1,8-Cineole is a widely distributed odorant that also shows physiological effects, but whose human metabolism has hitherto not been extensively investigated. The aim of the present study was, thus, to characterise the metabolites of 1,8-cineole, identified previously in human milk, after the oral intake of 100 mg of this substance. Special emphasis was placed on the enantiomeric composition of the metabolites since these data may provide important insights into potential biotransformation pathways, as well as potential biological activities of these substances, for example on the breastfed child. The volatile fraction of the human milk samples was therefore isolated via Solvent Assisted Flavour Evaporation (SAFE) and subjected to gas chromatography-mass spectrometry (GC-MS). The absolute concentrations of each metabolite were determined by matrix calibration with an internal standard, and the ratios of enantiomers were analysed on chiral capillaries. The concentrations varied over a broad range, from traces in the upper ng/kg region up to 40 μg/kg milk, with the exception of the main metabolite α2-hydroxy-1,8-cineole that showed concentrations of 100–250 μg/kg. Also, large inter- and intra-individual variations were recorded for the enantiomers, with nearly enantiomerically pure α2-hydroxy- and 3-oxo-1,8-cineole, while all other metabolites showed ratios of ~30:70 to 80:20.
References
[1]
Opdyke, D.L.J. Monographs of fragrance raw materials: Eucalyptol. Food Cosmet. Toxicol. 1975, 13, 105–106, doi:10.1016/0015-6264(75)90094-2.
[2]
de Vincenzi, M.; Silano, M.; de Vincenzi, A.; Maialetti, F.; Scazzocchio, B. Constituents of aromatic plants: Eucalyptol. Fitoterapia 2002, 73, 269–275, doi:10.1016/S0367-326X(02)00062-X.
[3]
Opinion of the scientific committee on food on eucalyptol, 2002. Available online: http://ec.europa.eu/food/fs/sc/scf/out126_en.pdf , accessed on 29 January 2013.
[4]
Iqbal, Z.; Akhtar, M.; Qureshi, T.M.; Akhter, J.; Ahmad, R. Variation in composition and yield of foliage oil of eucalyptus polybractea. J. Chem. Soc. Pak. 2011, 33, 183–187.
[5]
Barton, A.F.M.; Tjandra, J.; Nicholas, P.G. Chemical evaluation of volatile oils in eucalyptus species. J. Agric. Food Chem. 1989, 37, 1253–1257, doi:10.1021/jf00089a011.
[6]
Juergens, U.R.; Dethlefsen, U.; Steinkamp, G.; Gillissen, A.; Repges, R.; Vetter, H. Anti-inflammatory activity of 1.8-cineol (eucalyptol) in bronchial asthma: A double-blind placebo-controlled trial. Respir. Med. 2003, 97, 250–256, doi:10.1053/rmed.2003.1432.
[7]
Worth, H.; Schacher, C.; Dethlefsen, U. Concomitant therapy with cineole (eucalyptole) reduces exacerbations in COPD: A placebo-controlled double-blind trial. Respir. Res. 2009, 10, 69, doi:10.1186/1465-9921-10-69.
[8]
Nilberto, R.N.F.; Refosco, R.M.C.; Vasconcelos, E.C.F.; Kerntopf, M.R.; Santos, C.F.; Batista, F.J.A.; de Sousa, C.M.; Fonteles, M.C. 1,8-Cineole induces relaxation in rat and guinea-pig airway smooth muscle. J. Pharm. Pharmacol. 2009, 61, 361–366, doi:10.1211/jpp.61.03.0011.
[9]
Juergens, U.R.; Stober, M.; Schmidt-Schilling, L.; Kleuver, T.; Vetter, H. Antiinflammatory effects of eucalyptol (1.8-cineole) in bronchial asthma: Inhibition of arachidonic acid metabolism in human blood monocytes ex vivo. Eur. J. Med. Res. 1998, 3, 407–412.
[10]
Matthys, H.; de Mey, C.; Carls, C.; Rys, A.; Geib, A.; Wittig, T. Efficacy and tolerability of myrtol standardized in acute bronchitis - a multi-centre, randomised, double-blind, placebo-controlled parallel group clinical trial vs. cefuroxime and ambroxol. Arzneimittel-Forsch. 2000, 50, 700–711.
