- Syntheses of chiral 1,8-cineole metabolites and determination of their enantiomeric composition in human urine after ingestion of 1,8-cineole- containing capsules
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The chiral metabolites in human urine were investigated after ingestion of a 1,8-cineole (eucalyptol)-containing enterocoated capsule (Soledum). For identification of the various enantiomers the enantiomerically pure (-/+)-α2-hydroxy-1,8- cineole, (-/+)-β2-hydroxy-1,8-cineole, (-/+)-9-hydroxy-1,8-cineole, and (-/+)-2-oxo-1,8-cineole were prepared. To achievethis aim, after acetylation of the synthesized racemic 2-and 9-hydroxy-1,8-cineoles, pig liver esterase- or yeast-mediated hydrolysis provided the (-)-alcohols with their antipodal(+)-acetates with enantiomeric excess of 33-100 %. Dess-Martin periodinane oxidation of the alcohol (+)-α2-hydroxy-1,8-cineole, obtained by hydrolysis of the resolved acetate, provided the corresponding (+)-2-oxo-1,8-cineole, meanwhile the oxidation of (-)-α2-hydroxy-1,8-cineole gave (-)-2-oxo-1,8-cineole. Using these standards seven metabolites (+/-)-α2-hydroxy-1,8-cineole, (+/-)-β2-hydroxy-1,8-cineole, (+/-)-α3-hydroxycineole,(+/-)-3-oxo-1, 8-cineole, 4-hydroxy-1,8-cineole, 7-hydroxy-1,8-cineole, and (+/-)-9-hydroxy-1,8-cineole, all liberated from their glucuronides, were identified in urine by GCMS on a chiral stationary phase after consumption of 10 mg of 1,8-cineole. Metabolite screening using 2H3-1,8- cineol as the internal standard revealed (+/-)-α2-hydroxy-1,8-cineole as the predominant metabolite followed by (+/-)-9-hydroxy-1,8-cineole. Furthermore, the results showed that one enantiomer is always formed preferentially.
- Schaffarczyk, Monika,Balaban, Teodor Silviu,Rychlik, Michael,Buettner, Andrea
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- Microbial resolution of racemic 2-endo-acetoxy-1,8-cineole by Glomerella cingulata
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Resolution of (±)-2-endo-acetoxy-1,8-cineole by Glomerella cingulata is described. Both (+)-2-endo-acetoxy-1,8-cineole and (-)-2-endo-hydroxy-1,8-cineole could be quantitatively obtained in enantiomerically pure form (yield 50%; e.e. 100%). In addition, t
- Miyazawa, Mitsuo,Hashimoto, Yuya
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p. 3185 - 3187
(2007/10/03)
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- Enantiomeric purity and odor characteristics of 2- and 3-acetoxy-1,8- cineoles in the rhizomes of Alpinia galanga Willd.
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(S)-(+)-O-methylmandelate esters of trans- and cis-1,3,3-trimethyl-2- oxabicyclo[2.2.2]octan-5- and 6-ols (2- and 3-hydroxy-1,8-cineoles) were prepared, and eight diastereomers were separated. The absolute configuration of the asymmetric carbons of the cineole moiety of each diastereomer was determined by 1H NMR data according to the Mosher theory. Each mandelate was reduced with LiAlH4 to obtain optically pure hydroxy-1,8-cineoles, this being followed by acetylation to afford optically pure acetoxy-1,8-cineoles. These acetates were subjected to chiral GC, using a cyclodextrin column, and the enantiomeric purity of trans- and cis-1,3,3-trimethyl-2- oxabicyclo[2.2.2]octan-5-and 6-yl acetates in the aroma concentrate from the rhizomes of Alpinia galanga was determined as 93.9 (5S), 19.4 (5R), 63.5 (6R), and 100 (6R) % ee, respectively. The aroma character of each enantiomer was also evaluated by GC-sniffing.
- Kubota, Kikue,Someya, Yuki,Yoshida, Reiko,Kobayashi, Akio,Morita, Tetsu-Ichiro,Koshino, Hiroyuki
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p. 685 - 689
(2007/10/03)
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