Green Synthesis of Zinc Oxide Nanoparticles Using Butea Monosperma Flower Extract and Evaluation of Their Antioxidant and Anticancer Activities Against A-549 Lung Cancer Cells

Abstract

Cancer remains a leading cause of death worldwide, with lung cancer the most frequently diagnosed malignancy approximately 2.5 million new cases and 1.8 million deaths in 2022 alone. The present study reports a simple, cost-effective, and eco-friendly green synthesis of zinc oxide nanoparticles using the aqueous flower extract of Butea monosperma, whose flavonoids and phenolic constituents served as natural reducing and capping agents. The biosynthesized NPs were characterized by UV–visible spectroscopy, FT-IR, SEM, and XRD, and evaluated for antioxidant and anticancer activities by ABTS, hydrogen peroxide scavenging, and MTT assays against A549 lung adenocarcinoma cells. The UV–vis spectrum exhibited a broad absorption band with a maximum absorbance of 0.98 at 450 nm, while FT-IR confirmed the retention of phytochemical functional groups together with the characteristic Zn–O stretching vibration at 688.5 cm⁻¹. SEM revealed quasi-spherical to hexagonal-like particles with rough surfaces, and XRD confirmed the hexagonal wurtzite structure (JCPDS 36-1451) with an average crystallite size of 66.43 nm. The NPs showed dose-dependent radical scavenging, achieving 76.50% and 87.00% (H₂O₂) inhibition at 50 µg/mL exceeding the ascorbic acid standard (61.45% and 64.88%, respectively) at every concentration tested, with an IC₅₀ between 20 and 30 µg/mL. In the MTT assay, growth inhibition of A549 cells rose from 15.00% (18.75 µg/mL) to 72.00% (300 µg/mL; R² = 0.9915), yielding an IC₅₀ of 91.69 µg/mL, with dose-dependent morphological changes including cell rounding and detachment (p < 0.0001). These findings establish B. monosperma flower extract as an effective bio-reducing and stabilizing agent for producing phytochemically capped ZnO NPs with pronounced antioxidant and anticancer potential, meriting further mechanistic and in vivo investigation.