[11]
Federspil, P.; Wulkow, R.; Zimmermann, T. Efficacy of myrtol standardized in the therapy of acute sinusitis—Results of a double blind, randomized, placebo-controlled multicentered trial. Laryngo-Rhino-Otologie 1997, 76, 23–27.
[12]
Kohlert, C.; van Rensen, I.; Marz, R.; Schindler, G.; Graefe, E.U.; Veit, M. Bioavailability and pharmacokinetics of natural volatile terpenes in animals and humans. Planta Med. 2000, 66, 495–505, doi:10.1055/s-2000-8616.
[13]
Ishida, T. Biotransformation of terpenoids by mammals, microorganisms, and plant-cultured cells. Chem. Biodiversity 2005, 2, 569–590, doi:10.1002/cbdv.200590038.
[14]
Breitmaier, E. Terpenes: Importance, general structure, and biosynthesis. In Terpenes—Flavors, Fragrances, Pharmaca, Pheromones; WILEY-VCH: Weinheim, Germany, 2006.
[15]
Homburger, F.; Boger, E. Carcinogenicity of essential oils, flavors and spices—A review. Cancer Res. 1968, 28, 2372–2374.
[16]
Waddell, W.J. Thresholds of carcinogenicity of flavors. Toxicol. Sci. 2002, 68, 275–279, doi:10.1093/toxsci/68.2.275.
[17]
Opinion of the scientific committee on food on the safety of the presence of safrole in flavourings and other food ingredients with flavouring properties, 2002.
[18]
Opinion of the scientific committee on food on estragole (1-allyl-4-methoxybenzene), 2001.
[19]
Smith, R.L.; Adams, T.B.; Doull, J.; Feron, V.J.; Goodman, J.I.; Marnett, L.J.; Portoghese, P.S.; Waddell, W.J.; Wagner, B.M.; Rogers, A.E.; et al. Safety assessment of allylalkoxybenzene derivatives used as flavouring substances—Methyl eugenol and estragole. Food Chem. Toxicol. 2002, 40, 851–870, doi:10.1016/S0278-6915(02)00012-1.
[20]
Smith, R.L.; Cohen, S.M.; Doull, J.; Feron, V.J.; Goodman, J.I.; Marnett, L.J.; Munro, I.C.; Portoghese, P.S.; Waddell, W.J.; Wagner, B.M.; et al. Criteria for the safety evaluation of flavoring substances. The expert panel of the flavor and extract manufacturers association. Food Chem. Toxicol. 2005, 43, 1141–1177, doi:10.1016/j.fct.2004.11.012.
[21]
Opinion of the scientific committee on food on methyleugenol (4-allyl-1,2-dimethoxybenzene), 2001.
[22]
Jenner, P.M.; Hagan, E.C.; Taylor, J.M.; Cook, E.L.; Fitzhugh, O.G. Food flavourings and compounds of related structure I. Acute oral toxicity. Food Cosmet. Toxicol. 1964, 2, 327–343, doi:10.1016/S0015-6264(64)80192-9.
[23]
Engel, W. In vivo studies on the metabolism of the monoterpenes S-(+)- and R-(-)-carvone in humans using the metabolism of ingestion-correlated amounts (mica) approach. J. Agric. Food Chem. 2001, 49, 4069–4075, doi:10.1021/jf010157q.
[24]
Jager, W.; Mayer, M.; Platzer, P.; Reznicek, G.; Dietrich, H.; Buchbauer, G. Stereoselective metabolism of the monoterpene carvone by rat and human liver microsomes. J. Pharm. Pharmacol. 2000, 52, 191–197, doi:10.1211/0022357001773841.
[25]
Engel, W. Detection of a "nonaromatic" NIH shift during in vivo metabolism of the monoterpene carvone in humans. J. Agric. Food Chem. 2002, 50, 1686–1694, doi:10.1021/jf011199h.
[26]
Zeller, A.; Horst, K.; Rychlik, M. Study of the metabolism of estragole in humans consuming fennel tea. Chem. Res. Toxicol. 2009, 22, 1929–1937, doi:10.1021/tx900236g.
