EFFECT OF SOME ETHNO-MEDICINAL PLANTS EXTRACTS ON CULEX QUINQUEFASCIATUS (SAY)
EFFECT OF SOME ETHNO-MEDICINAL PLANTS EXTRACTS ON CULEX QUINQUEFASCIATUS (SAY)
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Date
2017-01
Authors
UBANDOMA, SAIDU YAHAYA
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Abstract
Studies on the ethanolic and aqueous leaf extracts of some ethno-medicinal plants
(Annona senegalensisPers,Hibiscus lunariifoliusWilld, HibiscusasperHook.f., Vernonia
amygdalina, HibiscuscannabinusLinn, H. SabdariffaLinn, UrenalobataLinn, H.
esculentus Linn.) for the control of Culex quinquefasciatuswas carried out from
December, 2013 to July, 2016,in Zaria metropolis, Kaduna State, Nigeria.Specimens of
the selected plants were obtainedfrom Zango, Hanwa, Samaru, Bomo, Danmagaji and
Dakache areas and identified by Herbarium Keepersin the Herbarium Unit of the
Department of Botany, Ahmadu Bello University Zaria and voucher numbers given.
Fractions of the leaf extracts were separated usingThin Layer Chromatography (TLC)
and Column chromatography; and the active compounds were characterized by Nuclear
Magnetic Resonance (NMR) spectroscopy. Secondary metabolites recovered from the
leaf extracts include sterols, flavonoids, saponins and tannins.Anthracenes and combined
anthracenes were present only in the leafextracts of Annona senegalensisand Vernonia
amygdalina except anthraquinones. Gravid females of Culexquinquefasciatuswere
collected from 6:00 am to 8:00 am in the morning from classrooms of the Faculty of
Science and Education, ABU, Zaria. They were introduced into rearing cages and
provided with oviposition bowls containing water for egg laying. The eggs, laid in rafts
hatched into 1st instar Larvae which were fed on Baker‟s Yeast once a day initially, and
twice during the later stages of the development. The larvicidal bioassay followed the
World Health Organization (2005) standard protocols in “Guidelines for laboratory and
field testing of mosquito larvicides‟‟. A narrower range of 4 concentrations (10.00mg/ml,
5.00mg/ml, 2.50mg/ml and 1.25mg/ml) was prepared and batches of 25 4
th larval instar
x
were introduced in four replicates. Probit analysis and one way ANOVA were used to
determine LC50, larval mortality and inhibition of adult emergence. Student t-test was
employed to determine the difference between ethanolic and aqueous leaf extracts of A.
senegalensis. Similarly, t-test was used to analyze differences in oviposition parameters
between Culex quinquefasciatusadults reared in ethyl acetate leaf fraction (LC50, 3.7
mg/ml) of A. senegalensis and those reared in water (control).The more effective
extractscomprisedA. senegalensis (LC50: 0.457),Vernonia amygdalina(LC50:
0.536),Hibiscusesculentus (LC50:0.571), and Urena lobata (LC50:0.625). However, A.
senegalensisleaf extract was the most effective. The least effect was observed in Hibiscus
asperleafextract with the LC50 of 4.032. Moderate effectivenesswasobservedin Hibiscus
cannabinus, Hibiscus sabdariffaand Hibiscus lunariifoliusextractswith LC50:1.237,
LC50:2.193 and LC50:2.568, respectively. The larvicidal activity of the ethanolic leaf
extract was higher than that of the aqueous extract at all concentrations, especially, at the
highest concentration, 10 mg/ml (24.25/25 or 99% and 7.00 or 28%, respectively).
Ethanol dissolves bipolar compounds that have insecticidal properties. The effects of the
leaf extract of A. senegalensis on larval histopathology resulted in apolysis of the head
cuticle, separation of the basement membrane from the midgut epithelium and the
degeneration of the microvilli. There was reduction in developmental stages of Culex
quinquefasciatus as there was 101 viable eggs produced in the control compared to 70
recorded in the one laid by mosquitoes that survived treatment. The percentage of female
to male in the control was 49% and 51%, respectively; while ethyl acetate fraction was
32% for female and 68% for male. The differences in the means were significant in all
cases except in the sex ratios. Bioassay with ergosterol, the isolated compound, recorded
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80.00% larval mortality at dose 1000 µg/ml. In consideration of its high activity, it can,
therefore, be suggested that ergosterol, might be responsible for the mortality observed in
4
th instar larvae, histological deformities, inhibition of emergence of survived larvae,
reduction in reproductive ability of survived adult, low egg count and hatching success,
and reduction in sizes of the second filial generation (F2) of Culex quinquefasciatus.
Ergosterol is a component of cell membrane of eukaryotes and in peroxidestate; it has
been shown to cause disruption of cellular constituents. Ergosterol has been reported to
have cytotoxicity and antimicrobial effects. The results of this study suggest that leaf
extracts and leaf fractions of A. senegalensis, Vernonia amygdalina, Urena lobata and
Hibiscus esculentuscontain sterols like ergosterol whichhave insecticidal properties. The
formulation of ergosterol as insecticide may contribute immensely to the control of
mosquito vector diseases.
Description
A THESIS SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES,
AHMADU BELLO UNIVERSITY, ZARIA
IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD
OF
DOCTOR OF PHYLOSOPHY IN ZOOLOGY.
DEPARTMENT OF ZOOLOGY,
FACULTY OF LIFE SCIENCES,
AHMADU BELLO UNIVERSITY,
ZARIA, NIGERIA
Keywords
EFFECT,, ETHNO-MEDICINAL,, PLANTS EXTRACTS,, CULEX QUINQUEFASCIATUS (SAY)