Two sulfated fucoidan fractions (Lj3 and Lj5) were extracted from Saccharina japonica and then subjected to acid hydrolysis to obtain Lj3h and Lj5h. Lj3h and Lj5h were characterized using IR, methylation analysis, and mass spectrometry. It was found that Lj3h and Lj5h were homogeneous low molecular weight fucoidans. Specifically, Lj3h was composed of the main chain of 1,3‐linked α‐L‐fucopyranose residues with sulfate at C‐2 and/or C‐4 and three different monosaccharides (galactose, glucose, mannose) branched at C‐2 and/or C‐4 of fucose residue. Lj5h contained backbones of alternating galactopyranose residues and fucopyranose residues attached via a 1→3 linkage (galactofucan) and 1→6 linked galactan. The sulfation pattern was mainly located at C2/C4 fucose or galactose residues and more branches occupied at C‐4 of fucose residue and C‐2, C‐3 or/and C‐6 of galactose residue. In vitro assay indicated that, among the four fucoidans tested, only Lj5 showed potent α‐glucosidase inhibitory activity with IC50 of 153.27±22.89 μg/mL, and the two parent fucoidans, Lj3 and Lj5, showed better antioxidant activity than their derivatives. These findings highlight the structure and bioactivity diversity of Saccharina japonica‐derived fucoidans.

中文翻译：

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从糖精中提取的褐藻糖胶的结构表征和α-葡萄糖苷酶抑制和抗氧化活性

从糖精中提取两种硫酸化岩藻依聚糖组分（Lj3 和 Lj5），然后进行酸水解得到 Lj3h 和 Lj5h。Lj3h 和 Lj5h 使用 IR、甲基化分析和质谱法进行表征。发现Lj3h和Lj5h是均质的低分子量岩藻依聚糖。具体来说，Lj3h 由 1,3-连接的 α-L-吡喃岩藻糖残基的主链和在 C-2 和/或 C-4 处带有硫酸盐的主链和三种不同的单糖（半乳糖、葡萄糖、甘露糖）在 C-2 和/或岩藻糖残基的C-4。Lj5h 包含交替的吡喃半乳糖残基和吡喃岩藻糖残基的骨架，它们通过 1→3 连接（半乳聚糖）和 1→6 连接的半乳​​聚糖连接。硫酸化模式主要位于 C2/C4 岩藻糖或半乳糖残基，更多的分支占据岩藻糖残基的 C-4 和 C-2，半乳糖残基的 C-3 或/和 C-6。体外试验表明，在测试的四种岩藻多糖中，只有 Lj5 显示出有效的 α-葡萄糖苷酶抑制活性，IC50 为 153.27±22.89 μg/mL，并且两种亲本岩藻依聚糖 Lj3 和 Lj5 显示出比其衍生物更好的抗氧化活性。这些发现突出了糖精衍生的岩藻多糖的结构和生物活性多样性。