Biofunctional Pectin Derived from Pomelo Peel: Structural Insights and Neuro–Gut Protective Mechanisms in Zebrafish under Bisphenol AF-Induced Neurotoxicity

cv. Wentan) peel represents a major agricultural byproduct rich in pectin with potential applications in functional foods and biomedical materials. This study aimed to elucidate the structure-activity relationship of pomelo peel pectin extracted at different temperatures (100 to 140 °C) and to evaluate its neuro-gut protective effects using a zebrafish model. Pectins obtained under varying thermal conditions were structurally characterized, and their bioactivities were systematically compared. Among them, pectin extracted at 130 °C (P-130) exhibited higher galacturonic acid content, molecular weight, and hydroxyl group abundance. Functionally, P-130 effectively mitigated bisphenol AF-induced toxicity in zebrafish. It significantly improved developmental outcomes, reduced oxidative stress, and preserved neuronal integrity by promoting axonal growth and up-regulating neurodevelopment-related genes. Notably, P-130 regulated the gut-brain axis by restoring neurotransmitter balance (5-hydroxytryptamine and dopamine), attenuating intestinal inflammation, and modulating gut microbiota composition, particularly by enriching beneficial taxa such as Bacteroidetes. These effects were associated with reduced anxiety-like behavior. Histopathological analyses further confirmed its protective roles in cerebellar and intestinal tissues. This study highlights the critical influence of extraction temperature on pectin structure and identifies P-130 as a promising natural agent against environmental toxicants. The findings provide novel insights into the synergistic mechanisms linking antioxidant activity, neuroprotection, and microbiota regulation, offering a scientific basis for the valorization of pomelo peel in developing plant-derived protective strategies.