Eupholine A and B, A Pair of Lathyrane Epimers with Inhibitory Activity of Fibrinogen from <i>Euphorbia helioscopia</i> L.

Phytochemistry investigation of Euphorbia helioscopia led to the isolation of 22 diterpenoids, including five lathyranes, 11 jatrophanes, and six other types. Among them, eupholine A and B (1 and 2) are a pair of previously undescribed C-6' lathyrane epimers. The chemical structures of 1-22 were elucidated using spectral data analysis, and the absolute configurations of 1 together with another jatrophane diterpenoid (3) were determined by X-ray single-crystal diffraction techniques. Besides, the full nuclear magnetic resonance (NMR) assignments of 3 and 4 were first determined by analysis of their two-dimensional NMR data. All the isolates were screened for inhibition activity of fibrinogen on transforming growth factor-β1-stimulated LX-2 cells, and seven compounds (mainly lathyranes and jatrophanes types) showed certain inhibitory effects at 20 µM, being comparable to that of the positive control, silymarin. Notably, compound 14 (jatrophane type) showed significant inhibitory activity that is superior to silymarin. The study suggested that jatrophane diterpenoids and their analogs (lathyrane types) may serve as a potential chemical entity against liver fibrosis.