Antioxidant, Antimicrobial, and Anticancer Potential of Green Synthesized ZnO Nanoparticles from Açaí (Euterpe oleracea Mart.) Berry Seed Residue Extract

Residue from the food agroindustry has been reported as an alternative source for generating novel by-products, potentially applied in green chemistry nanotechnology. In this work, the green synthesis of zinc oxide nanoparticles (ZnO NPs) using Brazilian Amazon açaí (Euterpe oleracea Mart.) berry seed residue extract was investigated as a sustainable alternative route. The formation of ZnO NPs was characterized by TGA, XRD, FTIR, and XPS. The characterization of ZnO NPs involved the examination of their morphology and size using TEM, SEM, EDX, and DLS techniques. ZnO NPs were assessed for their antioxidant, antimicrobial, and anticancer properties. The chromatographic results suggest that phytochemicals (e.g., flavonoids and alkaloids) from açaí berry seed influenced the formation of ZnO NPs, revealing a hexagonal wurtzite structure. The ZnO NPs exhibited a spherical morphology with a particle size of around 60 nm. ZnO NPs showed significant antioxidant activity radical scavenging by DPPH⋅ and FRAP assay, and they demonstrated antimicrobial activity against both Gram-negative (Escherichia coli and Salmonella enterica serovar Enteritidis) and Gram-positive (Staphylococcus aureus and Listeria monocytogenes) pathogenic bacteria. In vitro cytotoxicity results indicated that ZnO NPs had a significant biological and toxicological impact on the A431 human skin squamous carcinoma cell line (IC50 = 59.50 µg mL−1) and HaCaT human keratinocytes (IC50 = 57.58 µg mL−1). These findings suggest that ZnO NPs synthesized from the açaí berry seed agro-industrial residue hold potential as a sustainable alternative in several applications, including nanomedicine and food technology.