ABSTRACT
The
research was carried out to investigate phytochemicals present and mosquito
larvicidal activity of Solanum melogena ethanolic
leaves extract in laboratory conditions. The leaves were collected from garden
around Morre area of Sokoto North, identified and authenticated by taxonomist at
herbarium laboratory, Usmanu Danfodiyo University, Sokoto; ethanolic leaves
extract was obtained using cold maceration method, Phytochemical analysis
showed presence of saponins, tannins, terpenes, alkaloids, and flavonoids in
excess, while steroids were found in trace and volatile oils were not detected.
To determine toxicity of the leaves extract on Culex quinquefasciatus larvae, the larvae were obtained from
drainage around Faculty Building of Sokoto State University, Sokoto. Ten mosquito
larvae were transferred in to beakers containing different concentrations and
each concentration was replicated five times. Mortality was recorded after every
six hours up to 24 hours. Finally, it was observed that mortality ranged
between 52% and 100%; 10mg/ml showed
highest mortality 100% (10.0) followed by 8mg/ml 86% (8.6) then 6mg/ml 68%
(6.8), also 4mg/ml showed 57% (5.7), while 2mg/ml showed least mortality rate
of 52% (5.2). Statistically, significant difference was observed at p<0.05
using one way analysis of variance. The present investigation clearly exhibits that Solanum melogena leaves extract could
serve as a potential larvicidal agent against mosquito larvae Culex
quinquefasciatus.
CHAPTER ONE
1.0 Introduction
Mosquito vectors are solely responsible for transmitting
diseases such as malaria, dengue, Japanese encephalitis, and lymphatic
filariasis. There are 350–500 million clinical cases
of malaria per year with about one million deaths. In India, around two million
malaria cases are being reported annually (Kumar et al., 2007). Panicker et al., (1981) incriminated Anopheles
sub pictus as a vector of malaria in the coastal areas of south India. It is a
widespread and abundant species in India. It breeds profusely in water
collections and fallow rice fields of southern India, where the larval
incidence was high throughout the year (Rao, 1984; Dhanda and Kaul, 1980).
Culex quinquefasciatus is a vector of lymphatic filariasis affecting 120 million
people worldwide, and approximately 400 million people are at risk of
contracting filariasis worldwide, resulting into the annual economic loss of
1.5 billion dollars (WHO, 2002). Lymphatic filariasis is a serious public health problem in
India, comprising of one third of infected population of the world (WHO, 1996).
Insecticide applications,
although highly efficacious against the target species vector control, is
facing a threat due to the development of resistance to chemical insecticides resulting
in rebounding vectorial capacity (Liu et
al., 2006). It has also provoked undesirable effects, including toxicity
to non-target organisms and fostered environmental and human health concerns
(Casida and Quistad 2000; Lee et al., 2001; Yang et al., 2002). Extracts or essential
oils from plants may be alternative sources of mosquito control agents, since
they constitute a rich source of bioactive compounds that are biodegradable into
nontoxic products and potentially suitable for use to control mosquitoe larvae
(Amer and Mehlhorn, 2006; Rahuman and Venkatesan, 2008; Rahuman et al., 2009). It has been reported that this plant contain
betulinic acid, a steroidal pent acyclic triterpenoid, as one of the
phytomolecule which has proved to be a potent lead for several pharmacological activities
like anti-inflammatory and anti-tumour (Mukherjee et al., 1995; Chou et al. 2000). Ling et al., (2005) reported that the
procyanidins were isolated from the seedpods of Solanum melogena showing a strong antioxidant activity. Solanum melogena is shown to have
anti-arrhythmic action and also significantly inhibits rabbit platelet aggregation
(Li et al., 1990). Constituents of the
petals showed antioxidant properties and antibacterial bioactivities (Xingfeng et al., 2010). The crude methanol leaf
extracts of Solanum melogena showed
good larvicidal activity against the early second, third, and fourth larvae of Culex quinquefasciatus, Aedes aegypti, and Anopheles stephensi
(Govindarajan, 2010) and the larvicidal efficacy of the aqueous and ethanol extracts
from Solanum melogena was effective to control Anopheles culicifacies, Aedes stephensi, Aedes aegypti, and Culex quinquefasciatus (Bansal et
al., 2009).
1.1
Statement of the Problem
Although, insecticides applications are highly efficacious
against the species, vector control is facing a threat due to the development
of resistance to chemical insecticides resulting in rebounding vectorial
capacity (Liu et al., 2006). It has also provoked
undesirable effects, including toxicity to non-target organisms and fostered
environmental and human health concerns (Casida and Quistad, 2000; Lee et al., 2001; Yang et al., 2002).
The efficacy of Phytochemicals against mosquito larvae can vary
significantly depending on plant species, plant parts used, age of plant parts
(young, mature or senescent), solvent used during extractions as well as upon the
available vector species. (Shaalan et al.,
2005), have described the
existence of variations in the level of effectiveness of phytochemical
compounds on target mosquito species vis-a-vis
plant parts from which these were extracted, responses in species and their
developmental stages against the specified extract, solvent of extraction,
geographical origin of the plant, photosensitivity of some of the compounds in
the extract, effect on growth and reproduction. Changes in the larvicidal
efficacy of the plants extracts occurred due to geographical origin of the
plant, (Shaalan et al., 2005).
1.2
Justification
Extracts or essential oils from plants may be alternative
sources of mosquito control agents, since they constitute a rich source of
bioactive compounds that are biodegradable into nontoxic products and
potentially suitable for use to control mosquito larvae (Amer and Mehlhorn, 2006; Rahuman and Venkatesan, 2008; Rahuman et al., 2009).
Furthermore, Active bio chemicals
found in different plants species were non toxic to the people living in that
particular environment.
1.3
Aim and Objectives
Aim:
The aim of this research is to carryout investigation on
phytochemical analysis and mosquito
larvicidal activity of Solanum melogena.
Objectives were:
·
To carryout
preliminary phytochemical screening of the ethanolic extracts of Solanum melogena.
·
To find out
the most effective dose of the plant extract on mosquito larvae of Culex quinquefasciatus.
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