Larvicidal activity on fourth instar Culex pipiens L. and phytochemical characteristics of aqueous extracts from leaves and roots of two species from the genus Plantago

In this study, we assessed the larvicidal activity of aqueous extracts obtained from the leaves and roots of Plantago major L. and Plantago lagopus L. on fourth instar Culex pipiens L. larvae. Plant material was collected from two regions in Tunisia, Beja and Bizerte. The resulting extracts were prepared at concentrations of 10, 20, 50 and 100 ppm. The toxicity of the extracts was monitored over a 24-hour period. Our findings indicated that leaf extracts from Plantago lagopus L. collected in Bizerte exhibited higher toxicity compared to those collected in Beja up to 12 h, although these differences became insignificant at the 24-hour mark. Furthermore, extracts from the roots of Plantago lagopus L. from Bizerte demonstrated higher toxicity than those from Beja. Statistical analysis revealed no significant differences (P = 0.056) in the toxicity of leaf extracts at 100 ppm between the two species after 24 h of exposure. The root extracts exhibited lower toxicity, resulting in mortality rates ranging from 40 to 70% after 24 h. Specifically, the leaf extracts of Plantago major L. from Bizerte yielded a median lethal concentration (LC₅₀) of 16.068 ppm ± 8.440. Additionally, the quantification of total polyphenols and flavonoids revealed distinct variations between species, plant organs, and geographical origins. Root and leaf extracts from Plantago major L. collected in Beja exhibited higher concentrations compared to those from Bizerte. Conversely, root extracts from Plantago lagopus L. collected in Bizerte displayed the highest concentrations. These preliminary findings provide a foundation for the development of a novel natural biocide for mosquito control, utilizing the distinct larvicidal properties of Plantago species extracts.