Structural characterization of isoprenylated flavonoids from Kushen by electrospray ionization multistage tandem mass spectrometry

✍ Scribed by Yufeng Zhang; Peng Zhang; Yiyu Cheng

• Publisher: John Wiley and Sons
• Year: 2008
• Tongue: English
• Weight: 298 KB
• Volume: 43
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/jms.1423

✦ Synopsis

Abstract

Eighteen isoprenylated flavonoids (8 flavanones, 3 flavanols, and 7 chalcones) isolated from Kushen or synthesized were studied by positive and negative ion electrospray ionization multistage tandem mass spectrometry (ESI‐MS^n^). Plausible fragmentation patterns were obtained by comparing their MS^n^ spectra with each other, which were further supported by high‐resolution MS data and two model compounds. It was shown that the 2′‐OH group would make the C‐ring of flavonoids studied more labile through a six‐membered mechanism, resulting in base peaks of ^1, 3^A+ (positive mode) and ^1, 4^A^−^ (negative mode). In addition, the 2′‐OH is also responsible for the neutral loss of water in (+)ESI/MS^2^ of flavanones. The neutral loss of water (or methanol) in (−)ESI/MS^2^ of flavanols was elucidated by a E2 elimination mechanism. Different relative abundances (RA) of ^1, 3^A^+^ and S^+^ in (+)ESI/MS^2^ spectra were used to discriminate flavanones with their open‐ring products, chalcones, since the equilibrium for flavanone$\leftrightarrow$chalcone isomerization in ESI ion source could not be obtained in positive mode. Copyright © 2008 John Wiley & Sons, Ltd.