Anti-inflammatory Activity of 6-Hydroxy-2,7-dimethoxy-1,4-henanthraquinone from Tuberous Roots of Yam (Dioscorea batatas) through Inhibition of Prostaglandin D_2 and Leukotriene C4 Production in Mouse Bone Marrow-derived Mast Cells

6-Hydroxy-2,7-dimethoxy-1,4-phenanthraquinone (PAQ) isolated from the tuberous roots of Yam (Dioscorea batatas) inhibited cyclooxygenase-2 (COX-2) and cyclooxygenase-1 (COX-1) dependent prostaglandin D_2 (PGD_2) generation in mouse bone marrow-derived mast cells in a concentration-dependent manner with IC_50 values of 0.08 μM and 0.27 μM, respectively. In the Western blotting with specific anti-COX-2 antibodies, the decrease of the quantity of PGD2 was accompanied by a decrease in the COX-2 protein level. But PAQ did not affect COX-1 protein level. In addition, this compound inhibited 5-lipoxygenase (5-LOX) dependent production of leukotriene C_4 in a dose-dependent manner, with an IC_50 of 0.032 μM. These results demonstrate that PAQ has a dual COX-2/5-LOX inhibitory activity. This compound also inhibited the degranulation reaction in a dose-dependent manner with an IC_50 of 2.7 μM. Thus, these results suggest that PAQ may be useful in regulating mast cell-mediated inflammatory diseases. KCI Citation Count: 13