Cocarcinogens of the diterpene ester type from Croton flavens L. and esophageal cancer in Curaçao.

From the roots of Croton flavens L., 3 highly irritant and tumor promoting Croton factors F1--F3 and the corresponding 3 cryptic Croton factors F'1--F'3 were isolated and characterized as novel esters of 16-hydroxy- and 4-deoxy-16-hydroxyphorbol, respectively. These findings suggest that tumor promoters of the phorbol ester type, ingested through the widespread and frequent use of Croton flavens according to local habits, may be causally related to the well recognized high rate of esophageal cancer on Curaçao.