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VECTOR CONTROL, PEST MANAGEMENT, RESISTANCE, REPELLENTS
Evaluation of Contact Toxicity and Repellency of the Essential
Oil of Pogostemon cablin Leaves and Its Constituents Against
Blattella germanica (Blattodae: Blattelidae)
XIN CHAO LIU,1 QIYONG LIU,2 HAN CHEN,1 QI ZHI LIU,1 SHI YAO JIANG,1 AND
ZHI LONG LIU1,3
J. Med. Entomol. 52(1): 86–92 (2015); DOI: 10.1093/jme/tju003
ABSTRACT The aim of this research was to evaluate contact toxicity and repellency of the essential oil of
Pogostemon cablin (Blanco) Bentham leaves against German cockroaches (Blattella germanica) (L.) and to
isolate any active constituents. Essential oil of P. cablin leaves was obtained by hydrodistillation and analyzed by gas chromatography (GC) and gas chromatography–mass spectrometry (GC-MS). Twenty-three
components were identified in the essential oil, and the main constituents were patchoulol (41.31%), pogostone (18.06%), a-bulnesene (6.56%), caryophyllene (5.96%), and seychellene (4.32%). Bioactivitydirected chromatographic separation of the essential oil led to the isolation of pogostone, patchoulol, and
caryophyllene as active compounds. The essential oil of P. cablin leaves exhibited acute toxicity against male
B. germanica adults with an LC50 value of 23.45 lg per adult. The constituent compound, pogostone
(LC50 ¼ 8.51 lg per adult) showed stronger acute toxicity than patchoulol (LC50 ¼ 207.62 lg per adult) and
caryophyllene (LC50 ¼ 339.90 lg per adult) against the male German cockroaches. The essential oil of
P. cablin leaves and the three isolated constituents exhibited strong repellent activity against German cockroaches at a concentration of 5 ppm. The results indicated that the essential oil of P. cablin leaves and its
major constituents have good potential as a source for natural insecticides and repellents.
KEY WORDS pogostone, patchoulol, caryophyllene
Introduction
German cockroach, Blattella germanica (L.), is an important pest of homes, restaurants, and commercial
food processing facilities worldwide. They are a major
public health concern in hospitals, kitchens, and food
manufacturing plants because they are able to carry a
variety of bacteria and other pathogenic organisms.
They are the mechanical vectors to a few pathogens
that can cause disease such as food poisoning, typhoid,
and pneumonia (Brenner 1995). Currently, control of
cockroach populations is primarily dependent on continued applications of residual insecticides, such as propoxur, acephate, dimethyl 2, 2-dichlorovinyl phosphate
(dichlorvos), and pyrethroids and stomach poisons,
such as hydramethylnon, fipronil, and sulfluramid as
well dusts, such as boric acid, silica aerogel, and diatomaceous earth (Wang and Bennett 2006). The repeated
use of synthetic pesticides may disrupt naturally occurring biological control systems, result in insecticide
1
Department of Entomology, China Agricultural University, 2
Yuanmingyuan West Rd., Haidian District, Beijing 100193, China.
2
State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing
102206, China.
3
Corresponding author, e-mail: [email protected].
resistance, affect nontarget organisms, contaminate
food, present an occupational risk for workers, and
are sometimes expensive to procure (Isman 2006, Regnault-Roger et al. 2012). These problems have highlighted the need for the development of new types of
selective cockroach-control alternatives. From this
point of view, botanical pesticides, including essential
oils, are promising because they are effective, environmentally friendly, easily biodegradable, and often inexpensive. Moreover, herbal sources give a lead for
discovering new insect control agents (Regnault-Roger
et al. 2012). Repellents may play an important role in
certain situations or areas where insecticide application
is not practical or feasible (Nalyanya et al. 2000, Jung
et al. 2007). Moreover, highly repellent insecticides,
such as pyrethrum, are useful as flushing agents in
areas of low visibility to determine relative abundance
of cockroaches (Liu et al. 2011). Thus, many essential
oils and their components have been screened for repellent activity against cockroaches with some showing
potential further development (Ngoh et al. 1998, Appel
et al. 2001, Peterson et al. 2002, Paranagama and Ekanayake 2004, Yoon et al. 2009, Liu et al. 2011, Oz et al.
