Effect of Nanoemulsions of Chrysanthemum cinerariaefolium and Oenothera biennis Flowers Against the West Nile Virus Vector, Culex pipiens, with Phytochemical Profile.

(1) Background: Mosquitoes represent major vectors of human pathogens, and their control remains a global public health priority. However, the widespread use of synthetic insecticides has resulted in environmental contamination, adverse effects on non-target organisms, and the rapid emergence of insecticide resistance. These limitations have intensified the search for sustainable botanical alternatives. (2) Methods: The present study investigated the phytochemical composition and larvicidal efficacy of flower extracts from Chrysanthemum cinerariaefolium and Oenothera biennis, alongside their nanoemulsion formulations, against the third-instar larvae of Culex pipiens. Larvicidal assays demonstrated that nanoemulsion formulations markedly enhanced bioactivity compared with conventional extracts. (3) Results: After 48 h of exposure, C. cinerariaefolium nanoemulsion exhibited the strongest toxicity (LC50 = 26.63 ppm), followed by methanol (44.46 ppm), hexane (73.90 ppm), and aqueous extracts (209.99 ppm). Corresponding LC50 values for O. biennis were 31.89, 80.15, 140.69, and 393.22 ppm, respectively. Biochemical analyses indicated that C. cinerariaefolium treatments strongly inhibited detoxification and digestive enzymes (esterases, GABA-T, amylase, and lipase) and suppressed antioxidant defenses (SOD, GST, CAT, and GSH). This was accompanied by a significant elevation of oxidative stress biomarkers, including lipid peroxidation and protein carbonylation. In contrast, O. biennis induced comparatively moderate biochemical responses. The phytochemical profiling utilizing GC-MS revealed the identification of forty-nine and fifty volatile components from the C. cinerariaefolium (CW-Hex) and O. biennis (BOF) n-hexane extracts, respectively, primarily consisting of oxygenated hydrocarbons, fatty acids, and their esters. Furthermore, UPLC-MS/MS-assisted profiling of methanol, ethyl acetate, and aqueous extracts identified thirty-eight metabolites for CW and thirty-one for BOF. The CW extracts were predominant in flavonoids and fatty acids while also containing cinnamic acid derivatives, phenolic acids, diterpenoids, triterpenoids, pyrethrins, phenyl ethanoids, steroids, aurones, and tannins. BOF extracts were particularly rich in flavonoids, followed by fatty acids, cinnamic acid derivatives, tannins, and steroids. (4) Conclusions: These findings demonstrate that plant-derived formulations of C. cinerariaefolium, particularly in nanoemulsion form, exert potent larvicidal activity through the disruption of metabolic and antioxidant pathways, offering a promising eco-friendly strategy for vector control.