Alkyl-benzofuran Dimers from Eupatorium chinense with Insulin-sensitizing and Anti-inflammatory Activities

Abstract Five new racemic alkyl-benzofuran dimers, (±)-dieupachinins I–M (1–5), were isolated from the root tubers of Eupatorium chinense, a well-known traditional Chinese medicine for the treatment of diphtheria in Guangdong province. The structures of these compounds, especially the first examples of 12,10′-epoxy dimer dieupachinin I (1), 12-nor-dimer dieupachinin J (2), and 12,12′-dinor-dimer dieupachinin K (3), were elucidated by spectroscopic data analysis. Chiral resolution were further carried out on a cellulose column by HPLC, and compounds 2–5 were successfully separated into two enantiomers, respectively. The absolute configurations of (+)-(2–5) and (−)-(2–5) were established by theoretical ECD calculation. All the compounds were evaluated for insulin-stimulated glucose uptake in C2C12 myotubes and (±)-dieupachinin I (1) exhibited the best activity. Compound 1 enhanced insulin-stimulated glucose uptake via activating the insulin receptor substrate 1/protein kinase B/glycogen synthase kinase-3β signaling pathway. Moreover, all the isolates were tested for their nitric oxygen (NO) inhibitory effects in lipopolysaccharide-treated RAW264.7 macrophages, and compounds (±)-1, (±)-2, and (±)-4 showed promising inhibitory effects with IC50 values of 6.42 ± 1.85, 6.29 ± 1.94, and 16.03 ± 2.07 μM, respectively. (±)-Dieupachinin I (1) again dose-dependently suppressed LPS-induced expression of inducible NO synthase and nuclear translocation of p65.