Isolation and structure revision of pepluane diterpenoids from euphorbia peplus

Diterpenoids from Euphorbia peplus possessing cytotoxic and anti-inflammatory activities

Phytochemical investigation into the medium polar fraction of the ethanol extract of Euphorbia peplus led to the identification of 32 diterpenoids with five structural types. Compounds 1-5 and 7-11 are reported for the first time, while the configuration of 6,7-epoxy group of 6 was revised to be β-oriented. Compounds 1-5 feature a rare structural variation of the double bond at Δ1 migrating to Δ1(10) in the tigliane-type diterpenoid family. Biologically, compound 21 was found to be the only one to show moderate cytotoxic activity, associated with the presence of a benzoyloxy residue at C-16. Besides, compounds 4, 8, 12, 13, 16, and 19 show significant inhibitory activities against NO production induced by LPS in RAW264.7 macrophage cells, with IC50 values within 2-5 μM. Structure-activity relationship (SAR) analysis revealed that the ingenane-type diterpenoids have the best anti-inflammatory activity, and the esterification at 3-OH or 5-OH is crucial. Further biological researches demonstrated that 13, the predominant metabolite in this plant, exerts anti-inflammatory effects by blocking the activation of NF-κB and MAPK signaling pathways.

Jatrophane Diterpenoids from Euphorbia peplus Linn. as Activators of Autophagy and Inhibitors of Tau Pathology

Ten jatrophane diterpenoids were isolated from the whole plant Euphorbia peplus Linn. including seven new ones, named euphjatrophanes A-G (labeled compounds 1, 2, 4-8). Their structures were elucidated with a combination of spectroscopic and single-crystal X-ray crystallography, enabling the identification of compounds 3, 9, and 10 as the previously published euphpepluones G, K, and L, respectively. All compounds were evaluated for their bioactivity with flow cytometry in assays of autophagic flux in HM Cherry-GFP-LC3 (human microglia cells stably expressing the tandem monomeric mCherry-GFP-tagged LC3) cells. Euphpepluone K (9) significantly activated autophagic flux, an effect that was verified with confocal analysis. Moreover, cellular assays showed that euphpepluone K (9) induced autophagy and inhibited Tau pathology.

Iron-Catalyzed Skeletal Conversion of Lathyrane to Premyrsinane Euphorbia Diterpenes and Their Cytotoxic Activities

Two new premyrsinane-type diterpenes (2 and 3) as diastereomers were synthesized from lathyrane-type diterpene euphorbia factor L₃ (1) for the first time via an efficient Fe(acac)₃-catalyzed skeleton conversion process. This conversion features a biogenetically inspired strategy that relies on a concise reductive olefin coupling involving intramolecular Michael addition with free radicals. The structures of 2 and 3 were elucidated by a combination of the interpretation of their spectroscopic data and single-crystal X-ray diffraction analysis. The premyrsinane diterpenes 2 and 3 exhibited cytotoxic activity against the 4T1 breast cancer cell line, while the parent compound euphorbia factor L₃ (1) was inactive. The current results not only confirmed the biogenetic relationship between lathyranes and premyrsinanes for the first time but also suggested a novel method for the preparation of naturally rare premyrsinane diterpenes with high bioactivity from the more abundant natural lathyrane diterpenes.

Jatrophane Diterpenoids from the Seeds of Euphorbia peplus with Potential Bioactivities in Lysosomal-Autophagy Pathway

Euphopepluanones F - K (1 - 4), four new jatrophane type diterpenoids were isolated from the seeds of Euphorbia peplus, along with eight known diterpenoids (5 - 12). Their structures were established on the basis of extensive spectroscopic analysis and X-ray crystallographic experiments. The new compounds 1 - 4 were assessed for their activities to induce lysosomal biogenesis through LysoTracker Red staining. Compound 2 significantly induced lysosomal biogenesis. In addition, compound 2 could increase the number of LC3 dots, indicating that it could activate the lysosomal-autophagy pathway.

Macrocyclic diterpenoids from the seeds of Euphorbia peplus with potential activity in inducing lysosomal biogenesis

The first phytochemical investigation of the seeds of Euphorbia peplus led to the isolation and characterization of five new (1-5), named euphopepluanones A-E, and five known diterpenoids (6-10). Their structures were established by extensive spectroscopic analysis and X-ray crystallographic experiments. Euphopepluanones A-E (1-3) feature a very rare 5/11/5-tricyclic skeleton, and euphopepluanones D-E (4-5) represent the first report of lathyrane type diterpenoids found in E. peplus. The new compounds 1-5 were assessed for their activities to induce lysosomal biogenesis through LysoTracker Red staining, in which compounds 1 and 3 could significantly induce lysosomal biogenesis. In addition, compounds 1 and 3 could promote the nuclear translocation of TFEB, a master transcriptional factor of lysosomal genes, indicating that compounds 1 and 3 induced lysosomal biogenesis through activation of TFEB.

Three new diterpenoids from Euphorbia peplus

Three new diterpenoids (1-3) (two abietane type diterpenoids and a paralianone type diterpenoid), together with four known compounds (4-7) were isolated from the whole plants of Euphorbia peplus. Their structures were elucidated through spectroscopic analysis and physicochemical characteristics. The cytotoxic activities of compounds 1-7 against five human tumour cell lines were evaluated, however, they were inactive at the concentration of 40 μM. The compound 3 enhanced lysosomal biogenesis with Lyso Tracker staining intensity of 132.6%.

