FLAVOUR AND FRAGRANCE JOURNAL
Flavour Fragr. J. 2004; 19: 6–8
Published online 24 October 2003 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/ffj.1198
Copyright © 2003 John Wiley & Sons, Ltd.
John Wiley & Sons, Ltd.Chemical composition of the essential oils of Ageratum
conyzoides L. occurring in South China
Essential Oils of Ageratum conyzoidesAbu James Sundufu* and Huang Shoushan
Laboratory of Insect Ecology, South China Agricultural University, Guangzhou 510642, People’s Republic of China
Received 21 May 2002
Revised 16 July 2002
Accepted 15 August 2002
ABSTRACT: The essential oil isolated from the leaves and flowers of Ageratum conyzoides L. were analysed by
GC and GC–MS. The oil contained ageratochromene (precocene II, 25.89%); the sesquiterpene β-caryophyllene
(23.79%); demethoxyageratochromene (precocene I, 14.76%) and some monoterpene hydrocarbons, with percent-
ages of 2–5.5%. Comparative analysis with data from Cameroon, Ghana and Vietnam is also reported. Copyright ©
2003 John Wiley & Sons, Ltd.
KEY WORDS: Ageratum conyzoides L.; Asteraceae; Eupatorieae; chromenes; sesquiterpene; precocene
Introduction
Ageratum conyzoides L. (Asteraceae, tribe Eupatorieae)
originated from mid-Southern USA, is an important
and widespread weed in South China and South-east
Asia. It is reported that the leaves of this plant show
antifungal properties.1 Further investigations show the
occurrence of benzopyrans,2,3 as well as flavonoids4,5
and terpenoids.6–9 The essential oil contains chromenes,
of which precocene I and II, present in the species of
the genus Ageratum,9–12 exhibit remarkable biological
activity against several species of insects;2,12–15 some
insects treated with precocenes moult precociously into
small adults or attempt to moult too soon into the adult
stage.12–15
Since the discovery of precocenes as bioactive
plant products, considerable effort has been directed
towards the elucidation of the biological properties and
characterization of the major components of the essen-
tial oils of one species, Ageratum conyzoides L. The
numerous chemical analyses of its essential oil constitu-
ents from different regions6,7,9,16 indicate the presence
of benzopyran derivatives as typical components. How-
ever, to our knowledge, very little effort has been spent
on investigation of the chemical composition of the
essential oils of A. conyzoides L. Therefore, we report
here the essential oil composition of A. conyzoides L.
from South China. This is part of a research programme
especially focused on the effect of essential oils on
insect pests.
Experimental
Plant Material and Extraction of Volatiles
Ground-above plants (5 kg) of A. conyzoides L. were col-
lected from the Ecological Experimental Station of South
China Agricultural University, Guangzhou, People’s Repub-
lic of China. Fresh leaves and flowers were cut into pieces,
air-dried for 7 days at room temperature and steam distilled
for 4 h, furnishing 0.4% (v/w) of oil. The oils were dried
over anhydrous Na2SO4 and kept refrigerated until used.
Analysis of the Essential Oils
Chemical constituents of the volatile oil were separated
on a Finnigan TRACE 2000 GC–MS instrument (Finnigan-
Spectronex, USA), equipped with two fused-silica columns
(30 mm × 0.25 mm i.d.), coated with DB-1 (df = 0.25 µm).
Initial oven temperature was maintained at 60 °C for
2 min and then programmed at 5 °C/min to 280 °C (held
10 min); injector temperature, 220 °C; ion source temper-
ature, 200 °C; EI, 70 eV; carrier gas, He at 1 ml/min;
injection volume, 1 µl; split, 1:50; mass range, 35–450
amu. Quantification was performed by percentage peak
area calculations and identification of individual com-
ponents using the Wiley/NBS Registry of Mass Spectral
Data, similarity between the mass spectrum and a few
authentic reference compounds (Aldrich Chemical Co.).
