Volatile compounds released by enzymatic hydrolysis of glycoconjugates of leaves and grape berries from Vitis vinifera Muscat of Alexandria and Shiraz cultivars

Glycoconjugates from Muscat of Alexandria and Shiraz leaves and grape berri es were isolated by adsorption on Amberlite XAD-2 resin, and enzymatically released aglycons were analyzed by GC-FID and CC-MS. About 120 aglycons wer e fully or tentatively identified. Compositional differences were observed between leaves and berries of the two varieties in five aglycon chemical gr oups: C6 alcohols, aliphatic alcohols, monoterpenes, shikimates, and C-13-n orisoprenoids, which were much more abundant in the leaves than in the berr ies. The differences observed for C-13-norisoprenoids were in agreement wit h their hypothetical independent biosynthesis in leaves and berries. Thus, 3-hydroxy-beta -damascone, an important norisoprenoid aglycon of grape berr ies, was not detected in leaves, whereas its oxidized derivative, 3-oxo-alp ha -damascone, was absent in berries. Compositional differences were also o bserved between Muscat and Shiraz leaves. 3-Oxo-alpha -ionol was not detect ed in Shiraz leaves, and its retro derivatives were less abundant than in M uscat of Alexandria leaves. Conversely, in Shiraz leaves the levels of 7,8- dihydroionone derivatives, such as megastigman-3,9-diol and 3-oxo-7,8-dihyd ro-alpha -ionol, were higher than in Muscat of Alexandria leaves.