Nanotechnology is a new field that has gained considerable importance due to its potential uses in the field of biosciences, medicine, engineering, etc. In the present study, bio-inspired metallic iron nanoparticles (FeNPs) were prepared using biomass of Enterobacter train G52. The prepared particles were characterized by UV-spectroscopy, TGA, XRD, SEM, EDX, and FTIR techniques. The crystalline nature of the prepared FeNPs was confirmed by XRD. The SEM techniques revealed the particles size to be 23 nm, whereas in FTIR spectra the peaks in the functional group region indicated the involvement of bioactive compounds of selected bacterial strains in the capping of FeNPs. The EDX confirmed the presence of iron in the engineered FeNPs. The FeNPs were then evaluated for its antibacterial, antifungal, antioxidant, anti-inflammatory, anti-Alzheimer’s, anti-larvicidal, protein kinase inhibition, anti-diabetic, and biocompatibility potentials using standard protocols. Substantial activities were observed in almost all biological assays used. The antioxidant, anti-cholinesterase, and anti-diabetic potential of the prepared nanoparticles were high in comparison to other areas of biological potential, indicating that the FeNPs are capable of targeting meditators of oxidative stress leading to diabetes and Alzheimer’s disease. However, the claim made needs some further experimentation to confirm the observed potential in in vivo animal models.

The apple is the most widely used fruit globally. Apples are more prone to fungal spoilage, which leads to browning and subsequent changes in their flavor and texture. Browning is also caused by the tyrosinase enzyme. By inhibiting tyrosinase initiation and fungal spoilage in fruits, the natural flavor and texture of fruits can be maintained. Biogenic NPs can act as antioxidants to inhibit tyrosinase and due to oxidative stress, it also catalyzes the deformation of fungal hyphae and spores. Nanotechnology is a research hotspot that has gained considerable interest due to its potential inferences in biosciences and food preservation technology. The present study aims to use biomass from the Fagonia cretica to create bio-inspired manganese oxide MnO₂ NPs and to evaluate its bio-catalytic potential for antifungal anti-browning through the inhibition of tyrosinase and its antioxidant potential for preserving apple flavor and texture. The green synthesized nanoparticles were extensively analyzed using UV spectroscopy, XRD, SEM, EDX, and FTIR techniques. Moreover, the synthesized manganese oxide nanoparticles (MnO₂ NPs) were evaluated for their bio-catalytic potential as anti-fungal and anti-spoiling agents. The values of antifungal activity among all the samples were 14.2 ± 86 mm, 8.9 ± 6.0 mm, 17.7 ± 1.26, and 20.7 ± 4.38 mm for Penicillium expansum, Monilinia fructigena, Penicillium chrysogenum, and Aspergillus oryzae at 200 µg/well, respectively. Moreover, the biogenic NPs were evaluated for their anti-browning potential through the inhibition of tyrosinase. MnO₂ NPs have been shown to have considerable inhibitory effects on tyrosinase up to 64.8 ± 0.16 at 200 µg/mL and (27.2 ± 0.58) at 25 µg/mL. Biogenic MnO₂ NPs can also act as antioxidants to inhibit tyrosinase and fungal growth by the formation of free radicals that damage the fungal hyphae and, as a result, slow down browning. The maximum DPPH free radical scavenging activity was 74.5 ± 0.39% at 200 µg/mL, and the minimum was 12.4 ± 0.27 at 25 µg/mL. The biogenic MnO₂ NPs are biocompatible and play a potent role in maintaining the flavor and texture of apples.