Green Synthesis of Silver Nanoparticles From Macaranga tanarius (L.) Mull. Arg. Leaf Extract With Enhanced Antibacterial, Antioxidant, and Tyrosinase Inhibitory Activities.

Atopic dermatitis (AD) is a chronic inflammatory skin disorder characterized by microbial imbalance, particularly the overgrowth of Staphylococcus aureus. This study reports the green synthesis of silver nanoparticles (AgNPs) using Macaranga tanarius extract (MTE) and evaluates their in vitro antibacterial and bioactive properties. The synthesized MT-AgNPs exhibited a distinct surface plasmon resonance (SPR) peak at 430 nm, with TEM revealing predominantly spherical morphologies (mean size: 29.2 nm; range: 6-87 nm). Phytochemical analysis confirmed that MTE is rich in polyphenols (2429 ± 33.7 mg GAE/100 g) and flavonoids (236.3 ± 10.7 mg QE/100 mL), contributing to its strong antioxidant capacity (82.72% ± 3.12% DPPH scavenging; FRAP: 20.36 ± 0.02 mg FeSO4/100 mL). MT-AgNPs demonstrated potent antibacterial activity against 17 clinical S. aureus isolates (e.g., mecA-positive strains), with MICs of 9.375-18.75 μg/mL. At 6.25 μg/mL, MT-AgNPs significantly inhibited biofilm formation by up to 63% (p < 0.05). Crucially, MTE displayed a highly stable tyrosinase inhibitory profile, maintaining a consistent inhibition rate of approximately 45% throughout a 120-min kinetic assay (equivalent to 6.0-8.5 mg kojic acid/g). This sustained inhibitory stability suggests its potential application in addressing postinflammatory hyperpigmentation. These findings indicate that MT-AgNPs serve as a promising, eco-friendly antibacterial nanomaterial with potential in vitro applications for managing AD-related microbial challenges and skin recovery.