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Melokhanines A–J, Bioactive Monoterpenoid Indole Alkaloids with Diverse Skeletons from Melodinus khasianus
journal contribution
posted on 2016-09-01, 12:18 authored by Gui-Guang Cheng, Dan Li, Bo Hou, Xiao-Nian Li, Lu Liu, Ying-Ying Chen, Paul-Keilah Lunga, Afsar Khan, Ya-Ping Liu, Zhi-Li Zuo, Xiao-Dong LuoThe new melokhanines A–J (1–10) and 22 known (11–32) alkaloids
were isolated from the twigs and leaves of Melodinus khasianus. The new compounds and their absolute configurations were elucidated
by extensive analysis of spectroscopic, X-ray diffraction, and computational
data. Melokhanine A (1), composed of a hydroxyindolinone
linked to an octahydrofuro[2,3-b]pyridine moiety,
is an unprecedented monoterpenoid indole alkaloid. Melokhanines B–H
(2–8) possess a new 6/5/5/6/6 pentacyclic
indole alkaloid skeleton. Alkaloids 1–16, 25–27, 31, and 32 showed the best antibacterial activity against Pseudomonas aeruginosa (MIC range 2–22 μM).
Among the seven dermatophytes tested, compound 1 showed
significant inhibitory activity against Microsporum canis, M. ferrugineum, and Trichophyton ajelloi (MIC range 38–150 μM), i.e., half the efficacy of the
positive control, griseofulvin.