Food and Nutrition Sciences, 2013, 4, 305-314 Published Online March 2013 (
Analysis of Volatile Compounds and Identification of
Characteristic Aroma Components of Toona sinensis (A.
Juss.) Roem. Using GC-MS and GC-O
Changjin Liu1, Jie Zhang1, Zhongkai Zhou1*, Zetian Hua2, Hongying Wan1, Yanhui Xie1,
Zhiwei Wang1, Li Deng3
1Key Laboratory of Food Nutrition and Safety, Ministry of Education, Tianjin University of Science and Technology, Tianjin, China;
2Tianjin Tianlong Agricultural S & T Co., Ltd., Tianjin, China; 3Tianjin Chunfa Biotechnology Group CO., Ltd., Tianjin, China.
Email: *
Received December 3rd, 2012; revised January 22nd, 2013; accepted February 30th, 2013
In this study, volatile compounds present in Toona sinensis (A. Juss.) Roem (TS) were investigated and their character-
istic aromatic components were identified using Headspace Solid-phase Microextraction (HS-SPME) followed by Gas
Chromatography-Mass Spectrometry (GC-MS) and Gas Chromatography-Olfactometry (GC-O). The optimum condi-
tions for extracting the volatiles from TS were achieved with the experimental parameters including the use of a 65 μm
polydimethylsiloxane/divinyl benzene (PDMS/DVB) fibre, an extraction temperature of 40˚C and an extraction time of
30 min. Under these conditions, 56 volatile compounds were separated and 53 were identified by GC-MS. Among them,
21 sulfide compounds (42.146%) and 27 terpenes55.984%) were found to be the major components. The sample was
analyzed by GC-O and 26 elutes were sniffed and their sensory descriptions evaluated by an odor panelists. Analysis of
the data indicated, two compounds cis and trans isomers of 2-Mercapto-3,4-dimethyl-2,3-dihydrothiophene were major
contributors to the characteristic aroma of TS.
Keywords: Toona sinensis (A. Juss.) Roem.; Volatile Compounds; Characteristic Aroma Components; HS-SPME;
1. Introduction
Toona sinensis (A. Juss.) Roem. (TS), is a tree commonly
named Chinese toon or Chinese Mahogany and belongs
to the family of Meliaceae. It widely distributes in China
and some other Asian countries. Its tender leaves and
young sprouts have been commonly used as a spice in
China since the Han Dynasty around two thousand years
ago. Due to its very unique flavour, TS is a popular tradi-
tional spice in the Chinese diet. The unique aroma can be
sensed among almost all parts of TS, and provides a
pleasant fragrance when its buds germinate. The edible
buds are picked in the early spring annually, so TS is also
recognized as a seasonal vegetable as well. As a fresh
foliar vegetable, the delicious buds are usually cooked
with other foods such as eggs and bean curds, in dishes
known as Scrambled eggs with Chinese to on and Tofu
with Chinese toon.
Almost every part of TS has been widely used in Chi-
nese traditional medicine for treatment of enteritis, dys-
entery and itch during the period of ancient China [1].
Comprehensive investigations have demonstrated the
pharmacological and health promoting properties of its
high content flavonoid content [2,3]. Besides its medici-
nal functions, the most conspicuous trait of TS is its ap-
pealing flavours which are the results of its volatile com-
pounds. However, limited studies are available on the
volatile compounds in TS. Thus, experiments in this study
have been designed to identify and characterize impor-
tant volatile compounds in TS.
As a solvent-free extraction method, HS-SPME has
shown many advantages for volatile compound analysis
compared to traditional methods such as simultaneous
distillation-extraction, and steam distillation [4]. For in-
stance, the volatile compounds in garlic tend to be de-
graded during solvent extraction and steam distillation
but not with HS-SPME [5]. In the analysis of volatiles
from chili peppers, a 50/30 μm divinylbenzene/carboxen/
polydimethylsiloxane (DVB/CAR/PDMS) extraction me-
dium was showed to give the highest extraction effi-
ciency with ground samples [6]. These studies also con-
cluded that HS-SPME was a practical method to deter-
mine intermediate volatile compounds and even very
*Corresponding author.
Copyright © 2013 SciRes. FNS
Analysis of Volatile Compounds and Identification of Characteristic Aroma Components of Toona sinensis
(A. Juss.) Roem. Using GC-MS and GC-O
volatile constituents produced enzymatically after the rup-
ture of plant cells. Flavours present in TS is likely to be a
mixture of very volatile and intermediate volatile com-
pounds generated by physical cell disruption, thus, the
HS-SPME technique may be a suitable technique for
studying these compounds. GC-MS and GC-O have been
widely used in flavour analysis and are very useful tools
for identification of characteristic aroma compounds [7].
However, these combined techniques have not yet been
applied to TS flavour analysis so far. Thus, this is the
first attempt to use GC-MS and GC-O for TS flavour
compound analysis after extraction using HS-SPME.
2. Materials and Methods
2.1. Chemicals
Chromatographically pure standards used for identifica-
tion were supplied by several companies: (Z)-1-(Methy-
sulfany)-1-propene and (E)-1-(Methysulfany)-1-propene
were supplied by Heowns (Atlana, USA). 2,5-Dimethyl-
thiophene and 3,4-Dimethylthiophene were purchased
from AccuStandard (New Haven CT, USA). An n-Al-
kane (C7-C33) mix in Hexane (Supelco, Bellefonte, USA)
was also used to calculate the retention index (RI) of
each component.
