A theoretical and mass spectrometry study of the fragmentation of mycosporine-like amino acids
- 作者：Karina H.M. Cardozo ; Ricardo Vessecchi ; Valdemir M. Carvalho ; Ernani Pinto ; Paul J. Gates ; Pio Colepicolo ; Sé ; rgio E. Galembeck ; Norberto P. Lopes
- 关键词：Mycosporine-like amino acids ; Natural products ; High-resolution mass spectrometry ; Theoretical calculations ; Radical elimination ; Algae
- 刊名：International Journal of Mass Spectrometry
- 出版年：2008
- 期刊代码：43_13873806
- 类别：ch
- 出版时间：1 June 2008
- 卷：273
- 期：1-2
- 页码：11-19
- 文件大小：909 K
摘要
In the present study, the mycosporine-like amino acids (MAAs) were isolated from the marine red alga Gracilaria tenuistipitata and analysed by high-resolution accurate-mass sequential mass spectrometry (MSn). In addition to the proposed fragmentation mechanism based on the MSn analysis, it is clearly demonstrated that the elimination of mass 15 is a radical processes taking place at the methoxyl substituent of the double bond. This characteristic loss of a methyl radical was studied by theoretical calculations and the homolytic cleavage of the O
C bond is suggested to be dependent on the bond weakening. The protonation site of the MAAs was indicated by analysis of the Fukui functions and the relative Gibbs energies of the several possible protonated forms.