Characterization of non-covalent complexes of rutin with cyclodextrins by electrospray ionization tandem mass spectrometry.
Electrospray ionization tandem mass spectrometry (ESI-MS(n)) and the phase solubility method were used to characterize the gas-phase and solution-phase non-covalent complexes between rutin (R) and alpha-, beta- and gamma-cyclodextrins (CDs). The direct correlation between mass spectrometric results and solution-phase behavior is thus revealed. The order of the 1 : 1 association constants (K(c)) of the complexes between R and the three CDs in solution calculated from solubility diagrams is in good agreement with the order of their relative peak intensities and relative collision-induced dissociation (CID) energies of the complexes under the same ESI-MS(n) condition in both the positive and negative ion modes. Not only the binding stoichiometry but also the relative stabilities and even binding sites of the CD-R complexes can be elucidated by ESI-MS(n). The diagnostic fragmentation of CD-R complexes, with a significant contribution of covalent fragmentation of rutin leaving the quercetin (Q) moiety attached to the CDs, provides convincing evidence for the formation of inclusion complexes between R and CDs. The diagnostic fragment ions can be partly confirmed by the complexes between Q and CDs. The gas-phase stability order of the deprotonated CD-R complexes is beta-CD-R > alpha-CD-R > gamma-CD/R; beta-CD seems to bind R more strongly than the other CDs.
Guo
Mingquan
M
Laboratory of New Drug Research, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China.
Song
Fengrui
F
Liu
Zhiqiang
Z
Liu
Shuying
S
D003505:Cyclodextrins / Q000032:analysis* / Q000737:chemistry; D007700:Kinetics; D015394:Molecular Structure; D012431:Rutin / Q000032:analysis* / Q000737:chemistry; D012995:Solubility; D021241:Spectrometry, Mass, Electrospray Ionization
D003505:Cyclodextrins; D012431:Rutin