Chlorholones A−H, bioactive sesquiterpenoids with diverse skeletons from Chloranthus holostegius

Abstract

Eight previously undescribed sesquiterpenoids with different skeletons, designated as chlorholones A−H (1−8), including three noreudesmane-type sesquiterpenoids (1−3, the first discovery of this type in the genus), one germacrane-type sesquiterpenoid (4), one acorane-type sesquiterpenoid (5), two cadinene-type sesquiterpenoids (6−7) and one guaiane-type sesquiterpenoid (8), together with eight known sesquiterpenoids (9−16), were identified from the whole plant of Chloranthus holostegius. A combination of spectral analysis, electron circular dichroism calculations, and X-ray crystallography were employed in the structural characterization. Among the isolated compounds, 10 exhibited notable anti-inflammatory activity, showing significant inhibition of nitric oxide (NO) release in LPS-induced RAW 264.7 macrophages, with an IC₅₀ value of 8.94 ± 1.10 μM, surpassing the positive control, dexamethasone. Furthermore, 10 effectively reduced the expression of key inflammatory mediators, including TNF-α, IL-6, IL-1β, CXCL10, iNOS, and COX-2, as confirmed by RT-PCR and ELISA, indicating its promising anti-inflammatory effects. Additionally, compound 10 demonstrated significant inhibition of LPS-induced ROS production in RAW 264.7 cells, as evidenced by flow cytometry analysis. It also achieved an average ROS clearance rate of 85.45 ± 2.70 % in H₂O₂-induced zebrafish at a concentration of 20 μM, comparable to glutathione.