Comparative analysis of biological activities of green-synthesized silver and zinc oxide nanoparticles using <i>Pogonatherum crinitum</i> extracts

This research successfully demonstrated the green synthesis and characterization of silver (Ag) and zinc oxide (ZnO) nanoparticles (NPs) using the aerial parts of Pogonatherum crinitum , alongside the phytochemical screening, quantification of phenolic and flavonoid content, and the evaluation of their biological activities. Major phytochemicals, such as polyphenols, flavonoids, alkaloids, terpenoids, tannins, and carbohydrates, were detected. Ethanolic extracts had the highest total phenolic content (TPC) (72.32 ± 8.05 mg GAE/g), while ethyl acetate extracts showed the highest flavonoid content (59.93 ± 15.13 mg QE/g). In terms of bioactivity, ethyl acetate extracts exhibited the strongest antioxidant activity (IC 50 , 11.91 ± 0.46 µg/mL) compared to aqueous extracts and NPs. ZnO NPs showed superior antibacterial activity, effectively inhibiting Klebsiella pneumoniae and Staphylococcus aureus (zone of inhibition: 13-14 mm) with minimum inhibitory concentrations (MICs) of 3.12 mg/mL. Ag NPs displayed moderate activity against Staphylococcus aureus . The antidiabetic activity was observed with ZnO NPs, showing the most significant α-amylase inhibition (IC 50 , 0.35 ± 0.006 mg/mL). The brine shrimp lethality assay (BSLA) indicated moderate toxicity of the synthesized NPs, particularly ZnO NPs (LC 50 , 523.48 ± 51.84 µg/mL). The synthesis of NPs was confirmed by UV-visible spectroscopy and FTIR analysis, highlighting the role of biological moieties. X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) analyses revealed the spherical and hexagonal morphologies of Ag and ZnO NPs, with average particle sizes of 9.71-12.32 nm for Ag NPs and 18.20-23.75 nm for ZnO NPs. Cytotoxicity studies demonstrated that Ag and ZnO NPs exhibited significant activity against cervical cancer cell lines (IC 50 , 118.36 ± 6.30 µg/mL and 124.16 ± 4.51 µg/mL, respectively) and moderate activity against lung cancer cells while the rest were found to be non-toxic to non-cancerous epithelial cells. In conclusion, Pogonatherum crinum -synthesized Ag and ZnO NPs exhibit enhanced antibacterial, antioxidant, antidiabetic, and cytotoxic properties, suggesting their potential for therapeutic applications. Further research is warranted to optimize formulations for safe and effective clinical use.