A phorbol ester that is phorbol in which the hydroxy groups at the cyclopropane ring juction (position 13) and the adjacent carbon (position 12) have been converted into the corresponding acetate and myristate esters. It is a major active constituent of the seed oil of Croton tiglium. It has been used as a tumour promoting agent for skin carcinogenesis in rodents and is associated with increased cell proliferation of malignant cells. However its function is controversial since a decrease in cell proliferation has also been observed in several cancer cell types.