Chromatographic and mass spectrometric analyses of 1-monomycoloyl glycerol fraction from Rhodococcus lentifragmentus as per-O-benzoyl derivatives

Per-O-benzoylation of the 1-monomycoloyl glycerol fraction from Rhodococcus lentifragmentus gave a product that was amenable to fractionation into saturated (F-0), monounsaturated (F-1) and diunsaturated (F-2) species by argentation thin-layer chromatography. These fractions exhibited R(t)-values of 0.54, 0.22 and 0.05, respectively. Mass spectral analyses showed that F-0, F-1 and F-2 corresponded to derivatized 1-monomycoloyl glycerols in which mycolic acids ranged from C-32:0 to C-46:0, C-34:1 to C-48:1 and C-38:2 to C-50:2, respectively. Reversed-phase high-performance liquid chromatography revealed that per-O-benzoyl 1-monomycoloyl glycerols were amenable to fractionation into the corresponding homologous components. Moreover, the major individual homologous components could be collected for further structural investigation by mass spectrometry. The most significant peaks on the mass spectrum that represented per-O-benzoyl 1-monomycoloyl glycerol were: (1) the molecular ion; M(+); (2) the molecular ion minus benzoic acid, M(+)-122; (3) the molecular ion minus two units of benzoic acid, M(+)-244; and (4) the molecular ion minus 1-hydroxy-2,3-dibenzoyl glycerol and benzoic acid, M(+)-422. In addition, effluents emerging from the chromatographic column were detected at wavelength 230 nm that allowed quantification of the eluting compounds.