A bio‐guided isolation was applied to the Vietnamese lichen Roccella montagnei based on alpha‐glucosidase inhibition. Six compounds were isolated and structurally elucidated, including a new ortho depside, montagneside A (1), together with five known compounds, sekikaic acid (2), lanost‐7‐en‐3β‐ol (3), ethyl orsellinate (4), D‐montagnetol (5), and D‐erythrin (6). Their chemical structures were identified by extensive 1D and 2D NMR analysis, high‐resolution mass spectroscopy, and comparisons with those reported in the literature. D‐Erythrin (6), a major component, was selected for further modification using Smiles rearrangement. Three erythritol derivatives 6a‐6c were synthesized. Compounds 1‐3, 6, and 6a‐6c were evaluated for alpha‐glucosidase inhibition. Compounds 2 and 6a‐6c showed significant alpha‐glucosidase inhibition with IC50 values ranging from 7.9 to 149 µM, respectively. Molecular docking was applied to the most active compound 6a to clarify the inhibitory mechanism.

中文翻译：

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生物引导从越南地衣 Roccella montagnei 中分离α-葡萄糖苷酶抑制化合物

基于 α-葡萄糖苷酶抑制，对越南地衣 Roccella montagnei 进行了生物引导分离。分离并阐明了六种化合物的结构，包括一种新的邻缩酚酸 montagneside A (1)，以及五种已知化合物：关海酸 (2)、lanost-7-en-3β-ol (3)、奥赛酸乙酯 (4) 、D-montagnetol (5) 和 D-erythrin (6)。通过广泛的一维和二维核磁共振分析、高分辨率质谱分析以及与文献报道的比较，鉴定了它们的化学结构。选择主要成分 D-红曲蛋白 (6)，使用 Smiles 重排进行进一步修饰。合成了三种赤藓糖醇衍生物6a-6c。评估了化合物 1-3、6 和 6a-6c 的 α-葡萄糖苷酶抑制作用。化合物 2 和 6a-6c 显示出显着的 α-葡萄糖苷酶抑制作用，IC50 值范围分别为 7.9 至 149 µM。对最活跃的化合物 6a 进行分子对接，以阐明抑制机制。