Structural characterization of a pectic polysaccharide from Bombax ceiba L. flowers and its neuroprotective effects via the microbiota–gut–brain axis

A novel pectic polysaccharide, designated BCP-3, was isolated and purified from the flowers of kapok ( Bombax ceiba L.), with an average molecular weight of 86.9 kDa. Structural analysis revealed that BCP-3 is an acidic heteropolysaccharide mainly composed of Gal p A, Gal p , Ara f , Rha p , and Glc p , and its backbone mainly consists of alternating →4)-α-D-Gal p A-(1 → and →2)-α-L-Rha p -(1 → units, with the O-4 position of rhamnose residues serving as the primary branching site. Oral administration of BCP-3 significantly improved spontaneous locomotor activity and motor coordination in rotenone-treated mice. 16S rRNA sequencing showed that BCP-3 increased the abundance of short-chain fatty acid (SCFA)-producing bacteria, including members of the Lachnospiraceae family and Roseburia . Further analyses indicated that BCP-3 promoted SCFA production, enhanced intestinal barrier integrity, and alleviated the intestinal inflammatory microenvironment. Meanwhile, BCP-3 upregulated the intestinal FFAR3/TPH1 signaling pathway and modulated central 5-hydroxytryptamine (5-HT) signaling. In the substantia nigra, BCP-3 attenuated oxidative stress and neuroinflammation, possibly through activation of the PI3K/AKT/Nrf2 signaling pathway, ultimately contributing to the improvement of motor dysfunction. These findings suggest that BCP-3 may serve as a promising natural polysaccharide for neuroprotection through modulation of the microbiota–gut–brain axis.