[27]
Pass, G.J.; McLean, S.; Stupans, I.; Davies, N. Microsomal metabolism of the terpene 1,8-cineole in the common brushtail possum (trichosurus vulpecula), koala (phascolarctos cinereus), rat and human. Xenobiotica 2001, 31, 205–221, doi:10.1080/00498250110043535.
[28]
Duisken, M.; Sandner, F.; Blomeke, B.; Hollender, J. Metabolism of 1,8-cineole by human cytochrome P450 enzymes: Identification of a new hydroxylated metabolite. BBA—Gen. Subjects 2005, 1722, 304–311, doi:10.1016/j.bbagen.2004.12.019.
[29]
Horst, K.; Rychlik, M. Quantification of 1,8-cineole and of its metabolites in humans using stable isotope dilution assays. Mol. Nutr. Food Res. 2010, 54, 1515–1529, doi:10.1002/mnfr.200900528.
[30]
Kirsch, F.; Horst, K.; R？hrig, W.; Rychlik, M.; Buettner, A. Tracing metabolite profiles in human milk: Studies on the odorant 1,8-cineole transferred into breast milk after oral intake. Metabolomics 2012, 1–14.
[31]
Engel, W.; Bahr, W.; Schieberle, P. Solvent assisted flavour evaporation - a new and versatile technique for the careful and direct isolation of aroma compounds from complex food matrices. Eur. Food Res. Technol. 1999, 209, 237–241, doi:10.1007/s002170050486.
[32]
McManaman, J.L.; Neville, M.C. Mammary physiology and milk secretion. Adv. Drug Delivery. Rev. 2003, 55, 629–641, doi:10.1016/S0169-409X(03)00033-4.
[33]
Berlin, C.M.; Briggs, G.G. Drugs and chemicals in human milk. Semin. Fetal. Neonatal Med. 2005, 10, 149–159, doi:10.1016/j.siny.2004.09.016.
[34]
Arena, J.M. Contamination of the ideal food. Nutrition Today 1970, 5, 2–8, doi:10.1097/00017285-197000540-00001.
[35]
Committee on Drugs. The transfer of drugs and other chemicals into human milk. Pediatrics 2001, 108, 776–789, doi:10.1542/peds.108.4.1020.
[36]
Kroemer, H.K.; Fromm, M.F.; Eichelbaum, M. Stereoselectivity in drug metabolism and action: Effects of enzyme inhibition and induction. Ther. Drug Monit. 1996, 18, 388–392, doi:10.1097/00007691-199608000-00013.
[37]
Brocks, D.R. Drug disposition in three dimensions: An update on stereoselectivity in pharmacokinetics. Biopharm. Drug Dispos. 2006, 27, 387–406, doi:10.1002/bdd.517.
[38]
Lu, H. Stereoselectivity in drug metabolism. Expert Opin. Drug Metab. Toxicol. 2007, 3, 149–158, doi:10.1517/17425255.3.2.149.
[39]
Kirsch, F.; Beauchamp, J.; Buettner, A. Time-dependent aroma changes in breast milk after oral intake of a pharamcological preparation containing 1,8-cineole. Clin. Nutr. 2012, 31, 682–692, doi:10.1016/j.clnu.2012.02.002.
[40]
van den Dool, H.; Kratz, P.D. A generalization of retention index system including linear temperature programmed gas-liquid partition chromatography. J. Chromatogr. 1963, 11, 463–471, doi:10.1016/S0021-9673(01)80947-X.
[41]
Schaffarczyk, M.; Balaban, T.S.; Rychlik, M.; Buettner, A. Syntheses of chiral 1,8-cineole-metabolites and determination of their enantiomeric composition in human urine after ingestion of 1,8-cineole-containing capsules. Chem. Plus Chem. 2012, 10–1002, doi:10.1002/cplu.201200253.
[42]
Kent, J.C.; Mitoulas, L.R.; Cregan, M.D.; Ramsay, D.T.; Doherty, D.A.; Hartmann, P.E. Volume and frequency of breastfeedings and fat content of breast milk throughout the day. Pediatrics 2006, 117, e387–e395, doi:10.1542/peds.2005-1417.
