METHODS: Dichloromethane extracts of QC and NBZ were prepared (QCD and NBZD). Two compounds, QCD5 and AL-2, were isolated from QC and NBZ respectively. Human B cells (U266 cells) were used to test anti-IgE effects of each of the herbal medicines, dichloromethane extracts, and pure compounds. The total IgE levels were measured by ELISA. Cell viabilities were evaluated by counting under microscope. IC50 values of each testing-drug were calculated. Potential synergistic effects were analyzed by computing values of interaction index. Prism 4.0 was used for statistical analysis.
RESULTS: Two compounds isolated were identified as 1,3-dihydroxy-anthraquinone (QCD5) and Arctigenin (AL-2). The herbal water extracts (QC and NBZ), their dichloromethane extracts (QCD and NBZD), and compounds (QCD5 and AL-2) inhibited in vitro IgE production by U266 cells in a non-toxic dose-dependent manner. Interaction index values at IC50 were calculated as 0.3286 for the mixture of QC and NBZ; 0.7236 for the mixture of QCD and NBZD; 0.6509 for the mixture of QCD5 and AL-2. All interaction indices were below 1.
CONCLUSIONS: Herbal medicines Rubia cordifolia and Fructus Arctii; their dichloromethane exacts QCD and NBZD; and their isolated compounds QCD5 and AL-2 synergistically inhibit IgE production in vitro.