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Comprehensive Two-dimensional Gas Chromatography With Mass Espectrometry Applied to the Analyisi of Volatiles in Artichoke Leaves

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Análisis de compuestos volátiles de alcachofa
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  Industrial Crops and Products 62 (2014) 507–514 Contents lists available at ScienceDirect Industrial Crops and Products  journal homepage: www.elsevier.com/locate/indcrop Comprehensive two-dimensional gas chromatography with massspectrometry applied to the analysis of volatiles in artichoke( Cynara scolymus  L.) leaves Caroline Saucier a , Allan dos S. Polidoro a , Anaí L. dos Santos a , Jaderson K. Schneider a ,Elina B. Caramão a , b , Rosângela A. Jacques a , ∗ a Institute of Chemistry, Federal University of Rio Grande do Sul (UFRGS), 9500 Bento Gonc¸alves Av., ZIP 91501-970 Porto Alegre, RS, Brazil b INCT-E&A, Federal University of Rio Grande do Sul, RS, Brazil a r t i c l e i n f o  Article history: Received 5 June 2014Received in revised form 20 August 2014Accepted 10 September 2014Available online 30 September 2014 Keywords: Volatile compoundsHydrodistillationGC × GC/qMSTerpenesBioactive compoundsPlant analysis a b s t r a c t Artichoke ( Cynara scolymus  L.) is well known due to its medicinal properties and, as a result, a largenumber of studies have been conducted to determine the chemical constituents produced by the plant.However, investigations were mainly focused on the non-volatile compounds, while the volatile con-stituents remained largely neglected. This study was aimed at obtaining a deeper understanding of thevolatilecompositionofartichoke.Forthispropose,comprehensivetwo-dimensionalgaschromatographycoupled to a rapid scanning quadrupole mass spectrometer (GC × GC/qMS) and retention indices wereused to improve the chemical characterization of volatiles from leaves. A total of 130 compounds werefound, 109 of which are reported for the first time in  C. scolymus  L., including oxygenated monoter-penes, sesquiterpenes, oxygenated sesquiterpenes, norisoprenoids, lactones, alcohols, ketones andaldehydes. The major compounds were 1-octen-3-one (3.85%), ( E  )-2-hexenal (3.75%), benzene acetalde-hyde (2.90%), 2,2-dimethyl-4-pentenal (2.81%),   -ionone (1.94%), furfural (1.65%), ( E  )-  -damescenone(1.59%),   -methyl-  -butirolactone (1.53%), benzaldehyde (1.47%) and dihydroactinidiolide (1.44%). Thecomprehensive GC × GC/qMS approach enabled a greater number of analytes to be identified, approxi-mately four times higher than that obtained for GC/qMS. Additionally, the results imply that artichokeleaves are a potential source of volatile bioactive compounds.© 2014 Elsevier B.V. All rights reserved. 