Fractionation of the aqueous extract of Derris scandens stems extract using tests for eicosanoid inhibition resulted in the isolation of three isoflavonoids, genistein, its 7-O-α-rhamno(1→6)-β-glucosyl glycoside, a new compound, and two known isoprenyl derivatives 3′-γ,γ-dimethylallylweighteone and scandenin. The isoprenylated compounds showed a high inhibitory effect on eicosanoid production in vitro but HPLC analysis showed that the genistein accounted for most of the activity of the total extract. Antioxidant studies showed that genistein and the isoprenylated compounds showed activity comparable to standard antioxidants. Genistein and its glycoside demonstrated no cytotoxicity in the MTT test but the prenylated compounds showed some toxicity and also increased LDH release from polymorphonucleocytes, at concentrations much greater than would be encountered in an aqueous extract of D. scandens