Nicotinamide delays browning in fresh-cut apples through reducing Chlorogenic acid and inhibiting PPO activity

Post-cutting apple browning poses a major challenge in postharvest preservation, primarily driven by phenolic substrate accumulation and upregulated polyphenol oxidase (PPO) activity. This study systematically investigated the anti-browning mechanism of nicotinamide (NAM) using integrated approaches including visual assessment, enzyme activity assays, metabolomics, HPLC, molecular docking, and in vitro protein induction. Results demonstrate that NAM inhibits browning via a multi-dimensional strategy: enhancing antioxidant capacity, alleviating intracellular oxidative stress, reducing polyphenol content, and inhibiting activities of PPO and peroxidase (POD). Metabolomics and HPLC analyses revealed NAM-mediated reduction in chlorogenic acid and its precursor metabolites, while in vitro assays further confirmed inhibition of PPO catalytic activity. Crucially, NAM exhibits broad-spectrum efficacy against browning across diverse fruit species. Collectively, nicotinamide inhibits apple browning through dual pathways: substrate content modulation and enzymatic activity suppression. ONE-SENTENCE SUMMARY:: Nicotinamide (NAM) inhibits post-cutting apple browning through a dual mechanism: reducing phenolic substrates (notably chlorogenic acid and precursors) and suppressing polyphenol oxidase (PPO) activity, as validated by multi-omics and biochemical assays.