Metabolism of geraniol in grape berry mesocarp of Vitis vinifera L. cv. Scheurebe: demonstration of stereoselective reduction, E/Z-isomerization, oxidation and glycosylation.
The metabolism of deuterium labeled geraniol in grape mesocarp of Vitis vinifera L. cv. Scheurebe was studied by in vivo-feeding experiments. Stereoselective reduction to (S)-citronellol, E/Z-isomerization to nerol, oxidation to neral/geranial and glycosylation of the corresponding monoterpene alcohols could be demonstrated. Time course studies including the determination of conversion rates revealed that the activity of these secondary transformations of monoterpenes is dependent on the ripening stage and can be distinguished from the development of the primary monoterpene synthase activities by the sharp increase at the end of the ripening period. The stereoselective biosynthesis of the potent odorant cis-(2S,4R)-rose oxide from labeled geraniol in grape berry mesocarp is demonstrated as well. Since (S)-citronellol is the precursor of cis-(2S,4R)-rose oxide it can be concluded that especially the last part of the ripening period is important for the generation of this potent odorant. This finding confirms the conclusion that a higher concentration of flavor compounds could be established in the berries by leaving the fruit on the vine for extended periods.
Luan
Fang
F
Institut für Lebensmittelchemie, Johann Wolfgang Goethe-Universität, Marie-Curie-Strasse 9, D-60439 Frankfurt (Main), Germany.
Mosandl
Armin
A
Münch
Andreas
A
Wüst
Matthias
M
D000080462:Acyclic Monoterpenes; D005638:Fruit / Q000737:chemistry / Q000378:metabolism*; D006031:Glycosylation; D013058:Mass Spectrometry; D015394:Molecular Structure; D010084:Oxidation-Reduction; D013237:Stereoisomerism; D013379:Substrate Specificity; D013729:Terpenes / Q000737:chemistry / Q000378:metabolism*; D027843:Vitis / Q000737:chemistry / Q000378:metabolism*
D000080462:Acyclic Monoterpenes; D013729:Terpenes; C007836:geraniol