Toxicity of aqueous crude neem leaf extract against culex mosquitoes

Research article
Int J Pharm Biomed Sci 2011, 2(1), 1-3
ISSN No: 0976-5263
Research Drops
PharmaInterScience Publishers
Toxicity of aqueous crude neem leaf extract against culex
mosquitoes
G. Arunpandiyan*
Department of Biotechnology, St. Peter’s
Engineering College, Chennai, India
*Correspondence:
Mr. G. Arunpandiyan
Tel: +91 9952703849
Email: arunpandian08@gmail.com
Prevention of mosquitoes from biting is one of the major problems in the world.
Mosquitoes transmitting serious human diseases and causing millions of death
every year. The repeated use of synthetic insecticides to control mosquitoes has
created resistance to vectors and adverse environmental effects in addition to high
operational cost. Many natural products have been reported as insect antifeedants or
repellents. Azadirachta indica contains several active ingredients that are toxic to
insects and are safety to the environment. The safety evaluation of different parts of
neem preparations were made and used as an alternative insecticide in many parts
of the world. In the present study aqueous crude neem leaf extract shows 30% and
70% mortality rate of mosquitoes for 6 h and 12 h, respectively. The present study
was carried out to determine the efficacy of neem extract against culex mosquitoes
in laboratory studies and field evaluation.
Key words: Azadirachta indica, culex mosquitoes, mosquito refill apparatus, crude
neem leaf extract
Received: 24 Mar 2011 / Revised: 01 Apr 2011 / Accepted: 10 Apr 2011 / Online publication: 19 Apr 2011
1. INTRODUCTION
Azadirachta indica A.juss is a member of the mahogany
family, meliacea that is native to India and Burma, but it is
now well established in at least 30 countries [1]. Neem
contains several active constituents called limonoids. New
limonoids are still being discovered in neem, but
azadirachtin, salanin, nimbin, meliantriol are the major
components. Many of these derived products have
antifeedancy, growth regulator, sterilizing adults and
repellent against insects. Neem components show multiple
effects against insects such as mosquitoes, housefly, brown
plant hopper, cockroaches, aphids and leaf miners [2]. Neem
extracts are also proved to be soft to beneficial insect such as
earthworms, spiders and butterflies [1].
Culex mosquitoes play a vital role in transmitting
numerous human diseases like west nile, Japanese
encephalitis and filariasis [3]. Repeated use of chemical
insecticides for control of mosquitoes has lead to the
development of resistance phenomenon in many mosquito
species and also these insecticides are potential to human
health and environment. Even DEET the world’s most
popular and efficient repellent is now reported to be it won’t
protect against some dangerous mosquito species, including
aedes albimanus and it requires frequent application [4]. This
low irritancy may represent a serious risk against personal
protection and in some cases airway irritation have been
reported with the use of these products in indoor application
[5]. The numbers of new insecticides such as carbamates or
organophosphates have been used to control mosquitoes but
their low repellency allows mosquitoes to remain for
sufficient time in the environment [6]. Multiple preparations
from naturally occurring sources are repellent to certain
insects. Numerous plant products have been reported as
insect antifeedants and repellents [7]. The use of
scientifically proven non-chemical methods and limited use
of drug is being considered as safety to environment and
human health [7,8].
2. MATERIALS AND METHODS
The wild species of larvae of culex mosquito were
collected from stagnant water in and around area of Chennai,
Tamil Nadu. The larvae was transferred into a vessel
containing 500 mL water and are provided with dog biscuit
and yeast powder in the ratio of 3:2 as a nutrient. Emergences
of 10 adult mosquitoes from pupae were used for the test
conducted in a test box (45× 42× 41.5 cm 3 ) and the open end
of the test box was enclosed with mosquito nets. Field
evaluation of repellent activity of neem leaf extract was
carried out in empty room.
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G. Arunpandiyan et al., Int J Pharm Biomed Sci 2011, 2(1), 1-3
2
Five grams of fresh neem leaves were collected and
washed with distilled water. Using mortar and pestle the
neem leaves were grounded into thick paste and then 45mL
of distilled water are added to collect aqueous form of crude
neem leaf extract. This methodology is easily adopted by
local population and to be low cost. The prepared neem
extract was then transferred into a mosquito refill apparatus
as shown in Fig.1. Three replicates of same concentration
were carried out along with the control.
Fig.2. Toxicity of aqueous neem extract against culex mosquito in the
netted enclosure test box
Fig.1 Mosquito refill apparatus containing the aqueous neem leaf extract.
