Green Synthesis of Bioactive Silver Nanoparticles from Fagopyrum esculentum Hulls

Background/Objectives: The use of food waste in nanomaterial development represents an efficient and sustainable strategy for producing value-added products. Methods: In this study, silver nanoparticles (AgNPs) were synthesized from the hydroethanolic and aqueous extracts of buckwheat (Fagopyrum esculentum Moench) hulls, under optimized conditions. The resulting AgNPs were characterized using spectroscopic and microscopic techniques. To evaluate their bioactivity, free radical scavenging assays, cytotoxicity assays against tumor and normal cells, and broth microdilution assays were conducted. Results: AgNPs, synthesized from the hydroethanolic and aqueous buckwheat hull extracts under optimized conditions, were small (mean diameters of 19.97 ± 7.86 and 5.55 ± 1.34 nm, respectively), well dispersed (polydispersity index values of 0.204 and 0.345, respectively), negatively charged, and stable (zeta potential values of -24.10 ± 6.73 and -23.5 ± 10.3 mV, respectively). The latter were more homogenous in shape, being predominantly spherical. Both samples of AgNPs demonstrated remarkable cytotoxic activity against A-375 human malignant melanoma cells (IC₅₀ values below 5 μg/mL). AgNPs derived from the hydroethanolic buckwheat hull extract suppressed the growth of methicillin-resistant Staphylococcus aureus ATCC 43300 and Staphylococcus epidermidis ATCC 12228, with minimum inhibitory concentration (MIC) values of 37.50 and 4.68 μg/mL, respectively. AgNPs derived from the aqueous buckwheat hull extract exhibited higher free radical scavenging activity (EC₅₀ values of 132.6 ± 0.3 and 77.40 ± 3.52 μg/mL in the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays, respectively). Conclusions: AgNPs synthesized from the buckwheat hull extracts demonstrated notable potential as antimelanoma and antibacterial agents.