Bioengineered Gold Nanoparticles Strengthens Antioxidant Defense and Enhance Shelf Life of Tomato Fruits

Perishable fruits such as tomato undergo rapid postharvest deterioration due to oxidative stress and microbial contamination, leading to significant nutritional and economic losses. Here, we developed green-synthesized Vigabatrin (VGB)-conjugated gold nanoparticles (V-B-AuNPs) using Piper betle leaf extract (BLE) for postharvest preservation. UV-Vis spectroscopy, Fourier Transform Infrared (FTIR), transmission electron microscopy (TEM), and dynamic light scattering (DLS), analyses confirmed successful synthesis, spherical morphology (~15–25 nm), and surface functionalization of the nanoparticles. V-B-AuNPs-treated tomatoes-maintained freshness for up to 24 days with significantly reduced weight loss (24.16% lower than control) and improved retention of ascorbic acid (0.26 mg g⁻¹ FW) compared with control (0.21 mg g⁻¹ FW). Ripening was delayed, as indicated by lower lycopene accumulation (66.1 µg g⁻¹ FW) relative to BLE (72.5 µg g⁻¹ FW) and control (76.8 µg g⁻¹ FW), along with reduced titratable acidity loss (23.25% vs 43.13%) in control. V-B-AuNPs also enhanced γ-aminobutyric acid (GABA) accumulation (0.75 µmol g⁻¹ FW) compared with control (0.71 µmol g⁻¹ FW), suggesting improved stress tolerance and delayed senescence. Antioxidant defense was strengthened, with increased superoxide dismutase, catalase, and peroxidase activities, accompanied by reduced hydrogen peroxide and malondialdehyde levels. Furthermore, V-B-AuNPs exhibited strong antimicrobial activity, producing inhibition zones of (22 ± 0.5 mm) against Penicillium notatum , (21 ± 1.5 mm) against Fusarium oxysporum , and (19 ± 2.0 mm) against Escherichia coli , with lower IC₅₀ values (19.08–29.01 µM) than BLE. Overall, V-B-AuNPs represent a promising bio-nano strategy for enhancing antioxidant defense, suppressing microbial decay, and extending tomato shelf life.