Larvicidal and phytochemical properties of Callistemon rigidus R. Br. (Myrtaceae) leaf solvent extracts against three vector mosquitoes.

Sep 26, 2014Journal of vector borne diseases

Mosquito-killing effects and plant chemicals in Callistemon rigidus leaf extracts against three disease-carrying mosquitoes

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Abstract

Against Anopheles gambiae, the hexane fraction of Callistemon rigidus showed a LC50 of 17.11 ppm.

Callistemon rigidus leaf extracts contain various phytochemicals, including alkaloids, steroids, saponins, terpenoids, tannins, and phenolic compounds.
The hexane fraction was the most effective against Aedes aegypti, with an LC50 of 56.25 ppm.
Mortality rates were observed after exposing mosquito larvae to different concentrations of the extracts.
Methanol crude extract and hexane fraction displayed larvicidal activity against Culex quinquefasciatus, with LC50 values of 447.38 and 721.95 ppm, respectively.
The findings indicate potential for using plant extracts as alternative mosquito control agents.

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BACKGROUND & OBJECTIVES: Due to ever-growing insecticide resistance in mosquito vectors and environmental contamination by synthetic insecticides, plants may be a source of alternative agents for mosquito control. Therefore, the present investigation involved the determination of larvicidal and phytochemical properties of Callistemon rigidus leaf extracts against Anopheles gambiae, Aedes aegypti and Culex quinquefasciatus.

METHODS: The standard protocol of WHO was used for larval tests. Twenty five IV instar larvae were exposed to various concentrations from 125-1000 ppm for methanol crude extract (MCE), hexane (HF), chloroform (CF), ethyl acetate (EAF) and methanol (MF) fractions, from 250-2000 ppm for aqueous extract (AE) and 2500 ppm for Diclorvos. The mortality was observed 24 h post-exposure. The LC50 and LC90 values were determined by Probit analysis.

RESULTS: The phytochemical analysis revealed that the presence of alkaloids, steroids, saponins, terpenoids, tannins and phenolic compounds, lipids, fats and fixed oils in MCE; terpenoids, steroids, lipids, fats and fixed oils in HF; terpenoids in CF; tannins and phenolic compounds in EAF and alkaloids, tannins, saponins and phenolic compounds in MF. Against Ae. aegypti, HF was the most active fraction with LC50 of 56.25 ppm. Against An. gambiae, HF demonstrated its potential mosquito larvicide killing relatively all exposed larvae at all concentrations with LC50 of 17.11 ppm. Against Cx. quinquefasciatus, only MCE and HF exhibited larvicidal activity with LC50 of 447.38 and 721.95 ppm, respectively.

INTERPRETATION & CONCLUSION: Callistemon rigidus exhibited some promising larvicidal activity against medically important vector mosquitoes. Studies are indicated to identify the active compounds from this plant for developing mosquito larvicides.

Larvicidal and phytochemical properties of Callistemon rigidus R. Br. (Myrtaceae) leaf solvent extracts against three vector mosquitoes.

Abstract

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