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Methanolic extract of Agerantum conyzoides exhibited toxicity and growth disruption activities against Anopheles gambiae sensu stricto and Anopheles arabiensis larvae

View Article: PubMed Central - PubMed

ABSTRACT

Background: Vector control remains the mainstay to effective malaria management. The negative implications following persistent application of synthetic insecticides geared towards regulation of mosquito populations have necessitated prospection for ecofriendly effective chemistries. Plant-derived compounds have the potential to control malaria-transmitting mosquito populations. Previously, Agerantum conyzoides extracts have demonstrated toxicity effects on disease-transmitting mosquitoes. However, their efficacy in controlling Afrotropical malaria vectors remains unclear. Herein, the toxicity and growth disruption activities of crude methanolic leaf extract of A. conyzoides on Anopheles gambiae sensu stricto and An. arabiensis larvae were assessed.

Methods: Late third (L3) instars of An. gambiae s.s and An. arabiensis larvae were challenged with increasing doses of crude methanolic extract of A. conyzoides. The larval mortality rates were recorded every 24 h and the LC50 values determined at their associated 95% confidence levels. ANOVA followed by Post-hoc Student-Newman-Keuls (SNK) test was used to compare results between treatment and control groups. Phytochemical profiling of the extract was performed using standard chemical procedures.

Results: Treatment of larvae with the methanolic extract depicted dose-dependent effects with highest mortality percentages of ≥ 69% observed when exposed with 250 ppm and 500 ppm for 48 h while growth disruption effects were induced by sublethal doses of between 50–100 ppm for both species. Relative to experimental controls, the extract significantly reduced larval survival in both mosquito species (ANOVA, F(8,126) = 43.16776, P < 0.001). The LC50 values of the extract against An. gambiae s.s ranged between 84.71–232.70 ppm (95% CI 81.17–239.20), while against An. arabiensis the values ranged between 133.46–406.35 ppm (95% CI 131.51–411.25). The development of the juvenile stages was arrested at pupal-larval intermediates and adult emergence. The presence of alkaloids, aglycone flavonoids, triterpenoids, tannins and coumarins can partly be associated with the observed effects.

Conclusion: The extract displayed considerable larvicidal activity and inhibited emergence of adult mosquitoes relative to experimental controls, a phenomenon probably associated with induced developmental hormone imbalance. Optimization of the bioactive compounds could open pathways into vector control programmes for improved mosquito control and reduced malaria transmission rates.

No MeSH data available.


Related in: MedlinePlus

Development disruption effects of A. conyzoides extract to An. gambiae s.s and An. arabiensis. a Demelanized An. gambiae s.s larvae (b) Abnormal An. gambiae s.s larval-pupal intermediate (c) Arrested adult emergence in An. gambiae (d) Abnormal An. arabiensis larval-pupal intermediate (e) Failed adult emergence in An. arabiensis (f) An. gambiae s.s control larvae (g) Normal An. gambiae s.s larval-pupal intermediate (h) An. arabiensis control larvae (i) Normal An. arabiensis larval-pupal intermediate (Light microscopy visualization conducted at magnification 25×)
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Fig2: Development disruption effects of A. conyzoides extract to An. gambiae s.s and An. arabiensis. a Demelanized An. gambiae s.s larvae (b) Abnormal An. gambiae s.s larval-pupal intermediate (c) Arrested adult emergence in An. gambiae (d) Abnormal An. arabiensis larval-pupal intermediate (e) Failed adult emergence in An. arabiensis (f) An. gambiae s.s control larvae (g) Normal An. gambiae s.s larval-pupal intermediate (h) An. arabiensis control larvae (i) Normal An. arabiensis larval-pupal intermediate (Light microscopy visualization conducted at magnification 25×)

Mentions: Besides lethality of high doses, the extract remarkably accelerated the growth of larvae into pupae resulting into incomplete melanization and abnormal dead larval-pupal intermediates as depicted in Fig. 2. At sublethal doses of 50 ppm and 100 ppm, molting continued normally but the development of the immature stages was greatly affected. Microscopic examination of the dead immature stages at 25× magnification revealed morphological defects evident as:- abnormal dead larval-pupal intermediates and emergent adults with mouthparts and wings folded within the pupal exuvium (Fig. 2). The adults that luckily emerged from the extract-treated water were unable to escape from the pupal caste and died on the surface of test solution. Overall, the extract at sublethal doses induced prolonged larval phase duration by 7 more days prior to pupation relative to negative controls (2 days).Fig. 2


