title: Electrospray ionization tandem mass spectrometry of chaetoglobosins.
abstract: BACKGROUND
  Chaetoglobosins are a family of macrocyclic polyketide alkaloids. They possess many similar isomers and exhibit a wide range of biological activities. Thus, there is a need for reliable, fast, and low-cost analysis of this class of compounds.
  
  
  METHODS
  A series of seven chaetoglobosins from Chaetomium globosum, including two types of isomers, were investigated using electrospray ionization quadrupole time-of-flight tandem mass spectrometry (ESI-QTOF-MS/MS) in both positive- and negative-ion mode. The identity of major product ions was supported by deuterium-labeling experiments.
  
  
  RESULTS
  In positive-ion mode, the product ion at m/z 130 is the characteristic ion of the indolyl group. A McLafferty rearrangement might play a significant role in the fragmentation of the macrocycle moiety for most chaetoglobosins and produces two series of characteristic product ions, accompanied by neutral losses. The characteristic product ion at m/z 309 in the MS/MS spectrum of chaetoglobosins E indicates the structure of the cyclic olefinic bond in ring B and can be used to distinguish it from the isomers, chaetoglobosins F(ex) , which has an exocyclic double bond on ring B. In negative-ion mode, the McLafferty rearrangement has an important role in the fragmentation pattern of the macrocycle. Some high-abundance radical ions were detected. The radical product ion at m/z 138 might differentiate chaetoglobosins F and penochalasin F, isomers which have very similar structures.
  
  
  CONCLUSIONS
  In summary, complementary information obtained from fragmentation experiments of [M+H](+) and [M-H](-) precursor ions is especially valuable for rapid identification of chaetoglobosins. The high-abundance radical ions in negative-ion mode are also of scientific interest.
authors.affiliation: Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, P.R. China.
authors.forename: Guo-Bo
authors.initials: GB
authors.lastname: Xu
authors.forename: Li-Mei
authors.initials: LM
authors.lastname: Li
authors.forename: Dong-Mei
authors.initials: DM
authors.lastname: Fang
authors.forename: Guo-You
authors.initials: GY
authors.lastname: Li
authors.forename: Guo-Lin
authors.initials: GL
authors.lastname: Zhang
authors.forename: Zhi-Jun
authors.initials: ZJ
authors.lastname: Wu
mesh_terms: D002597:Chaetomium / Q000737:chemistry; D026121:Indole Alkaloids / Q000737:chemistry* / Q000302:isolation & purification; D007477:Ions / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D026121:Indole Alkaloids; D007477:Ions; C019290:chaetoglobosins