Chemical Identity of a Rotting Animal-Like Odor Emitted
from the Inﬂorescence of the Titan Arum (Amorphophallus titanum)
Mika SHIRASU,1Kouki FUJIOKA,2Satoshi KAKISHIMA,3Shunji NAGAI,4Yasuko TOMIZAWA,5
Hirokazu TSUKAYA,6Jin MURATA,3Yoshinobu MANOME,2and Kazushige TOUHARA1;y
1Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences,
The University of Tokyo, Tokyo 113-8657, Japan
2Department of Molecular Cell Biology, Institute of DNA Medicine, Jikei University School of Medicine,
Tokyo 105-8461, Japan
3Botanical Gardens, Graduate School of Science, The University of Tokyo, Tokyo 112-0001, Japan
4National Cancer Center, Hospital East, Chiba 277-8577, Japan
5Department of Cardiovascular Surgery, Tokyo Women’s Medical University, Tokyo 162-8666, Japan
6Department of Biological Science, Graduate School of Science, The University of Tokyo, Tokyo 113-0033, Japan
Received September 28, 2010; Accepted November 3, 2010; Online Publication, December 7, 2010
The titan arum, Amorphophallus titanum, is a ﬂower-
ing plant with the largest inﬂorescence in the world. The
ﬂower emits a unique rotting animal-like odor that
attracts insects for pollination. To determine the chemi-
cal identity of this characteristic odor, we performed gas
chromatography-mass spectrometry-olfactometry anal-
ysis of volatiles derived from the inﬂorescence. The
main odorant causing the smell during the ﬂower-
opening phase was identiﬁed as dimethyl trisulﬁde, a
compound with a sulfury odor that has been found to be
emitted from some vegetables, microorganisms, and
Key words: Amorphophallus titanum; odor; gas chroma-
tography-mass spectrometry; olfactometry;
The genus Amorphophallus is well known for the
characteristic odor of its inﬂorescence.
species of the genus Amorphophallus,Amorphophallus
titanum (Becc.) Becc. ex Arcangeli is famous for the
large size of the inﬂorescence (Fig. 1A) and for emitting
a rotting animal-like odor.
This odor probably attracts
pollinators such as carrion beetles and ﬂies.
studies using gas chromatography-mass spectrometry
(GC-MS) have identiﬁed several odorants, including
dimethyl oligosulﬁdes, that are emitted from A. tita-
but it is not certain whether these odorants reﬂect
the odor of the ﬂower as humans experienced it. In
addition, due to the rarity of ﬂowering events, detailed
study of this species was limited until recently. In the
Botanical Gardens of The University of Tokyo, on July
22, 2010, we had an opportunity to analyze the smell of
the inﬂorescence of an A. titanum plant. The GC-MS-
olfactometry (GC-MS-O) technique allowed us to
analyze emitted odorous compounds that contribute to
the rotting animal-like smell during the ﬂowering
First we evaluated the intensity and quality of the
odors emitted from the inﬂorescence of A. titanum
during ﬂowering by human nose (Fig. 2A). At the
beginning of ﬂowering, a faint rotten fruit-like odor was
detected occasionally. Then the odor emitted from the
ﬂower gradually intensiﬁed. During full opening of the
spathe, a strong rotting animal-like odor was emitted
constantly. In addition, infrared radiation from the
surface of the inﬂorescence was measured with a
thermograph (Neothermo TVS-600; Avionics Japan,
Tokyo), as described elsewhere.
The odor became
stronger with heat production from the spadix, as
previously reported (Fig. 2B and C).
After the peak
of the spadix temperature, the inﬂorescence began to
secrete a ﬂuid from the spadix in which a rotten ﬁsh-like
odor was sensed.
Next we collected volatile compounds emitted from
the A. titanum. The volatiles derived from the inﬂor-
escence were absorbed directly to Carboxen/PDMS
(Carboxen/Polydimethylsiloxane) SPME (solid phase
micro extraction) ﬁbers (SUPELCO, Bellefonte, PA)
that had been placed inside of the inﬂorescence from
21:00 to 23:00 on July 22 (Figs. 1B(a) and 2A). The
compounds on the SPME ﬁbers were then analyzed by
GC-MS-O which enabled us to examine the mass spectra
and odor qualities of individual GC-separated odorants
simultaneously. Shimadzu GCMS-QP2010 (Shimadzu,
Kyoto) (a stabilwax column of 60 m 0.32 mm i.d.
with a ﬁlm thickness of 0.5 mm) was combined with a
sniﬃng port equipped with a Sniﬀer9000 system
(Brechbuhler, Houston, TX) in splitless mode (MS and
sniﬃng port at ratio of 1:4.7). The column temperature
was programmed to rise at 5 C/min from 50 C (2-min
hold) to 230 C (30-min hold) (total run time, 68 min).
