Effects of an aqueous extract of cocoa on nitric oxide production of macrophages activated by lipopolysaccharide and interferon-γ

OBJECTIVE: Macrophages are the primary targets of bacterial lipopolysaccharide (LPS). The effects of cocoa extract on production of nitric oxide (NO) by murine J774.1 macrophages activated by LPS and interferon-gamma (IFN-gamma) were examined. METHODS: Cocoa was suspended in heated water and centrifuged, and the supernatant was then filtered. Nitrite was measured as a quantitative indicator of NO by spectrophotometry. LPS (1.0 mg/mL) and IFN-gamma (100 U/mL) were added to cultured macrophages with 0.05% cocoa extract, 0.25% cocoa extract, or pure water. NO synthesis by macrophages was significantly inhibited by cocoa extract (P < 0.01). RESULTS: The inhibitory effect increased with concentration of the extract (P < 0.01). IFN-gamma (100 U/mL) and, later, LPS (100 mug/mL) were added, together with 2.0% cocoa or pure water, to cultured macrophages. An inhibitory effect on NO production was observed on addition of only IFN-gamma, but more significant effects were obtained with addition of LPS (P < 0.01) and addition of both was most effective (P < 0.01). CONCLUSIONS: These data suggested that cocoa extract contains a suppressor of NO production in murine macrophages activated by LPS and IFN-gamma. This effect does not appear to be caused merely by neutralization of LPS.