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, ion chromatography, 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 and 20.8 kDa), whereas LXHP-4 showed a monodisperse structure (75.6 kDa, polymer dispersity index=1.011). FT-IR analysis revealed no significant changes in functional groups after purification; however, 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 excellent thermal stability in LXHP-3, with the highest residual mass (42.51%) at 600 ℃. Additionally, LXHP exhibited strong 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.
