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Published on: March 15, 2017
Highly Oxidized Germacranolides from Elephantopus tomentosus and the Configurational Revision of Some Previously
1Key Laboratory of Computational Chemistry-Based Natural Antitumor Drug Research & Development, Liaoning Province; Engineering Research Center of Natural Medicine Active Molecule Research & Development, Liaoning Province; Key Laboratory of Natural Bioactive Compounds Discovery & Modification, Shenyang; School of Traditional Chinese Materia Medica, Shenyang Pharmaceutical University, Shenyang 110016, People's Republic of China.
Abstract:
Highly oxidized germacranolides are mainly found in the genus Elephantopus, contain a characteristic ten-membered molecular core that is highly flexible, and exhibit potential cytotoxic properties. However, their configurations were assigned ambiguously in previous reports due to spectroscopic observation of macrocyclic systems. Herein, 17 highly oxidized germacranolides, including 12 new germacranolides (1-12), were isolated from Elephantopus tomentosus. Their structures were characterized by spectroscopic data analysis combined with X-ray crystallography and ECD calculations, and it was possible to propose configurational revisions of five previously reported analogues (13-17). Cytotoxic activities for 1-17 against two hepatocellular carcinoma cell lines (HepG2 and Hep3B) were tested, and compounds 1-10 and 13-16 generated IC50 values of 2.2-9.8 μM. Furthermore, the observed cytotoxic activity of 1 was determined as being mediated by inducing the apoptosis of HepG2 and Hep3B cells via mitochondrial dysfunction.
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