Structural characterization and anti-inflammatory activity of a pectin polysaccharide AP2-c from the lignified okra

In this paper, a pectin polysaccharide AP2-c with molecular weight 6.69 × 10⁵  Da was obtained from the lignified okra. The monosaccharide composition analysis indicated that AP2-c consisted of galactose, rhamnose and galacturonic acid in a molar ratio of 2.3: 1.5: 1.5. The structural characterization indicated that the main chain of AP2-c was composed of →2)-α-L-Rhap-(1→ and →4)-α-D-GalAp-(1→. →2)-α-L-Rhap-(1→ was branched at position O-4 and the branched chain consisted of →3,6)-β-D-Galp-(1→, →6)-β-D-Galp-(1→, α-L-Rhap-(1→ and β-D-Galp-(1→. AP2-c could inhibit the mRNA expression levels of TNF-α, IL-1β and iNOS in LPS-induced macrophages with a dose-dependent manner. Furthermore, AP2-c inhibited the phosphorylation of IκB and p65 via NF-κB pathway. The results indicated that AP2-c had obvious anti-inflammatory activity. PRACTICAL APPLICATIONS: When okra seeds were harvested, lignified okra was always abandoned as waste and had not been fully used for exploitation. Nevertheless, it accounted for more than half of the total plant's weight and was abundant in cell wall polysaccharides, which were the main components of okra to perform a variety of biological functions. In the research, the purified pectin polysaccharide AP2-c was obtained from lignified okra and its physicochemical properties, structural features and anti-inflammatory activity were systematically researched. It was detected that AP2-c exhibited anti-inflammatory activity by blocking NF-κB pathway and thus lowering the expression of related inflammatory factors. The results have significant implications for the value-added application of okra and its processing side products can obviously help to promote the anti-inflammatory application of AP2-c and avoid wasting resources.