Dual antibacterial and selective anticancer activities of biogenic ZnO nanoparticles from durian flower waste: impact of surface phytochemicals

Zinc oxide nanoparticles (ZnO NPs) are widely studied for biomedical and environmental applications; however, conventional synthesis methods raise concerns about sustainability and safety. In this work, we developed an eco-friendly approach to synthesize ZnO NPs using antioxidant-rich durian flower (DF) extract, an agricultural waste product. Phytochemical profiling confirmed that DF extract contained high levels of procyanidins and (−)-epicatechin and exhibited strong antioxidant activity (IC 50 ≈ 167–175 μg/mL in the DDPH assay; TEAC ≈ 850–854 mM/g DW in the FRAP assay). ZnO NPs synthesized using DF ethanolic extract (ZnO-DF-E) showed high crystallinity and quasi-spherical morphology, with a crystallite size of ~40.33 nm and lattice parameters a = 3.2520 Å, c = 5.2089 Å), as well as a direct band gap of ~3.2 eV. Calcination at 600 °C (ZnO-DF- E -Burnt) further increased crystallinity and crystallite size (~72.28 nm; a = 3.252 Å and c = 5.210 Å), enhanced visible- light absorption via defect formation (bandgap ~3.0 eV), and reduced surface phytochemical residues. Both ZnO-DF-E and ZnO-DF- E -Burnt exhibited antibacterial activity against Cutibacterium acnes , as evidenced by inhibition zones in agar diffusion, growth inhibition (~50% inhibition at 3 mg/mL), and SEM observations consistent with membrane disruption. Notably, ZnO-DF-E selectively reduced the viability of A431 epidermoid carcinoma cells in a dose-dependent manner (~ 70% inhibition at 600 μg/mL) without affecting normal HaCaT keratinocytes. In contrast, ZnO-DF- E -Burnt show no anticancer activity, suggesting that surface-associated phytochemicals contribute to selective cytotoxicity. These findings highlight the potential of DF extract-derived ZnO NPs as sustainable nanomaterials with dual antibacterial and anticancer properties and underscore the importance of synthesis conditions in modulating their biological activity. • Biogenic synthesis of ZnO NPs using 80% durian flower ethanolic extract produces high crystallinity. • Bioactive compound analysis of durian flower ensures consistent ZnO NPs size and shape. • Synthesized ZnO NPs strongly inhibited Cutibacterium acnes, disrupting membranes. • Removing phytochemicals from ZnO NPs did not reduce antibacterial activity. • Removal of phytochemicals from ZnO NPs lowered selective cytotoxicity to skin cancer.