Four sesquiterpene lactones (SLs), including three undescribed proline-SL conjugates, the guaianolides calophyllamine A and 8-epiixerisamine A, and the eudesmanolide calophyllamine B, were isolated from the methanol extract of Hieracium calophyllum R. Uechtr. (Compositae) flowering heads. Another known guaianolide, crepiside E, was detected in Hieracium L. species for the first time. Their structures were elucidated using extensive 1D and 2D NMR spectroscopy in combination with HRMS. The isolated SLs were used as external standards for qualitative and quantitative LC-MS analysis of the dry methanol extracts of the flowering aerial parts of 28 Hieracium species from the Balkan Peninsula. Guaianolides were the dominant SLs in 27 species studied. The chemosystematic significance of detected SLs was evaluated using multivariate statistics (PCA, nMDS and UPGMA). Differentiation between the main groups was well supported. All four compounds significantly and equally contributed to the differences between the species. In addition, the eudesmanolide calophyllamine B could be a significant chemosystematic marker for H. sect. Villosa (Griseb.) Gremli s.l. and Glauciformia (Freyn) Zahn-Italica (Fr.) Av. Touv.

中文翻译：

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巴尔干半岛 28 种山桧属植物甲醇提取物中的倍半萜内酯及其化学系统学意义

从 Hieracium calophyllum R. Uechtr 的甲醇提取物中分离出四种倍半萜内酯 (SL)，包括三种未描述的脯氨酸-SL 缀合物、愈创木酚内酯 calophyllamine A 和 8-epiixerisamine A 以及 eudesmanolide calophyllamine B。(菊科)花头。另一种已知的愈创木酚内酯，crepiside E，首次在 Hieracium L. 物种中被检测到。使用广泛的 1D 和 2D NMR 光谱结合 HRMS 阐明了它们的结构。分离出的 SL 用作外部标准，用于对来自巴尔干半岛的 28 种 Hieracium 物种的开花地上部分的干燥甲醇提取物进行定性和定量 LC-MS 分析。愈创木内酯是所研究的 27 个物种中的优势 SL。使用多变量统计（PCA，nMDS 和 UPGMA）。主要群体之间的区分得到了很好的支持。所有四种化合物均显着且同等地促成了物种之间的差异。此外，eudesmanolide calophyllamine B 可能是 H. sect 的重要化学系统标记。Villosa (Griseb.) Gremli sl 和 Glauciformia (Freyn) Zahn-Italica (Fr.) Av. 托夫。