Available online at www.pelagiaresearchlibrary.com
Pelagia Research Library
Asian Journal of Plant Science and Research, 2011, 1 (4):33-38
ISSN : 2249 – 7412
Production of natural insecticide from Neem leaves (Azadirachta indica)
Kwasi Opoku Boadu, Samuel Kofi Tulashie, Michael Akrofi Anang, Jerome Desire Kpan
Department of Chemistry, Industrial Chemistry Section, School of Physical Sciences, University of Cape Coast, Cape Coast, Ghana
______________________________________________________________________________
ABSTRACT
Research into the insecticidal effects of azadirachtin, a limonoid from the Neem tree
(Azadirachta indica) has been ongoing for some 30 years. Its strong antifeedant, insect growth regulatory and reproductive effects are now well understood and documented. Antiffedancy varies markedly between species with mosquitoes being particularly sensitive to azadirachtin.
The mode of action of azadirachtin lies in (i) effects on deterrent and other chemoreceptors resulting in antifeedancy and (ii) direct effects on most other tissues studied resulting in an overall loss of fitness of the insect. The complexity of the molecular structure of azadirachtin has precluded its synthesis for pesticide use although novel synthesis of the parent molecule is now almost complete and research into simpler mimetic substances is ongoing. Applied research has concentrated on a variety of natural formulations from neem seed kernels which contain azadirachtin together with several structurally related molecules. This study brings the reader up to date with both pure and applied research in the field, and provides a detailed overview of present thinking into the mode of action of azadirachtin. Wherever possible comparative approaches have been made between species of the effects of pure azadirachtin and areas for future research are indicated.
Keywords: Azadirachtin indica; Neem leaves; Green Chemistry, Synthetic Insecticide,
Limonoid; triterpense; Pest control; Antifeedancy; Reproduction; Beta-sitossterol Mode of action. _____________________________________________________________________________
INTRODUCTION
In developing countries, the losses of crops due to pest, plant disease and competition from weeds is great. In households, pest and insects such as mosquitoes, cockroaches, mice etc pose risks such as the destruction of furniture, clothing and to the causation of various diseases, most seriously; malaria.
33
Pelagia Research Library
Kwasi Opoku Boadu et al
Asian J. Plant Sci. Res 2011, 1(4):33-38
Res.,
_____________________________________________________________________________
Pesticides/insectides produced to kill these pests in order to prevent these damages, also tend to have adverse effects on humans in various ways, most especially those produced from synthetic materials. These adverse effects of headache, dizziness, catarrh and other factors make this topic worth investigating. The insecticides range from agricultural to household pesticides. Every category has its own effect, both on the targeted pest/insect and the environment in which it lives. This research targets insecticide produced from natural products and the need to choose these pesticides rather than those of synthetic origin.[1] origin. The neem tree is drought resistant and thrives normally in areas with sub-arid to sub-humid sub conditions, with an annual rainfall between 400-1200mm. Neem is a life giving tree, especially
400 1200mm. for the dry coastal, southern districts. [2]
It has been observed that the various medicinal values of neem are its constituent phytochemicals present. The seed kernels of neem yield about 90% of a fixed oil comprised primarily of glycerides. The yellow, bitter oil has a garlic-like odor and contains approximately 2% of bitter garlic like principles including nimbidin, nimbrin, nimbinin, nimbidol and other related minor limonoid rela triterpense [Windholz, 1987] [3] All parts of the tree yield beta-sitosterol. Azdirachtin is the
[3].
sitosterol. most complex secondary metabolite present in the plant.
The neem is a bitter tonic herb that reduces inflammation and clears toxins, while promoting healing and improving all body functions. Apart from this,it has parasitic, insecticidal this,it spermicidal properties and hence destroys a wide range of organisms according to [Dixit 1988]
[4].
The Chemical structure of Azadirachtin is shown in scheme 1 below.
Figure 1: Chemical structure of Azadirachtin.
34
Pelagia Research Library
Kwasi Opoku Boadu et al
Asian J. Plant Sci. Res., 2011, 1(4):33-38
_____________________________________________________________________________
MATERIALS AND METHODS
Study area
The research was conducted in the University of Cape Coast, Cape Coast, Ghana, West
Africa.The samples of the neem leaves were obtained from Apewosika, Kokoado and
Amamoma; communities around the University of Cape Coast campus. The plant was identified according to the description by Felter and Lloyd [1898 [5] and later authenticated by comparing with voucher specimens at the herbarium section of the University of Cape Coast.
Preparation of the insecticide
A weighed quantity of dried neem leaves were blended into powder with a blender to obtain a homogeneous mixture. The dried neem powder was used for making the insecticide while the fresh blended leaves were used for the extraction.
10.00g of the powdered neem leaves sample was weighed into a 200ml beaker. 5.0g of a binding material (starch) was weighed and added to the neem sample in the beaker. The mixture was stirred to obtain a homogeneous mixture. 5.0ml of distilled water was added gradually to the mixture in quantity of 1.0ml while stirring [6].
The cleaned weighed beaker (M1) was filled with the mixture and the weight taken (M2). To obtain the true weight of the prepared mixture (M), the difference between the weights M2and
M1was computed as M. thus M= M2-M1
The beaker with the wet insecticide mixture was dried in an oven at a regulated temperature range of 30o-40oC. The sample was weighed after every 10 minutes until a constant dried weight was obtained after 30minutes. The beaker with the dried insecticide was weighed to obtain the accurate weight by deducting from that of M.
Statistical analysis
Data were analyzed statistically using student’s t-test. The results were expressed at the mean (±)
S.D. the significance of the differences between control and the test groups were determined by the student’s t-test and the values of P 