Twenty-four diterpenoids of abietane family, including thirteen undescribed compounds and eleven known ones, were isolated from the leaves of Leucosceptrum canum. Their structures were elucidated by comprehensive spectroscopic analyses (including 1D and 2D-NMR and HRMS), and in the case of 15-hydroxy-abieta-8,11,13-trien-3-one by single-crystal X-ray diffraction. Their frameworks are highly diversified, involving normal abietane, 9,10-epoxy-9,10-seco-abietane, 18(4 → 3)-abeo-abietane, 3,4-seco-18(4 → 3)-abeo-abietane, and 16-nor-abietane. Selected compounds were evaluated for their cytotoxic activity against three human tumor cell lines, NCI-H1975, HepG2 and MCF-7. Among them, 3β-hydroxy-abieta-8,13-diene, 3β-hydroxy-abieta-8,11,13,15-tetraene, and 3β-hydroxy-9,10-epoxy-9,10-seco-abieta-8,11,13-triene exhibited moderate cytotoxicity against all three cell lines with IC50 values ranging from 8.11 to 50.73 μM, while 3α-hydroxy-abieta-8,11,13,15-tetraene, 3β-hydroxy-abieta-8,11,13,15-tetraen-7-one, and 15-hydroxy-18(4 → 3)-abeo-abieta-3,8,11,13-tetraene were selectively active with IC50 values ranging from 28.80 to 71.29 μM.

中文翻译：

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来自 Leucosceptrum canum 叶子的多样化松香烷家族二萜及其细胞毒活性

从 Leucosceptrum canum 的叶子中分离出 24 种松香烷家族的二萜类化合物，包括 13 种未描述的化合物和 11 种已知的化合物。它们的结构通过综合光谱分析（包括 1D 和 2D-​​NMR 和 HRMS）阐明，在 15-羟基-abieta-8,11,13-trien-3-one 的情况下通过单晶 X 射线衍射阐明。他们的框架高度多样化，包括普通松香烷、9,10-epoxy-9,10-seco-abietane、18(4 → 3)-abeo-abietane、3,4-seco-18(4 → 3)-abeo- abietane 和 16-nor-abietane。评估了所选化合物对三种人类肿瘤细胞系 NCI-H1975、HepG2 和 MCF-7 的细胞毒活性。其中，3β-羟基-松香-8,13-二烯、3β-羟基-松香-8,11,13,15-四烯和3β-羟基-9,10-环氧-9,10-seco-松香- 8,11,