The extract of the roots of Euphorbia kansui, which has been widely used in Chinese folk medicine for the treatment of cancer, demonstrated antileukemic activity against the P-388 lymphocytic leukemia in mice. Bioassay-directed fractionation of the active extract led to the isolation and characterization of two novel antileukemic diterpene esters, kansuiphorin A  [13-hydroxyingenol-3-<2,3-dimethylbutanoate)-13-dodecanoate-20-hexadecanoate] and kansuiphorin B  [6,7-epoxy-13-hydroxyingenol-3-(2,3-dimethylbutanoate)-13-dodecanoate-20-hexadecanoate], whose structures were established from spectral evidence and chemical transformation. Kansuiphorins A and B demonstrated potent antileukemic activity with T/CS176 and 177% at 0.1 and 0.5 mg/kg, respectively. The selectivity of kansuiphorin A, which inhibits the growth of particular cell types within the disease-oriented human cancer cell line panels, is discussed.
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