Dietary polyphenols and gut–brain axis modulation: the neuroprotective role of quercetin, allicin, and ferulic acid in traumatic brain injury and neurodegeneration

The gut–brain axis exerts critical control over neuroinflammation and neuronal resilience in traumatic brain injury (TBI) and neurodegenerative disorders. Dysregulated immune signaling, oxidative stress, and microbial dysbiosis are key pathological drivers. This review integrates current evidence on three dietary polyphenols, quercetin, allicin, and ferulic acid, that strengthen intestinal barrier integrity, remodel gut microbiota, and modulate neuroinflammatory cascades through antioxidant, anti-inflammatory, and gene-regulatory pathways. Emphasizing a mechanism-to-formulation translation, we link molecular bioactivity with the challenges of bioavailability and highlight food-grade delivery platforms such as encapsulation and microbiota-targeted systems to enhance stability, transport, and efficacy. By combining perspectives from foodomics, nutrigenomics, and neurobiology, this review proposes design principles for developing next-generation functional foods aimed at mitigating TBI- and aging-associated neurodegeneration. The work uniquely bridges nutritional biochemistry, microbiome modulation, and food processing to guide translational neuroprotective interventions. • Polyphenols regulate gut–brain axis to reduce post-TBI inflammation. • Quercetin, allicin, ferulic acid reshape microbiota and fortify barriers. • Bioavailability strategies enhance stability, solubility, and absorption. • Food-grade carriers enable translational validation via in vitro models.