title: Structure-Odor Relationship Study on Geraniol, Nerol, and Their Synthesized Oxygenated Derivatives.
abstract: Despite being isomers having the same citrus-like, floral odor, geraniol, 1, and nerol, 3, show different odor thresholds. To date, no systematic studies are at hand elucidating the structural features required for their specific odor properties. Therefore, starting from these two basic structures and their corresponding esters, namely, geranyl acetate, 2, and neryl acetate, 4, a total of 12 oxygenated compounds were synthesized and characterized regarding retention indices (RI), mass spectrometric (MS), and nuclear magnetic resonance (NMR) data. All compounds were individually tested for their odor qualities and odor thresholds in air (OT). Geraniol, the Z-isomer, with an OT of 14 ng/L, was found to be more potent than its E-isomer, nerol, which has an OT of 60 ng/L. However, 8-oxoneryl acetate was the most potent derivative within this study, exhibiting an OT of 8.8 ng/L, whereas 8-oxonerol was the least potent with an OT of 493 ng/L. Interestingly, the 8-oxo derivatives smell musty and fatty, whereas the 8-hydroxy derivatives show odor impressions similar to those of 1 and 3. 8-Carboxygeraniol was found to be odorless, whereas its E-isomer, 8-carboxynerol, showed fatty, waxy, and greasy impressions. Overall, we observed that oxygenation on C-8 affects mainly the odor quality, whereas the E/ Z position of the functional group on C-1 affects the odor potency.
authors: Department of Chemistry and Pharmacy, Food Chemistry, Emil Fischer Center , Friedrich-Alexander-Universität Erlangen-Nürnberg , Henkestrasse 9 , 91054 Erlangen , Germany.
authors: Shaimaa Awadain
authors: SA
authors: Elsharif
authors: Department of Chemistry and Pharmacy, Food Chemistry, Emil Fischer Center , Friedrich-Alexander-Universität Erlangen-Nürnberg , Henkestrasse 9 , 91054 Erlangen , Germany.|Department of Sensory Analytics , Fraunhofer Institute for Process Engineering and Packaging (IVV) , Giggenhauser Strasse 35 , 85354 Freising , Germany.
authors: Andrea
authors: A
authors: Buettner
mesh_terms: D000080462:Acyclic Monoterpenes; D008401:Gas Chromatography-Mass Spectrometry; D007536:Isomerism; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D009812:Odorants / Q000032:analysis*; D064367:Olfactometry; D010100:Oxygen / Q000737:chemistry; D013729:Terpenes / Q000138:chemical synthesis / Q000737:chemistry*
chemical_list: D000080462:Acyclic Monoterpenes; D013729:Terpenes; C007836:geraniol; D010100:Oxygen
keywords: 8-hydroxygeraniol; gas chromatography−olfactometry; mass spectrometry; odor threshold in air; retention indices