Diterpenoids from Euphorbia paralias

In silico assessment of diterpenes as potential inhibitors of SARS-COV-2 main protease

Aim

We aimed to investigate the potential inhibitory effects of diterpenes on SARS-CoV-2 main protease (Mpro).

Materials & methods

We performed a virtual screening of diterpenoids against Mpro using molecular docking, molecular dynamics simulation and absorption, distribution, metabolism and excretion) analysis.

Results

Some tested compounds followed Lipinski's rule and showed drug-like properties. Some diterpenoids possessed remarkable binding affinities with SARS-CoV-2 Mpro and drug-like pharmacokinetic properties. Three derivatives exhibited structural deviations lower than 1 Å.

Conclusion

The findings of the study suggest that some of the diterpenes could be candidates as potential inhibitors for Mpro of SARS-CoV-2.

Macrocyclic Diterpenoid Constituents of Euphorbia deflexa, an Endemic Spurge from Greece

Euphorbia deflexa, an endemic spurge from Greece, was investigated for the occurrence of its diterpene constituents. Through continuous monitoring by ¹H NMR, 22 diterpenoids were isolated, including 16 previously undescribed compounds (euphodeflexins A-P), which belong to the jatrophane, ingenane, segetane, and pepluane diterpene types. Their chemical structures were elucidated through a combination of HRESIMS, NMR spectroscopy, and X-ray data. The isolated diterpenoids were tested against a panel of human cancer cell lines, as well as against two bacterial strains. Compounds 1, 13, and 17 were active against the HeLa cell line with IC₅₀ values 9.9, 9.8, and 5.8 μM, respectively.

Nephroprotective, cytotoxic and antioxidant activities of Euphorbia paralias

Objective

To investigate the effect of the ethyl acetate fraction of the aerial parts of E. paralias L. F. Euphorbiaceae on nephroprotective, cytotoxic, and antioxidant.

Methods

different spectroscopic and spectrophotometric methods were applied to identify phytoconstituents. The nephroprotective potential of E. paralias ethyl acetate fraction (Ep EtOAc) was evaluated in male rats with thioacetamide-induced kidney injury, as wll as cytotoxic activity was evaluated using a viability assay, and the antioxidant activity was evaluated using the DPPH method. Results: quantitative estimation of total phenolics and flavonoids of E. paralias was performed using unique spectrophotometric methods. The polyphenolic compounds gallic acid (1), ellagic acid (2), kaempferol-3-O-(6″-O-galloyl-β-D-glucopyranoside) (3), quercetin-3-O-β-D-glucopyranoside (4) and quercetin-3-O-β-D-arabinoside (5) were isolated from the ethyl acetate fraction of the aerial parts of E. paralias. The thioacetamide administration resulted in marked nephrotoxicity, but pretreatment with Ep EtOAc significantly attenuated the nephrotoxicity through alteration of kidney biomarkers, thereby improving the redox status of the tissue and restoring serum biochemical parameters nearly to normal levels. This study revealed a significant cytotoxic and strong antioxidant effect. Conclusion: we conclude that the Ep EtOAc may be used in the future as nephroprotective, cytotoxic, and antioxidant agent derived from a natural source.

Comparative Chloroplast Genomics of Endangered Euphorbia Species: Insights into Hotspot Divergence, Repetitive Sequence Variation, and Phylogeny

Euphorbia is one of the largest genera in the Euphorbiaceae family, comprising 2000 species possessing commercial, medicinal, and ornamental importance. However, there are very little data available on their molecular phylogeny and genomics, and uncertainties still exist at a taxonomic level. Herein, we sequence the complete chloroplast (cp) genomes of two species, E. larica and E. smithii, of the genus Euphorbia through next-generation sequencing and perform a comparative analysis with nine related genomes in the family. The results revealed that the cp genomes had similar quadripartite structure, gene content, and genome organization with previously reported genomes from the same family. The size of cp genomes ranged from 162,172 to 162,358 bp with 132 and 133 genes, 8 rRNAs, 39 tRNA in E. smithii and E. larica, respectively. The numbers of protein-coding genes were 85 and 86, with each containing 19 introns. The four-junction regions were studied and results reveal that rps19 was present at J_LB (large single copy region and inverted repeat b junction) in E. larica where its complete presence was located in the IRb (inverted repeat b) region in E. smithii. The sequence comparison revealed that highly divergent regions in rpoC1, rpocB, ycf3, clpP, petD, ycf1, and ndhF of the cp genomes might provide better understanding of phylogenetic inferences in the Euphorbiaceae and order Malpighiales. Phylogenetic analyses of this study illustrate sister clades of E. smithii with E. tricullii and these species form a monophyletic clade with E. larica. The current study might help us to understand the genome architecture, genetic diversity among populations, and evolutionary depiction in the genera.

