Biosynthesized Gold Nanoparticles from Mill. Leaf Extract Exhibit In Vivo Biocompatibility, Antimicrobial, and Antioxidant Activities.

Antimicrobial resistance (AMR) is a health related threat world-wide. Biosynthesized gold nanoparticles (AuNPs) using plant extracts have been reported to exhibit certain biological activity. This study aimed to biosynthesize AuNPs using an aqueous extract of leaves and to evaluate their biocompatibility, antimicrobial activity, and antioxidant properties. AuNPs were biosynthesized using an aqueous extract of leaves. Their biocompatibility was evaluated through hemolytic activity and assessments of hepatic and renal functions in rats. AuNPs were biologically evaluated as antimicrobial and antioxidant agents. The AuNPs exhibited particle sizes of 27.78 nm (XRD) and 69.41 nm (AFM). Hemolysis assays on red blood cells revealed negligible hemolytic activity (<1%). Hepatic enzyme levels, including alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), and lactate dehydrogenase (LDH) were studied. ALT, AST, and ALP levels showed no significant changes compared to the negative control. However, LDH levels were elevated at higher concentration (52.8 µg/mL), while the lower concentration (26.4 µg/mL) appeared to be safer. Renal biomarkers, urea and creatinine, showed no significant changes at either concentration, indicating minimal nephrotoxicity. The antimicrobial activity of AuNPs, plant extract, and gold salt was tested against five microorganisms: two Gram-positive bacteria (, ), two Gram-negative bacteria (, ), and a fungal strain (). The AuNPs exhibited minimum inhibition concentrations (MICs) of 13.2 µg/mL against and , 26.4 µg/mL against and , and 39.6 µg/mL against , suggesting selectivity towards Gram-positive bacteria. Furthermore, the AuNPs demonstrated strong antioxidant activity, surpassing that of vitamin C. The biosynthesized AuNPs exhibited promising biocompatibility, selective antimicrobial properties, and potent antioxidant activity, supporting their potential application in combating the AMR.