Results and Discussion
GC and GC–MS analyses led to the detection of 42
compounds (Table 1), of which benzopyrans and
* Correspondence to: A. J. Sundufu, Laboratory of Insect Ecology, South China
Agricultural University, Guangzhou 510642, People’s Republic of China.
E-mail: jasundufu@hotmail.com

ESSENTIAL OILS OF AGERATUM CONYZOIDES 7
Copyright © 2003 John Wiley & Sons, Ltd. Flavour Fragr. J. 2004; 19: 6–8
sesquiterpene derivatives dominated. The main compo-
nents were ageratochromene (precocene II, 25.89%), β-
caryophyllene (23.79%) and demethoxyageratochro-
mene (precocene I, 14.76%). These compounds, as
well as caryophyllene oxide, the monoterpene hydro-
carbons α-farnesene, γ-cadinene, δ-elemene, β-elemene,
muurolene and the compound coumarin, occurring in
amounts of 2–5.5%, have been already reported.
Benzofuran derivatives are well-known characteristic
components of A. houstonianum Mill. However, 2-
amylfuran and 2,3-dihydrobenzofuran occurred in minute
amounts of <1% in A. conyzoides L. been reported. In
addition, we identified widdrol, melitol and α-funebrene,
which have not been reported previously.
Although, studies on the comparative percentage
composition of A. conyzoides L. essential oils from dif-
ferent regions are well documented,6,7,9,16 this is the first
report for A. conyzoides L. from Southern China. Results
in Table 2 indicate that, whilst the essential oils of A.
conyzoides L. from South China and Vietnam contain
precocene II (25.9 and 31.1%, respectively) as the main
component, oils from Cameroon and Ghana are rich in
precocene I (81.0 and 80.3%, respectively). However,
β-caryophyllene is present in all samples, although its
amount is quite different. Quantitatively, whilst only a
trace (0.2%) of precocene II is found in the essential oil
from Cameroon, oil from Ghana is completely devoid of
it. In contrast, the percentage composition of precocene
II in oils from South China and Vietnam are roughly
comparable.
It is worth noting that the precocenes are known to
exhibit anti-juvenile effects, such as antigonadotropic
ovicidal, precocious metamorphosis and diapause in-
duction on insects.12–15 Therefore, the presence of these
Table 1. Percentage composition of essential oils of South China Ageratum conyzoides L.
Constituents Rentention index (DB-1) Essential oil (%)
Phytane 594 0.18
Spathulenol 693 0.12
α-Himachalene 646 0.12
Widdrold 679 0.12
α-Myrcene 705 0.11
Caryophyllene oxide 741 2.36
Melitold 759 0.36
n-Nonanal 775 0.13
n-Octacosane 776 0.31
n-Heneicosane 782 0.78
1-Borneol 787 0.18
Isocaryophyllene 788 0.24
2-Amylfuran 789 0.29
Hexadecane 790 0.33
n-Octacosane 809 0.37
n-Tricosane 815 0.25
Ageratochromene 825 25.89
n-Eicosane 828 0.45
6,10,14-Trimethyl-2-pentadecanone 831 0.13
α-Copaene 836 0.39
α-Farnesene 837 5.42
α-Pinene 838 0.22
γ-Cadinene 840 2.32
4-Vinyl-2-methoxyphenol 841 0.20
α-Amorphene 842 0.39
Bicycloelemene 844 2.65
2,3-Dihydrobenzofuran 845 0.58
Coumarin 846 5.18
α-Funebrened 847 4.84
α-Sesquiphellandrene 848 4.84
α-Ylangene 849 0.39
Bornyl Formate 850 0.18
δ-Elemene 851 2.65
α-Cubebene 851 0.90
Muurolene 853 4.84
Demethoxyageratochromene 857 14.76
α-Terpinolene 863 0.29
Germacrene-B 873 2.65
β-Caryophyllene 888 23.79
Camphene 904 0.56
Germacrene-D 907 2.32
7-methoxy-2-dimethy1-6-vinyl-2H-chromene 924 1.30
Bornyl acetate 935 0.95
d Tentative identification.