Structure Analysis of O-Glycans from Edible Bird's Nest and Its Antioxidant Effects against H₂O₂-induced Oxidative Damage in PC12 Cells

Objective: To elucidate the specific structure of O-glycans of edible bird's nests and their antioxidant protective effects on neuronal cells. Methods: O-glycans from the mucin of edible bird's nests were released using a chemical method, and their potential composition was characterized using ultra-high-performance liquid chromatography, matrix-assisted laser desorption/ionization-time of flight mass spectrometry, and enzymatic digestion. In addition, the monosaccharide composition of the saccharide chains in edible bird's nests was determined using acid hydrolysis. Cellular experiments were performed to assess the antioxidant protective effects of O-glycans against H₂O₂-induced damage in PC12 cells. Results: Twenty potential structures for O-glycans in edible bird's nests were identified, with Neu5Acα2-3Gal being predominant at an abundance of 40%, which is significantly higher than that of other structures. The monosaccharide constituents included Gal, Fuc, GalNAc, GlcNAc, and Man, with elevated levels of Gal, GlcNAc, and GalNAc. The total sialic acid content measured 150.99±3.04 mg/g, whereas bound sialic acid accounted for 139.06±3.96 mg/g, most sialic acids were present in their terminal glycosylation forms. Our findings showed that O-glycans of edible bird's nests can significantly reduce oxidative stress levels and upregulate the antioxidant mechanisms of cells, thus exerting an antioxidant protective effect on nerve cells. Moreover, compared to the positive control (sialic acid treatment), edible bird's nest O-glycans showed superior efficacy in enhancing GSH-Px enzyme activity, reducing reactive oxygen species levels, and upregulating HO-1 gene expression (P<0.05). Conclusion: O-glycans of bird nests may include 20 different structures, among which a major special structure, Neu5Acα2-3Gal, was detected. The O-glycan fraction derived from edible bird's nests exhibits a significant protective effect on PC12 cells subjected to oxidative damage induced by H₂O₂.