2.2. Sample Collection and Preparation
Fresh buds of TS were collected from Linfen city in
Shanxi province, China, during spring, 2012. Before
analysis, they were manually ground at room temperature
using a mortar in order to release the fragrance ade-
quately. A 10.0 g aliquot of sample was immediately
transferred into a 40 ml gas-tight glass vessel and incu-
bated at room temperature for 30 min to achieve partition
equilibration for the volatile compounds.
Four extraction fibres; 30/50 μm DVB/CAR/PDMS,
65 μm PDMS/DVB, 75 μm CAR/PDMS and 100 μm
PDMS (Supelco, Bellefonte, USA) were evaluated. Be-
fore extraction, the fibres were preconditioned for 30 min
in the injection port of the GC as indicated by the manu-
facturer. The fibre was then inserted into the vessel and
exposed to the headspace. The procedure was repeated
using different extraction times (10 min to 50 min) and
temperatures (10˚C to 50˚C) to determine the optimal
HS-SPME conditions. Finally the fibre was removed and
the components were desorbed in the GC injection port
for 5 min.
2.3. GC-MS Operation Conditions
A Varian 4000 GC-MS (Walnut Creek, CA, USA) was
used for separation and qualitative determination of the
volatiles. Ultra-high purity helium was used as the carrier
gas at a flow rate of 1.5 ml/min into the column. Injec-
tion was at 250˚C in split mode (20:1) onto a 30 m × 0.25
m DB-5 capillary column with 0.25 μm film thickness
(Varian, USA). The oven temperature was set at 40˚C for
3 min, then increased to 150˚C at 4˚C/min, and kept at
this temperature for 1 min, ultimately increased to 260˚C
at 8˚C/min, and kept at this temperature for 6 min. MS
conditions were: ionization energy, 70 eV, full scan
mode with a scan frequency of 1.2 scan/s and a scan
range of 50 - 550 amu in all experiments and the transfer
line was at 250˚C. The ion trap was operated at 220˚C in
the electron impact mode.
2.4. GC-O Operation Conditions
The GC-O analysis was conducted using an Agilent 5975
gas chromatograph equipped with a FID detector (Agilent
Technologies, SantaClara, CA, USA) and a sniffing port
(Sniffer 9000, Brechbühler, Switzerland). Injection and
separation conditions were as indicated above. Gas chro-
matography effluents of TS extracts were split between
the sniffing port and the FID at a ratio of 1:1. The tem-
perature of the sniffing port was 240˚C. The sniffing port
was supplied with humidified air at 40˚C with a flow of
600 ml/min in order to avoid nasal dehydration.
2.5. Sniffing Test
Sniffing tests were performed on eight chromatographic
runs by four panelists (two males and two females in the
age range of 20 to 30 years old). A panel consisting of 4
people was thought to be suitable for sniffing test based
on previous studies [8,9]. An aroma evaluation approach
outlined by Lv et al. [10] was used to describe aroma
properties and intensities at the sniffing port under the
conditions outlined above (see Section 2.4). According to
the experience of previous TS flavour study, vocabulary
pool for describing TS aroma was made. Prior to the ex-
perience, the panelists were familiarized with the pool of
aromatic compounds and instructed on how to use suit-
able descriptors to describe the individual compounds in
TS. They were asked describe the aroma properties and
intensities of the compounds eluted from the GC column.
An independent recorder was requested to write down the
panelist’s evaluation instantly. A compound was deemed
as aromatically active if detected in at least half of all
sniffs (four of eight runs). The intensity of each com-
pound was evaluated by using a five-point intensity in-
terval scale (1-very mild; 2-mild; 3-moderate; 4-strong;
5-very strong). A score was not given if no aroma was
perceived. Finally the recorded data were collected, the
mean values of related compounds were calculated to the
nearest whole number (showed as the numbers of “*”)
and the most frequent descriptions of each compound
Copyright © 2013 SciRes. FNS
Analysis of Volatile Compounds and Identification of Characteristic Aroma Components of Toona sinensis
(A. Juss.) Roem. Using GC-MS and GC-O
Copyright © 2013 SciRes. FNS
were applied. The retention time and corresponding peaks
were used to match the compounds measured in the
GC-MS and GC-O system so as to determine the struc-
ture of the components sniffed in GC-O runs.
2.6. Qualitative and Quantitative Methods
Compound identification was confirmed on the basis of
matching mass spectra of the database (NIST08, USA)
and the odor descriptions of the related compounds (AD).
Linear retention indexes (LRI) were also used to identify
the compounds in the GC-O and GC-MS chromatograms.
The retention index (RI) was determined using an n-Al-
kane mix at the same chromatography conditions and
calculated according to the Kratz formula [11]:
 
100n100Rt xRt nRt n1Rt n
ity were used to extract volatiles from TS. The different
extraction efficiencies are shown in Figure 1. The results
showed that the 65 μm PDMS/DVB fibre was the best
choice to extract volatiles from TS. Mu et al. (2007) also
found this type of fibre absorbed the maximum number
of TS flavour compounds compared to other types of
fibre. The extraction temperature and duration were also
investigated to improve the efficiency. The data are shown
in Figures 2(a) and (b). In general, extracting at 40˚C
showed the highest absorption of the flavour compounds.
