Sequencing of new beauverolides by high-performance liquid chromatography and mass spectrometry

Mass spectrometry (MS) and tandem mass spectrometry (MSn) were used for the identification of beauverolides in the fermentation broth of Beauveria bas siana and for evaluation of the purified fraction obtained by sublimation o f beauverolides. Besides being a new efficient route for purification of be auverolides, sublimation provided an enrichment of new minor lipophilic bea uverolides of lower molecular weight from the original complex mycelial ext ract. The product ion collision-induced dissociation (CID) spectra obtained on an ion trap (electrospray ionization), the in-source CID mass spectra o n a sector instrument (atmospheric-pressure chemical ionization) and the po st-source decay matrix-assisted laser desorption/ionization mass spectra of beauverolides were compared and evaluated. All MSn experiments started wit h singly charged precursor ions. The following two new representatives of t his group of compounds were identified by high-performance liquid chromatog raphy and MS (HPLC/MS): cyclo-(3-hydroxy-4-methyloctanoyl-valyl-alanyl-leuc yl) and cyclo-(3-hydroxy-4-methyloctanoyl-tyrosyl-alanyl-leucyl). Individua l structures were confirmed by preparative isolation and nuclear magnetic r esonance spectroscopy. The structure of a third novel and minor beauverolid e was tentatively assigned by HPLC/MS only as cyclo-(3-hydroxy-4-methyldeca noyl-valyl-alanyl-Lxx), Lxx = leucyl, isoleucyl, or allo-isoleucyl. Copyrig ht (C) 2001 John Wiley & Sons, Ltd.