Controlled green synthesis of ZnO nanoparticles via Chlorophytum borivilianum roots reveals structure–bioactivity relationships

Green synthesis of metal oxide nanoparticles offers a sustainable alternative to conventional chemical routes. This study synthesized zinc oxide nanoparticles (ZnO NPs) using Chlorophytum borivilianum root extract and systematically evaluated their physicochemical properties alongside newly established quantitative bioactivity metrics. Characterisation confirmed the formation of crystalline, phase-pure ZnO NPs with a hexagonal structure (XRD: ∼28 nm), an optical absorption at ∼360 nm (UV-Vis), and strong initial colloidal stability (Zeta potential: –28.0 mV). FTIR analysis identified surface-bound phenolics and carboxylates involved in nanoparticle stabilization. Quantitative antibacterial evaluation against clinical isolates revealed significant potency, with minimum inhibitory concentration (MIC) values ranging from 31.25 ± 1.5 µg/mL ( Streptococcus pneumonia ) to 500.00 ± 12.4 µg/mL ( E. faecalis ). Crucially, time-kill kinetics demonstrated rapid bactericidal action, achieving total elimination of Streptococcus pneumoniae within 12 h ( p < 0.001). Furthermore, nanoparticle formation nearly doubled the antioxidant efficiency of the crude extract, achieving an activity of ∼142.5 µg/mL and 58.64% scavenging at 200 µg/mL. The study establishes C. borivilianum root extract as a robust biogenic source for synthesizing rapid-acting, stable ZnO nanoparticles with defined structure–bioactivity relationships, supporting their potential as sustainable biofunctional nanomaterials.