The interface temperature was maintained at 200 C and
the ion source temperature at 230 C. Mass spectra were
obtained in full scan mode (range 20–400) by electron
impact using the NIST library database.
yTo whom correspondence should be addressed. Fax: +81-3-5841-8024; E-mail: firstname.lastname@example.org
Abbreviations: GC-MS, gas chromatography-mass spectrometry; GC-MS-O, GC-MS-olfactometry; TIC, total ion chromatogram; RT, retention
time; DMTS, dimethyl trisulﬁde; DMDS, dimethyl disulﬁde
Biosci. Biotechnol. Biochem.,74 (12), 2550–2554, 2010
Figure 3A shows total ion chromatograms (TIC) of a
SPME-absorbed sample collected by the method shown
in Fig. 1B(a). The odor characters sensed at the sniﬃng
port are described under the chart. GC-MS-O analysis
and evaluation of odors were performed by three
persons. The sensory characters of the odor-positive
peaks and the identiﬁed odorants are summarized in
Fig. 3D. The characteristic rotting animal-like surfury
odor, which was identical to the odor we sensed in the
inﬂorescence during the opening of the spathe, came
out at a retention time (RT) of 18.79 min. The mass
spectrum of the peak predicted the structure of dimethyl
trisulﬁde (DMTS) (Fig. 3C). The mass spectrum and the
retention time of authentic DMTS (Wako, Tokyo) were
identical to those of the peak compound, conﬁrming
that the sulfury odor at RT ¼18:79 min was DMTS
In addition, the gaseous odor (RT ¼9:06 min) was
identiﬁed as methyl thiolacetate, and the cheesy, foot-
like valerian odor (RT ¼25:93 min) was identiﬁed as
isovaleric acid (Fig. 3A). The green odor at RT ¼16:19
could not be identiﬁed due to low concentration or to
overlapping peaks in the TIC. Dimethyl disulﬁde
(DMDS), which has been reported to be a major odorant
emitted from A. titanum, was also detected abundantly
at RT ¼9:80 min, but we could not sense the odor by
GC-MS-O analysis due to a high threshold,
ing that the contribution of DMDS to human olfactory
perception is not signiﬁcant. The presence of a large
amount of DMDS, however, is plausible, because
DMDS is thought to be a precursor of DMTS which is
biosynthesized from methionine or S-methyl-L-cysteine
sulfoxide via methanethiol, which was also detected by
GC-MS (Fig. 3A).
Considering that GC-MS-O anal-
ysis directly identiﬁes crucial volatiles that contribute to
the quality of the smell that humans sense, these results
suggest that the main odorous component of A. titanum
is DMTS. GC-MS-O analysis of another ﬂowering
A. titanum cultivated in a greenhouse at Flower Park
Kagoshima gave the same results (ﬂower opening on
August 2, 2010) (data not shown).
At the end of the ﬂower-opening phase, the odor
quality of the inﬂorescence changed gradually following
secretion of the odorous ﬂuid from the spadix. The ﬂuid
secreted from the spadix was collected from 1:00 to 3:00
on July 23, and head-space volatile compounds from a
10 ml sample enclosed in a 40 ml glass vial were absorbed
to SPME ﬁbers for 7 h (Fig. 1B(b)). GC-MS-O analysis
of the SPME sample showed a strong rotten ﬁsh-like
odor similar to the odor we sensed at the end of the
ﬂower-opening phase at RT ¼3:33 min, and this was
identiﬁed as trimethylamine (Fig. 3B, inset). Green,
burnt odor (RT ¼6:13 min) was identiﬁed as 3-methyl
butanal, and a vinegary odor (RT ¼20:47 min) as acetic
acid (Fig. 3B).
Time Event Odor quality
14:00 Opening of the spathe Slight rotten fruit-like odor
Yellow pickled radish
Spathe full opened Rotting animal-like odor
22:00 Spadix warming phase
Fluid exuded from the spadix
Rotten fish, Rotten egg
8:00 Closing of the spathe
Strong rotting animal-like odor
Spadix temperature (oC)
Spadix temp - ambient temp (oC)
Fig. 2. Scheme of the Flowering Behavior, Odor Quality and Thermogenesis of A. titanum.
(A) Flowering events and characteristic odors of A. titanum. The darkness of the gray indicates the intensity of the rotting animal-like odor.
(B) Time course record of spadix temperature (black line). Diﬀerence between the spadix and the ambient temperature (red line).
(C) Representative thermographic images (top, taken at 19:47 on July 22, 2010; bottom, taken at 0:47 on July 23, 2010). Scale bar, 20 cm.
Fig. 1. Odor Sampling from a Flower of Amorphophallus titanum.
(A) Full opening of the spathe of an A. titanum with a height of
1.6 m in the Koishikawa Botanical Gardens in July 2010. Scale bar,
20 cm. (B) Methods of collecting volatiles emitted from A. titanum.
(a) Volatile compounds from the inﬂorescence were directly
absorbed to SPME ﬁbers placed between the spadix and the spathe.
(b) A ﬂuid secreted onto the spadix was collected, and the head-
space volatiles from the ﬂuid were absorbed to SPME ﬁbers. Scale
bar, 20 cm.
