Artemzhongdianolides A1-A21, antihepatic fibrosis guaiane-type sesquiterpenoid dimers from Artemisia zhongdianensis

In the search for new antihepatic fibrosis candidates, it was observed that the EtOH extract of Artemisia zhongdianensis and EtOAc fraction had cytotoxicity against hepatic stellate cell line LX2 (HSC-LX2) with the inhibitory ratios of 85.7 % and 83.9 % at 400 mu g/mL. 21 new guaianolide dimers, artemzhongdianolides A1 - A21 (1-21) were isolated from the active fractions under the guidance of bioassay, and elucidated by spectral analyses (HRESIMS, 1D and 2D NMR, IR, ECD). The absolute stereochemistry of compounds 1, 13, and 14 was determined by single-crystal X-ray diffraction analyses. Cytotoxicity evaluation suggested that nine compounds exhibited activity against HSC-LX2 with IC50 values ranging from 14.0 to 95.2 mu M. Of them, compounds 2, 6, and 13 displayed significant cytotoxicity against HSC-LX2 with IC50 values of 22.1, 24.3 and 14.0 mu M, which were 6 to 10 times more active than the positive drug silybin (IC50, 148.6 mu M). Preliminary mechanism study revealed that compounds 2, 6, and 13 could markedly inhibited the deposition of human collagen type I (Col I), human hyaluronic acid (HA), and human laminin (HL) with IC50 values of 37.9, 54.8, and 28.0 mu M (Col I), 29.5, 25.3, and 42.9 mu M (HL), 31.2, 94.6, and 12.4 mu M (HA), which were 1.5 to 13-fold more potent than silybin.