2013). During our mass screening program for new agrochemicals from wild plants and Chinese medicinal
herbs, essential oil of patchouli, Pogostemon cablin
(Blanco) Bentham (Family: Labiatae) leaves were
C The Author 2015. Published by Oxford University Press on behalf of the Entomological Society of America.
V
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January 2015
LIU ET AL.: CONTACT TOXICITY AND REPELLENCY OF P. CABLIN
found to possess insecticidal and repellent activity
against the German cockroach, B. germanica.
Patchouli (P. cablin) is native to Malaysia and India
and was imported into China for perfume and medicine centuries ago. Currently, patchouli occurs across
southern China, including Fujian, Guangdong,
Guangxi, Hainan, and Taiwan Province (Editorial Committee of Flora Republicae Popularis Sinicae 1977). It
can be used for cooking in some uncommon dishes and
snacks for the purposes of adding the flavor layers and
increasing nutritional value. The medicinal properties
of P. cablin leaves are well known in China (Jiangsu
New Medical College 1985). The essential oil of
P. cablin leaves exhibited high insecticidal and repellent
activity against several insects and mites, e.g., urban
ants [Camponotus melanoticus Emery, Camponotus
novogranadensis Mayr, and Dorymyrmex thoracicus
Gallardo (Albuquerque et al. 2013)], Formosan subterranean termites [Coptotermes formosanus Shiraki (Zhu
et al. 2003) and Nasutitermes corniger (Motschulsky)
(Lima et al. 2013)], the obliquebanded leafroller (Choristoneura rosaceana Harris) and the cabbage looper
(Trichoplusia ni Huebner) (Machial et al. 2010), sweetpotato whitefly [Bemisia tabaci (Gennadius) (Yang
et al. 2010)], Spodoptera littoralis (Boisduval) (Pavela
2005), and house dust mite, Dermatophagoides farinae
Hughes (Wu et al. 2010). The essential oil also exhibited strong larvicidal activity against Culex pipiens
pallens (L.) (Park and Park 2012). However, no studies
have been carried out to examine the potential of
P. cablin for the management of German cockroaches.
Thus, we decided to investigate insecticidal and repellent activity of the essential oil against German cockroaches and to isolate any active constituents from the
essential oil.
Materials and Methods
Plant and Extractions. Dried leaves of P. cablin
(5 kg, harvested from Hainan Province) were purchased at Anguo Chinese Herbs Market, Hebei Province, China, and ground to a powder in lab. The plant
was identified by Dr. Liu QR (College of Life Sciences,
Beijing Normal University, Beijing 100875, China), and
a voucher specimen (CAU-CMH-Guanghuoxiang2013-07-003) was deposited at the Department of
Entomology, China Agricultural University, Beijing,
China. Each portion of the powder was subjected to
hydrodistillation using a modified Clevenger-type apparatus for 6 h and extracted with n-hexane. The solvent
was evaporated at 40 C using a BUCHI Rotavapor
R-124 vacuum rotary evaporator (BUCHI, www.buchi.
com). Anhydrous sodium sulfate was used to remove
water after extraction. The essential oil was stored in
airtight containers in a refrigerator at 4 C for subsequent experiments.
Gas Chromatography and Mass Spectrometry.
Components of the essential oil of P. cablin leaves were
separated and identified by gas chromatography–flame
ionization
detection
(GC-FID)
and
gas
chromatography–mass spectrometry (GC-MS) using a
Agilent 6890N gas chromatograph connected to an
87
Agilent 5973N mass selective detector (www.agilent.
com). The same column and analysis conditions were
used for both GC-FID and GC-MS. They were
equipped with capillary column with HP-5MS (30 m by
0.25 mm, df ¼ 0.25 lm). The GC settings were as follows: the initial oven temperature was held at 60 C for
1 min and ramped at 10 C/min to 180 C where it was
held for 1 min, and then ramped at 20 C/min to 280 C
and held there for 15 min. The injector temperature
was maintained at 270 C. The samples (1 ll, diluted to
1% with acetone) were injected, with a split ratio of
1:10. The carrier gas was helium at flow rate of 1.0 ml/
min. Spectra were scanned from 20 to 550 m/z at two
scansper second. Most constituents were identified by
GC by comparison of retention indices with those of
the literature or of authentic compounds available in
our laboratories. The retention indices were determined in relation to a homologous series of n-alkanes
(C8–C24) under the same operating conditions. Further
identification was made by comparison of their mass
spectra with those stored in NIST 05 (Standard Reference Data, Gaithersburg, MD) and Wiley 275 libraries
(Wiley, New York, NY) or with mass spectra from literature (Adams 2007). Relative percentages of the individual components of the essential oil were obtained by
averaging the GC-FID peak area% reports.
