Abstract: The polysaccharide AP1-c was isolated and purified from the lignified okra (Abelmoschus esculentus (L.) Moench) by hot water extraction and DEAE-Cellulose-52 chromatography. The physicochemical properties and structural characterization of AP1-c were investigated. The results show that the AP1-c is a homogeneous polysaccharide with molecular weight of 658 kDa, the contents of total sugar, glucuronic acid and protein are 95.36%, 24.83% and 0.72%, respectively. The Fourier transform infrared (FTIR) analysis shows that AP1-c has typical characteristic absorption peaks of polysaccharides. Monosaccharide composition analysis indicates that AP1-c consists of galactose (Gal), rhamnose (Rha), arabinose (Ara) and glucose (Glc) at a molar ratio of 1.85:1.00:0.24:0.67. Methylation analysis of AP1-c reveals the presence of 1,3,4-linked-Rhap, 1-linked-Araf, 1,4-linked-Galp, 1-linked-Galp and 1,6-linked-Glcp with the molar ratio of 2.9:1.6:2.7:2.3:0.7. Structural analysis determines that AP1-c possesses a backbone consisting of $ \rightarrow3,4)-\alpha $-D-Rhap-(1 $ \rightarrow $ and $ \rightarrow4)-\beta $-D-Galp-(1 $ \rightarrow $ residues, while the branched chain is composed of $ \alpha $-L-Araf-(1 $ \rightarrow $, $ \beta $-D-Galp-(1 $ \rightarrow $ and $ \rightarrow6)-\beta $-D-Glcp-(1 $ \rightarrow $ residues. The results of this study lay a theoretical foundation for the development and utilization of lignified okra.
Keywords: lignified okra (Abelmoschus esculentus (L.) Moench); polysaccharide; physicochemical