Isolation of anti-inflammatory and cytotoxic secondary metabolites from Valeriana phu and evaluation of their mechanisms of action

Abstract

As a result of anti-inflammatory activity-guided fractionation, 16 secondary metabolites from the underground parts of Valeriana phu L. were obtained, including five new ones belonging to iridoid (1, 2, and 5), phenylpropanoid (6) and neolignan (7) chemical classes. Their structures were elucidated by 1D and 2D NMR analyses as well as HRESIMS. The in vitro anti-inflammatory activities of the extract, fractions and isolates were evaluated through NO inhibition assay on LPS-induced RAW 264.7 cells. Compounds 1–3, 7–9, 11, 13, and 16 which significantly inhibited the nitrite release (IC₅₀ 14.94–94.81 μM) were also assessed for their reducing capacity on TNF-α, IL-1β, IL-6, PGE2 and COX-2 production. Compounds 3, 8, and 16 inhibited LPS induced iNOS expression levels in Western blotting. Molecular docking studies for the active compounds targeting iNOS, TNF-α and COX-2 were also carried out. Moreover, compounds with remarkable anti-inflammatory activities were tested for their potential cytotoxicity against breast (MCF-7 and MDA-MB-231), glioblastoma (U87 and A172), pancreas (MIA PaCa-2 and PANC-1), hepatocellular (Mahlavu and Hep3B) cancer cell lines by WST-8. Compounds, 7, 8, and 16 showed significant cytotoxicity against A172 and PANC-1 cell lines (IC₅₀ 18.3–21.8 μM) via causing cell cycle arrest, especially in the G2/M phase and triggering the apoptotic pathway.