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Inhibitory activity of Cynara scolymus L. on inducible nitric oxide synthase (iNOS)
For testing iNOS inhibitory effects of plant extracts, macrophages (RAW 264.7) were stimulated with lipopoly-saccharides (LPS) and interferon-gamma in presence or absence of the respective sample. The NO release was quantified photometrically as its stable product nitrite in the cell culture supernatants using the Griess assay and comparing with a sodium nitrite standard curve.
In a previous screening we showed that Cynara scolymus L. (Asteraceae) exhibited a remarkable inhibitory effect on inducible nitric oxide synthase (iNOS).  Among the three extracts tested (n-hexane, dichloromethane and methanol) the dichloromethane extract revealed the highest inhibitory potential and was subjected to activity guided isolation which led to the compounds cynaropicrin (1), aguerin B (2), grosheimin (3). They inhibit NO production with IC50 values in the range of 1.5–9.5µM.
References: 1. Blunder, M. et al. (2007) Planta Med 73:845.