Yamagaki Tohru, Watanabe Takehiro, Tanaka Masaki, Sugahara Kohtaro
Suntory Institute for Bioorganic Research, Shimamoto, Mishima, Osaka, 618-0001, Japan,
J Am Soc Mass Spectrom. 2014 Jan;25(1):88-94. doi: 10.1007/s13361-013-0764-0. Epub 2013 Nov 19.
Negative-ion matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectra and tandem mass spectra of flavonoid mono-O-glycosides showed the irregular signals that were 1 and/or 2 Da smaller than the parent deprotonated molecules (M - H) and the sugar-unit lost fragment ions (M - Sugar - H). The 1 and/or 2 Da mass shifts are generated with the removing of a neutral hydrogen radical (H*), and/or with the homolytic cleavage of the glycosidic bond, such as M - H* - H, M - Sugar - H* - H, and M - Sugar - 2H* - H. It was revealed that the hydrogen radical removes from the phenolic hydroxy groups on the flavonoids, not from the sugar moiety, because the flavonoid backbones themselves absorb the laser. The glycosyl positions depend on the extent of the hydrogen radical removals and that of the homolytic cleavage of the glycosidic bonds. Flavonoid mono-glycoside isomers were distinguished according to their TOF MS and tandem mass spectra.
黄酮类单 - O - 糖苷的负离子基质辅助激光解吸/电离（MALDI）飞行时间质谱和串联质谱显示出不规则信号，这些信号比母体去质子化分子（M - H）和糖单元丢失的碎片离子（M - 糖 - H）小1和/或2 Da。1和/或2 Da的质量位移是由于中性氢自由基（H*）的去除，和/或糖苷键的均裂产生的，例如M - H* - H、M - 糖 - H* - H和M - 糖 - 2H* - H。研究表明，氢自由基是从黄酮类化合物上的酚羟基去除的，而不是从糖部分去除的，因为黄酮类骨架本身吸收激光。糖基位置取决于氢自由基去除的程度和糖苷键均裂的程度。黄酮类单糖苷异构体根据其飞行时间质谱和串联质谱进行区分。