1. Introduction Artichoke ( Cynara scolymus  L.) is a herbaceous perennial cropthat srcinates from the Mediterranean area and is widely culti-vated around the world. Since ancient times, artichoke extractshave been used in herbal medicine because of their recognizedtherapeuticeffects.Severalstudieshavedemonstratedhepatopro-tective, anticarcinogenic, antioxidative, antibacterial, antifungal,anti-HIV, urinative, anticholesterol and glycaemia reduction phar-macological activities (Adzet et al., 1987; Brown and Rice-Evans,1998;CairellaandVecchi,1969;Clifford,2000;CliffordandWalker,1987; Gebhardt, 1997; Preziosi, 1969; Rondanelli et al., 2011;Rodriguez et al., 2002; Zhu et al., 2005). Water and polar organicsolvents were typically used in these studies. Such a broad range ∗ Corresponding author. Tel.: +55 51 3308 7213; fax: +55 51 3308 7213. E-mail addresses:  rosangela.j@gmail.com, rosangela.j@globo.com, rosangela.j@iq.ufrgs.br (R.A. Jacques). of therapeutic activities was ascribed to several active compoundsprovidingsynergisticpharmacologicaleffects(Romanoetal.,2005;Zhu et al., 2004).Because of these diverse beneficial properties, the literaturecontains numerous studies on non-volatile artichoke constituents,particularly the phenolic compounds (as reviewed by Lattanzioetal.,2009).However,therearefewinvestigationsontheirvolatileconstituents. Some researchers have reported that monoterpenes,sesquiterpenes, alcohols, aldehydes and ketones are the mainvolatile constituents of the leaves and heads of   C. scolymus  L.(Butteryetal.,1978;Ghanemetal.,2009;Guillén-Ríosetal.,2006;H˘ad˘arug˘a et al., 2009; MacLeod et al., 1982; Nassar et al., 2013). Plant volatiles are usually complex samples that containhundreds of compounds, including alcohols, aldehydes, esters,ketones, phenols, lactones, phenylpropanoids and terpenoids(Brielmann et al., 2006; Rowshan et al., 2013). One-dimensional gas chromatography (1D-GC) has been used for many years asthe standard tool for separating volatiles from plants. However,obtainingthebestcomponentseparationvia1D-GCisdifficultdue http://dx.doi.org/10.1016/j.indcrop.2014.09.0230926-6690/© 2014 Elsevier B.V. All rights reserved.  508  C. Saucier et al. / Industrial Crops and Products 62 (2014) 507–514 to the insufficient resolution power of a single column (Purcaroetal.,2009).Thisproblempersistsdespitethecontinuousdevelop-mentofchromatographs,techniquesandanalyticalmethodologies(Mateus et al., 2010). Overlapping peaks usually significantly com- plicate compound identification and accurate quantification (Zhuet al., 2007). In addition, plant volatiles are present in a wide rangeof concentrations, and the trace analytes that are occasionally thebiologically active matrix components may not be detected, par-ticularly if they are co-eluted with high concentration compounds(Mateus et al., 2010).Comprehensive two-dimensional gas chromatography(GC × GC) has emerged as a powerful separation techniquefor overcoming these limitations and is widely used to character-izecomplexsamples.GC × GCusestwoorthogonalmechanismstoseparate the sample constituents through two columns connectedin series with different stationary phases and a transfer device,definedasthemodulator.Themodulatorcontinuouslyisolates,re-concentrates,andintroducessmallportionsoftheprimarycolumneffluenttoasecondarycolumn.Thetimerequiredtocompletethisprocess is defined as the modulation period (Marriott et al., 2012;Mondello et al., 2008). The chromatographic resolution is greatlyenhanced by this technology (Marriott et al., 2004).ThedetectorsusedinGC × GCrepresentanadditionalchallengebecause high spectral acquisition rates are required for correctpeak assignment and quantification (Adahchour et al., 2005). The time-of-flight