To find anti-inflammatory compounds from the tuberous roots of Dioscorea batatas, we isolated 6-hydroxy-2,4,7-trimethoxyphenanthrene (batatasin I) from the dichloromethane (CH(2)Cl(2)) fraction of this plant. Batatasin I inhibited both the generation of prostaglandin D(2) (PGD(2)), leukotriene C(4)