Extraction time studies indicated extraction efficiency
was increased with absorption time from 10 to 50 min
and almost reached the Max at 30 min. Consequently, a
series of extractions at 40˚C for 30 min were conducted
using a 65 μm PDMS/DVB fibre to determine the char-
acteristic aroma compounds of TS.
3.2. Precision of HS-SPME
where Rt(x) is the retention time of each targeted com-
pound (x), Rt(n) and Rt(n + 1) are retention times of
n-Alkane eluting directly before and after the compound
(x) under the same chromatographic conditions. For dif-
ficulty to recognize optical isomers and cis-trans isomers,
the retention time of the standard was applied for identi-
fication under the same chromatographic conditions.
The precision of the method was evaluated by perform-
ing 6 replicated runs of the TS sample using the optimum
conditions. The relative standard deviation (RSD) values
were calculated by the peak areas obtained by replicate
analyses. As shown in the last colum of Table 1, the
calculated RSD values were less than 9%, which indi-
cates the method consisting of HS-SPME followed by
GC-MS and GC-O has an acceptable level of precision.
The relative proportions of the constituents were ob-
tained by peak area normalization. Quantitative results
were obtained using the method as follows: 3.3. Volatile Compounds in TS
Relative content%
single constituent areatotal area100%
(2) Volatile compounds identified in the TS sample by
GC-MS and GC-O are summarized in Table 1. The
table shows the chromatographic retention data (reten-
tion time and retention index) of each component in the
GC-MS runs, the odor descriptions and intensities of the
detected eluates given by the trained panel (including the
identification method) and the similarity index of the
3. Results and Discussion
3.1. Optimal Extraction Conditions
Four fibres with different coating thicknesses and polar-
Figure 1. Influence of fibre type on extracting efficiency, the last type is 65 μm PDMS/DVB.
Analysis of Volatile Compounds and Identification of Characteristic Aroma Components of Toona sinensis
(A. Juss.) Roem. Using GC-MS and GC-O
Figure 2. (a) Effect of absorption temperatures on peak area of TS volatile compounds using a 65 μm PDMS-DVB fibre for
30 min; (b) Effect of absorption time on peak area of TS volatile compounds using a 65 μm PDMS-DVB fibre at 40˚C.
unknown compared with the spectrum of the MS data-
base. Mean- while, the relative amounts of these volatile
compounds are also listed in Table 1. A total ion chro-
matogram of volatile constituents in TS is given in Fig-
ure 3.
The analysis of TS volatile compounds revealed a total
of 56 compounds with 53 of these identified. The major
classes included 24 terpenes (55.984%), 7 thiophenes
(32.660%) and 11 thioethers (8.764%). In addition, there
were 2 aldehydes (0.049%), 2 thioesters
0.782%, 1 ester
(0.296%), 1 thiapyrans (0.030%), and 1 ketone (0.010%).
Among all the separated compounds, β-caryophyllene
(21.450%) followed by cis-2-Mercapto-3,4-dimethyl-2,3-
dihydrothiophene (16.960%), trans-2-Mercapto-3,4-dime-
thyl-2,3-dithydrothiophene (9.484%), 3,4-Dimethylthio-
phene (6.010%), Aristolene (5.413%), Germacrene D
Copyright © 2013 SciRes. FNS
Analysis of Volatile Compounds and Identification of Characteristic Aroma Components of Toona sinensis
(A. Juss.) Roem. Using GC-MS and GC-O 309
Table 1. Volatile compounds present in TS determined by GC-MS and GC-O runs.