mass spectrometer (TOFMS) can be used to obtainsuch data; however, its high cost limits its laboratory utilization(Mondello et al., 2005). In contrast, a quadrupole mass spectrom- eter (qMS) is much less expensive and more user-friendly, andseveral authors have reported the use of qMS hyphenated toGC × GC (Adahchour et al., 2008; Mondello et al., 2008). Recent studies have shown the effectiveness of GC × GC in combinationwith qMS operating in the rapid scanning mode to achieve satis-factory data acquisition rates (Cordero et al., 2007; Purcaro et al.,2010; Tranchida et al., 2013).The aim of this study was to investigate the volatile con-stituents of artichoke leaves via comprehensive two-dimensionalgas chromatography coupled to a rapid scanning quadrupolemass spectrometer. The linear temperature programmed reten-tionindices(LTPRI)wereusedtoconfirmthepeakassignments.Tothe best of the authors’ knowledge, this is the first report detailingvolatile compounds in artichoke leaves using GC × GC. 2. Materials and methods  2.1. Plant material Artichoke ( C. scolymus  L.) was collected in the municipal dis-trict of Riozinho (29 ◦ 38  27  S and 50 ◦ 27  10  W), Rio Grande doSul State, Brazil, in February 2011 and identified by the specialistbotanist Dr. Eduardo Pasini (Bio-sciences Institute, Department of Botany,UFRGS,RioGrandedoSul,Brazil).Avoucherspecimen(ICN:166985) was deposited in the Herbarium of UFRGS, Rio Grande doSul, Brazil. The leaves were dried at 35 ◦ C until their weight wasconstant, and they were then stored in dark bags to protect themfrom humidity and light.  2.2. Chemicals and solvents All of the solvents and standards (linear alkanes) used werepurchased from Sigma–Aldrich (St. Louis, MO, USA). All water waspurifiedusingaMilli-Qsystem(Millipore,Bedford,MA,USA).Otherunmarked reagents were of analytical grade.  2.3. Volatile compounds extraction Driedartichokeleaves(100g)werehydrodistilledfor4husingaClevenger-type apparatus following the method recommended bythe Brazilian Official Pharmacopoeia V (2010). The obtained distil- latewasextractedwithdichloromethaneanddriedoveranhydroussodium sulfate. The organic layer was transferred into dark vialsand stored at 4 ◦ C until its analysis.  2.4. GC/qMS analysis The GC/qMS measurements were performed on a ShimadzuGC/qMS system, consisting of a GC2010 Gas Chromatograph anda QP2010 Plus Mass Spectrometer (qMS) (Kyoto, Japan). TheGC was equipped with an AOC-20i auto-injector (split/splitless).The separation was performed on a ZB-5MS (5% phenyl,95% dimethylpolysiloxane) column with 60m length × 0.25mmI.D. × 0.25  mfilmthickness(Phenomenex,Torrance,CA,USA).TheGCovenstartedat40 ◦ C,washeatedat2 ◦ C/minto300 ◦ C,andthenmaintained for 20min. The injector temperature was 300 ◦ C, andtheinjectionwasperformedinthesplitlessmodeusing0.5  L.Highpurityhelium(99.99%,LindeGases,Canoas,PortoAlegre,RS,Brazil)ataflowrateof0.91mL/minwasusedasthecarriergas.Theinter-faceandionsourcetemperaturewas300 ◦ C.Themassspectrometeroperated in the electron impact mode (EI) at 70eV and scannedfrom 40 to 500 m /  z   in a full scan acquisition mode. The data wereacquired using GCMS-solution software version 2.6 (Shimadzu,Kyoto, Japan). The mass spectrum of each detected compound wascompared with those