From the fresh latex of Euphorbia cooperi N E Br was isolated by parti
tion and chromatographic methods, a diterpene ester 12-deoxyphorbol-16
-isobutyrate-3-tigliate. The phorbol ester exhibited highly irritant a
ctivity on the mouse ear. Since skin irritancy is an indication of pos
sible tumour promotion, the use of this plant as a medicine should be
discouraged.