Biogenic ZnO nanostructures from Mansoa alliacea leaf extract: Synergistic antibacterial, antibiofilm, and antioxidant efficacy

The growing interest in nanotechnology has steered attention toward environmentally sustainable routes for nanoparticle synthesis. Green synthesis methods, utilizing plant extracts as reducing and stabilizing agents, offer a cost effective and eco-friendly alternative to conventional chemical processes. In the present study, ZnO NPs were biosynthesized using fresh leaf extract of M. alliacea , a medicinal plant known for its rich phytochemical profile and therapeutic properties. The synthesized ZnO NPs were subjected to comprehensive characterization and biological evaluation to assess their potential biomedical applications. Preliminary phytochemical screening of M. alliacea extract confirmed the presence of flavonoids and steroids which likely facilitated the reduction and capping of nanoparticles. UV-Visible spectroscopy revealed a sharp absorption peak at 360 nm, indicating the successful formation of ZnO NPs. FTIR analysis confirmed the involvement of functional groups such as OH, and C-C in nanoparticle stabilization. XRD analysis confirmed the crystalline nature of the synthesized ZnO NPs with an average crystallite size of 14.44 nm, corresponding to the characteristic hexagonal wurtzite structure of ZnO. FESEM analysis demonstrated predominantly quasi-spherical to irregular nanoparticles with slight agglomeration and nanoscale dimensions. HRTEM analysis revealed predominantly quasi-spherical ZnO NPs with well-defined lattice fringes and an average particle size of 17.57 ± 4.88 nm, while SAED confirmed their polycrystalline hexagonal wurtzite structure. The antimicrobial potential of the biosynthesized ZnO NPs was evaluated against both gram positive and gram negative bacterial strains. The nanoparticles exhibited significant antibacterial activity, as evidenced by the zones of inhibition and MIC values. The antibiofilm activity assessed by crystal violet assay demonstrated substantial inhibition of biofilm formation in S. aureus and P. aeruginosa , which was further supported by fluorescence microscopy observations showing disruption of biofilm architecture in treated samples. Biocompatibility assessment using the MTT assay demonstrated a concentration-dependent cellular response in L929 fibroblast cells, with cell viability remaining above 50% up to a concentration of 0.75 mg/mL, indicating satisfactory cellular compatibility within the lower concentration range. In addition, the ZnO NPs exhibited appreciable antioxidant activity in the DPPH free radical scavenging assay, particularly at lower concentrations. Overall, the study highlights the effectiveness of M. alliacea, mediated green synthesis of ZnO NPs and their promising antimicrobial, antibiofilm, antioxidant and favourable cellular compatibility at lower concentrations. These findings suggest the potential of ZnO NPs as bioactive agents in pharmaceutical or biomedical applications, while also supporting the continued development of green nanotechnology