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.

Euphorbia-Derived Natural Products with Potential for Use in Health Maintenance

Euphorbia genus (Euphorbiaceae family), which is the third largest genus of angiosperm plants comprising ca. 2000 recognized species, is used all over the world in traditional medicine, especially in the traditional Chinese medicine. Members of this taxa are promptly recognizable by their specialized inflorescences and latex. In this review, an overview of Euphorbia-derived natural products such as essential oils, extracts, and pure compounds, active in a broad range of biological activities, and with potential usages in health maintenance, is described. The chemical composition of essential oils from Euphorbia species revealed the presence of more than 80 phytochemicals, mainly oxygenated sesquiterpenes and sesquiterpenes hydrocarbons, while Euphorbia extracts contain secondary metabolites such as sesquiterpenes, diterpenes, sterols, flavonoids, and other polyphenols. The extracts and secondary metabolites from Euphorbia plants may act as active principles of medicines for the treatment of many human ailments, mainly inflammation, cancer, and microbial infections. Besides, Euphorbia-derived products have great potential as a source of bioactive extracts and pure compounds, which can be used to promote longevity with more health.

E. fischeriana Root Compound Dpo Activates Antiviral Innate Immunity

E. fischeriana has long been used as a traditional Chinese medicine. Recent studies reported that some compounds of E. fischeriana exhibited antimicrobial and immune enhance activity. Innate immune system is essential for the immune surveillance of inner and outer threats, initial host defense responses and immune modulation. The role of natural drug compounds, including E. fischeriana, in innate immune regulation is largely unknown. Here we demonstrated that E. fischeriana compound Dpo is involved in antiviral signaling. The genome wide RNA-seq analysis revealed that the induction of ISGs by viral infection could be synergized by Dpo. Consistently, Dpo enhanced the antiviral immune responses and protected the mice from death during viral infection. Dpo however was not able to rescue STING deficient mice lethality caused by HSV-1 infection. The enhancement of ISG15 by Dpo was also impaired in STING, IRF3, IRF7, or ELF4 deficient cells, demonstrating that Dpo activates innate immune responses in a STING/IRFs/ELF4 dependent way. The STING/IRFs/ELF4 axis is therefore important for Dpo induced ISGs expression, and can be used by host to counteract infection.

Genicunolide A, B and C: three new triterpenoids from Euphorbia geniculata

Three new triterpenoids, designated as genicunolide A (1), B (2) and C (3), along with friedelin (4) and friedelinol (5), were isolated from the aerial parts of Euphorbia geniculata. They were characterized as 1β-acetoxy-3β-hydroxy-11α,12α-oxidotaraxer-14-ene, 1β,3β-diacetoxy-21α-hydroxy-11α,12α-oxidotaraxer-14-ene and 3β,9α,20α-trihydroxy-Ψ-taraxast-5-ene, respectively, by spectral and chemical methods.

Headspace, Solid-phase Micro-extraction, Gas Chromatographic-Mass Spectrometric Analysis of Terpenoids in the Latex of Euphorbia Species

The volatile and semi-volatile terpenoids in the latex of Euphorbia amygdaloides, E. exigua, E. helioscopia, and E. peplus were analyzed by headspace, solidphase micro-extraction (HS-SPME), coupled with gas chromatography-mass spectrometry. The volatiles were extracted using a 100 μm polydimethylsiloxane SPME fiber under optimized extraction conditions. The compounds detected encompassed a range of chemical classes, but only terpenoids were evaluated. Only sesquiterpene hydrocarbons were detected in the tested samples of E. exigua, E. helioscopia, and E. peplus, with β-caryophyllene being the major one, but were never recorded in latex samples of E. amygdaloides, in which only the diterpene hydrocarbon kaur-16-ene was detected. α-Humulene was consistently found in samples of E. helioscopia, and E. peplus, but never in those of the other two species. These preliminary results show that the developed procedure is suitable for the analysis of small samples of Euphorbia latex and that, for each individual species, there is very little qualitative difference between samples, regardless of either place or date of collection.

