Mosquito-borne diseases represent a growing health challenge over time. Numerous potential
phytochemicals are target-specific, biodegradable, and eco-friendly. The larvicidal activity of essential
oils, a jasmine blend consisting of Jasmine oil and Azores jasmine (AJ) (Jasminum sambac and
Jasminum azoricum) and peppermint (PP) Mentha arvensis and their nanoformulations against 2nd
and 4th instar larvae of Culex pipiens, was evaluated after subjecting to different concentrations (62.5,
125, 250, 500, 1000, and 2000 ppm). Two forms of phase-different nanodelivery systems of layered
double hydroxide LDH and oil/water nanoemulsions were formulated. The synthesized nanoemulsions
showed particle sizes of 199 and 333 nm for AJ-NE and PP-NE, with a polydispersity index of 0.249
and 0.198, respectively. Chemical and physiochemical analysis of TEM, SEM, XRD, zeta potential, drug
loading capacity, and drug release measurements were done to confirm the synthesis and loading
efficiencies of essential oils’ active ingredients. At high concentrations of AJ and PP nanoemulsions
(2000 ppm), O/W nanoemulsions showed higher larval mortality than both LDH conjugates and crude
oils. The mortality rate reached 100% for 2nd and 4th instar larvae. The relative toxicities revealed
that PP nanoemulsion (MA-NE) was the most effective larvicide, followed by AJ nanoemulsion (AJNE).
There was a significant increase in defensive enzymes, phenoloxidase, and α and β-esterase
enzymes in the treated groups. After treatment of L4 with AJ, AJ-NE, PP, and PP-NE, the levels of
phenoloxidase were 545.67, 731.00, 700.00, and 799.67 u/mg, respectively, compared with control
669.67 u/mg. The activity levels of α-esterase were 9.71, 10.32, 8.91, and 10.55 mg α-naphthol/min/
mg protein, respectively. It could be concluded that the AJ-NE and PP-NE nanoformulations have
promising larvicidal activity and could act as safe and effective alternatives to chemical insecticides. |