Jatrophane and rearranged jatrophane-type diterpenes: biogenesis, structure, isolation, biological activity and SARs (1984-2019)

Diterpene compounds specially macrocyclic ones comprising jatrophane, lathyrane, terracinolide, ingenane, pepluane, paraliane, and segetane skeletons occurring in plants of the Euphorbiaceae family are of considerable interest in the context of natural product drug discovery programs. They possess diverse complex skeletons and a broad spectrum of therapeutically relevant biological activities including anti-inflammatory, anti-chikungunya virus, anti-HIV, cytotoxic, and multidrug resistance-reversing activities as well as curative effects on thrombotic diseases. Among macrocyclic diterpenes of Euphorbia, the discovery of jatrophane and modified jatrophane diterpenes with a wide range of structurally unique polyoxygenated polycyclic derivatives and as a new class of powerful inhibitors of P-glycoprotein has opened new frontiers for research studies on this genus. In this review, an attempt has been made to give in-depth coverage of the articles on the naturally occurring jatrophanes and rearranged jatrophane-type diterpenes isolated from species belonging to the Euphorbiaceae family published from 1984 to March 2019, with emphasis on the biogenesis, isolation methods, structure, biological activity, and structure-activity relationship.

Chemical profile and defensive function of the latex of Euphorbia peplus

Plant latex is an endogenous fluid secreted from highly specialized laticifer cells and has been suggested to act as a plant defense system. The chemical profile of the latex of Euphorbia peplus was investigated. A total of 13 terpenoids including two previously unknown diterpenoids, (2S*,3S*,4R*,5R*,6R*,8R*,l1R*,13S*,14S*,15R*, 16R*)-5,8,15-triacetoxy-3-benzoyloxy-11,16-dihydroxy-9-oxopepluane and (2R*,3R*, 4S*,5R*,7S*,8S*,9S*,l3S*,14S*,15R*)-2,5,8,9,14-pentaacetoxy-3-benzoyloxy-15-hydroxy-7-isobutyroyloxyjatropha-6(17),11E-diene), ten known diterpenoids, and a known acyclic triterpene alcohol peplusol, were identified, using HPLC and UPLC-MS/MS analyses and through comparison with the authentic compounds isolated from the whole plant. The diterpenoids exhibited significant antifeedant activity against a generalist plant-feeding insect, the cotton bollworm (Helicoverpa armigera), with EC₅₀ values ranging from 0.36 to 4.60 μg/cm². In particular, (2R*,3R*,4S*,5R*,7S*,8S*,9S*,l3S*,14S*,15R*)-2,5,9,14-tetraacetoxy-3-benzoyloxy-8,15-dihydroxy-7-isobutyroyloxyjatropha-6(17),11E-diene and (2R*,3R*, 4S*,5R*,7S*,8S*,9S*,l3S*,14S*,15R*)-2,5,14-triacetoxy-3-benzoyloxy-8,15-dihydroxy-7-isobutyroyloxy-9-nicotinoyloxyjatropha-6(17),11E-diene had EC₅₀ values of 0.36 and 0.43 μg/cm², respectively, which were approximately 7-fold more potent than commercial neem oil (EC₅₀ = 2.62 μg/cm²). In addition, the major peplusol showed obvious antifungal activity against three strains of agricultural phytopathogenic fungi, Rhizoctonia solani, Colletotrichum litchi and Fusarium oxysporum f. sp. niveum. The results indicated that terpenoids in the latex of E. peplus are rich and highly diversified, and might function as constitutive defense metabolites against insect herbivores and pathogens for the plant.

Pepluane and Paraliane Diterpenoids from Euphorbia peplus with Potential Anti-inflammatory Activity

Twelve new diterpenoids based on two rare skeletal types, namely, paralianones A-D (1-4) and pepluanols A-H (5-12), along with five known compounds, were isolated from an acetone extract of Euphorbia peplus. Their structures were proposed based on 1D and 2D NMR spectroscopic data analysis. These diterpenoids were evaluated for potential anti-inflammatory activity in a lipopolysaccharide-stimulated mouse macrophage cellular model. Compounds 3, 4, 11, 13, and 16 displayed moderate inhibitory effects on NO inhibition, with IC50 values ranging from 29.9 to 38.3 μM.

Advanced Structural Determination of Diterpene Esters Using Molecular Modeling and NMR Spectroscopy

Three new jatrophane esters (1-3) were isolated from Euphorbia amygdaloides ssp. semiperfoliata, including an unprecedented macrocyclic jatrophane ester bearing a hemiketal substructure, named jatrohemiketal (3). The chemical structures of compounds 1-3 and their relative configurations were determined by spectroscopic analysis. The absolute configuration of compound 3 was determined unambiguously through an original strategy combining NMR spectroscopy and molecular modeling. Conformational search calculations were performed for the four possible diastereomers 3a-3d differing in their C-6 and C-9 stereocenters, and the lowest energy conformer was used as input structure for geometry optimization. The prediction of NMR parameters ((1)H and (13)C chemical shifts and (1)H-(1)H coupling constants) by density functional theory (DFT) calculations allowed identifying the most plausible diastereomer. Finally, the stereostructure of 3 was solved by comparison of the structural features obtained by molecular modeling for 3a-3d with NMR-derived data (the values of dihedral angles deduced from the vicinal proton-proton coupling constants ((3)JHH) and interproton distances determined by ROESY). The methodology described herein provides an efficient way to solve or confirm structural elucidation of new macrocyclic diterpene esters, in particular when no crystal structure is available.