Green synthesis of gold nanoparticles utilizing Raphanus sativus root extract: characterization and in vitro investigation of its antioxidant, antimicrobial and anticancer impact

Abstract Gold nanoparticles (AuNPs) are recently investigated as substantial tools in cancer therapy due to their biocompatibility and tunable surface properties. Raphanus sativus or red radish root (RRR), a Cruciferaceae vegetable, has notable medicinal and nutritional value owing to its highly polyphenolic content and antioxidant property. The aim of this study is to synthesize the gold nanoparticles by a green method using the Raphanus sativus root extract and to study its antioxidant, antimicrobial and anticancer impact. The resultant RRR-AuNPs were characterized by TEM, UV/Vis spectroscopy, DLS, Zeta potential, XRD, AFM, BET and pore size analysis and assessed for antioxidant, antimicrobial and anticancer activity. The greenly synthesized gold nanoparticles showed ruby red color with a distinct absorption peak at 526 nm. The resultant AuNPs were spherical with an average size of 31 nm and average zeta potential of -36.8 mV. Results clearly demonstrated that the RRR-AuNPs possess high total polyphenolic content and potent antioxidant activity (DPPH). Moreover, RRR-AuNPs exhibited a considerable antibacterial efficacy against Staphylococcus aureus (80.9% inhibition) and Escherichia coli (78.22% inhibition) with a uniform MIC value of 0.977 µg/mL. Furthermore, RRR-AuNPs reduced the viability of Caco-2 and HepG2 cancer cells to 31.9% and 26.4%, respectively, at 250 µg/mL. Notably, a remarkable Antimicrobial Selectivity Index (SI) of 303.04 was established, confirming a toxicity over 300-fold higher toward bacterial pathogens than toward normal HEK-293 cells. These findings highlight RRR-AuNPs as a promising, biocompatible platform with potent antioxidant, antimicrobial, and anticancer properties for biomedical applications.