1,1,6-TRIMETHYL-1,2-DIHYDRONAPHTHALENE (TDN) FORMATION IN WINE .2. APPLICATION OF MULTILAYER COIL COUNTERCURRENT CHROMATOGRAPHY FOR THE STUDY OF VITIS-VINIFERA CV RIESLING LEAF GLYCOSIDES

The glycosidic fraction isolated from Vitis vinifera cv. Riesling leaves by XAD-2 adsorption and methanol elution was separated by multilayer coil countercurrent chromatography (MLCCC) to identify genuine precursors of the off-flavor-causing compound 1,1,6-trimethyl-1,2-dihydronaphthalene (TDN). A two-step procedure utilizing preparative MLCCC in combination with analytical MLCCC yielded two major vine leaf glycosides in pure form, i.e., the beta-glucopyranosides of 3-oxo-7,8-dihydro-alpha-ionol (Blumenol C) and 3-oxo-4,5-dihyaro-alpha-ionol, respectively. The determination of minor vine leaf constituents in separated MLCCC fractions was achieved after acetylation and subsequent HPLC purification of the per-O-acetylated derivatives. This procedure allowed the identification of 3,4-dihydroxy-7,8-dihydro-beta-ionone 3-O-beta-D-glucopyranoside as a major TDN precursor in Riesling leaves. In addition, the beta-D-glucopyranosides of 3,4-dihydroxy-beta-ionone and zingerone were identified.