Content of trans-resveratrol, trans-epsilon-viniferin and trans-8-viniferin in young spring grapevine canes- the influence of samples drying

The main objective was to study the effect of sample preparation on the content of trans-resveratrol, trans- epsilon-viniferin and trans-8-viniferin in young spring grapevine canes. The samples of six varieties of Vitis vinifera L. (`Hibernal,' `Malverina,' `Kolor,' `Fioletovij Augustovskij,' `Gruner Veltliner' and `Blaufrankisch') were either lyophilised or slow dried at room temperature (three months), extracted and analysed by HPLC using DAD and FLD detectors and by LC-MS. The presence of trans-8-viniferin was confirmed by comparison with trans-8-viniferin prepared by dimerization of trans-resveratrol using laccase and its structure was verified by LC-NMR. The slow drying of the samples at room temperature enables the synthesis of a significant amount of stilbenes in all the studied varieties of V vinifera canes resulting in a higher stilbene content compared to the lyophilised samples. The results of this study show the importance of the method of drying the cane sample before the extraction and analysis.