2. Materials and methods
2.1. Experimental samples and the extraction of essential oils
The experimental samples of the plants were collected in
Guangxi and Yunnan province, China respectively. The species of
plants were identified by Dr. Liu, Q.R. (College of Life Sciences,
Beijing Normal University, Beijing, China) and voucher specimens
were deposited at the Herbarium (BNU) of College of Life Sciences,
Beijing Normal University. The background information about the
samples was summarized in Table 1. The branches with leaves of
the six Murraya species were air dried and grounded to powders.
The hydro-distillation of sample powders was done using a modi-
fied Clevenger type apparatus for 6 h to get the essential oils. The
extra water was removed out by adding anhydrous sodium sulphate.
The pure essential oils were removed out and their volumes
were recorded. The essential oils were stored in airtight containers
in a refrigerator at 4 ◦C for subsequent experiments. The results of
this step were listed in Table 2.
2.2. Insects
A laboratory-reared strain of the red flour beetles maintained in
the dark cabinet of an incubator at 29 ± 1 ◦C and 70–80% relative
humidity for the last 2 years. The larvae were picked up and reared
in glass containers (0.5 L) containing wheat flour at 12–13% moisture
content mixed with yeast (10:1, w/w). Insects used in all of the
experiments were approximately 7 ± 2 days old adults.
2.3. Gas chromatography and mass spectrometry
Chemical components of essential oils were identified with
GC/MS. All the experiments were carried out on a gas chromatographic
instrument (Agilent 6890N) which was equipped with gas
chromatography-flame ionization detector (GC-FID) and hooked to
a mass spectrometer (Agilent 5973N). A capillary column of HP-
5MS (30 m × 0.25 mm × 0.25 m) was selected for this work. The
column temperature was initially set at 50 ◦C for 2 min, and then
gradually ramped at 2 ◦C/min to 150 ◦C. After maintaining at this
temperature for 2 min, the column temperature were increased at
a speed of 10 ◦C/min until researched at 250 ◦C, where it was kept
for 5 min before the sample was introduced. The carrier gas was
helium with a linear velocity of 1.0 mL/min. The scan range was
from 50 to 550 m/z and samples were injected atthe temperature of
250 ◦C. The injected sample was 1 L of 1% n-hexane solution
2. Materials and methods2.1. Experimental samples and the extraction of essential oilsThe experimental samples of the plants were collected inGuangxi and Yunnan province, China respectively. The species ofplants were identified by Dr. Liu, Q.R. (College of Life Sciences,Beijing Normal University, Beijing, China) and voucher specimenswere deposited at the Herbarium (BNU) of College of Life Sciences,Beijing Normal University. The background information about thesamples was summarized in Table 1. The branches with leaves ofthe six Murraya species were air dried and grounded to powders.The hydro-distillation of sample powders was done using a modi-fied Clevenger type apparatus for 6 h to get the essential oils. Theextra water was removed out by adding anhydrous sodium sulphate.The pure essential oils were removed out and their volumeswere recorded. The essential oils were stored in airtight containersin a refrigerator at 4 ◦C for subsequent experiments. The results ofthis step were listed in Table 2.2.2. InsectsA laboratory-reared strain of the red flour beetles maintained inthe dark cabinet of an incubator at 29 ± 1 ◦C and 70–80% relativehumidity for the last 2 years. The larvae were picked up and rearedin glass containers (0.5 L) containing wheat flour at 12–13% moisturecontent mixed with yeast (10:1, w/w). Insects used in all of theexperiments were approximately 7 ± 2 days old adults.2.3. Gas chromatography and mass spectrometryChemical components of essential oils were identified withGC/MS. All the experiments were carried out on a gas chromatographicinstrument (Agilent 6890N) which was equipped with gaschromatography-flame ionization detector (GC-FID) and hooked toa mass spectrometer (Agilent 5973N). A capillary column of HP-5MS (30 m × 0.25 mm × 0.25 m) was selected for this work. Thecolumn temperature was initially set at 50 ◦C for 2 min, and thengradually ramped at 2 ◦C/min to 150 ◦C. After maintaining at thistemperature for 2 min, the column temperature were increased ata speed of 10 ◦C/min until researched at 250 ◦C, where it was keptfor 5 min before the sample was introduced. The carrier gas washelium with a linear velocity of 1.0 mL/min. The scan range wasfrom 50 to 550 m/z and samples were injected atthe temperature of250 ◦C. The injected sample was 1 L of 1% n-hexane solution
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