass spectra. Details about position of O-acetyla tion can be obtained from CID mass spectra of [M + H](+) and [M - H](- ) ions and from the NMR spectra, Differences in CID fragmentation betw een protonated and sodiated molecular ions are discussed in detail, En zymatic hydrolysis of 6',6''-di-O-acetyl sophorolipid lactone by cutin ase from Fusarium solani results specifically in the removal of the 6' -O-acetyl group, whereas the 6''-O-acetyl and lactone group are resist ant. This specificity is explained from a three-dimensional model of t he sophorolipid generated on the basis of the short H-1, H-1 distances as inferred from the NMR (ROESY) spectra. (C) 1995 Academic Press, In c.