Anti-inflammatory activity of herbal medicines: Inhibition of nitric oxide production and tumor necrosis factor-alpha secretion in an activated macrophage-like cell line

Houttuynia cordata Thunb. (HQ, Glycyrrhiza uralensis Fischer (GU), Forsythia suspense (Thunb.) Vahl (FS), and Lonicera japonica Thunb. (U) are Chinese herbs known to possess anti-inflammatory properties. The effects of aqueous extracts of these herbs on the production of the pro-inflammatory mediators, nitric oxide (NO) and tumor necrosis factor-alpha (TNF-alpha) were examined in an activated macrophage-like cell line, RAW 264.7 cells. Aqueous extracts from FS at 0.0625-2.0 mg/ml inhibited in vitro production of NO and secretion of TNF-alpha in a dose-dependent manner. FS at 1.0-2.0 mg/ml and 0.125-2.0 mg/ml significantly inhibited NO production and TNF-alpha, respectively. An extract of LJ demonstrated potent inhibition of both NO production and TNF-alpha secretion in a dose-dependent manner. An aqueous extract from HC inhibited NO production in a dose-dependent manner, but minimally (approximately 30%) inhibited TNF-alpha secretion at 0.0625 and 0.125 mg/ml. In contrast, an aqueous extract of GU had a minimal effect on both the production of NO and the secretion of TNF-alpha. Viability of cells at all concentrations studied was unaffected as determined by MTT cytotoxicity assay and trypan blue dye exclusion. These results suggest that aqueous extracts from FS, LJ and HC have anti-inflammatory actions as measured by inhibition of NO production and/or TNF-alpha secretion.