Meliaceae plants and vector control of malaria: Larvicidal studies of Ekebergia senegalensis A Juss and Cedrela odorata Linn

Background: Plant species are known to produce metabolites of value used as pest control that target specific organisms. Two Meliaceae plants identified and tested for their larvicidal activity against the fourth instars larva of Anopheles gambiae, the primary vector of malaria in sub-Saharan Africa.

Methods: Dried powdered leaves of these medicinal plants were extracted by maceration in methanol. The most active extracts from Ekebergia senegalensis and Cedrela odorata were fractionated into hexane, chloroform and ethyl acetate solvents by liquid-liquid partitioning. Larvae of A. gambiae were collected. Toxicity was evaluated by exposing 4th instar larvae to different concentrations (62.5 – 1000 µg/mL) of extracts, larval mortality and LC₅₀ values were determined after 24h.

Results: The hexane fraction of E. senegalensis displayed an absolute mortality at 0.63 mg/mL with an LC₅₀ value of 0.81 mg/mL; also hexane soluble fraction of C. odorata had inhibitory toxicity on mosquito larvae with an LC₅₀ value of 0.83 mg/mL. Results were compared to those of larvae exposed to N,N-diethyl-3-methylbenzamide (1.09 mg/mL), the reference insecticide and untreated groups. The hexane fractions of both plants displayed good activities compared to the reference insecticide. Ekebergia senegalensis extract had a very impressive larvicidal activity recording the highest mortality rate when exposed to the larvae.

Conclusion: Though a battery of plants from different families have been reported as useful larvicides on A. gambiae, only a few botanicals have moved from the laboratory to field use. Ekebergia senegalensis crude extract showed promising activity in mosquito control, commercial utilization should be feasible, and contribute significantly to malaria control.