Bioassay-Directed Fractionation. The crude
essential oil of P. cablin leaves (20 ml) was chromatographed on a silica gel (Merck 9385, 1,000 g) column
(inside diameter: 85 mm, length: 850 mm) by gradient
elution with a mixture of solvents (n-hexane, n-hexaneethyl acetate). Fractions (500 ml each) were collected
and concentrated at 40 C, and similar fractions according to thin layer chromatography (TLC) profiles were
combined to yield 12 fractions. Fractions (4–5, 8–9)
that possessed contact toxicity, with similar TLC profiles, were pooled and further purified by preparative
silica gel column chromatography (PTLC) until to
obtain the pure compound for determining structure as
caryophyllene (1, 65 mg), patchoulol (2, 145 mg), and
pogostone (3, 98 mg). The structure of the compounds
was elucidated based on high-resolution electron
impact MS and nuclear magnetic resonance. 1H and
13
C NMR spectra were recorded on Bruker Avance
DRX 500 instruments using CDCl3 as solvent with
tetramethylsilane as internal standard. EIMS were
determined on a ThermoQuest Trace 2000 mass spectrometer at 70 eV (probe). The 1H- and 13C-NMR and
MS data of the constituents were matched with previous reports (Liu et al. 2013b, Yi et al. 2013).
Insect Cultures and Rearing Conditions. German cockroaches tested in this study were from a laboratory culture (State Key Laboratory for Infectious
Disease Prevention and Control, National Institute for
Communicable Disease Control and Prevention, CDC,
China), nonresistant to conventional insecticide, that
were maintained under a photoperiod of 12:12 (L:D) h
at 26–28 C, and 70–80% relative humidity (RH). All
colonies were kept in plastic tanks at room temperature. Unsexed nymphs used in repellency testing were
1-wk old from hatching. Adult males for contact toxicity testing were 5–10 d post molt. Specimens used for
88
JOURNAL OF MEDICAL ENTOMOLOGY
this study were collected form a synchronously reared
laboratory colony of insecticide susceptible German
cockroaches. Cockroaches were supplied ad libitum
with Purina No. 5012 Rat Chow (Laboratory Animal
Centre, Chinese Academy of Medicinal Sciences, Beijing 100021), and water was provided in glass tubes
with cotton stoppers.
Topical Application Bioassay. Range-finding studies were run to determine the appropriate testing concentrations (Zhu et al. 2012). Groups of 10 adult male
cockroaches were anaesthetized with carbon dioxide
for 15 s before treatment. A serial dilution of the essential oil (7.0–1.3%, five concentrations) and pure compounds (10–0.6%, 6 concentrations) was prepared in
acetone. Aliquots of 2 ml of the solution were dispensed
from an Arnold Automatic Micro-applicator (Burkard,
Ricksmanworth, England) and applied to the dorsal
thorax of individual insects. Controls were determined
using acetone. Both treated and control cockroaches
were then transferred to glass vials (10 insects per vial)
and kept in incubators (26–28 C, 75% RH, and a photoperiod of 12:12 (L:D) h). Mortality of cockroaches
was observed at 24 h posttreatment. Five replicates
were carried out for all treatments and controls. Results
from all replicates were subjected to probit analysis
using the PriProbit Program V1.6.3 to determine LC50
(median lethal concentration) values (Sakuma 1998).
Positive control, pyrethrum extract (25% pyrethrin I
and pyrethrin II) was purchased from Fluka Chemie.
Repellent Assays. Circular white filter paper No.
40 (9 cm in diameter, Whatman International Ltd.,
Maidstone, England), divided in two halves, were used
(Liang et al. 2013). One of the halves was treated with
0.5 ml of acetone; the other half was treated with 0.5 ml
acetone solutions of essential oils or compounds. Each
essential oil was assayed at two concentrations of 5 and
1 ppm (w/v) after preliminary experiments. After solvent evaporation (2 min), each treated half disc was
then attached lengthwise, edge-to-edge, to a control
half-disc with adhesive tape to form a full disc. Precautions were taken so that the attachment did not prevent
the free movement of the insects from one half to
another, but a small distance between the filter-paper
halves was left to prevent seepage of the test samples
from one half to the other. Each filter paper was then
placed in a Petri dish (diameter 9 cm) covered with polytetrafluoroethylene to prevent insects from escaping.