in the NIST-05 mass spectral library, usingsimilarity matches of at least 80% for identification. This identi-fication was supported by the experimentally determined lineartemperatureprogrammedretentionindex(LTPRI)valuesandcom-pared with the values reported in the bibliography when available(Adams, 2007; NIST 11, 2013). The LTPRI values were determined using a C 6 –C 30  n -alkane series and calculated from the van denDool and Kratz equation (van den Dool and Kratz, 1963). The rel- ative amounts (%) for each individual component in the samplewere expressed as percent peak areas relative to the total peakarea.  2.5. GC  × GC/qMS analysis TheGC × GC/qMSwasperformedusingaShimadzuGC × GCsys-temconsistingofaGC2010gaschromatographandaQP2010Ultramass spectrometer (qMS) (Kyoto, Japan). The GC was equippedwithanAOC-20iauto-injector(split/splitless)anddual-stageloop-type modulator ZX1-GC × GC (Zoex Corporation, Houston, TX,USA). Cryogenic modulation occurred every 5s, with a hot jetduration of 0.5s. The first-dimension chromatographic separationwas performed on a OV-5 (5% phenyl, 95% dimethylpolysiloxane)column with 60m length × 0.25mm I.D. × 0.10  m film thick-ness (Ohio Valley Specialty Company, Marietta, OH, USA). ADB-17 (50% phenyl and 50% dimethylpolysiloxane) column with2.15m × 0.18mm × 0.18  m(J&WScientific,AgilentTechnologies,Palo Alto, CA, USA) was used as the second dimension. The GCconditions are the same as for GC/qMS. The data were acquiredusingtheGCImagesoftwareversion2.2(ZOEXCorporation,Hous-ton, TX, USA). The identification methods were the same as thoseused previously. The relative amounts (%) for each individual com-ponent in sample were expressed as the percent of the peakvolume relative to the total peak volume. The sum of the retentiontime from the first and second dimensions were used to iden-tify each peak. This procedure was validated by von Mühlen et al.(2008).  C. Saucier et al. / Industrial Crops and Products 62 (2014) 507–514  509  Table 1 Volatile compounds identified in  Cynara scolymus  L. leaves using GC/qMS.No. Compound  t  R   (min)  A  (%) LTPRI exp  LTPRIl it 1  Furfural  14.47 1.84 834 828 a 2  (  E  )-2-Hexenal  15.37 1.42 853 846 a 3  Benzaldehyde  21.48 1.44 961 952 a 4  1-Octen-3-one  22.55 11.30 978 980 b 5 6-Methyl-5-hepten-2-one 23.19 0.37 988 981 a 6  Octanal  24.21 0.40 1004 998 a 7  Benzene acetaldehyde  27.01 8.86 1044 1036 a 8 ( E  )-2-Octenal 28.05 0.62 1058 1060 b 9 Acetophenone 28.62 0.11 1067 1059 a 10 ( E,E  )-3,5-Octadien-2-one 28.97 0.25 1072 1072 b 11  Nonanal  31.20 1.68 1103 1100 a 12 ( E  )-6-Methyl-3,5-heptadien-2-one 31.35 0.62 1106 1106 b 13  Phenethyl alcohol  31.93 0.46 1114 1107 a 14 Isophorone 32.47 1.18 1122 1118 a 15 3-Nonen-2-one 33.74 0.26 1140 1141 b 16 ( E,Z  )-2,6-Nonadienal 34.68 0.30 1153 1150 a 17 4-Methyl-acetophenone 36.93 0.36 1185 1179 a 18 Safranal 37.95 1.15 1200 1196 a 19  Decanal  38.29 0.28 1205 1201 a 20   -Cyclocitral 39.39 1.35 1221 1220 b 21 Neral 40.77 0.22 1241 1235 a 22   -Homocyclocitral 41.87 0.24 1257 1254 b 23 Geranial 42.76 0.80 1270 1264 a 24  p -Vinylguaiacol 45.66 0.68 1314 1314 b 25  Eugenol  48.51 0.69 1358 1356 a 26   -Nonalactone 48.86 0.85 1363 1358 a 27  (  E  )-  -Damascenone  50.24 5.02 1385 1386 a 28 Geranyl acetone 