Metabolic Enzyme Inhibitory and Larvicidal Activity of Biosynthesized and Heat Stabilized Silver Nanoparticles Using Annona muricata Leaf Extract

The synthesis of silver nanoparticles (AgNPs) using Annona muricata ( A. muricata ) leaf extract and its larvicidal, metabolic enzyme inhibitory properties was demonstrated here. The AgNPs were synthesized and analyzed by using UV-visible spectroscopy and observed a maximum absorbance peak at 420 nm which corresponds to the AgNPs. The XRD analysis showed the 2 θ intense values (111, 200, 220, and 311) within the ranges of Bragg’s reflection; Fourier transform infrared spectroscopy (FTIR) showed that AgNPs were capped with alkanes, amides, and alkenes functional groups which act as a reducing, capping, and stabilizing agent; and field emission scanning electron microscope (FESEM) and high-resolution transmission electron microscopy (HRTEM) results indicated that synthesized AgNPs were spherical in shape with the size of 20–34 nm and energy-dispersive X-ray (EDX) spectroscopy exhibited a strong signal of silver. Various concentrations of AgNPs (6, 12, 18, 24, 30 μg mL −1 ) and aqueous leaf extract (ALE) (30, 60, 90, 120, 150 μg mL −1 ) were evaluated, and in all the concentrations, AgNPs showed significant larvicidal properties against three different second instar larvae, when compared to ALE. ALE exhibited LC 50 and LC 90 values of (LC 50 45.521 μg/mL; LC 90 456.406 μg/mL) against Ae. aegypti followed by An. stephensi (LC 50 61.878 μg/mL; LC 90 565.309 μg/mL) and Cx. quinquefasciatus (LC 50 68.952 μg/mL; LC 90 444.512 μg/mL), and AgNPs were exhibited LC 50 and LC 90 values (LC 50 3.089 μg/mL; LC 90 18.467 μg/mL) against Ae. aegypti followed by An. stephensi (LC 50 3.155 μg/mL; LC 90 39.888 μg/mL) and Cx. quinquefasciatus (LC 50 5.188 μg/mL; LC 90 31.660 μg/mL), respectively. The A. muricata leaf extract-mediated AgNPs were also evaluated for the first time to identify their metabolic enzyme inhibitory activity which also showed significant results.