Identification of isomers of resveratrol dimer and their analogues from wine grapes by HPLC/MSn and HPLC/DAD-UV

A facile method based on HPLC/(−)ESI-MSn is established for the analysis of seven isomers of resveratrol dimers and three of their analogues in Xinjiang wine grapes. The structures of these compounds are positively or tentatively determined. Among them, three are tentatively identified as new compounds. MSn experiments on the [M−H]− ions provide abundant structural information, especially regarding the relative abundance of the key product ions, m/z 333 and 369 (385 in compound 3), which can be utilised to distinguish whether or not the compound identified contains the scaffold of the isomer of a resveratrol dimer. The relative abundance of key product ions remains unchanged as collision energy varies from 0.60 to 0.95 V. All the trans-, and cis-isomers could be identified by HPLC/DAD-UV spectra. The UV spectra of compounds 2 and 9 tentatively show cis and trans- configurations, respectively.