NO. Retention
Time (min) RIa Compounds Aroma property
intensity MIb Similc RCdRSDe (%)
1 2.762 610 Methylthiirane Fresh, garlic *** MS, RIL, AD 780 1.9026.47
2 4.357 696 (Z)-1-(Methysulfany)-1-propene Garlic, onion * MS, RS, AD 894 0.1504.95
3 4.658 712 (E)-1-(Methysulfany)-1-propene Garlic, onion * MS, RS, AD 909 0.0536.96
4 6.157 789 5-Methyl-2,3-dihydrothiophene MS, RIL 819 0.0256.56
5 6.500 802 Hexanal Grass, leafy ** MS, RIL, AD 790 0.0022.31
6 8.341 863 (E)-2-Hexenyl Grass, leafy ** MS, RIL, AD 872 0.0475.21
7 9.146 876 2,5-Dimethylthiophene Fried, onion, rubber ** MS, RS, AD 900 0.1302.34
8 10.133 887 3,4-Dimethylthiophene Fried, onion, rubber *** MS, RS, AD 905 6.0102.17
9 10.456 894 (Z,E)-Bis(1-propenyl)sulfide Onion, garlic ** MS, RIL, AD 761 0.0315.25
10 10.746 901 (E,E)-Bis(1-propenyl)sulfide Onion, garlic ** MS, RIL, AD 845 0.0264.12
11 11.218 916 α-Pinene Fruity, resin ** MS, RIL, AD 888 1.3655.67
12 12.819 967 α-Thujene MS, RIL 849 0.0343.32
13 13.472 987 β-Pinene MS, RIL 860 0.0854.67
14 14.079 1005 cis-2-Ethyl-3-methylthiophene MS, RIL 767 0.0203.46
15 15.055 1030 Limonene MS, RIL 874 0.0833.56
16 15.726 1047 cis-Ocimene MS, RIL 893 0.2562.59
17 16.602 1070 3-Ethyltetrahydro-2H-thiopyran MS, RIL 789 0.0304.69
18 17.981 1105 2-Ethenyl-1,3,3-trimethylcyclohexene MS, RIL 809 0.0413.45
19 18.500 1119 3-Ethyl-1,2-dithiacyclohex-4-ene Pungent, sulphur ** MS, RIL, AD 845 3.7217.56
20 18.677 1124 3-Ethyl-1,2-dithiacyclohex-5-ene Pungent, sulphur * MS, RIL, AD 789 0.9416.54
21 18.853 1128 2-Ethyl-1,3-dithiacyclohex-4-ene Pungent, sulphur ** MS, RIL, AD 756 1.7107.45
22 19.225 1138
dihydrothiophene Cooked, TS, rubber**** MS, RIL 845 9.484 4.65
23 20.051 1160 Allyl dithiopropanoate Onion, garlic ** MS, AD 867 0.2015.56
24 20.266 1166 Prop-1-enyl dithiopropanonate
MS, RIL 745 0.5817.24
25 20.408 1170 2-Ethyl-5-propyl thiophene 754 0.0316.14
26 20.990 1185
dihydrothiophene Fresh, TS ***** MS, RIL 827 16.960 4.44
27 21.313 1194 2-Ethyl-1,3-dithiacyclohex-4-ene Pungent, sulphur * MS, RIL, AD 748 0.1014.78
28 22.793 1236 1,2-Dithiocane MS, RIL 856
29 23.704 1262 5,5-Dimethyl-1,3-dithian-2-one MS, RIL 611 0.0328.45
30 24.958 1298 Pelargonic acid methyl ester MS, RIL 787 0.2963.43
31 26.267 1337 δ-elemene MS, RIL 874 0.1122.35
32 26.662 1349 α-Cubebene Herb * MS, RIL, AD 877 3.4262.79
33 27.456 1369 Ylangene Fruity, sweet * MS, RIL, AD 849 1.8155.63
34 27.668 1373 α-Copaene Cinnamon, floral * MS, RIL, AD 886 4.4147.45
35 28.093 1392 α-Elemene Flower, sweet * MS, RIL, AD 867 1.4865.43
36 28.605 1408 (Z)-Caryophyllene MS, RIL 875 0.5444.78
37 29.140 1425 β-Caryophyllene Fruity, sweet, flower*** MS, RIL, AD 885 21.4505.79
38 29.347 1431 δ-Elemene MS, RIL 865 0.3525.89
39 29.560 1438 α-Guaiene: MS, RIL 881 0.7277.46
40 29.770 1444 Aristolene Flower, sweet * MS, RIL, AD 834 5.4132.35
41 30.048 1453 δ-Gurjunene Flower, sweet * MS, RIL, AD 864 1.6884.45
42 30.251
1459 α-Caryophyllene Mild, mint * MS, RIL, AD 900 3.1622.67
43 30.849 1478 γ-muurolene MS, RIL 874 0.1225.21
44 31.095 1486 Germacrene D Oily, green * MS, RIL, AD 911 4.8568.08
45 31.588 1501 α-Selinene MS, RIL 874 0.7274.52
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Analysis of Volatile Compounds and Identification of Characteristic Aroma Components of Toona sinensis
(A. Juss.) Roem. Using GC-MS and GC-O
46 31.799 1509 α-Muurolene MS, RIL 883 0.3457.01
47 32.119 1521 γ-cadinene MS, RIL, AD 880 0.5914.09
48 32.224 1525 δ-cadinene 745 0.0475.20
49 32.581 1538 Selina-3,7(11)-diene MS, RIL 812 0.1345.18
50 32.938 1552 α-Calacorene MS, RIL 767 0.1023.46
51 33.447 1570 Germacrene B MS, RIL 854 0.6074.67
52 34.025 1591 Caryophyllene oxide MS, RIL 796 0.1632.68
53 34.275 1601 Unknown 2.1016.31
54 34.842 1628 Unknown 0.3424.57
55 37.253 1754 Unknown 0.9117.09
56 38.223 1812 2-Ethyl-3-hydroxy-1,
4-naphthalenedione MS 799 0.0103.67
aRetention indices; bMethods of identification: MS, identified by MS; RS, identified by retention time of standard; AD, identified by aroma descriptions; RIL,
identified by retention index and compared with those reported in the literatures; cSimilarity index of the unknown compared with the spectrum of the MS
database; dRelative content by area normalization method; eRelative standard deviation of each component’s RC.
