Bioactive Pentacyclic Triterpenoids from the Leaves of Cleistocalyx operculatus

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Abstract
Thirteen new pentacyclic triterpenoids, cleistocalyxic acids A–K (1, 2, 4, 5, and 7–13) and cleistocalyxolides A (3) and B (6), and 15 known analogues (14–28), based on taraxastane, oleanane, ursane, multiflorane, and lupane skeletons, were isolated from the leaves of Cleistocalyx operculatus. The structures of 1–13 were elucidated by analysis of their spectroscopic data and ECD/TDDFT computations. Cleistocalyxolide A (3), presumed to be derived from the known taraxastane-type compound 14, has a rare rearranged triterpenoid backbone. Cleistocalyxic acid B (2) displayed cytotoxicity against HepG2, NCI-N87, and MCF-7 cancer cell lines with IC50 values ranging from 3.2 to 6.5 μM, and cleistocalyxic acid D (5) was active against HepG2 and NCI-N87 cells with values around 5.0 μM. The noncytotoxic cleistocalyxic acid E (7) inhibited production of IL-6 by 68.1% and TNF-α by 53.7% in LPS-induced RAW 264.7 macrophages at a concentration of 2 μM.
Funding Information
  • National Natural Science Foundation of China (31470423)

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