Pulp Callus Extract From Malus domestica var. Mela Rosa Marchigiana Preserves Intestinal Barrier Integrity and Confers Neuroprotection in a Gut–Brain Axis Co‐Culture Model

The gut–brain axis is a key target in neuroinflammatory disorders. We investigated the protective effects of Mela Rosa Marchigiana pulp callus extract (MRME), a phytocomplex with a unique triterpenic profile. Using a validated transwell co-culture model of the intestinal-neural interface, differentiated Caco-2 cells formed a polarized epithelial barrier (apical), while BV2 microglia or SH-SY5Y neurons were seeded in the basolateral compartment. Apical MRME pretreatment preserved Caco-2 barrier integrity against lipopolysaccharide or dextran sodium sulfate-induced damage. MRME maintained occludin integrity and transepithelial electrical resistance (TEER), effectively neutralizing “leaky gut”-like conditions. By stabilizing the barrier, MRME exerted indirect neuroprotection since high-throughput live-cell imaging revealed dose-dependent reductions in reactive oxygen species generation and apoptosis (caspase-3/7 activation) in both BV2 and SH-SY5Y cells. MRME demonstrated a microbiologically neutral profile, exerting no inhibitory effects on either pathogenic or probiotic strains up to 10,000 μg/mL. MRME provides dual protection by strengthening the intestinal barrier and shielding the neural environment from systemic inflammation through host cellular modulation rather than microbial interference. These findings suggest MRME as a promising nutraceutical candidate for gut–brain axis dysregulation.