54.40 2.23 1452 1455 a 29   -Ionone 56.51 6.05 1487 1487 a 30 Dicyclohexyl-methanone 58.50 5.18 1520 –31 Dihydroactinidiolide 59.25 3.43 1533 1532 b 32 Phytone 75.90 0.19 1844 1844 b t  R   (min):retentiontimes(inminutes),  A (%):peakareapercentages,LTPRI exp :exper-imental linear temperature programmed retention indices values, LTPRI lit : lineartemperatureprogrammedretentionindicesvaluesforthecorrespondentcompoundreported in the literature. a Adams. b NIST 11 library.Compounds in bold are previously reported for  Cynara scolymus  L. (Buttery et al.,1978; Ghanem et al., 2009; Guillén-Ríos et al., 2006; H˘ad˘arug˘a et al., 2009; Nassaret al., 2013). Data are the mean of three replicates. The retention times showedvariation coefficient less than 2%. 3. Results and discussion  3.1. GC/qMS analysis The yield (w/w) of essential oil obtained from artichoke leaveswas 0.1%. As a preliminary application, the volatile composition of artichoke leaves was investigated via GC/qMS. Table 1 shows the identified compounds, their retention times and area percentages,and their LTPRI values. These values are listed in the order of theirelution through the ZB-5MS capillary column.For GC/qMS, 32 compounds were tentatively identified usingthe NIST mass spectra library and retention index criteria, includ-ing 7 aldehydes, 7 norisoprenoids, 6 phenylpropanoids, 6 ketones,4 oxygenated monoterpenes, 1 lactone and 1 alcohol. Accordingto Table 1, the major components present in artichoke leaves were identified as 1-octen-3-one (11.30%), benzene acetaldehyde(8.86%),   -ionone (6.05%), dicyclohexyl-methanone (5.18%), ( E  )-  -damescenone (5.02%), dihydroactinidiolide (3.43%) and geranylacetone (2.23%).  3.2. GC  × GC/qMS analysis Artichokeleafessentialoilcanbeconsideredacomplexsample,and thus, 1D-GC could fail to satisfactorily elucidate its composi-tion. The main consequence of an insufficient resolving power isoverlappinganalytes,whichshouldbeavoidedbecauseitcanyieldimpure mass spectra. With this in mind, artichoke leaf volatileswereanalyzedviaGC × GC/qMS.Table2showstheidentifiedcom- pounds,boththeirfirstandseconddimensionretentiontimes,theirvolume percentages and their LTPRI values. These values are listedin order of their elution through the OV-5 capillary column.Figs. 1 and 2 present the 1D-GC/qMS(A) and GC × GC/qMS(B)total ion current chromatogram expansions of   C. scolymus  L.leaf volatiles. The 1D chromatogram contains several overlap-ping peaks. However, adding a second dimension to separate thecompounds according to their polarity increased the GC chro-matographic space and enhanced the separation potential. Manycomponents that were obscured in the 1D-GC analysis are imme-diately revealed using GC × GC.Fig. 3 shows a section of the contour plot as an example (theTIC is shown in Figs. 1 and 2) of the second-dimension separa- tion (upon polarity) for the four compounds that overlapped inthe first dimension (separation upon volatility). They were sep-arated by GC × GC due to their different polarities with a higherchromatographic resolution than for 1D-GC. These compoundswere not identified by the 1D-GC system because of the lowspectral match given by the library database search. Anotherconsequence of GC × GC is the increased signal to