The Petri dish had a seam orientated in one of four
randomly selected directions to avoid any incidental
stimuli affecting the distribution of insects. The orientation of the seam was changed in replicates. Ten
nymphs of cockroaches were released in the middle of
each filter-paper circle, and a plastic cover with some
small holes was placed on the Petri dish. Five replicates
were used. Counts of the insects present on each filter
paper disc half were made after 1 h and subsequently
at hourly intervals up to the fourth hour. No significant
difference was detected between the repellency of acetone impregnated and plain filter papers in tests
designed to check any possible influence of acetone on
the insects. The average of the counts was converted to
percentage repellency (PR) as PR ¼ 2 (C 50).
Vol. 52, no. 1
Where C is the percentage of insects on the
untreated half. The averages were then categorized
according to the following scale (Ferrero et al. 2007,
Zhang et al. 2011, Liu et al. 2013a):
Class
Percent repulsion
0
I
II
III
IV
V
>0.01–0.1
0.1–20
20.1–40
40.1–60
60.1–80
80.1–100
PR was analyzed using analysis of variance (ANOVA)
and Tukey’s tests after transforming them into arcsine
percentage values. Permethrin was used as a positive
control, because it has been widely used in the survey
of cockroach population density in China (Liu et al.
2011). Permethrin were purchased from Sigma-Aldrich
Chemical Co. (St. Louis, MO).
Results
The yield of the essential oil of P. cablin leaves (yellow) was 0.33% (v/w based on fresh weight), while its
density was determined to be 0.93 g/ml. In total, 23
components from the essential oil of P. cablin were
identified, accounting for 96.65% of the total oil. The
principal constituents of P. cablin essential oil were
patchoulol (41.31%), pogostone (18.06%), a-bulnesene
(6.56%), caryophyllene (5.96%) and seychellene
(4.32%; Table 1).
The essential oil of P. cablin exhibited contact activity
against male cockroaches with an LC50 value of
23.45 lg per adult (Table 2). The constituent compound, pogostone (LC50 ¼ 8.51 lg per adult), showed
stronger acute toxicity than patchoulol (LC50 ¼
207.62 lg per adult) and caryophyllene (LC50 ¼
339.90 lg per adult) against the male German cockroaches (Table 2).
At a concentration of 5 ppm, the essential oil and the
three isolated compounds as well as the positive control, permethrin, showed strong repellent activity (Class
V) against the German cockroaches after 1-h exposure
(Table 3). Repellency of the essential oil, patchoulol,
caryophyllene, and permethrin decreased to Class III
after 4-h exposure, whereas pogostone had Class IV
repellency against cockroaches (Table 3).
At a lower concentration of 1 ppm, the essential oil
of P. cablin and the three isolated constituents exhibited moderate repellent activity (Class III) against the
German cockroaches after 1-h exposure, whereas the
positive control, permethrin, exhibited only Class II
repellency (Table 4). Moreover, at 4-h exposure, the
essential oil of P. cablin and the constituents, caryophyllene and pogostone, still had Class II repellent activity
against the German cockroaches, whereas no repellent
activity of the positive control, permethrin, was
observed (Table 4).
