Activity of Three Nigerian Mistletoes against Culex quinquefasciatus Larvae

Abstract

The development of resistance to the available larvicidal agents by mosquitoes has necessitated continued search for larvicidal compounds from plants. Therefore, in this study, the larvicidal activity of the extracts and fractions of flowers, leaves, and stems of Tapinanthus bangwensis, Phragmanthera incana, and Tapinanthus globiferus were investigated against C. quinquefasciatus. The leaf, flower, and stem of T. bangwensis, P. incana, and T. globiferus were collected, authenticated, air-dried, powdered, and extracted with methanol for 72 hours. The extracts were filtered and concentrated in vacuo and tested against C. quinquefasciatus fourth instar larvae. The most active extract of each plant was successively partitioned into n-hexane and ethyl acetate to obtain their corresponding fractions which were similarly tested. The methanol extract of Nicotiana tabacum, a known insecticidal plant, was used as the positive control. After 48 hours of exposing the test organism to the extracts, the leaf of T. bangwensis (LC₅₀ 3.68 mg/mL), the flowers of T. globiferus (LC₅₀ 7.55 mg/mL) and P. incana (LC₅₀ 4.00 mg/mL) were the most active. After partitioning, the n-hexane fraction of T. bangwensis (LC₅₀ 1.28 mg/mL), ethyl acetate fraction of P. incana (LC₅₀ 1.91 mg/mL), and the aqueous fraction of T. globiferus (LC₅₀ 2.24 mg/mL) had the highest activity for each extract. This is the first report of the larvicidal activity of these plants against C. quinquefasciatus.