Tumor promoting constituent of Euphorbia serrata L. latex

The Role of Ingenane Diterpenes in Cancer Therapy: From Bioactive Secondary Compounds to Small Molecules

Diterpenes are a class of critical taxonomic markers of the Euphorbiaceae family, representing small compounds (eg, molecules) with a wide range of biological activities and multi-target therapeutic potential. Diterpenes can exert different activities, including antitumor and multi-drug resistance-reversing activities, and antiviral, immunomodulatory, and anti-inflammatory effects, mainly due to their great structural diversity. In particular, one polycyclic skeleton has been highlighted: ingenane. Besides this natural diterpene, promising polycyclic skeletons may be submitted to chemical modification—by in silico approaches, chemical reactions, or biotransformation—putatively providing more active analogs (eg, ingenol derivatives), which are currently under pre-clinical investigation. This review outlines the current mechanisms of action and potential therapeutic implications of ingenol diterpenes as small cancer molecules.

Potent Anti-HIV Ingenane Diterpenoids from Euphorbia ebracteolata

Two new (1 and 2) and 14 known (3-16) ingenane diterpenoids were isolated from the roots of Euphorbia ebracteolata by bioassay-guided fractionation together with UPLC-MS ⁿ analysis. The absolute configurations of the new diterpenoids were established from electronic circular dichroism (ECD) data and ECD calculations. Except for ingenol (16), the ingenane diterpenoids with long aliphatic chain substituents (1-15) exhibited potent activities against HIV-1, with IC₅₀ values of 0.7 to 9.7 nM and selectivity index values of 96.2 to 20 263. From the results, it was concluded that long aliphatic chain substituents are required for the enhanced anti-HIV activity of ingenane diterpenoids.

Cocarcinogenic and Irritant Factors of Euphorbia Esula L. Latex

The latex of « Euphorbia esula » has been found to contain highly skin irritant and inflammatory ingenol-3-Δ2,4,6,8,10 pentene tetradecanoate and another factor, ingenol-3-dodecanoate, which is less irritating but which can be responsible for the cocarcinogenic activity exhibited by the latex preparation in the mice back skin experiment.

A screen for Fli-1 transcriptional modulators identifies PKC agonists that induce erythroid to megakaryocytic differentiation and suppress leukemogenesis

The ETS-related transcription factor Fli-1 affects many developmental programs including erythroid and megakaryocytic differentiation, and is frequently de-regulated in cancer. Fli-1 was initially isolated following retrovirus insertional mutagenesis screens for leukemic initiator genes, and accordingly, inhibition of this transcription factor can suppress leukemia through induction of erythroid differentiation. To search for modulators of Fli-1, we hereby performed repurposing drug screens with compounds isolated from Chinese medicinal plants. We identified agents that can transcriptionally activate or inhibit a Fli-1 reporter. Remarkably, agents that increased Fli-1 transcriptional activity conferred a strong anti-cancer activity upon Fli-1-expressing leukemic cells in culture. As opposed to drugs that suppress Fli1 activity and lead to erythroid differentiation, growth suppression by these new Fli-1 transactivating compounds involved erythroid to megakaryocytic conversion (EMC). The identified compounds are structurally related to diterpene family of small molecules, which are known agonists of protein kinase C (PKC). In accordance, these PKC agonists (PKCAs) induced PKC phosphorylation leading to activation of the mitogen-activated protein kinase (MAPK) pathway, increased cell attachment and EMC, whereas pharmacological inhibition of PKC or MAPK diminished the effect of our PKCAs. Moreover, in a mouse model of leukemia initiated by Fli-1 activation, the PKCA compounds exhibited strong anti-cancer activity, which was accompanied by increased presence of CD41/CD61 positive megakaryocytic cells in leukemic spleens. Thus, PKC agonists offer a novel approach to combat Fli-1-induced leukemia, and possibly other cancers,by inducing EMC in part through over-activation of the PKC-MAPK-Fli-1 pathway.

Ingenane Diterpenoids

Despite a more recent isolation and chemical characterization when compared to phorbol, along with its chemical instability, limited distribution in Nature, and scarce availability, ingenol is the only Euphorbia diterpenoid that has undergone successful pharmaceutical development, with ingenol 3-angelate (ingenol mebutate, Picato(®)) entering the pharmaceutical market in 2012 for the treatment of actinic keratosis. The phytochemical, chemical, and biological literature on members of the ingenane class of diterpenoids is reviewed from their first isolation in 1968 through 2015, highlighting unresolved issues both common to phorboids (biogenesis, relationship between molecular targets, and in vivo activity) and specific to ingenol derivatives (two-dimensional representation, in-out stereoisomerism, versatility of binding mode to PKC, and inconsistencies in the structural elucidation of some classes of derivatives). The biogenesis of ingenol is discussed in the light of the Jakupovic proposal of a dissection between the formation of the macrocyclic Euphorbia diterpenoids and the phorboids, and the clinical development of ingenol mebutate is chronicled in the light of its "reverse-pharmacology" focus.

Biologically active diterpenes containing a gem-dimethylcyclopropane subunit: an intriguing source of PKC modulators

This review describes diterpenes containing thegem-dimethylcyclopropane subunit isolated from natural sources with a special emphasis on their intriguing biological activities as a source of PKC modulators.

Chemistry and biological activity of secondary metabolites in Euphorbia from Iran

The chemical constituents of some species of Euphorbia, which grow mostly in semi-desert areas in Iran and on the Alborz Mountains in the north of Tehran, have been found to include chemotaxonomically important myrsinane diterpenoids and cycloartane triterpenoids. The Euphorbia plants collected in province of Azarbaijan in the northwestern part of Iran contained mostly derivatives of skin-irritating ingenol esters. Some of the diterpenoids with myrsinane carbon skeleton inhibited enzymes such as alpha-glycosidase, urease, HIV-1 reverse transcriptase, and prolyl endopeptidase. They also showed analgesic and DNA-damaging activities. The present review describes the chemistry and biological activity of several compounds isolated from different species of Iranian Euphorbia: diterpenoids with myrsinane skeletons, flavonoids, tannins, alkanes, sterols, mono-, sesqui- and triterpenoids, skin-irritating and tumor-promoting latexes and their active ingenol diterpenoids.