Lupine Publishers | Current Trends on Biotechnology & Microbiology
Abstract
Objective: To evaluate the mosquito repelling effects of four
plant essential oils. Methods National standard method was
adopted to test the mosquito repelling effects of four plant essential
oils. Response surface methodology was used to analyze the
optimum ratio of the essential oils.
Results: The repellent effects ranked as follows:
Chrysanthemum oil>Calendula oil>Holly oil>Anise-star oil.
And the synergistic effects were regarded with the combination
of chrysanthemum and calendula oil. The mosquito repelling effect was up
to (93.33±2.57)% when 50ฮผL chrysanthemum oil and
18.49ฮผL calendula was mixed together in the 0.075m3 cylinder.
Conclusion: The four plant essential oils all have good mosquito repelling effect and show synergism when they are mixed
Keywords: Plant essential oil; Mosquito repelling effect; Complex with; Synergism; Response Surface methodology
Introduction
Every spring and summer, the mosquito breeding speed
increases, which brings great trouble to people’s life and work.
Not only it itches badly after the mosquito biting, but also it can
spread malaria, dengue fever, yellow fever and other diseases [1-
3]. In daily life, people will use a variety of mosquito repellents.
Repellents are divided into chemical synthesis and plant source
repellents. Among all these chemical syntheses, DEET has the
most widely use [4,5]. But in recent years, Research have shown
that DEET has a negative effect upon human body and is harmful
to the environment. As the mosquitoes have been producing
resistance to chemical repellents and the environmental pollution
of chemical repellents has been worse [6]. People are paying more
and more attention to environmentally friendly plant repellents [7].
Therefore, how to look for some new plant repellents taking place
of DEET has become a hot topic.
Plants essential oils have the following advantages: low toxicity,
without injury to the human body, environment-friendly and easily
degradable. However, the repellency and permanence of plants
essential oils are lower than synthetic repellents. Peppermint leaf
and basil extracts have high repellent activity, but still below DEET’s
[8] & Kwaka et al. [9] found that the protective rates on anopheles
arabiensis mosquitoes of sweetscented basil leaf oil, african basil
oil and DEET was respectively 91.98%, 89.75% and 93.40%, and
the protection rate of culex pipiens fatigans was 88.65%, 90.50%
and 91.30%. Weibin M [10] has studied the fumigation activity of
holly essential oil against culex pipiens pallens. Holly essential oil
had a good knockdown activity against culex pipiens pallens and
KT50 was 3.91min with 12ฮผL/L concentration.
Holly oil, chrysanthemum essential oil, calendula and star anise
oil these four kinds was chosen and assessed the repellent against
aedes albopictus for their broad source. The plant essential oils
with good repellent ability were screened out by the combination
of essential oils. It will provide experimental datum for finding
natural mosquito repellent substances.
Experimental Materials and Instruments
Experimental material
Plant essential oils: chrysanthemum essential oil, holly oil,
calendula, star anise oil. The four plant essential oils were all
extracted by steam distillation and should be stored in cool 4 ℃ and
dark condition. All oils were provided by Ningbo Dayang Limited
Company.
Test mosquitoes: Aedes albopictus female adults (3-4days old)
were taken for the research. Larvae were reared at 12:12 light/
dark photoperiod, 70±2% RH, and 26 ℃ in an insectary in Ningbo
Dayang Limited Company.
Experimental instrument
Mosquito cage(40cm×30cm×30cm), Cylinder (The cage is
composed of three cages which diameter 25cm and length 50cm.
The three cylinders are separated by baffles). The fittings were all
our own making.
Experimental Method
Determination of mosquito repellent properties of
essential oils[11]
Determination of laboratory mosquitoes and workers: Using
aggressivity experiment, 300 mosquitoes were placed in the
mosquito cage. Experimenter (men and women are not limited.
Don’t drink alcohol, tea or coffee during the test and fragrance
products are not used). The dorsum of the hand was exposed to a
40mm×40mm area and the rest of skins were sheltered closely. The
experimenters extend their hands into the mosquito cage, shaking
their hands to disperse the mosquitoes before the mosquito
mouthparts pierce the skin, as 1 mosquito stop. The number of
mosquitoes stopping on the skin during 2min were observed.
More than 30 mosquitoes were stopped, the experimenters and
mosquitoes, attack was up to standard.
Determination of effective protection time: Four qualified
experimenters (male and female were half each) were selected.
