Green Fabrication of Copper and Zinc Nanoflowers Using Rheum tataricum L. and Evaluation of their Antioxidant, Enzyme-Inhibitory, Antimicrobial, and Anticancer Properties.

In this study, Zn- and Cu-based nanoflowers were synthesized using Rheum tataricum L. root extract through a green and eco-friendly approach. The nanostructures were preliminarily characterized using SEM, FTIR, XRD, and EDX analyses. Subsequently, their biological activities were comprehensively evaluated, including antioxidant potential (DPPH and ABTS assays), acetylcholinesterase (AChE) inhibitory properties, cytotoxic effects on A549 lung cancer cells, and antimicrobial as well as antibiofilm activities against clinically relevant pathogenic bacteria with different resistance profiles. RT@Cu-hNFs exhibited IC₅₀ values of 221 µg/mL (DPPH) and 146 µg/mL (ABTS), whereas RT@Zn-hNFs showed stronger antioxidant activity with IC₅₀ values of 62.7 µg/mL and 4.7 µg/mL, respectively. The AChE inhibitory IC₅₀ values were 53 µg/mL for RT@Cu-hNFs and 29.6 µg/mL for RT@Zn-hNFs, indicating a higher enzyme inhibitory potential for the Zn-based nanoflowers. Cytotoxicity assays revealed that RT@Cu-hNFs and RT@Zn-hNFs exhibited IC₅₀ values of 1977 ± 357 µg/mL and 1511 ± 392 µg/mL, respectively, confirming their low cytotoxicity toward A549 cells. Among the tested bacterial strains, RT@Cu-hNFs demonstrated stronger antibacterial activity than RT@Zn-hNFs, particularly against Staphylococcus aureus. Overall, the findings highlight the promising multifunctional potential of R. tataricum-derived nanoflowers for antioxidant, enzyme-inhibitory, and antimicrobial applications.