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

The polysaccharide (AP1-b) of molecular weight 6.59 x 105 Da was isolated from lignified okra (Abelmoschus esculentus (L.) Moench) by hot-water extraction, 40 % ethanol precipitation and purified by DEAE Cellulose chromatography, respectively. The structure and anti-inflammatory activity of AP1-b were investigated. AP1-b was composed of galactose, rhamnose, gluctose, arabinose and galacturonic acid in a molar ratio of 1.98:1.00:0.15:0.32:0.29. The structural features showed that the AP1-b consisted of -> 2)-alpha-D-Rhap-(1 ->, -> 4)beta-D-Galp-(1 ->, -> 4)-alpha-D-GalpA-(1 ->, -> 6)-beta-D-Galp-(1 ->, beta-D-Glcp-(1 -> and alpha-L-Araf-(1 ->. AP1-b could observably improve the inflammatory injury of LPS-induced RAW 264.7 cells by inhibiting the secretion of NO and decreasing the levels of pro-inflammatory factors (IL-1 beta, iNOS and TNF-alpha). AP1-b also inhibited the phosphorylation levels of I kappa B and p65 proteins, manifesting the anti-inflammatory activity of AP1-b may associated with inhibition of NF-kappa B signaling pathway. Therefore, AP1-b had potential value in treating inflammatory injury.