noise ratio (S/N)for all of the analyte peaks. The increased S/N combines with theenhanced resolution of GC × GC to maximize the purity of theobtained mass spectra, which allows for a more accurate identi-ficationofthesamplecompounds.PeaksB–D(Fig.3)arepresentin low concentrations; however, their improved S/N ratio due to themodulatorprovidesabetterseparationfromthesystemnoisethanthat obtained for the 1D-GC. Consequently, better mass spectraare recorded, which allowed the compounds tentative identifica-tion.AsurveyoftheAdamsdatabaseallowedthecompoundstobeidentified by their retention index.AdetailedGC × GC/qMSanalysisofthesampletentativelyiden-tified 130 compounds, 109 of which were reported for the firsttime for artichoke ( C. scolymus  L.). The tentatively identified com-pounds included 24 aldehydes, 24 ketones, 14 norisoprenoids, 19oxygenated monoterpenes, 9 oxygenated sesquiterpenes, 9 alco-hols, 9 lactones, 5 phenylpropanoids, 4 unsaturated hydrocarbons,3sesquiterpenes,3fattyacids,2furans,2nitrogenatedcompounds,1 flavonoid, 1 ether and 1 tiazol. The major components identi-fied in the artichoke leaves via GC × GC/qMS were 1-octen-3-one(3.85%), ( E  )-2-hexenal (3.75%), benzene acetaldehyde (2.90%), 2,2-dimethyl-4-pentenal (2.81%),   -ionone (1.94%), furfural (1.65%),( E  )-  -damescenone (1.59%),   -methyl-  -butirolactone (1.53%),benzaldehyde (1.47%) and dihydroactinidiolide (1.44%).The first authors to study the volatile fraction of   C. scolymus  L.wereButteryetal.(1978).Theyanalyzedsteamdistillatesfromarti- chokeheadsusinggas–liquidchromatography/massspectrometry.A total of 32 compounds were characterized, including alcohols,aldehydes, ketones, oxygenated terpenes and sesquiterpenes. Themajor components were   -selinene and caryophyllene. Similarly,MacLeodetal.(1982)usedsteamdistillationandGC/MStoanalyze C. scolymus  L. volatiles. They reported the tentative identificationof 28 compounds, and sesquiterpenes composed the major groupcomponents for  C. scolymus  L. with   -selinene as the major con-stituent.The prominent volatile compounds found in dichloromethaneextracts from artichoke hearts by Guillén-Ríos et al. (2006) using GC/MS were   -selinene, isoamyl acetate, trans-caryophyllene,limonene, 2-hexanol, benzaldehyde and aromadrendene.Ghanemetal.(2009)investigatedthepotentialprotectiveeffectof   C. scolymus  L. leaves versus the hepatic and renal toxicity of lead in male rats and explored the volatile constituents using adynamic headspace system and GC/MS analysis. A total of 23 com-poundswereidentified.Thisanalysisindicatedthatbenzaldehyde,selinene,phenethylalcoholandcaryophylleneoxidewerethemain  510  C. Saucier et al. / Industrial Crops and Products 62 (2014) 507–514  Table 2 Volatile compounds identified in  Cynara scolymus  L. leaves using GC × GC/qMS.No. Compound  1 t  R   (min)  2 t  R   (s)  V   (%) LTPRI exp  LTPRI lit 1 2,3-Dihydro-3-methyl-furan 11.00 0.58 0.38 766 –2 4-pentenal 11.33 0.58 0.51 773 –3 2,2-dimethyl-4-pentenal 12.67 0.55 2.81 802 –4  Furfural  14.08 1.54 1.65 833 828 a 5 3-Furfural 14.17 1.27 0.36 835 831 b 6  (  E  )-2-Hexenal  15.00 0.82 3.75 853 846 a 7 2-Cyclopentene-1,4-dione 16.75 1.75 0.57 891 884 b 8 2-Heptanone 16.92 0.82 0.35 895 889 a 9  Heptanal  17.42 0.82 0.96 904 901 