Tumor inhibitors. 114. Aloe emodin: antileukemic principle isolated from Rhamnus frangula L.

A systematic fractionation of an ethanol-water (1:1) extract of the seeds of Rhamnus frangula L., guided by assays for tumore-inhibitory activity, led to the isolation of aloe emodin (1). This compound was found to show significant antileukemic activity against the P-388 lymphocytic leukemia in mice. A note-worthy vehicle-dependence of the testing results is reported. In the light of this vehicle-dependence, the re-examination of other anthraquinone derivatives is recommended.