Morinda citrifolia, commonly known as noni, has a long history of utilization throughout much of tropical Polynesia and is considered to be the second most important medicinal plant in the Hawaiian Islands. Recently, the use of noni as a dietary supplement in the United States has greatly increased. Bioassay-guided fractionation of a dichloromethane-soluble partition of a MeOH extract of noni fruits has led to the isolation of an extremely potent quinone reductase inducer, 2-methoxy-1,3,6-trihydroxyanthraquinone (1). This new anthraquinone (1) was nearly 40 times more potent than a positive control, l-sulforaphane. Furthermore, compound 1 demonstrated no discernible cytotoxicity at the highest dose tested. In addition to compound 1, 11 known compounds were also isolated and identified in the present investigation. This is the first report of the isolation of anthraquinones from noni fruits.