a 10 ( E,E  )-2,4-Hexadienal 18.08 1.33 0.45 915 907 a 11 Dihydro-3-(2H)-thiophenone 20.42 2.20 0.34 953 952 b 12 6-Methyl-2-heptanone 20.67 0.91 0.17 957 956 b 13 (  Z  )-2-Heptenal 20.75 1.12 0.39 958 964 b 14  Benzaldehyde  21.00 1.72 1.47 962 952 a 15   -Methyl-  -butyrolactone 21.08 2.35 1.53 964 957 b 16 7-Oxabicyclo[4.1.0]heptan-2-one 21.67 1.66 0.23 973 –17  1-Octen-3-one  22.08 1.06 3.85 980 980 b 18 6-Methyl-5-hepten-2-one 22.67 1.12 0.74 989 981 a 19  2-Pentyl-furan  22.83 0.85 0.23 992 993 b 20 ( E,E  )-2,4-Heptadienal 23.50 1.39 0.30 1003 1003 b 21  Octanal  23.67 1.00 0.72 1005 998 a 22 2-Etil-1-hexanol 25.50 0.94 0.36 1031 1030 b 23 2,2,6-Trimethyl-cyclo-hexanone 25.75 1.42 0.50 1035 1035 b 24  Benzyl alcohol  25.92 1.99 0.45 1038 1026 a 25  Benzene acetaldehyde  26.50 2.08 2.90 1046 1036 a 26 ( E  )-2-Octenal 27.50 1.48 0.69 1060 1060 b 27   -Caprolactone 27.50 2.53 0.25 1061 1063 b 28 Acetophenone 28.08 2.11 0.40 1069 1059 a 29 4-Methyl-benzaldehyde 28.25 1.93 0.17 1071 1076 b 30 Octanol 28.42 1.06 0.34 1074 1063 a 31 ( E,E  )-3,5-Octadien-2-one 28.50 1.51 0.32 1075 1072 b 32 (  Z  )-5-Undecene 28.92 1.18 0.15 1081 –33 1-Nonen-4-ol 30.17 1.33 0.13 1099 1109 b 34  Linalool  30.33 1.03 0.26 1101 1095 a 35  Nonanal  30.67 1.12 0.75 1106 1100 a 36 ( E  )-6-Methyl-3,5-heptadien-2-one 30.83 1.63 0.51 1109 1107 b 37 2,5-Dimethyl-cyclohexanol 31.00 1.48 0.68 1111 1099 b 38  Phenethyl alcohol  31.42 2.11 0.60 1117 1107 a 39 2,4-Dimethyl-2,4-heptadienal 31.58 1.51 0.12 1119 1129 b 40 (  Z  )-2-Undecene 31.75 1.06 0.17 1122 1114 b 41 Isophorone 31.92 1.75 0.66 1124 1118 a 42 3-Nonen-2-one 33.17 1.72 0.30 1142 1141 b 43  trans -3-Nonen-2-one 33.25 1.33 0.09 1143 1144 b 44 Oxophorone 33.50 2.02 0.46 1147 1147 b 45 Camphor 33.58 1.63 0.24 1148 1141 a 46  cis -Verbenol 33.58 1.39 0.14 1148 1147 b 47 5-Ethyl-6-methyl-( E  )-3-hepten-2-one 33.67 1.15 0.16 1149 1144 b 48 4-(5-Methyl-2-furanyl)-2-butanone 34.00 1.78 0.20 1154 –49 ( E,Z  )-2,6-Nonadienal 34.25 1.45 0.50 1157 1150 a 50 Phenyl-2-propenal 34.42 2.38 0.26 1160 1161 b 51  (  E  )-2-Nonenal  34.58 1.60 0.37 1162 1162 a 52 Propiophenone 35.00 2.05 0.34 1168 1164 b 53  p -mentha-1,5-dien-8-ol 35.17 1.54 0.41 1170 1166 a 54 1-Nonanol 35.50 1.36 0.35 1175 1165 a 55 Caprylic acid 35.58 1.21 0.15 1176 1177 b 56  Terpinen-4-ol  35.83 1.33 0.11 1180 1174 a 57 4-Methyl-acetophenone 36.42 2.14 0.27 1188 1179 a 58  p -Cymen-8-ol 36.42 1.78 0.18 1188 1179 a 59 Safranal 37.42 1.75 0.64 1203 1196 a 60  Decanal  37.75 1.18 0.19 1207 1201 a 61 3-Phenyl-butanal 38.58 1.78 0.14 1220 –62 Coumaran 38.83 2.20 0.53 1223 1223 b 63   -Cyclocitral 38.92 1.66 0.70 1224 1224 b 64 Benzothiazol 39.17 2.98 0.23 1228 1227 b 65 Nerol 39.42 1.36 0.19 1231 1227 a 66 2-Pentyl-cyclopentanone 39.67 1.87 0.09 1235 –67 Neral 40.33 1.54 0.44 1245 1235 a 68 Carvone 40.50 1.84 0.08 1247 1239 a 69 Geraniol 41.17 1.42 0.11 1257 1249 a 70 Piperitone 41.25 1.84 0.09 1258 1249 a 71   -Homocyclocitral 41.42 1.51 0.19 1260 1261 b 72   -Octanolactone 41.50 2.38 0.12 1262 1262 b 73 ( E  )-2-Decenal 41.58 1.66 0.16 1263 1264 a 74 1,12-Tridecadiene 42.17 2.02 0.17 1271 –75 Pelargonic acid 42.17 1.30 0.27 1271 1267 a 76 Geranial 42.33 1.60 0.25 1274 1264 a
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