Figure 3. Total ion chromatogram of volatile components identified in TS. Peak numbers correspond to those listed in Table
1. Peak 22 and 25 were considered as the characteristic aroma of TS.
(4.856%), α-Copaene (4.414%),3-Ethyl-1,2-dithiacyclohex-
4-ene (3.721%), α-Cubebene (3.426%), α-Caryophyllene
(3.162%), were found to be present in the highest con-
The olfactometric strategy consisting of the measure-
ment of aroma intensities and odor descriptions has been
widely used [12,13]. In this study, the method was opti-
mised to make method more convenient and accurate.
For example, the use of an independent recorder was
introduced to avoid the interruption between recording
and sniffing. As shown in Table 1, GC-O analysis pro-
vided information about the impact of the major and sub-
sidiary volatile components on the aroma of TS. A total
of 26 components were considered aroma-active and
their odor descriptions including aroma properties and
intensities were evaluated by the panelists.
Terpene and sulfur compounds (especially terpenes with
molecular weights of 204) thiophenes, thioethers were of
the greatest importance to the aroma of TS (Table 1).
Because of the high similarity in the MS of the terpene
compounds, their structures were defined by calculating
the retention index and comparing with the values in the
database. Most of the terpenes found in TS can also be
found in other foods such as carrot [14], grape and wine
[15]. Anecdotal reports have suggested that terpene com-
pounds were the major contributor to TS aroma. How-
ever, this study indicates these compounds are less im-
A total of 21 sulfur compounds were identified in TS
extracts with thiophenes and thioethers representing the
two most abundant groups of volatile compounds repre-
senting 32.660% and 8.764% of the total aroma (Table 1).
Copyright © 2013 SciRes. FNS
Analysis of Volatile Compounds and Identification of Characteristic Aroma Components of Toona sinensis
(A. Juss.) Roem. Using GC-MS and GC-O 311
These sulfur compounds possess higher odor intensities
and lower threshold values and have subsequently been
confirmed to be the most important compounds of TS
aromas. Large amounts of sulfur compounds can also be
found in other foods such as cooked chicken [16], roast
beef [17], heated leek [18], raw and processed garlic [19]
and sliced onion [20].
Sniffing test of TS revealed 2,5-Dimethylthiophene
and 3,4-Dimethylthiophene have an aroma of sulphur,
fried onion and rubber (Table 1). Mu [21] also identified
the two compounds in TS, but they did not describe their
individual aromas. A small amount of Methylthiirane
was found to be responsible for a “***” moderate pun-
gent perception, and is also found to be one of the vola-
tile components in garlic [22]. The thioethers, such as
(Z)-1-(Methysulfany)-1-propene, (E)-1-(Methysulfany)-1-
propene, (Z,E)-Bis(1-propenyl) sulfide and (E,E)-Bis(1-
propenyl)sulfide are also found in onions and scallions
[23]. Small amounts of aldehyde (0.049%) and ester
(0.296%) compounds were also detected in TS (Table1).
It is not surprising to see that TS contains Hexanal and
(E)-2-Hexenal, which is common in many plant extracts
and are perceived as green and grassy odors [24]. Abun-
dant terpenes give an aroma of sweet, fruit and flower,
but the threshold of these compounds appear to be slightly
higher than that of other compounds, such as sulfur com-
pounds. Consequently, only those constituents with higher
concentrations can be perceived. For example, β-Cary-
ophyllene was found to have the highest concentration in
TS, which is also present in many other plants such as
clove [25] and cassia [26] as a major volatile compound.
To the best of our knowledge, this study is the first report
to identify a number of volatile compounds in TS, includ-
ing cis-, trans-2-Mercapto-3,4-dimethyl-2,3-dihydrothio-
phene, Allyl dithiopropanoate, α-Calacorene, Selina-3,7
(11)-diene, 3-Ethyl-1,2-dithiacyclohex-4-ene, 3-Ethyl-1,2-
dithiacyclohex-5-ene, cis -2-Ethyl-3-methylthiophene, (Z)-
Caryophyllene, α-Thujene 2-Ethyl-1,3-dithiacyclohex-4-
ene,2-Ethenyl-1,3,3-trimethylcyclohexene and 5,5-Dime-
thyl-1,3-dithian-2-one (Table 1).
3.4. Identification of the Key Aroma Compounds
The most important aroma compounds of TS, isomers of
2-Mercapto-3,4-dimethyl-2,3-dihydrothiophene (the iden-
tification method is discussed in the following paragraph),
as indicated by peak 22 and 25, were first identified in
this study. GC-O analysis indicated that the two peaks
were demonstrated to be the characteristic peaks of TS.
The two compounds eluted from the GC column one
after another within two minutes, but their mass spectro-
grams seemed to be nearly identical (Figures 4(a) and (b)),
which implied the hypothesis that they might be isomers.
Furthermore, the two mass spectrograms were difficult to
identify even though many parallel tests were conducted
(data not shown). By meticulously comparing the two
mass spectrograms of 2-Mercapto-3,4-dimethyl-2,3-di-
hydrothiophene and 3,4-Dimethylthiophene with com-
pounds in the NIST08 database (Figures 4(a) and (b)),
the similarity of these compounds was noticed. This ob-
servation resulted in the hypothesis that peaks 22 and 25
corresponded to cis and trans isomers of 2-Mercapto-3,4-
dimethyl-2,3-dihydrothiophene (Figures 5(a) and (b)). The
presences of these two compounds may be due to the loss
of H2S from 2-Mercapto-3,4-dimethyl-2,3-dihydrothio-
phene to form 3,4-Dimethylthiophene which would ex-
plain the similarity of the MS for the two compounds.
