Green Synthesis of Silver Nanoparticles Using Curcuma longa: Evaluation of Antimicrobial Activity, In Vivo Imaging-Based Toxicity, and In Vitro Biocompatibility

This study aimed to compare the bioactive profiles and biological activities of methanolic extracts from Curcuma aromatica (CA) and Curcuma longa (CL) rhizomes. Fourier-transform infrared spectroscopy (FTIR) and gas chromatography-mass spectrometry (GC-MS) analyses revealed the presence of bioactive functional groups and identified 19 and 14 phytocompounds in the CA and CL extracts, respectively. The CL extract exhibited higher flavonoid, alkaloid, and phenol contents, along with superior antioxidant activity in 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) assays, while CA showed greater metal-chelating activity. The CL extract showed strong antimicrobial activity against Streptococcus pneumoniae and Klebsiella pneumoniae (1.46 cm inhibition zone), while the CA extract exhibited no antimicrobial efficacy. Silver nanoparticles (Ag NPs) synthesized using CL extract displayed an ultraviolet-visible (UV-Vis) absorption peak at 410 nm, spherical morphology, and a face-centered cubic structure with an average crystallite size of 9.32 nm. These Ag NPs exhibited dose-dependent antimicrobial activity against Bacillus megaterium, S. pneumoniae, and K. pneumoniae at a concentration of 100 µg/mL. In vivo toxicity studies of Ag NPs revealed 26.33–76.33% mortality in Artemia salina nauplii at 10 mg/mL after 24 h, while an in vitro cell viability assay in RAW 264.7 cells at 1 µg/mL confirmed cytocompatibility with a stimulatory hormesis effect. These findings suggest that CL extract acts as an antioxidant and antimicrobial agent. The CL extract-mediated synthesis of Ag NPs can be used in antimicrobial coatings, wound dressings, and topical ointments to prevent and treat infections