Cytotoxic 14-Membered Macrolides from a Mangrove-Derived Endophytic Fungus, <i>Pestalotiopsis microspora</i>

Seven new 14-membered macrolides, pestalotioprolides C (2), D–H (4–8), and 7-O-methylnigrosporolide (3), together with four known analogues, pestalotioprolide B (1), seiricuprolide (9), nigrosporolide (10), and 4,7-dihydroxy-13-tetradeca-2,5,8-trienolide (11), were isolated from the mangrove-derived endophytic fungus Pestalotiopsis microspora. Their structures were elucidated by analysis of NMR and MS data and by comparison with literature data. Single-crystal X-ray diffraction analysis was used to confirm the absolute configurations of 1, 2, and 10, while Mosher’s method and the TDDFT-ECD approach were applied to determine the absolute configurations of 5 and 6. Compounds 3–6 showed significant cytotoxicity against the murine lymphoma cell line L5178Y with IC50 values of 0.7, 5.6, 3.4, and 3.9 μM, respectively, while compound 5 showed potent activity against the human ovarian cancer cell line A2780 with an IC50 value of 1.2 μM. Structure–activity relationships are discussed. Coculture of P. microspora with Streptomyces lividans caused a roughly 10-fold enhanced accumulation of compounds 5 and 6 compared to axenic fungal control.本研究从红树林来源的内生真菌小孢拟盘多毛孢（Pestalotiopsis microspora）中分离得到7个新的14元大环内酯类（14-membered macrolides）化合物，分别为拟盘多毛孢内酯C（2）、D~H（4~8）以及7-O-甲基黑孢菌素内酯（3）；同时还分离得到4个已知类似物：拟盘多毛孢内酯B（1）、赛里库内酯（seiricuprolide，9）、黑孢菌素内酯（nigrosporolide，10）以及4,7-二羟基-13-十四碳-2,5,8-三烯内酯（11）。通过核磁共振波谱（NMR）与质谱（MS）数据分析，并结合文献数据比对，阐明了所有化合物的平面结构。单晶X射线衍射分析被用于确定化合物1、2和10的绝对构型，而针对化合物5和6，则采用莫斯耶法（Mosher’s method）与时间密度泛函理论-电子圆二色谱技术（TDDFT-ECD）解析其绝对构型。化合物3~6对小鼠淋巴瘤细胞株L5178Y表现出显著的细胞毒性，半数抑制浓度（IC50）分别为0.7、5.6、3.4和3.9 μM；其中化合物5对人卵巢癌细胞株A2780亦显示出强效抑制活性，IC50值为1.2 μM。本研究还探讨了该类化合物的构效关系。与纯培养真菌对照组相比，小孢拟盘多毛孢与淡青链霉菌（Streptomyces lividans）共培养时，化合物5和6的积累量提升约10倍。