Caryophyllene (1, Fig. 1), colorless oil, 1HNMR
(CDCl3, 500 MHz) d (ppm): 5.00 (1H, s, H-12), 4.88
(1H, s, H-12), 2.90 (1H, dd, J ¼ 4.1 and 10.7 Hz, H-9),
2.64 (1H, d, J ¼ 9.1 Hz, H-2), 2.33–2.37 (1H, m, H-11),
January 2015
LIU ET AL.: CONTACT TOXICITY AND REPELLENCY OF P. CABLIN
2.28 (1H, dd, J ¼ 3.6 and 8.4 Hz, H-10), 2.09–2.15 (2H,
m, H-7, H-11), 1.72–1.74 (1H, m, H-5), 1.69 (1H, br. s,
H-3), 1.65–1.67 (1H, m, H-6), 1.62 (1H, br. s, H-3.),
1.44 (1H, d, J ¼ 2.8 Hz, H-6), 1.36–1.39 (1H, m, H-10),
1.23 (3H, s, H-15), 1.03 (3H, s, H-13), 1.01 (3H, s,
H-14), 0.99 (1H, br. s, H-7); 13CNMR (CDCl3,
125 MHz): d (ppm): 151.8 (C-1), 112.8 (C-12), 63.8
(C-9), 59.9 (C-8), 50.7 (C-5), 48.9 (C-2), 39.7 (C-3),
39.1 (C-7), 34.0 (C-4), 30.2 (C-10), 29.9 (C-14), 29.8
(C-11), 27.2 (C-6), 21.6 (C-13), 17.0 (C-15). EI-MS
m/z: 222 (Mþ, 6), 121 (60), 109 (66), 107(65), 93 (100),
91 (73), 81 (51), 79 (90), 69 (60), 55 (43), 43 (63), 41
(82), 39 (31), 27 (17).
Patchoulol (2, Fig. 1), white solid, 1H NMR
(300 MHz, CDCl3þCCl4): d (ppm): 0.80 (3H, d,
J ¼ 6.6 Hz, H-15), 0.86 (3H, s, H-14), 1.04 (3H, s, H12), 1.06 (3H, s, H-13), 1.11–1.55 (9H, m), 1.55–1.75
(1H, m), 1.80–2.00 (3H, m). 13C NMR (CDCl3,
125 MHz): d (ppm): d 75.6 (C-1), 43.7 (C-9), 40.1
(C-11), 39.1 (C-4), 37.6 (C-2), 32.7 (C-6), 28.9 (C-10),
28.6 (C-8), 28.1 (C-3), 26.9 (C-7), 24.6 (C-5), 24.4
(C-12, C-13), 20.7 (C-14), 18.6 (C-15). EI-Ms: m/z 222
Table 1. Chemical constituents of the essential oil of P. cablin
leaves
No.
Compounds
Monoterpenoids
a-Pinene
b-Pinene
b-Thujene
2-Carene
b-Phellandrene
Fenchol
Borneol
Pinocarvone
4-Terpineol
a-Terpineol
Sesquiterpenoids
b-Patchoulene
Caryophyllene
a-Guaiene
Seychellene
c-Gurjunene
b-Selinene
b-Guaiene
a-Bulnesene
Spathulenol
Caryophyllene oxide
Patchoulol
Others
Cinnamaldehyde
Pogostone
Total identified
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
RIa
931
981
975
1,001
1,027
1,116
1,160
1,162
1,175
1,189
1,382
1,420
1,437
1,458
1,479
1,485
1,487
1,506
1,578
1,585
1,672
1,266
1,720
Content (%)
4.36
0.48
0.55
0.11
0.35
0.75
0.66
0.32
0.24
0.19
0.71
73.98
2.39
5.96
3.24
4.32
2.79
3.65
2.14
6.56
0.57
1.05
41.31
18.31
0.25
18.06
96.65
a
RI, retention index as determined on a HP-5MS column using the
homologous series of n-hydrocarbons.
89
(Mþ, 70), 207 (25), 161 (41), 138 (100), 125 (70), 98
(97), 43 (67), 41 (82).
Pogostone (3, Fig. 1), colorless oil, 1HNMR (CDCl3,
500 MHz): d (ppm): 5.92 (1H, d, J ¼ 0.75 Hz), 3.13
(3H, d, J ¼ 0.75 Hz), 3.07 (2H, t, J ¼ 7.64 Hz), 1.64
(1H, m), 1.54 (2H, m), 0.95 (3H, d, J ¼ 6.52 Hz), 0.93
(3H, d, J ¼ 6.52 Hz); 13CNMR (CDCl3, 125 MHz): d
(ppm): 208.3 (C-6), 181.3 (C-3), 168.8 (C-1), 160.9
(C-5), 101.5 (C-4), 99.5 (C-2), 39.7 (C-7), 32.9 (C-8),
27.8 (C-9), 22.4 (C-10), 22.4 (C-11), 20.6 (C-12);
EI-MS m/z: 224 (Mþ, 11), 209 (12), 181 (37), 168
(100), 153 (73), 85 (17), 55 (21), 43 (41).
