Evaluation of four ornamental plant extracts as insecticidal, antimicrobial, and antioxidant against the West Nile vector, Culex pipiens (Diptera: Culicidae) and metabolomics screening for potential therapeutics

Abstract Mosquitoes, one of the deadliest animals on the planet, cause millions of fatalities each year by transmitting several human illnesses. Phytochemicals are possible biological agents for controlling pests that are harmful to both human and animal health as well as crops. Plants contain a wide range of potential phytochemicals that are target-specific, rapidly biodegradable, and eco-friendly. The potential of leaf extracts of Bougainvillea glabra, Delonix regia, Lantana camara , and Platycladus orientalis against Culex pipiens and microbial agents was evaluated. Acetone extracts had more toxic effects against Cx. pipiens larvae (99.0–100%, 72 h post-treatment), and the LC 50 values were 142.8, 189.5, 95.4, and 71.1 for B. glabra, D. regia, L. camara , and P. orientalis , respectively. Plant extracts tested in this study showed high insecticidal and antimicrobial potential. L. camara acetone extract inhibited all the tested microbial isolates. D. regia showed higher antioxidant activity than other plant extracts in scavenging free radicals. GC-MS results showed the acetone extract had a higher number of chemical classes, with more terpene compounds. HPLC analysis showed the presence of flavonoids and phenolic compounds in L. camara and P. orientalis acetone extracts, and Sylimarine and Rutin were the most abundant. ADME analysis of elemene, caryophyllene oxide, caryophyllene, and copaene showed drug-likeness and revealed better gastrointestinal absorption and permeation of the blood-brain barrier by all the tested phytochemicals. Our results confirm that the diversity of phytochemicals found in ornamental plants has promising larvicidal activity and is a safe and effective alternative to chemical insecticides and biotechnology.