Fast-atom bombardment mass spectrometric and tandem mass spectrometric study of (-)-menthol-Beta-(D)-glucopyranoside, neohesperidin dihydrochalcone and their non-covalent association with Beta-cyclodextrin. Two examples of interaction of a carbohydrate host with glycoconjugate guests

(-)-Menthol-?-(D)-glucopyranoside 1 and neohesperidin dihydrochalcone 2 are glycoconjugates of practical interest. Compound 1 releases (-)-menthol in foods by slow hydrolysis and 2 is a sweetener used as an alternative to sucrose for diet food and beverages. Their molecular encapsulation in ?-cyclodextrin (?CD) is currently under investigation with the purpose of obtaining long lasting properties in the final product. From a mass spectrometric point of view, the study of the protonated gaseous 1 : 1 host-guest complexes of 1 and 2 with ?CD is of particular interest, since the guest molecules possess an apolar aglycon, likely to interact with the lipophilic cavity of ?CD, and a saccharidic part, whose capability of interaction with the polar external surface of ?CD has not been investigated so far. We carried out a fast-atom bombardment (FAB) mass spectrometric and tandem mass spectrometric (MS/MS) study in thioglycerol on 1 and 2 and their gaseous protonated 1 : 1 association complexes with ?CD. The FAB and tandem mass spectrometry results are later presented and discussed. Collisionally-activated decomposition data from native 1 and 2 are compared with those of the complexes of 1 and 2 with ?CD. The experimental data indicate that the presence of ?CD may dramatically alter the fragmentation pattern of the two glycoconjugates. The observed fragmentation patterns are consistent with an attractive interaction between the polar external surface of ?CD and the sugar residues of the guest molecules 1 and 2. The mass spectrometric data not only provide information on the nature of non-covalent interaction in controlling binding phenomena, but also point out a role for carbohydrate-carbohydrate interactions, possibly mediated via hydrogen bonding.