Discussion
GC-MS results showed the major constituents in P.
cablin essential oil were patchoulol, pogostone, a-bulnesene, and caryophyllene (Table 1). Great variations
were observed in chemical composition of the essential
oils derived from various cultivation regions and harvesting times (Luo et al. 2003, Guo et al. 2004, Hu
et al. 2006). Two chemotypes, patchoulol-type and
pogostone-type, were suggested based on the chemical
compositions. The pogostone-type oil contains rich oxygenated components, especially pogostone and poor
nonoxygenated composition with patchoulol (Luo et al.
2003). However, besides the two typical chemotypes,
an interim type of P. cablin essential oil was also developed based on characteristics of 10 investigated peaks
in GC profiles (including b-patchoulene, caryophyllene,
a-guaiene, seychellene, b-guaiene, d-guaiene, spathulenol, patchouli alcohol, and pogostone; Hu et al. 2006).
Thus, for practical use, it is necessary to standardize
the essential oil of P. cablin leaves because great
variations were observed in chemical composition of
the essential oils derived from different cultivation
regions.
The essential oil of P. cablin leaves and the three
constituent compounds exhibited contact activity
against male cockroaches (Table 2). When compared
with the positive control, pyrethrum extract (25% pyrethrin I and pyrethrin II, LC50 value of 1.70 lg per
adult), the essential oil of P. cablin leaves was 14 times
less toxic (LC50 value of 23.45 lg per adult) to adult
male cockroaches (Table 2). Among the three constituent compounds, pogostone exhibited strongest acute
toxicity and stronger toxicity than the essential oil
against male B. germanica adults. It is suggested
that pogostone maybe a major contributor to the acute
toxicity of the essential oil of P. cablin leaves. Moreover,
compared with pyrethrum extract, pogostone
exhibited only one-fifth level of acute toxicity against
Table 2. Contact toxicity of the essential oil and its isolated components from P. cablin leaves against male cockroach adults
Compounds
Patchoulol
Pogostone
Caryophyllene
Crude oil
Pyrethrum extract
LD50 (mg per adult)
95% Fiducial limits
Slope 6 SE
v2
207.62
8.51
339.90
23.45
1.70
19.92-24.43
102.13-143.51
302.84-374.32
59.21-70.46
1.16-3.78
5.67 6 0.56
5.91 6 0.58
5.23 6 0.47
6.10 6 0.59
4.23 6 0.47
10.36
12.23
13.40
11.40
6.80
90
JOURNAL OF MEDICAL ENTOMOLOGY
Vol. 52, no. 1
Table 3. Repellency (PR) after two exposure times for P. cablin essential oil and its isolated constituents against the nymphs of B. germanica at a concentration of 5 ppm
Treatment
1h
2h
P. cablin
Patchoulol
Pogostone
Caryophyllene
Permethrin
80.8 6 3.6b
82.9 6 2.5a
90.2 6 2.9a
81.2 6 2.7a
88.9 6 3.2a
V
V
V
V
V
3h
73.1 6 3.7ab
69.5 6 2.7b
82.6 6 3.3a
73.4 6 2.5ab
75.4 6 2.6ab
IV
IV
V
IV
IV
4h
56.6 6 5.7b
58.7 6 2.5b
70.9 6 2.3a
70.6 6 2.8a
66.5 6 5.3ab
III
III
IV
IV
IV
47.6 6 4.7bc
40.5 6 2.6c
62.4 6 3.8a
55.2 6 2.5ab
49.3 6 2.6b
III
III
IV
III
III
Means within a column followed by the same lower case letter are not significantly different (P < 0.05,
ANOVA and Tukey’s tests).
Table 4. Repellency (PR) after two exposure times for P. cablin essential oil and its major constituents
against the nymphs of B. germanica at a concentration of 1 ppm
Treatment
1h
2h
P. cablin
Patchoulol
Pogostone
Caryophyllene
Permethrin
46.1 6 3.4a
47.7 6 1.8a
51.5 6 3.2a
53.1 6 2.2a
28.1 6 3.0b
III
III
III
III
II
3h
38.4 6 3.5a
42.7 6 1.4a
45.5 6 2.7a
43.3 6 3.7a
20.2 6 2.6b
II
III
III
III
II
34.5 6 4.3e
24.3 6 1.1d
37.9 6 2.2a
37.9 6 2.2a
14.1 6 2.2e
4h
II
II
II
II
I
23.1 6 3.7ab
13.1 6 4.7b
22.9 6 2.5ab
27.5 6 2.6a
0
II
I
II
II
-
Means within a column followed by the same lower case letter are not significantly different (P < 0.05,
ANOVA and Tukey’s tests).
