Metarhizin C, a stereoisomer of BR-050 was isolated from a fungus Tolypocladium album RK17-F0007 through a screening program to search for new antitumor compounds. A structure of the isomer was determined by spectroscopic methods including detailed analysis of NOESY correlation and mass spectrometry, and found to be identical to that of 3-desacylmetarhizin A with the absolute structure. Previously, it had been isolated by Kikuchi et al and proposed as BR-050 including the stereo-structure. However, detailed analysis for the newly isolated isomer confirmed that 3-desacylmetarhizin A was not identical to BR-050. Therefore, we assigned it metarhizin C as a new BR-050 isomer. Metarhizin C showed selective cytotoxicity against osteosarcoma MG-63 cells in a glucose independent condition with IC50 value of 0.79 µg/ml, while > 30 µg/ml of IC50 value in a normal condition, and inhibited a mitochondrial respiration.

中文翻译：

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Metarhizin C 的结构和生物活性，一种来自 Tolypocladium album RK17-F0007 的 BR-050 ​​的立体异构体。

通过筛选程序从真菌 Tolypocladium 专辑 RK17-F0007 中分离出 BR-050 ​​的立体异构体 Metarhizin C，以寻找新的抗肿瘤化合物。该异构体的结构通过NOESY相关性详细分析和质谱分析等光谱方法确定，与3-脱酰基绿豆蔻苷A的绝对结构相同。此前，它已被 Kikuchi 等人分离并提出为 BR-050，包括立体结构。然而，对新分离的异构体的详细分析证实 3-desacylmetarhizin A 与 BR-050 ​​不同。因此，我们将它指定为新的 BR-050 ​​异构体。绿僵菌素 C 在不依赖葡萄糖的条件下对骨肉瘤 MG-63 细胞表现出选择性细胞毒性，IC50 值为 0.79 µg/ml，而 >