Tetrahydrofuran- and dihydrofuran-containing nor-clerodane diterpenoids from Teucrium viscidum: Isolation, stereochemical assignment, and anti-hepatic fibrosis activity.

Ten previously undescribed nor-clerodane diterpenoids, teuvinoids A-J (1-10), were isolated from the whole plants of Teucrium viscidum. Comprehensive structural elucidation, including unambiguous determination of absolute configurations, was accomplished using spectroscopic analysis, electronic circular dichroism, and single-crystal X-ray diffraction. Teuvinoids A (1) and B (2) are particularly noteworthy for featuring an unusual 2,3,4,5-tetrahydroxylated tetrahydrofuran moiety. Compounds 1 and 2 exhibited anti-hepatic fibrosis effects in TGF-β1-induced LX-2 hepatic stellate cells, as demonstrated by downregulation of key fibrotic biomarkers including fibronectin, collagen I, and α-smooth muscle actin.