Apply a certain amount of plant essential oils being tested to a hand
which exposed to 40mm×40mm skin (closely masking the rest).
After 5 minutes, put the experimenters’ hands into the mosquito
cage for 2 minutes. Observe whether it has any mosquitoes came
landing frequency and blood feeding. Than the essential oils were
tested every fifteen minutes after that. The essential oils were
judged to invalid as long as a mosquito comes to suck blood. Record
effective protection time(min) for plant essential oils repellents.
The other hand was served as blank control.
Determination of repellent rate of compound plant essential
oil: To select the essential oils with effectively repellent from
“2.1.2”, and use Optimal in Design-Expert 8.0.6 software to design
compound experiment of essential oils of plant.100 female
mosquitoes were placed in the middle cylinder of three 0.025m3
cylinders (separated by baffles). Put the test oil in the other side
of the cylinder. Two pieces of baffle between 3 cylinders are drawn
at the same time in 2 minutes. Plug the bezel back in 10 minutes.
Record the number of mosquitoes on both sides of the cylinder.
Calculate the rate of essential oil repellent according to the
following formula.
Results
The results of plant essential oil effective protection
time
The effective time of four plant essential oils to repel
mosquitoes: Four essential oils showed different repellent effects
to Aedes albopictus. The repelling effectiveness time of the four
essential oils ranked as follows: Chrysanthemum oil> Calendula>
Holly oil> Anise-star oil. The repelling effectiveness time of
chrysanthemum essential oil was up to 151.67 minutes (Table 1).
The repellent efficiency of mosquitoes to compound plant
essential oil: According to the experimental results of four
essential oils repellent effective protection time and considering
the adaptation of essential oils aroma to the population. The
essential oil of chrysanthemum and marigold was screened and
compounded to test the rate of mosquito repellent. The results are
shown in Table 2, 3 and Figure 1.
According to Table 3, the quadric polynomial fitting equations
of the effect of plant essential oils on the rate of insect repellent was
obtained.
Figure 1: RSM analysis for interactive effects of chrysanthemum oils and calendula complexed
Table 1. The effective protection time of mosquitoes on plant essential
oils.
Table 2. The experimental results of chrysanthemum oils and calendula
complex.
Table 3. ANOVA for response surface quadratic model analysis
of variance table on chrysanthemum oils and calendula complex.
The repellent rate=85.91+15.05A+13.51B-24.76AB-10.44A2-
21.57B2, R2=0.9646
The result shows that the regression model (P<0.01) has very
significant statistical significance. The two kinds of essential oils
on the repellent rate have a significant impact (The P value of
A、B、AB、B2 was less than 0.05). The influence sequence is as
follows: Combination of chrysanthemum and marigold essential oil
AB>Chrysanthemum oil A>Calendula oil B. From the experimental
data and statistical analysis, there is obvious interaction between
the two essential oils, compound essential oil repellent rate was
significantly stronger than that of chrysanthemum and Calendula
essential oil and the two essential oils have synergistic effect.
According to the analysis of the software, the mosquito repelling
effect was 91.99% when 50ฮผL chrysanthemum oil and 18.49ฮผL
calendula was mixed in the 0.075m3 cylinder. Under this condition,
three verification experiments were carried out. The average
mosquito repelling rate was 93.33%, the RSD was 2.57%(n=3). This
result was close to the value predicted. It shows that the regression
model has a certain prediction reliability.
Discussion
The research and development of plant essential oil repellent
products cannot meet the current market demand. In this
experiment, four essential oils were used to do mosquito repellent
test on Aedes albopictus. The essential oils of Chrysanthemum
oil, Calendula, Holly oil and Anise-star oil have repellent effects
on Aedes albopictus. Among them, effects of chrysanthemum oil
and Calendula repellent are good. The combination of the two
has synergistic effect on mosquito repellent. Chrysanthemum
and Calendula belong to the composite. They smell alike and are
popular with the public. It has the potential to develop into a
new generation of mosquito repellents and insect repellents. As a
purely natural extract, it has an obvious advantage over chemically
synthesized insecticides of the same kind.
Conclusion
The composition of essential oils is very complex. Now most of
the studies focus on the use of plant essential oils as a whole or as
a single ingredient in essential oils. However, there are few studies
on the interaction between various components and essential oils.
The synergistic effects between different essential oils and different
active components need to be studied.
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