Isolation and Partial Purification of Lectins from the Stem Bark of Ordeal Tree (Erythrophleum suaveolens) and their Possible Larvicidal Activities against Culex quinquefasciatus
– Isolation and Partial Purification of Lectins from the Stem Bark of Ordeal Tree (Erythrophleum suaveolens) and their Possible Larvicidal Activities against Culex quinquefasciatus –
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ABSTRACT
Lectins from the saline extract of Erythrophleum suaveolens stem bark, were isolated, partially purified, characterized and evaluated in terms of their larvicidal properties against Culex quinquefasciatus. Purification was done by precipitation with ammonium sulfate at 20% – 90% saturation. The ammonium sulfate precipitate was subjected to gel filtration using Sephadex G-75 resin.
The two fractions with the highest heamaglutinating activity were further subjected separately to ion-exchange chromatography using Sp- Sephadex C-50 resin. The lectins in the crude extract and the purified lectins appeared as five bands at positions 38KDa, 28KDa, 26KDa, 11KDa and 9KDa on a SDS-PAGE electrophoregram.
The lectins were found to be stable at the temperature range of 30- 600C and pH range of 3-7. The carbohydrate content of the crude extract, Gel I, Gel II, Ion I and Ion II peaks were 0.04%, 0.04%, 0.03%, 0.02%, and 0.01% respectively and showed specificity to mannose and galactose.
A series of nine concentrations of the extracts ranging from 0.0001 mg/L, 0.001 mg/L, 0.01 mg/L, 0.1 mg/L, 1mg/L, 5mg/L, 10 mg/L, 50 mg/L and 100mg/L were tested against the third instar larvae of Culex quinquefasciatus and their percentage mortalities and LC50 values were obtained.
The crude extract of Erythrophleum suaveolens show very high larvicidal activity with 96% mortality achieved at a concentration of 100 mg/L and had an LC50 of 4.39 mg/L.
The gel peaks of Erythrophleum suaveolens showed larvicidal activities to Culex quinquefasciatus larvae with 74.67% and 69.33% mortality achieved at a concentration of 100 mg/L and had LC50 of 43.73mg/L and 43.65mg/L respectively.
The ion exchange purified extracts of Erythrophleum suaveolens showed low larvicidal activity to Culex quinquefasciatus larvae with 10.67% and 9.33% mortality achieved at a concentration of
100 mg/L respectively. These results suggest that the saline stem bark extract of Erythrophleum suaveolens is promising as a larvicide against mosquito larvae and can be used directly in small volumes in aquatic habitats and in mosquito population management programme.
INTRODUCTION
Insect transmitted diseases are important health problems in the world. These vectors are insects such as mosquitoes (Roberts, 2002).
Mosquitoes are among the most important group of insects in terms of their medical importance to both humans and animals. Most insecticides are non-selective, not biodegradable and can be harmful to other organisms and to the environment.
An approach to obtain new efficient, safe and selective insecticides is the study of natural models such as the defensive mechanisms of plants (Ciccia et al., 2000).
Bioactive organic compounds produced by plants can act as repellant, food deterrents, growth inhibitors, and toxins (Ezeonu et al., 2001; Carlini and Grossi-de-Sá, 2002).
Thus, crude plant extracts have been screened as natural and biodegradable forms to control pests and vectors of infectious diseases (Omena et al., 2007).
Plant essential oils are, in some cases, highly active and economically viable for Insect control (Silva et al., 2008). The larvicidal activity of essential oils from Hyptis fruticosa, Hyptis pectinata and Lippia gracilis has been reported (Silva et al., 2008).
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CSN Team.
