老香黄多糖的提取纯化、结构表征与抗氧化活性评价

Extraction, Purification, Structural Characterization and Antioxidant Activity of Polysaccharide from Laoxianghuang

摘要:

老香黄是潮汕地区药膳两用的特色制品，其多糖成分具有潜在药理活性，但其结构特征尚不清晰。为解析老香黄多糖的结构特征和抗氧化活性能力，该研究通过水提醇沉法提取粗多糖（LXHP），经分离纯化得到两种组分（LXHP-3和LXHP-4），并采用高效凝胶渗透色谱、离子色谱、红外光谱、X-射线衍射、扫描电镜和热重分析等技术表征其组成、结构、形态及热稳定性，同时以DPPH和ABTS自由基清除能力评估体外抗氧化活性。结果表明，两种组分均为以半乳糖醛酸为主的酸性多糖；LXHP-3的分子量呈双峰分布（75.3 kDa和20.8 kDa），而LXHP-4为单峰均一结构（75.6 kDa，PDI=1.011）；FTIR分析表明分离纯化不改变多糖的官能团，但LXHP-3的酯化度显著降低；SEM显示纯化前后的多糖均由片状结构和纤维状结构组成；XRD分析表明LXHP-3呈现半结晶结构，LXHP和LXHP-4则为无定型态；TGA显示LXHP-3的热稳定性更优，最终残留质量最高（42.51%）；LXHP具有更好的DPPH和ABTS自由基的清除效果。该研究可提高对老香黄多糖结构的了解，为其功能性开发利用及构效关系研究提供理论。

Abstract:

Laoxianghuang , a medicinal and edible specialty from the Chaoshan region, contains polysaccharides with potential pharmacological activities, yet their structural characteristics remain unclear. To investigate the structural features and antioxidant capacity of Laoxianghuang polysaccharides, crude polysaccharides (LXHP) were extracted via water extraction and alcohol precipitation, followed by purification to obtain two fractions (LXHP-3 and LXHP-4). The composition, structure, morphology, and thermal stability of these polysaccharides were systematically characterized by high-performance gel permeation chromatography (HPGPC), ion chromatography (IC), Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The in vitro antioxidant activity was evaluated based on DPPH and ABTS radical scavenging capacities. The results demonstrated that both fractions were acidic polysaccharides primarily composed of galacturonic acid. LXHP-3 exhibited a bimodal molecular weight distribution (75.3 kDa and 20.8 kDa), while LXHP-4 showed a monodisperse structure (75.6 kDa, PDI = 1.011). FT-IR analysis revealed no significant changes in functional groups after purification, but the degree of esterification in LXHP-3 was notably reduced. SEM imaging indicated that both crude and purified polysaccharides consisted of sheet-like and fibrous structures. XRD analysis suggested that LXHP-3 displayed a semi-crystalline structure, whereas LXHP and LXHP-4 were amorphous. TGA revealed superior thermal stability in LXHP-3, with the highest residual mass (42.51%) at 600℃. Additionally, LXHP exhibited superior DPPH and ABTS radical scavenging effects. This study enhances the understanding of the structural properties of Laoxianghuang polysaccharides and provides a theoretical foundation for their functional exploitation and structure-activity relationship research.