Euphorbias of South Africa: two new phorbol esters from Euphorbia bothae

Abstract

Two known phorbol esters, 12-deoxyphorbol-13-isobutyrate-20-acetate (1) and 12-deoxyphorbol-13-(2-methylbutyrate)-20-acetate (2), and two new phorbol esters, 12-deoxyphorbol-13-isobutyrate-16-angelate-20-acetate (3) and 12-deoxyphorbol-13-(2-methylbutyrate)-16-angelate-20-acetate (4), were isolated from the endemic South African plant Euphorbia bothae. Standard spectroscopic techniques were used to elucidate the structures of all four compounds. The interaction of 1-4 with opioid receptors was explored in an attempt to explain the unexplained stupor occasionally observed in herbivores browsing on E. bothae