OBJECTIVETo examine the anti-inflammatory mechanism of total flavonoids of Glycyrrhizae Radix et Rhizoma (TFGR) and its ingredient on IFN-gamma and LPS-induced macrophage RAW264.7.

METHODSolvent extraction and macroporous resin enrichment were adopted for preparing ethanol extracts of Glycyrrhizae Radix et Rhizoma, components and total flavonoids. Ultraviolet spectroscopy was used to determine the content of total flavonoids. An IFN-gamma and LPS-induced cell inflammatory model was established. Griess reaction was used for detecting the effect of extracts at all levels and flavonoid monomers on nitrite content in cell culture supernatant. FRAP was used for measuring anti-oxidation capacity. RT-PCR was used for determining the effect of TFGR and isoliquiritigenins on intracellular inducible nitric oxide synthase iNOS, COX-2, IL-6 and PPAR-gamma. Western blot was used for detecting the effect of TFGR and isoliquiritigenins on iNOS, COX-2 and MAPK signal transduction pathways.

RESULTCompared with other extracts, ethyl acetate fractions from Glycyrrhizae Radix et Rhizoma showed the highest inhibition ratio on nitrite content at the same concentration. After being enriched with macroporous resin, TFGR (60. 08% of liquiritin) of ethyl acetate extracts from Glycyrrhizae Radix et Rhizoma showed dose-dependence, and inhibited the nitrite content in cell culture supernatant, which was superior to ethyl acetate extracts, and had the protective effect on post-stimulated cell activity, with a stronger total anti-oxidation than other extracts. TFGR inhibited iNOS, IL-6 mRNA, protein expressions of iNOS, COX-2 and IL-6. Isoliquiritigenin, a flavonoid monomer, could inhibited iNOS, COX-2 gene and protein expression and gene expressions of IL-1beta and IL-6, and upside-regulated gene expression of PPAR-gamma.

CONCLUSIONActivity-oriented extraction suggests that ethyl acetate fractions from Glycyrrhizae Radix et Rhizoma is one of components with anti-inflammatory activity. TFGR obtained by enriching the active component showed dose-dependence, and inhibited the nitrite content in cell culture supernatant. The anti-inflammatory effect is partially achieved by regulating ERK signal pathway and inhibiting iNOS and COX-2 gene and protein expressions through extracellular signals of mitogen activated protein kinases (MAPKs). Specifically, isoliquiritigenin may be a component with TFGR anti-inflammatory activity.