14
13
H 6
5
4
H
9
1
12
8
11
10
Caryophyllene (1)
Fig. 1.
15
5
O 13
1 OH
12
H
2
3
6
7
11
15 4
H
14
2
7
10
OH
13
9
8
Patchoulol (2)
O
2 6
4
7
5
12
8
O
1 O
10
9
11
Pogostone (3)
Bioactive compounds isolated from P. cablin essential oil.
B. germanica adults (Table 2). In the previous reports,
pogostone exhibited strong contact toxicity against the
fourth-instar larvae of cabbage butterfly (Pieris rapae
L.) with an LC50 value of 32.20 lg/ml (Zeng et al.
2006) and also possessed contact toxicity to the thirdinstar larvae of oriental leafworm (Spodoptera litura F.)
and beet armyworm (Spodoptera exigua Hubner) with
LC50 values of 1,041.42 mg/liter and 519.48 mg/liter,
respectively (Huang et al. 2014). It also exerted significant antifeedant, larvicidal (oral toxicity and contact
toxicity), pupicidal, growth inhibitory, and ovicidal
properties against insects (Zeng et al. 2006, Huang
et al. 2014). The hydrolysate of pogostone was shown
to have strong acaricidal activities against the house
dustmite (D. farinae Hughes) (Wu et al. 2012). Another
major constituent in the essential oil, patchoulol was
found to possess strong acute toxicity against several
insects, e.g., the booklice (Liposcelis bostrychophila
Badonnel) (Liu et al. 2013b), Formosan subterranean
termites (C. formosanus Shiraki) (Zhu et al. 2003). It
also exhibited pupicidal and repellent activities against
three important vector mosquitoes (Aedes aegypti L.,
Anopheles stephensi Liston, and Culex quinquefasciatus
Say) (Gokulakrishnan et al. 2013) and weak larvicidal
activity of patchoulol against house mosquito (Cu.
pipiens pallens Coquillett) was also observed (Park and
Park 2012).
At a lower concentration of 1 ppm, the essential oil
of P. cablin leaves and the three constituent compounds exhibited stronger repellent activity than the
positive control, permethrin, against German cockroach nymphs (Table 4). After 4-h exposure, pogostone and caryophyllene exhibited stronger repellent
(Class II) than patchoulol (Class I; Table 4). Repellence of the essential oil of P. cablin leaves has been
demonstrated to other insects (Zhu et al. 2003, Yang
et al. 2010, Albuquerque et al. 2013, Gokulakrishnan
et al. 2013, Zhang et al. 2013). One of the main components, patchoulol also has been demonstrated to
possess repellent activity against several other insects
(Zhu et al. 2003, Albuquerque et al. 2013, Gokulakrishnan et al. 2013). However, no reports on repellence of pogostone against insects are known at the
time this article was written.
January 2015
LIU ET AL.: CONTACT TOXICITY AND REPELLENCY OF P. CABLIN
The above findings suggest that the essential oil and
the major constituent compounds of P. cablin show
potential for further development as possible natural
insecticides and repellents for cockroaches. However,
to develop a practical application for the essential oil
and its constituents as novel insecticides and repellents,
further research into the safety of the essential oil or
compounds to humans is needed. Additional studies on
the development of formulations are also necessary to
improve the efficacy and stability and to reduce cost.
Moreover, field evaluation and further investigations on
the effects of the essential oil and its constituent compounds on nontarget organisms are necessary.
The essential oil of P. cablin leaves demonstrates
strong insecticidal and repellent activity against German cockroaches. The isolated constituents, especially
pogostone exhibited strong insecticidal and repellent
activity against German cockroaches. Our results suggest the essential oil of P. cablin leaves and the three
constituents may be considered for future cockroach
management program.
Acknowledgments
This work was supported by Special Fund for Agro-scientific Research in the Public Interest (grant 201003058). We
thank Dr. Liu Quan Ru from the College of Life Sciences,
Beijing Normal University, Beijing 100875, for the identification of the investigated medicinal herb.
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Received 19 March 2014; accepted 5 September 2014.