This hypothesis is supported by the study that demon-
strated 3,4-Dimethylthiophene can be produced by from
bis(1-Propenyl) disulfide in a series of reactions [27]
(Figure 6). Nevertheless, because of the lack of studies
in this area, the identity of the target compounds were
unknown before the present study. According to Kuo &
Ho [23] the two peaks were located on their correspond-
ing positions, that is, the former is cis-2-Mercapto-3,4-
dimethyl-2,3-dihydrothiophene while the latter is trans-2-
Mercapto-3,4-dimethyl-2,3-dihydrothiophene. Referring
to the flavour formation mechanism, 3,4-Dimethylthio-
phene and 2-Mercapto-3,4-dimethyl-2,3-dihydrothio-
phene tracely exist in slicing onions and garlics, but the
latter compound does not emanate its TS aroma in the
allium vegetables, which may contribute to the other po-
tent compounds such as allicin and allitride [28] and
mask their odors. Due to the lack of the other pungent
compounds and high amounts of 2-Mercapto-3,4-dime-
thyl-2,3-dihydrothiophene (both isomers, the former smelt
like cooked TS while the latter showed its fresh TS aroma)
it is likely that 3,4-Dimethylthiophene was available by
heating 2-Mercapto-3,4-dimethyl-2,3-dihydrothiophene in
garlic [29], which implied they might be genarated from
the same precursor in TS. However, the aroma chemisrty
in TS is very complicated, and requires further investiga-
tion. Although there have not been any reports on the
mechanisms of TS aroma compound formation, a num-
ber of studies on compound formation in garlic, onions
and leeks [30,31] suggest it may be possible to elucidate
these mechanisms. For instance, some sulfur compounds
act as aroma precursors, in that, as they are broken down
via physiological metabolism, and aroma-active products
are rapidly formed. Further investigation into the reaction
mechanisms, related enzymes and substrates in TS is
4. Conclusions
This study indicated that HS-SPME coupled with GS-MS
Copyright © 2013 SciRes. FNS
Analysis of Volatile Compounds and Identification of Characteristic Aroma Components of Toona sinensis
(A. Juss.) Roem. Using GC-MS and GC-O
Copyright © 2013 SciRes. FNS
Figure 4. (a) Mass spectrogram of peak 22 comparing with 2-Mercapto-3,4-dimethyl-2,3-dihydrothiophene and 3,4-Dime-
thylthiophene; (b) Mass spectrogram of peak 25 comparing with 2-Mercapto-3,4-dimethyl-2,3-dihydrothiophene and 3,4-
and GC-O could be used to investigate the characteristic
aroma components present in TS. A 65 μm DVB/PDMS
fibre was found to be an appropriate fibre for analyzing
the volatiles in TS, and the optimal extraction conditions
were 40˚C for 30 min. Under these conditions, 56 peaks
were separated and 53 compounds in TS volatiles were
identified. Among them, sulfur compounds and terpenes
accounted for a large proportion of the TS extract
(42.146%, 55.984%, respectively). GC-O runs revealed
the odor profiles of the extracted compounds. A total of
26 compounds were considered to be “aroma-active” and
their odor intensities were evaluated. However, only a
few of these compounds were found to contribute to the
unique aroma of TS. Based on the data presented in this
study, two compounds, cis and trans isomers of 2-Mer-
capto-3,4-dimethyl-2,3-dihydrothiophene appeared to de-
termine the aroma of TS. This is the first report to con-
firm the identity of the key volatile compounds in TS.
(a) (b)
Figure 5. (a) The chemical structure of cis-2-Mercapto-
3,4-dimethyl-2,3-dihydrothiophene; (b) The chemical struc-
ture of trans-2-Mercapto-3,4-dimethyl-2,3-dihydrothiophene.
Figure 6. Formation of cis-, trans-2-Mercapto-3,4-dimethyl-
2,3-dihydrothiophene and 3,4-Dimethyl-2,3-dihydrothiophene
from bis(1-propenyl)disulfide during heating process.
Analysis of Volatile Compounds and Identification of Characteristic Aroma Components of Toona sinensis
(A. Juss.) Roem. Using GC-MS and GC-O 313
5. Acknowledgements
We would like to thank all the panelists participating in
the sensory tests. Special thanks to Dr. Chris Blanchard
(School of Biomedical Science, Charles Sturt University,
Wagga, NSW 2650, Australia) for reviewing the manu-
[1] J. M. Edmonds and M. Staniforth, “Plate 348. Toona
sinensis,” Curtiss Botanical Magazine, Vol. 15, No. 3,
1998, pp. 186-193. doi:10.1111/1467-8748.00169
[2] T. J. Hsieh, J. C. Wang, C. Y. Hu, C. T. Li, C. M. Kuo
and S. L. Hsieh, “Effects of Rutin from Toona sinensis on
the Immune and Physiological Responses of White Shrimp
(Litopenaeus vannamei) under Vibrio alginolyticus Chal-
lenge,” Fish & Shellfish Immunology, Vol. 25, No. 5,
2008, pp. 581-588. doi:10.1016/j.fsi.2008.07.014
[3] Y. C. Hseu, S. C. Chen, W. H. Lin, D. Z. Hung, M. K.
