Discovery of hepatoprotective activity components from Thymus quinquecostatus celak. by molecular networking, biological evaluation and molecular dynamics studies

Thymus quinquecostatus Celak. is an edible herb that widely cultivated in Asia and possesses hepatoprotective activity, but the underlying non-volatile components of this protective activity are not well studied. In this study, combining molecular networking visualization and bioassay-guided fractionation strategies, a pair of novel skeleton diterpenoid enantiomers, (+)- and (−)-thymutatusone A [(+)- and (−)-1], along with one new and one known biogenetically related compounds (2–3) and 16 other known compounds (4–19), were identified from T. quinquecostatus. Their structures were exhaustively characterized by comprehensive spectroscopic data, X-ray diffraction analysis, and ECD calculations. Compounds (±)-1, (−)-1, and (+)-1, with a rare tricyclo [7.3.1.0^2,7] tridecane skeleton, exhibited potent hepatoprotective activity in HepG2 cells injured by acetaminophen, with EC₅₀ values of 11.5 ± 2.8, 8.4 ± 1.9, and 12.2 ± 0.3 μM respectively. They were more potent than positive drug bifendate (EC₅₀ 15.2 ± 1.3). Further, the underlying mechanism for the hepatoprotective activity of compound (−)-1 related to activating the Nrf 2 signaling pathway. What's more, molecular docking and molecular dynamics simulation analysis showed that compound (−)-1 could dock with the active site of Nrf 2 protein and form a stable system through hydrogen bonding. These results suggest that T. quinquecostatus can be used as a valuable source of hepatoprotective activity compounds.