Scrophularia striata (Scrophulariaceae), a traditional Iranian medicine, has been used for the treatment of allergy, rheumatics and chronic inflammatory disorders.

In the present study, we investigated the in vitro and ex vivo suppressive effects of Scrophularia striata ethanolic extract on nitric oxide production in mouse peritoneal macrophages.

Peritoneal macrophages were harvested by lavaging with ice cold phosphate buffer saline. Macrophages obtained from mice not treated were cultured with 10μg/mL lipopolysaccaride (LPS), 20U/mL interferon-γ (IFN-γ), and various concentrations of Scrophularia striata extract for the in vitro experiments and those obtained from mice treated with different doses of the extract for 7 days were cultured with 10μg/mL LPS, 20U/mL IFN-γ for the in vivo experiments. Nitrit levels were measured by using the diazotization method based on the Griess reaction, which is an indirect assay for NO production.

In vitro exposure of mouse peritoneal macrophages with various concentrations of Scrophularia striata extract (10, 50 and 100μg/mL) significantly suppressed NO production in a dose-dependent manner. In vivo administration of Scrophularia striata extract (50 and 100mg/kg) to Balb/c mice inhibited LPS and IFN-γ induced production of NO in the isolated mouse peritoneal macrophages ex vivo in a dose-dependent manner. Exposure to Scrophularia striata extract had no effect on cell viability.

The results of the study demonstrated that the Scrophularia striata extract inhibit NO production in activated murine macrophages and we suggest that Scrophularia striata may be used in treating the inflammatory diseases.