Eco-friendly fabrication of ZnO quantum dots using Brassica rapa (L.): metabolomic profiling and antimicrobial efficacy against foodborne pathogens supported by in-silico insights.

The growing challenge of drug-resistant pathogens has forced the urgent need for natural and sustainable antimicrobial alternatives. This research explores the green chemistry-based synthesis of zinc oxide quantum dots (ZnO-QDs) employing the ethanolic root extract of Brassica rapa (L.) to assist their formation and stabilization. Characterization of ZnO-QDs confirmed their hexagonal crystalline structure with a nanoscale size (0.8-2.6 nm) and their good stability. GC/MS assay identified β-phenylethyl isothiocyanate and hydroquinone as the main antimicrobial compounds in the essential oil, while LC-ESI-TOF-MS profiling pinpointed the existence of glucosinolates, flavonoids, and phenolic acids as potential active compounds contributing to nanoparticle formation and antimicrobial potential. The combination of B. rapa essential oil and ZnO-QDs exhibited the strongest antibacterial and antifungal activity among the all investigated samples, showing the highest inhibition against Listeria monocytogenes (30.5 mm), Aspergillus niger (20.5 mm), and Fusarium verticillioides (18.2 mm). Molecular docking revealed powerful binding affinities of key phytochemicals to fungal sterol demethylase CYP51B and bacterial DNA gyrase 2, reinforcing their antimicrobial activity. The study's outcomes reveal that B. rapa-derived ZnO-QDs could be a novel, eco-friendly antimicrobial agent for controlling food spoilage bacteria and mycotoxigenic fungi in food products. Future research should focus on in-vivo efficacy and biocompatibility to fully utilize their potential in food preservation, the pharmaceutical industry, and biomedicine.