Browning suppression and yield improvement in Solanum diphyllum L. callus cultures

PPO-mediated phenolic compound oxidation causes callus browning, a major plant tissue culture limitation. The medicinal shrub Solanum diphyllum L. has little tissue culture research, and browning destroys its culture. Ascorbic acid and citric acid (0-600 mg/L) were tested for 30 days to reduce oxidative discoloration and improve biomass, TPC, and PPO activity in Solanum diphyllum L. callus. In leaf explants on MS medium with antioxidants, both acids dose-dependently reduced browning and PPO activity, with citric acid (600 mg/L) inhibiting PPO the most. At 200 mg/L ascorbic acid, biomass peaked, while TPC peaked at 500 mg/L and 600 mg/L citric acid. Due to phytotoxicity, high antioxidant levels reduced growth but avoided browning. Citric acid inhibited PPO with moderate biomass gains, while ascorbic acid promoted phenolic biosynthesis. These results show that antioxidant supplementation reduces oxidative stress, improves callus viability, and increases metabolite accumulation. This is the first optimized antioxidant-assisted Solanum diphyllum L. callus culture protocol, applicable to other phenolic-rich medicinal plants.