Lin, Y. H. Kuo, M. T. Wang, H. J. Cho, L. Wang and H.
L. Yang, “Toona sinensis (Leaf Extracts) Inhibit Vascular
Endothelial Growth Factor (VEGF)-Induced Angiogene-
sis in Vascular Endothelial Cells,” Journal of Ethno-
pharmacology, Vol. 134, No. 1, 2011, pp. 111-121.
[4] H. Kataoka, H. L. Lord and J. Pawliszyn, “Applications
of Solid-Phase Microextraction in Food Analysis,” Jour-
nal of Chromatography A, Vol. 880, No. 1-2, 2000, pp.
35-62. doi:10.1016/S0021-9673(00)00309-5
[5] S. N. Lee, N. S. Kim and D. S. Lee, “Comparative Study
of Extraction Techniques for Determination of Garlic Fla-
vor Components by Gas Chromatography-Mass Spec-
trometry,” Analytical and Bioanalytical Chemistry, Vol.
377, No. 4, 2003, pp. 749-756.
[6] S. B. Junior, A. M. T. De Melo, C. A. Zini and H. T.
Godoy, “Optimization of the Extraction Conditions of the
Volatile Compounds from Chili Peppers by Headspace
Solid Phase Micro-Extraction,” Journal of Chromatog-
raphy A, Vol. 1218, No. 21, 2011, pp. 3345-3350.
[7] B. D Acampora Zellner, P. Dugo, G. Dugo and L. Mon-
dello, “Gas Chromatography-Olfactometry in Food Fla-
vour Analysis,” Journal of Chromatography A, Vol. 1186,
No. 1, 2008, pp. 123-143.
[8] Á. Högnadóttir and R. L. Rouseff, “Identification of
Aroma Active Compounds in Orange Essence Oil Using
Gas Chromatography-Olfactometry and Gas Chromatog-
raphy-Mass Spectrometry,” Journal of Chromatography
A, Vol. 998, No. 1-2, 2003, pp. 201-211.
[9] S. Guillot, L. Peytavi, S. Bureau, R. Boulanger, J. P. Le-
poutre, J. Crouzet and S. Schorr-Galindo, “Aroma Char-
acterization of Various Apricot Varieties Using Head-
space-Solid Phase Microextraction Combined with Gas
Chromatography-Mass Spectrometry and Gas Chroma-
tography-Olfactometry,” Food Chemistry, Vol. 96, No. 1,
2006, pp. 147-155. doi:10.1016/j.foodchem.2005.04.016
[10] H.-P. Lv, Q.-S. Zhong, Z. Lin, L. Wang, J.-F. Tan and L.
Guo, “Aroma Characterisation of Pu-erh Tea Using Head-
space-Solid Phase Microextraction Combined with GC/
MS and GC-Olfactometry,” Food Chemistry, Vol. 130,
No. 4, 2012, pp. 1074-1081.
[11] H. Van den Dool and P. Dec Kratz, “A Generalization of
the Retention Index System Including Linear Tempera-
ture Programmed Gas—Liquid Partition Chromatogra-
phy,” Journal of Chromatography A, Vol. 11, No. 2, 1963,
pp. 463-471.
[12] G. Botelho, A. Mendes-Faia and M. C. Clímaco, “Char-
acterisation of Free and Glycosidically Bound Odourant
Compounds of Aragonez Clonal Musts by GC-O,” Ana-
lytica Chimica Acta, Vol. 657, No. 2, 2010, pp. 198-203.
[13] L. Culleré, F. San-Juan and J. Cacho, “Characterisation of
Aroma Active Compounds of Spanish Saffron by Gas
Chromatography-Olfactometry: Quantitative Evaluation of
the Most Relevant Aromatic Compounds,” Food Chemis-
try, Vol. 127, No. 4, 2011, pp. 1866-1871.
[14] S. Kreutzmann, A. K. Thybo and W. L. P. Bredie, “Train-
ing of a Sensory Panel and Profiling of Winter Hardy and
Coloured Carrot Genotypes,” Food Quality and Prefer-
ence, Vol. 18, No. 3, 2007, pp. 482-489.
[15] J. Marais, “Terpenes in the Aroma of Grapes and Wines:
A Review,” South African Journal for Enology and Viti-
culture, Vol. 4, No. 2, 1983, pp. 49-60.
[16] J. H. Kwon, K. Akram, K. C. Nam, E. J. Lee and D. U.
Ahn, “Evaluation of Radiation-Induced Compounds in
Irradiated Raw or Cooked Chicken Meat during Storage,”
Poultry Science, Vol. 90, No. 11, 2011, pp. 2578-2583.
[17] S. Rochat, J. Y. S. Laumer and A. Chaintreau, “Analysis
of Sulfur Compounds from the In-Oven Roast Beef Aroma
by Comprehensive Two-Dimensional Gas Chromatogra-
phy,” Journal of Chromatography A, Vol. 1147, No. 1,
2007, pp. 85-94. doi:10.1016/j.chroma.2007.02.039
[18] S. Wang, S. Yang, L. Ren, C. Qian, F. Liu and S. Jiang,
“Determination of Organophosphorus Pesticides in Leeks
(Allium porrum L.) by GC-FPD,” Chromatographia, Vol.
