From the unripe fruits of Snfi'unz indicum L. (Euphorbiaceae) a biologicall>- active nitrogen-containing phorbol ester was isolated by a combination of centrifugal liquid chromatography and thin-layer chromatography-. This com- pound was identified as 12U[~~-mcth~laminobenzoylj-phorbol-13-acetate (sapintoxin D) by spectroscopic and hydrolysis methods. Sapintosin D occurred in a yield of 5 mgm per kilogram of dried fruits.The phorbol esters have been isolated as the toxic constituents of several genera of the family Euphorbiaceae. In particular, the genus Euphorbia has been shown to produce a variety of related diterpenes (1). The genus Sapium, also of the family Euphorbiaceae, has been less well investigated phytochemically despite the fact that these plants are a known toxicological hazard (2). Phorbol traditionally occurs in plants as a series of long chain aliphatic diesters, as in the case of tetradecanoylphorbol-acetate (TPA), the tumor-promoting constituent of Croton tiglium (3). A similar long chain aliphatic phorbol diester has previously been isolated from Sapium japonicum (4). Our previous investigations of S. indicum have shown that the major toxic constituents of this plant are 4-deoxyphorbol and 4-deoxy-5-hydroxyphorbol esters (5, 6) in contrast to the phorbol esters of 5'. japonicum. Furthermore, these esters all exhibited an S-methylamino-benzoate moiety and represent the first biologically active tigliane derivatives to be obtained containing a nitrogen atom in their structure. Re-examination of S. indicum fruits demonstrated the presence of a minor bright blue uv fluorescent compound in a yield of 6 mg per kilogram of dried plant material. We report here the isolation of this new nitrogen-containing phorbol ester