Syringa vulgaris bark as a source of compounds affecting the release of inflammatory mediators from human neutrophils and monocytes/macrophages

In traditional European medicine, common lilac (Syringa vulgaris L., Oleaceae) bark has been used in the form of an infusion, decoction or alcoholic extract as an antipyretic and a cold and cough treatment. Our primary study showed that alcoholic extract of the bark was able to decrease the release of interleukin- 8 in an in vitro model The aim of the study was to investigate the phytochemical composition of common lilac bark extract by the HPLC-DAD-MS/MS method, isolate the dominant compounds and investigate their effects on the proinflammatory functions of human neutrophils and monocytes/macrophages. Syringin (sinapyl alcohol-O-glucoside), olivil-4′-O-glucoside, sinapyl aldehyde-O-glucoside and forsythoside B were isolated using RP-18, Sephadex LH-20 column chromatography and preparative chromatography. The structures were confirmed by the UV, MS and 1H and 13C NMR spectra. The effects on cytokine (TNF-α, IL-1β, IL-6) and chemokine (IL-8 and MCP-1) production by neutrophils and monocytes/macrophages were measured using an enzyme-linked immunosorbent assay (ELISA). Moderate anti-inflammatory activity was observed in the neutrophil model for all compounds compared with oleuropein, a common compound in the Oleaceae family with well-documented anti-inflammatory effects. However, syringin at concentration of 50 μM significantly inhibited TNF-α production and stimulated TGF-β release in LPS-treated monocytes/macrophages. Our results demonstrated that common lilac bark is a valuable source of active compounds, especially syringin.