Methanolic extract of Agerantum conyzoides exhibited toxicity and growth disruption activities against Anopheles gambiae sensu stricto and Anopheles arabiensis larvae
Development disruption effects of A. conyzoides extract to An. gambiae s.s and An. arabiensis. a Demelanized An. gambiae s.s larvae (b) Abnormal An. gambiae s.s larval-pupal intermediate (c) Arrested adult emergence in An. gambiae (d) Abnormal An. arabiensis larval-pupal intermediate (e) Failed adult emergence in An. arabiensis (f) An. gambiae s.s control larvae (g) Normal An. gambiae s.s larval-pupal intermediate (h) An. arabiensis control larvae (i) Normal An. arabiensis larval-pupal intermediate (Light microscopy visualization conducted at magnification 25×)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC5120420&req=5

Fig2: Development disruption effects of A. conyzoides extract to An. gambiae s.s and An. arabiensis. a Demelanized An. gambiae s.s larvae (b) Abnormal An. gambiae s.s larval-pupal intermediate (c) Arrested adult emergence in An. gambiae (d) Abnormal An. arabiensis larval-pupal intermediate (e) Failed adult emergence in An. arabiensis (f) An. gambiae s.s control larvae (g) Normal An. gambiae s.s larval-pupal intermediate (h) An. arabiensis control larvae (i) Normal An. arabiensis larval-pupal intermediate (Light microscopy visualization conducted at magnification 25×)
Mentions: Besides lethality of high doses, the extract remarkably accelerated the growth of larvae into pupae resulting into incomplete melanization and abnormal dead larval-pupal intermediates as depicted in Fig. 2. At sublethal doses of 50 ppm and 100 ppm, molting continued normally but the development of the immature stages was greatly affected. Microscopic examination of the dead immature stages at 25× magnification revealed morphological defects evident as:- abnormal dead larval-pupal intermediates and emergent adults with mouthparts and wings folded within the pupal exuvium (Fig. 2). The adults that luckily emerged from the extract-treated water were unable to escape from the pupal caste and died on the surface of test solution. Overall, the extract at sublethal doses induced prolonged larval phase duration by 7 more days prior to pupation relative to negative controls (2 days).Fig. 2

View Article: PubMed Central - PubMed

ABSTRACT

Background: Vector control remains the mainstay to effective malaria management. The negative implications following persistent application of synthetic insecticides geared towards regulation of mosquito populations have necessitated prospection for ecofriendly effective chemistries. Plant-derived compounds have the potential to control malaria-transmitting mosquito populations. Previously, Agerantum conyzoides extracts have demonstrated toxicity effects on disease-transmitting mosquitoes. However, their efficacy in controlling Afrotropical malaria vectors remains unclear. Herein, the toxicity and growth disruption activities of crude methanolic leaf extract of A. conyzoides on Anopheles gambiae sensu stricto and An. arabiensis larvae were assessed.

Methods: Late third (L3) instars of An. gambiae s.s and An. arabiensis larvae were challenged with increasing doses of crude methanolic extract of A. conyzoides. The larval mortality rates were recorded every 24 h and the LC50 values determined at their associated 95% confidence levels. ANOVA followed by Post-hoc Student-Newman-Keuls (SNK) test was used to compare results between treatment and control groups. Phytochemical profiling of the extract was performed using standard chemical procedures.

Results: Treatment of larvae with the methanolic extract depicted dose-dependent effects with highest mortality percentages of ≥ 69% observed when exposed with 250 ppm and 500 ppm for 48 h while growth disruption effects were induced by sublethal doses of between 50–100 ppm for both species. Relative to experimental controls, the extract significantly reduced larval survival in both mosquito species (ANOVA, F(8,126) = 43.16776, P < 0.001). The LC50 values of the extract against An. gambiae s.s ranged between 84.71–232.70 ppm (95% CI 81.17–239.20), while against An. arabiensis the values ranged between 133.46–406.35 ppm (95% CI 131.51–411.25). The development of the juvenile stages was arrested at pupal-larval intermediates and adult emergence. The presence of alkaloids, aglycone flavonoids, triterpenoids, tannins and coumarins can partly be associated with the observed effects.

Conclusion: The extract displayed considerable larvicidal activity and inhibited emergence of adult mosquitoes relative to experimental controls, a phenomenon probably associated with induced developmental hormone imbalance. Optimization of the bioactive compounds could open pathways into vector control programmes for improved mosquito control and reduced malaria transmission rates.

No MeSH data available.


Related in: MedlinePlus