Ten stigmastane-type steroids bearing unusual Δ28-24-hydroxy side chains, dictyopterisins A-J, including three pairs of C-24 epimers, dictyopterisins B/C, F/G, and I/J, were isolated from the brown alga Dictyopteris undulata Holmes, together with two previously reported analogues, (24S)- and (24R)-saringosterol. Their structures were elucidated on the basis of extensive spectroscopic analysis, with their absolute configurations at the stereogenic center C-24 of the side chain being assigned by a direct comparison of 1H NMR data with those of related known compounds. The absolute configurations of the steroidal nuclei of dictyopterisins A, B, and H were determined using the modified Mosher's method. The mixture of dictyopterisins D and E and dictyopterisin I exhibited promising PTP1B inhibitory activities with IC50 values of 1.88 and 3.47 μM, respectively, comparable to the positive control oleanolic acid (IC50, 2.78 μM). In addition, the mixture of dictyopterisins D and E and dictyopterisins F-J displayed significant cytotoxicities against the human cancer cell lines HL-60 (IC50 from 1.02 to 2.70 μM) and A-549 (IC50 from 1.35 to 2.85 μM).

中文翻译：

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PTP1B 抑制性和细胞毒性 C-24 差向异构体的 Δ 28 -24-羟基柱头烷型类固醇，来自褐藻 Dictyopteris undulat a Holmes

从褐藻 Dictyopteris undulata Holmes 中分离出 10 种带有不寻常 Δ28-24-羟基侧链的柱头烷型类固醇, dictyopterisin AJ, 包括三对 C-24 差向异构体、dictyopterisin B/C、F/G 和 I/J ，连同两个先前报道的类似物，(24S)-和(24R)-沙林甾醇。它们的结构是在广泛的光谱分析的基础上阐明的，它们在侧链立体中心 C-24 的绝对构型是通过 1H NMR 数据与相关已知化合物的数据直接比较确定的。使用改进的 Mosher 方法确定 dictyopterisin A、B 和 H 的甾体核的绝对构型。dictyopterisin D 和 E 以及 dictyopterisin I 的混合物表现出有希望的 PTP1B 抑制活性，IC50 值为 1.88 和 3.47 μM，分别与阳性对照齐墩果酸 (IC50, 2.78 μM) 相当。此外，dictyopterisins D 和 E 以及 dictyopterisins FJ 的混合物对人癌细胞系 HL-60（IC50 从 1.02 到 2.70 μM）和 A-549（IC50 从 1.35 到 2.85 μM）显示出显着的细胞毒性。