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Ervatamines A–I, Anti-inflammatory Monoterpenoid Indole Alkaloids with Diverse Skeletons from Ervatamia hainanensis

Zhang, Dong-Bo, Yu, Dao-Geng, Sun, Meng, Zhu, Xu-Xin, Yao, Xiao-Jun, Zhou, Shuang-Yan, Chen, Jian-Jun, Gao, Kun
Journal of natural products 2015 v.78 no.6 pp. 1253-1261
Tabernaemontana, X-ray diffraction, anti-inflammatory activity, carbon, circular dichroism spectroscopy, indole alkaloids, indomethacin, inhibitory concentration 50, monoterpenoids, spectral analysis
Nine new monoterpenoid indole alkaloids, ervatamines A–I (1–9), and five known ones (10–14), were isolated from Ervatamia hainanensis. The new structures were elucidated by extensive spectroscopic analysis and comparison to known compounds. Their absolute configurations were determined by various methods including computational methods, X-ray diffraction analysis, and electronic circular dichroism spectroscopy, as well as chemical transformations. Ervatamine A (1) is a ring-C-contracted ibogan-type monoterpenoid indole alkaloid with an unusual 6/5/6/6/6 pentacyclic rearranged ring system. Ervatamines B–E (2–5) display a nitrogen-containing 9/6 ring system, which is rarely observed in nature. The epimeric ervatamines B (2) and C (3) possess a 22-nor-monoterpenoid indole alkaloid carbon skeleton, which was only found in deformylstemmadenine. Compounds 10 and 14 exhibited significant anti-inflammatory activities, with IC₅₀ values of 25.5 and 41.5 μM, respectively, while the IC₅₀ value of indomethacin as a positive control was found to be 42.6 μM. Additionally, compound 9 showed mild activity against 786-O and HL-60 cell lines.