69, No. 1, 2009, pp. 79-84.
[19] I. S. Chung, K. Y. Chae and K. H. Kyung, “Thermal Gen-
eration and Antimicrobial Activity of Unusual Heterocyc-
lic Sulfur Compounds in Garlic,” Food Science and Bio-
technology, Vol. 17, No. 5, 2008, pp. 1032-1037.
[20] C. C. Eady, T. Kamoi, M. Kato, N. G. Porter, S. Davis, M.
Shaw, A. Kamoi and S. Imai, “Silencing Onion Lachry-
matory Factor Synthase Causes a Significant Change in
the Sulfur Secondary Metabolite Profile,” Plant Physiol-
ogy, Vol. 147, No. 4, 2008, pp. 2096-2106.
[21] R. Mu, X. Wang, S. Liu, X. Yuan, S. Wang and Z. Fan,
Copyright © 2013 SciRes. FNS
Analysis of Volatile Compounds and Identification of Characteristic Aroma Components of Toona sinensis
(A. Juss.) Roem. Using GC-MS and GC-O
Copyright © 2013 SciRes. FNS
“Rapid Determination of Volatile Compounds in Toona
sinensis (A. Juss.) Roem. by MAE-HS-SPME Followed
by GC-MS,” Chromatographia, Vol. 65, No. 7-8, 2007,
pp. 463-467. doi:10.1365/s10337-007-0183-0
[22] A. Bianchi, A. Zambonelli, A. Z. D’Aulerio and F. Belle-
sia, “Ultrastructural Studies of the Effects of Allium sati-
vum on Phytopathogenic Fungi in Vitro,” Plant Disease,
Vol. 81, No. 11, 1997, pp. 1241-1246.
[23] M. C. Kuo and C. T. Ho, “Volatile Constituents of the
Solvent Extracts of Welsh Onions (Allium fistulosum L.
variety Maichuon) and Scallions (A. Fistulosum L. Vari-
ety Caespitosum),” Journal of Agricultural and Food
Chemistry, Vol. 40, No. 10, 1992, pp. 1906-1910.
[24] M. R. Corbo, R. Lanciotti, F. Gardini, M. Sinigaglia and
M. E. Guerzoni, “Effects of Hexanal, trans-2-Hexenal,
and Storage Temperature on Shelf Life of Fresh Sliced
Apples,” Journal of Agricultural and Food Chemistry,
Vol. 48, No. 6, 2000, pp. 2401-2408.
[25] R. Marín, M. A. Apel, R. P. Limberger, M. C. B. Raseira,
J. F. M. Pereira, J. A. S. Zuanazzi and A. T. Henriques,
“Volatile Components and Antioxidant Activity from
Some Myrtaceous Fruits Cultivated in Southern Brazil,”
Latin American Journal of Pharmacy, Vol. 27, No. 2,
2008, pp. 172-177.
[26] I. A. Ogunwande, G. Flamini, P. L. Cioni, O. Omikorede,
R. A. Azeez, A. A. Ayodele and Y. O. Kamil, “Aromatic
Plants Growing in Nigeria: Essential Oil Constituents of
Cassia alata (Linn.) Roxb. and Helianthus annuus L.,”
Records of Natural Products, Vol. 4, No. 4, 2010, pp.
[27] E. Block, D. Putman and S. H. Zhao, “Allium Chemistry:
GC-MS Analysis of Thiosulfinates and Related Com-
pounds from Onion, Leek, Scallion, Shallot, Chive, and
Chinese Chive,” Journal of Agricultural and Food Chem-
istry, Vol. 40, No. 12, 1992, pp. 2431-2438.
[28] E. Block, “The Chemistry of Garlic and Onions,” Scien-
tific American, Vol. 252, No. 3, 1985, pp. 114-119.
[29] E. Block and S. H. Zhao, “Onion Essential Oil Chemistry.
cis-and trans-2-mercapto-3,4-dimethyl 2,3-dihydrothio-
phene from Pyrolysis of Bis(1-propenyl) Disulfide,” Tet-
rahedron Letters, Vol. 31, No. 35, 1990, pp. 4999-5002.
[30] E. Block, T. Bayer, S. Naganathan and S. H. Zhao, “Al-
lium Chemistry: Synthesis and Sigmatropic Rearrange-
ments of Alk (en) yl 1-Propenyl Disulfide S-Oxides from
Cut Onion and Garlic1,” Journal of the American Chemical
Society, Vol. 118, No. 12, 1996, pp. 2799-2810.
[31] G. S. Nielsen and L. Poll, “Determination of Odor Active
Aroma Compounds in Freshly Cut Leek (Allium ampelo-
prasum Var. Bulga) and in Long-Term Stored Frozen
Unblanched and Blanched Leek Slices by Gas Chroma-
tography Olfactometry Analysis,” Journal of Agricultural
and Food Chemistry, Vol. 52, No. 6, 2004, pp. 1642-
1646. doi:10.1021/jf030682k