Tumour-promoting Action of Croton Oil Fractions

SINCE Berenblum (1941) demonstrated the power of croton oil, the expressed or extracted oil of the seeds of Croton tiglium (L.), to promote skin-tumour formation in the mouse, its use has come to have an important place in investigations of the process of carcinogenesis. Its well-known pharmacological properties had stimulated several attempts, some time before this, to separate the active principle or principles. Cherbuliez and his colleagues (Cherbuliez, Ehninger and Bernhard, 1932), who review work up to that date, separated a resinous substance from the oil by solvent partition between petroleum ether and 90 per cent methanol. This resin was strongly vesicant; it was concentrated in the latter solvent, while most of the purgative principle of the oil remained in the former. A further purification of the vesicant principle was achieved by other physical procedures. Berenblum (1941) subjected the oil to solvent partition between petroleum ether and 90 per cent methanol, and obtained a resin from the latter solvent which was approximately ten times more potent as a promoter of skin tumour formation than the original oil. In the present investigation fractionation of croton oil, first by methods based on those of Cherbuliez, and then by chromatographic analysis, was undertaken. Fractions obtained at successive stages were tested for tumour-promoting power by methods which have been previously described (Gwynn and Salaman, 1953).