Using the relative abundance of characteristic product ions in UHPLC-ESI-QTOF-MS methods to identify isomers of resveratrol oligomers in extracts of Xinjiang winegrape stems.

Stilbenoids, particularly resveratrol and its oligomer, are abundantly present in grapes, and their antioxidant activities have been widely reported. A quick and simple method based on UHPLC-ESI-QTOF-MS was established for the fragmentation pathways analysis of trans-ε-Viniferin, cis-ε-Viniferin, trans-δ-Viniferin and (-)-Hopeaphenol. MS/MS experiments on the [M-H] ions provided abundant structural information, especially regarding the relative abundance of the key product ion at m/z 347. The product ion was used to further identify structures in isomers of resveratrol dimers and its analogues. Based on the fragmentation pathways, we tentatively determined two compounds from the crude extracts of Xinjiang winegrape stems as Gnetin C and cis-Scirpusin A. Results from these experiments contribute to a more complete understanding of the stilbene compounds found in grape stems. The UHPLC-QTOF-MS method can be used for the rapid analysis of stilbenes compounds in plant materials, foods and wine.