Published: May 25, 2011 Copyright r 2011 American Chemical Society and American Society of Pharmacognosy 1453 dx.doi.org/10.1021/np200202h | J. Nat. Prod. 2011, 74, 1453–1461 ARTICLE pubs.acs.org/jnp Jatrophane Diterpenes from Euphorbia esula as Antiproliferative Agents and Potent Chemosensitizers to Overcome Multidrug Resistance Andrea Vasas, † Edv  ard Sulyok, † D ora R  edei, † Peter Forgo, † P  al Szab o, ‡ Istv  an Zupk o, §  Agnes Ber  enyi, § Joseph Moln  ar, ^ and Judit Hohmann* ,† † Department of Pharmacognosy, University of Szeged, E€ otv€ os u. 6, H-6720 Szeged, Hungary ‡ Institute of Chemistry, Chemical Research Centre, Hungarian Academy of Sciences, H-1525 Budapest, Hungary § Department of Pharmacodynamics and Biopharmacy, University of Szeged, H-6720 Szeged, Hungary ^ Department of Medical Microbiology and Immunobiology, University of Szeged, H-6720 Szeged, Hungary b S Supporting Information P lants of the genus Euphorbia are characterized by a unique profile of diterpenoid polyesters, often accumulated in relatively large amounts and generally occurring in complex mixtures, based on the acylation of several different skeletons (e.g., ingenane, 1 lathyrane, 2 tigliane, 3 jatrophane, 4 and daphnane 5 ) with different acids. Certain of these compounds exhibit extremely strong skin-irritating and tumor-promoting effects, and some display therapeutically relevant biological properties, such as antiprolifera- tive, cytotoxic, antiviral, antibacterial, platelet aggregation-inhibiting, and vasoconstrictor activities. 4À11 The cytotoxic activities of jatrophane diterpenes have been studied previously in different test models. Compounds obtained from E. esula demonstrated in vitro cytotoxicity on cultured B16 cells, 12 and euphornin and helioscopinolide A from E. helioscopia proved active against HeLa and MDA-MB-231 cells. 13 Diter- penes of the jatrophane type isolated from E. tuckeyana were reported to exert moderate inhibitory activity on the growth of gastric and pancreatic tumor cell lines. 14 The microtubule- interacting activity of jatrophane polyesters of E. semiperfoliata was assessed, and they were found to stimulate purified tubulin assembly in vitro and to induce paclitaxel-like microtubules. These compounds inhibited the growth of some human cancer cells without inducing cell cycle arrest in the G2/M phase. 15 The discovery of jatrophane diterpenes as a new class of potent inhibitors of P-glycoprotein (P-gp, ABCB1) has led to increasing interest in research on this type of compounds. 16 P-gp is one of the most important and best-studied ABC transporter proteins and acts as an energy-dependent pump of chemother- apeutic agents, thereby decreasing the intracellular concentration of drugs and resulting in multidrug resistance (MDR). Many powerful inhibitors have been identified among jatrophane and modified jatrophane diterpenes, which are promising com- pounds for drug development because of their manifold higher potencies than those of cyclosporin A or verapamil. 17,18 Euphorbia esula L., or leafy spurge (Euphorbiaceae), produces a skin-irritant, toxic, milky latex and is a promising source of biologically active diterpenes. Ingenane, 19 lathyrane, 20 and jatro- phane 12,21 polyesters were isolated previously from the root, seed, and herb of the plant. Some of them have antileukemic, cytotoxic, MDR-modifying, and anti-herpes simplex activities. 6,22À24 In the course of our earlier work, six new jatrophane diter- penes, named esulatins AÀF(10À14), were reported from E. esula. 25À27 We now report further six new (esulatins HÀM, 1À6) and three known (7À9) diterpenes from this plant. The antiproliferative activities of compounds 1À14 and their MDR- reversing activities have also been assessed. Received: March 4, 2011 ABSTRACT: Phytochemical study of whole, undried plants of Euphorbia esula led to the isolation of six new (1À6) jatrophane diterpene polyesters, named esulatins HÀM, together with the known compounds 2R,3β,5R,7β,15β-pentaacetoxy-9R-nicoti- noyloxyjatropha-6(17),11-dien-14-one (7), salicinolide (8), and euphosalicin (9). The structures and relative configuration of 1À6 were established on the basis of extensive spectroscopic analysis, including HRESIMS and one- and two-dimensional NMR techniques. All these compounds, together with diter- penes (10À14) isolated previously from this plant, were evaluated for their antiproliferative activity against HeLa, Ishikawa, and MCF7 cells. The multidrug-resistance-reversing activities were also investigated on L5178 mouse lymphoma cells transfected with the pHa MDR1/A retrovirus DNA. Preliminary structureÀactivity relationship data are discussed.