Preparation and Characterization of Bael (<i>Aegle marmelos</i>) Leaf Essential Oil Nanoemulsion With Enhanced Antifungal Activity Against <i>Drechslera oryzae</i>

In the current study, bael (Aegle marmelos) leaf essential oil nanoemulsion (BLEON) was formulated by ultrasonication method using varying oil-to-surfactant ratios (1:1, 1:2, and 1:3) and different sonication times (5, 10, and 15 min). The stable nanoemulsions were characterized by measuring particle size, polydispersity index (PDI), and zeta potential by dynamic light scattering (DLS) technique. The most stable formulation with an oil-to-surfactant ratio of 1:3 and a sonication time of 15 min was selected, having minimum particle size (179.6 nm), least PDI (0.101), and maximum negative zeta potential (-24 mV). Stability tests showed that the nanoemulsion was stable for up to 60 days. Transmission electron microscopy (TEM) analysis revealed spherical particles having a diameter between 45 and 65 nm. The nanoemulsion showed enhanced antifungal activity compared to the essential oil against Drechslera oryzae (ED₅₀ = 560 µg/mL: minimum inhibitory concentration [MIC] = 20 µg/mL) but was ineffective against Fusarium fujikuroi. The time-kill kinetics assay also suggested the effectiveness of the nanoemulsion over the corresponding essential oil against D. oryzae. The nanoemulsion also effectively reduced fungal mitochondrial reductase enzyme activity as visualized by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. Thus, BLEON may be used as a natural and safe antifungal agent against D. oryzae.