木质化秋葵均一多糖的理化特性及结构表征研究

文章以木质化秋葵为原料, 采用水提醇沉法和 DEAE-Cellulose 阴离子交换层析法获取木质化秋葵纯化多糖 AP1-c, 并对 AP1-c 的理化性质和结构进行研究。结果表明, AP1-c 是分子量为 658 kDa 的均一多糖, 总糖、糖醛酸、蛋白质的质量分数分别为 95.36%、24.83%、0.72%。傅里叶变换红外 (Fourier transform infrared, FTIR) 光谱分析表明 AP1-c 具有典型的多糖特征吸收峰。单糖组成结果显示, AP1-c 主要由半乳糖 (Gal)、鼠李糖 (Rha)、阿拉伯糖 (Ara) 和葡萄糖 (Glc) 组成, 摩尔比为 1.85:1.00:0.24:0.67。甲基化分析表明 AP1-c 主要存在 5 种糖苷键连接方式, 分别为 1, 3, 4-linked-Rha p、1-linked-Araf p、1, 4-linked-Gal p、1-linked-Gal p、1, 6-linked-Glc p, 对应的摩尔比为 2.9:1.6:2.7:2.3:0.7。结合化学和仪器方法可推断出 AP1-c 的主链由 $ \rightarrow 3, 4 $-α-D-Rha p- $ (1\rightarrow,\rightarrow4) $- $ \beta $-D-Gal p- $ (1\rightarrow $ 组成, 而支链包括 $ \alpha $-L-Araf p- $ (1\rightarrow,\beta $-D-Gal p- $ (1\rightarrow,\rightarrow6) $- $ \beta $-D-Glc p- $ (1\rightarrow $。研究结果为木质化秋葵的开发利用奠定了理论基础。

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.