In the control, 1% ethanol was added instead of neem
extract. The mosquito refill apparatus is connected to the
electric vaporizer and is kept inside the test box. The
mortality rate was monitored at an interval of 6 h for 12 h.
The mortality rate was calculated by using Abbot’s formula
[9].
Fig.3. Mosquitoe get attached to the support as the vapors of neem leaf
emitted
3. RESULTS AND DISCUSSION
The mortality rate was found to be 30% and 70% for 6 h
and 12 h respectively. In the control group no mortality was
recorded. These studies indicates that neem based pesticides
are not rapidly lead to mortality but it can cause certain
changes in their activity. The biological activity of the plant
extract might be due to active compounds in neem including
phenolics, terpenoids, and alkaloids [10]. These compounds
may contribute to the death of mosquitoes. The electric
vaporizer starts to emit vapors of neem leaf extract that
disturb the mosquitoes from flying and they fall down within
10 min but didn’t kill the mosquitoes. Some mosquitoes
showed swirling movement at the end of 25 min treatment
with neem extract. The toxic effect of neem leaf extract
against culex mosquitoes in the netted enclosure was shown
in Fig.2. In the field trials, the result indicates that the
mosquitoes are repelled within 1 h and some changes are
observed in the mosquitoes are, they get attached to any
support the vapors of neem leaf extract emitted as shown in
Fig.3, and some mosquitoes shown swirling movement for a
short period as shown in Fig.4.
Fig.4. Toxicity of aqueous neem extract against culex mosquito in open areas
The result indicates that the immediate contact of
mosquitoes with the vapor of neem leaf extract leads to
increase the mortality rate as the time of treatment increases.
In addition to the insecticidal activity neem products also
reported to be anti-inflammatory, antipyretic, antimalarial,
antibacterial and anticancer activity. A paste prepared with
©2011 PharmaInterScience Publishers. All rights reserved. www.pharmainterscience.com

G. Arunpandiyan et al., Int J Pharm Biomed Sci 2011, 2(1), 1-3
neem and turmeric was found to be effective in the treatment
of scabies in nearly 814 people. A recent study has been
carried out to see the efficacy of neem extract to treat the
malarial patients severely infected with
plasmodiumfalciparum [11]. The bioactive compounds
azadirachtin showed complete ovicidal activity in the eggs of
culex tarsalis and culex quinquefasciatus. The maximum
protection was observed in methanolic and ethyl acetate
extract exerted a protection time of more than 3 h for
cucurbita maxima and c. colocynthis [12]. Repellent activity
was assessed by topical application of the test sample to the
ventral surface of test rodents and subsequent exposure of the
treated area to unfed female mosquitoes. The crude extracts
from ethnomedical plants were found to be effective as 80%
repellency against culex mosquitoes [13]. Petroleum ether
extract of Zanthoxylemlimonella were found equally effective
and afforded significantly the better protection time than the
oil of Citrusaurantifolia at 10% concentration in mustard oil
[14]. All parts of neem tree contain bitter compounds that
often have an antifeedants effect and can interfere with
hormonal processes in insects. Extracts from the neem are
often mixed with seeds to protect it against insects upon
storage [15]. The neem based pesticides does not rapidly
knockdown insects it might be an advantage it to be used as
an alternative pesticides for control of vector-borne diseases
without any side effects and are environmentally safe. The
future repellents mark an addition departure because they
could be incorporated into time release system that put active
ingredients into the air. The main action of crude neem leaf
extract was found to prevent the host seeking vectors from
landing on or biting animals. In the present study neem
leaf extract showed promising insecticidal activity against
Culex mosquitoes.
4. CONCLUSIONS
The neem leaf extracts have been therapeutically used as
general health promoters. Many researchers concluded that
neem is a “practical solution to curtail mosquito nuisance”.
Insect repellents generally work by masking human scent
which attract mosquitoes or by using a scent which naturally
avoids. An outbreak of Japanese encephalitis was apparently
ended when the children were dosed twice a day with crushed
neem leaves. In spite of its broad-spectrum action neem
based products generally doesn’t harm to natural beneficial
insects. The neem extracts are relatively less toxic, low
cost, eco-friendly and the chemical structure of neem is so
complex the insects do not develop much resistance so it
may be used as alternative pesticides to control
mosquito-borne diseases. The findings stress the need for
extended laboratory and field evaluation to determine the
optimum conditions of application in the control of
mosquitoes without any side effects to public health.
ACKNOWLEDGEMENTS
I would like to thank to Dr. K. Valivitan and
Mr. S. Antony Ceaser, Department of Biotechnology, St.
Peter’s Engineering College, for their valuable suggestions
and help.
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