Background : The biosynthesis of metal nanoparticles is an important broad and developing field of research in many fields, especially medical fields. Material and methods: in current study, iron oxide nanoparticles (Fe₃O₄-NPs) were synthesized from aqueous ferric chloride in a clear, simple, biosynthetic way using the aqueous extract of Curcuma longa powder, which is considered at the same time a reductant and a stabilizer as well. The prepared samples were characterized using several techniques: UV-Visible, TEM, SEM, and FT-IR. Through the color change, the formation of Fe₃O₄-NPs is evident through the appearance of the characteristic black color of the solution. Formation of Fe from C. Longa was also determined by UV spectroscopy where surface plasmon absorption was observed at 223-303 nm. Well-dispersed Fe₃O₄-NPs with isotropic and anisotropic morphology are seen for 20 mL of C. longa water extract with a size of 40 nm in the TEM images. The functional groups present in the NPs were mainly –OH and –COOH identified using FT-IR which makes them hydrophilic and hence the NPs do not need any functional modification. This study included bacterial isolates obtained from urine samples of patients suffering from urinary tract infections (UTIs), and then the antimicrobial activity of Fe₃O₄-NPs was evaluated against Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria, and it was found that the zone of inhibition was 10.5 mm for (E. coli) and 17.6 mm for (Staphylococcus aureus). Thus naturally stabilized Fe₃O₄-NPs with herbal properties can be used in various biological applications.

Keywords: Green synthesis, Curcuma longa, Iron Oxide Nanoparticles (Fe₃O₄), urinary tract infections (UTIs)