Odor from a Flower of the Titan Arum 2551
Finally, we attempted to evaluate ﬂower odor objec-
tively by using an electronic nose, FF-2A (Shimadzu,
The device contains electronic sensors with
various sensitivities and selectivities for volatile com-
pounds, and is standardized with nine gases (hydrogen
sulﬁde, methylmercaptan, ammonia, trimethylamine,
propionic acid, butylaldehyde, butylacetate, toluene,
and heptane), the odor quality of which can be
categorized into nine groups (hydrogen sulﬁde, sulfur,
ammonia, amine, organic acid, aldehyde, ester, aromatic
group and carbon hydrate). The ﬂower smell was
collected directly into a 2 L tedlar bag (SUPELCO,
Bellefonte, PA) with a sampling pump (GL Sciences) at
21:00 on July 23. The collected air was diluted 5-fold
with odorless nitrogen gas and injected into the FF-2A.
Various concentrations of DMTS and DMDS were also
applied to the device. The virtual odor index in terms of
the nine aromatic categories is plotted in Fig. 4. For the
sample of A. titanum, the sulfur category was identiﬁed
as the highest odor index, and organic acid, aldehyde,
amine, and ester categories constituted lower index
categories (Fig. 4A). In a series of diluted DMTS, the
chart pattern of 0.01 ppm DMTS was similar to that of
the A. titanum sample (Fig. 4), which was fairly
consistent with the approximate concentration of DMTS
emitted as calculated at the basis of the GC-MS analysis
(data not shown). The chart pattern of DMDS was also
similar to that of the A. titanum sample, but the overall
odor intensity was weaker than that of DMTS (see
Fig. 4B and E). These results again conﬁrm that DMTS
is the major contributor to the ﬂower smell for human
In conclusion, simultaneous evaluation of odor qual-
ity and the molecular masses of volatiles by GC-MS-O
enabled us to identify DMTS as the main odorant that
causes the rotting animal-like odor of A. titanum during
20 40 60 80 100 120
20 40 60 80 100 120
2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
S O SSS
2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
3.33 Rotten fish Trimethylamine - ++
6.13 Green, burnt 3-Methyl-butanal - +
9.06 Gaseous Methyl thiolacetate + -
16.19 Green + -
18.79 Surfury Dimethyl trisulfide ++ +
20.47 Acidity Acetic acid - +
25.93 Valerian, cheese, feet Isovaleric acid + -
RT Odor character Odorant Odor intensity
2 3 4 5
2 3 4
Fig. 3. GC-MS-O Analysis of SPME-Absorbed Head-Space Volatiles Emitted from A. titanum.
(A) Total ion chromatogram of volatile compounds absorbed to SPME ﬁbers by the method described in Fig. 1B(a). Characteristics of odors
sensed at the sniﬃng port of GC-MS-O are described at the bottom of the chart. (B) Total ion chromatogram of head-space volatiles emitted from
the ﬂuid of spadix, as described in Fig. 1B(b). Inset in (A) and (B) is the close-up TIC from 2 min to 5 min. The light gray and dark gray lines
indicate extracted ion chromatograms of the molecular ion peaks of trimethylamine (m=z59) and methanethiol respectively (m=z48)
respectively. (C) Mass spectrum of the peak at 18.8 min of TIC in Fig. 3A (top). Mass spectrum of authentic DMTS (bottom). (D) Retention
times (RTs), odor characters, and chemical identities of odor-positive peaks by GC-MS-O analysis. The intensities of the odors at the odor-
positive peaks in Fig. 3A (odor intensity, Gas) and 3B (odor intensity, Fluid) are categorized into three groups: not detected (), slight (þ),
2552 M. SHIRASU et al.
the opening of the spathe. Trimethylamine was found to
be the odorant that caused the rotten-ﬁsh odor at the end
of ﬂowering. We also identiﬁed several other com-
pounds contributing to the odor of the inﬂorescence,
including methyl thiolacetate, 3-methyl butanal, acetic
acid, and isovaleric acid.
DMTS has been reported to be present in volatiles
emitted from vegetables such as cooked onion and
cabbage, decayed meats, and fermented food and drink,
which usually cause ﬂy attraction.
sulphides emitted from the ﬂower of dead-horse arum
(Helicodiceros muscivorus) have been reported to be
attractants for ﬂies,
suggesting that A. titanum also
fools ﬂies into pollinating it by mimicking the odors of
fermented products and rotting animal bodies. On the
other hand, an interesting coincidence is that DMTS is
known to be the main source of the malodor of fungating
cancer wounds in human.
Indeed, the odor index
pattern of the head-space volatiles of a gauze pad placed
on a breast cancer wound was very similar to that of
A. titanum on electronic nose FF-2A (Fig. 4G). It is an
intriguing question how mechanisms of producing
DMTS have been acquired in various organisms as a
signal for various purposes during the process of
We are grateful to Tadashi Yamaguchi (Botanical
Gardens, Graduate School of Science, the University of
Tokyo) for the photograph of A. titanum in Fig. 1A.
This research was approved by the Research Ethics
Committee of the University of Tokyo. It was supported
in part by grants from the Ministry of Education,
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