RESEARCH ARTICLE

 

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

 

 

Wendy L. Popplewell^I; Eloise A. Marais^I; Linda Brand^II; Brian H. Harvey^II; Michael T. Davies-Coleman^{I, *}

^IDepartment of Chemistry, Rhodes University, Grahamstown, 6140 South Africa
^IIUnit for Drug Research and Development, Division of Pharmacology, School of Pharmacy, North-West University, Potchefstroom, 2520 South Africa

 

 

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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.

Keywords: Euphorbia bothae, Euphorbiaceae, phorbol ester, opioid receptor

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Acknowledgements

Senior Ranger Brad Fike of the Great Fish River Reserve and Dr Peter Lent of the University of Fort Hare are respectively thanked for providing unlimited access to E. bothae in the GFFR and drawing our attention to this research project. Funding for this research project was provided by a Joint Research Committee (JRC) research grant from Rhodes University and is gratefully acknowledged.

 

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Received 28 September 2010
Revised 19 October 2010
Accepted 27 October 2010

 

 

* To whom correspondence should be addressed. E-mail: m.davies-coleman@ru.ac.za