[43]
Lee, I.S.; Kim, D. Polymorphic metabolism by functional alterations of human cytochrome P450 enzymes. Arch. Pharm. Res. 2011, 34, 1799–1816, doi:10.1007/s12272-011-1103-2.
Daly, A.K. Pharmacogenetics of the major polymorphic metabolizing enzymes. Fundam. Clin. Pharmacol. 2003, 17, 27–41, doi:10.1046/j.1472-8206.2003.00119.x.
[46]
Guengerich, F.P. Polymorphism of cytochrome-p-450 in humans. Trends Pharmacol. Sci. 1989, 10, 107–109, doi:10.1016/0165-6147(89)90207-1.
[47]
Caldwell, J. Stereochemical determinants of the nature and consequences of drug metabolism. J. Chromatogr. A 1995, 694, 39–48, doi:10.1016/0021-9673(94)00812-N.
[48]
Guengerich, F.P. Common and uncommon cytochrome P450 reactions related to metabolism and chemical toxicity. Chem. Res. Toxicol. 2001, 14, 611–650, doi:10.1021/tx0002583.
[49]
Testa, B.; Kr？mer, S. The biochemistry of drug metabolism—An introduction. Part 2. Redox reactions and their enzymes. Chem. Biodiversity 2007, 4, 257–405, doi:10.1002/cbdv.200790032.
[50]
Malatkova, P.; Maser, E.; Wsol, V. Human carbonyl reductases. Curr. Drug MeTable 2010, 11, 639–658, doi:10.2174/138920010794233530.
[51]
Prasad, B.; Rojubally, A.; Plettner, E. Identification of camphor oxidation and reduction products in pseudomonas putida: New activity of the cytochrome p450(cam) system. J. Chem. Ecol. 2011, 37, 657–667, doi:10.1007/s10886-011-9959-7.
[52]
Pilka, E.S.; Niesen, F.H.; Lee, W.H.; El-Hawari, Y.; Dunford, J.E.; Kochan, G.; Wsol, V.; Martin, H.J.; Maser, E.; Oppermann, U. Structural basis for substrate specificity in human monomeric carbonyl reductases. PLoS One 2009, doi:10.1371/journal.pone.0007113.
[53]
Ishida, T.; Toyota, M.; Asakawa, Y. Terpenoid biotransformation in mammals. V. Metabolism of (+)-citronellal, (±)-7-hydroxycitronellal, citral, (-)-perillaldehyde, (-)-myrtenal, cuminaldehyde, thujone, and (±)-carvone in rabbits. Xenobiotica 1989, 19, 843–855, doi:10.3109/00498258909043145.
[54]
Miyazawa, M.; Shindo, M. Biotransformation of 1,8-cineole by human liver microsomes. Natural Product Letters 2001, 15, 49–53, doi:10.1080/10575630108041257.
[55]
Miyazawa, M.; Shindo, M.; Shimada, T. Oxidation of 1,8-cineole, the monoterpene cyclic ether originated from eucalyptus polybractea, by cytochrome P450 3A enzymes in rat and human liver microsomes. Drug Metab. Dispos. 2001, 29, 200–205.
[56]
Wahlstr？m, A.; Pacifici, G.M.; Lindstrom, B.; Hammar, L.; Rane, A. Human-liver morphine UDP-glucuronyl transferase enantioselectivity and inhibition by opioid congeners ans oxazepam. Br. J. Pharmacol. 1988, 94, 864–870, doi:10.1111/j.1476-5381.1988.tb11598.x.
[57]
Fournel-Gigleux, S.; Hamar-Hansen, C.; Motassim, N.; Antoine, B.; Mothe, O.; Decolin, D.; Caldwell, J.; Siest, G. Substrate specificity and enantioselectivity of arylcarboxylic acid glucuronidation. Drug Metab. Dispos. 1988, 16, 627–634.
[58]
Bemelmans, J.M.H. Rewiev of isolation and concentration techniques. In Progress in Flavour Research; Land, D.G., Nursten, H.E., Eds.; Applied Science Publishers: London, UK, 1979; pp. 79–88.