Chemical composition, antimicrobial and antitumor activities of the essential oils and crude extracts of Euphorbia macrorrhiza

The present study aimed to examine the chemical composition and biological activity of essential oils extracted from Euphorbia macrorrhiza collected from Northwest China. The major constituents of the essential oils of aerial parts and roots of E. macrorrhiza are acorenone B (16.72% and 25.80%), (+)-cycloisosativene (14.94% and 12.40%), 3a-hydroxy-5b-androstane (10.62% and 5.52%), copaene (7.37% and 6.29%), l-calamenene (4.13% and 4.65%) and β-cedrene (8.40% and 7.98%), respectively. The minor components of them are thymene, γ-terpinene, thymecamphor, α-cedrene, zingiberene, trans-caryophyllene, β-chamigrene, curcumene, pentadecane, (−)-α-muurolene, cuparene, γ-cadinene, (Z)-3-heptadecene, 1,3,7,7-tetramethyl-2-oxabicyclo(4.4.0)dec-5-en-4-one, hexahydrofarnesyl acetone, γ-elixene and palmitinic acid. The antimicrobial and antitumor activitiy of the E. macrorrhiza essential oil against Staphyloccocus aureus, Escherichia coli, Canidia Albicans and Caco-2 cells were evaluated. Among all the tested microorganisms and Caco-2 cells, the essential oils showed the strongest inhibitory effect on Staphyloccocus aureus (MIC = 2.8 μg/mL) and Caco-2 cell (IC₅₀= 11.86 μg/mL), whereas no effect on Escherichia coli and Candida albicans. The data of this study suggested that the E. macrorrhiza essential oils have great potential as a natural medicine for microbial infections and cancers.

Triterpenes from Euphorbia rigida

Phytochemical studies of the aerial parts of Euphorbia rigida afforded three triterpenes: betulin (1), cycloart-23Z-ene-3, 25-diol (2) and cycloartan-3, 24, 25-triol (3), firstly isolated from this plant. The structures and relative stereochemistry were determined on the basis of extensive spectroscopic analyses, including 1D and 2D NMR experiments (1H NMR, 13C NMR, COSY, NOESY, HMQC and HMBC).

In vitro anti-influenza screening of several Euphorbiaceae species: structure of a bioactive Cyanoglucoside from Codiaeum variegatum

A bio-guided screening against influenza A virus (FLUAV) was carried out with seven Euphorbiaceae species. The results showed that chromatographic fractions from Phyllantus niruri, Euphorbia pulcherrima and Codiaeum variegatum had relevant anti-FLUAV activity, although only chromatographical subfractions from C. variegatum kept the activity. From this plant, the active compound against FLUAV was isolated. Its structure was assigned as 2-(3,4,5)-trihydroxy-6-hydroxymethyltetrahydropyran-2-yloxymethyl)acrylonitrile (1) on the basis of NMR, mass spectrometry and X-ray diffraction analysis. The compound displayed virucidal activity without impairment of haemagglutination properties of the used virus strain. This is the first report indicating antiviral activity of a cyanoglucoside.

Diterpenes from Euphorbia as Potential Leads for Drug Design

In the course of our chemical survey of bioactive plant metabolites, a large number of diterpenes have been isolated from Euphorbia species that showed interesting pharmacological activities. In particular, over sixty jatrophane, modified jatrophane, segetane, pepluane, and paraliane diterpenoids, fifty of them reported for the first time, were extracted, purified and characterized from Euphorbia dendroides, E. characias, E. peplus, E. amygdaloides, and E. paralias. The compounds based on jatrophane and modified jatrophane skeletons were shown to be potent inhibitors of P-glycoprotein, a membrane protein that confers upon cells the ability to resist lethal doses of certain cytotoxic drugs by pumping them out of the cells, thus resulting in a reduced cytotoxic effect. Those belonging to the rare classes of pepluane and paraliane were shown to be promising anti-inflammatory agents in vivo. In addition, by using LPS-stimulated J774 murine macrophages, it was demonstrated that the effect is ascribable to the reduction in the production of nitric oxide, prostaglandin E2 and TNF-α by inhibiting the expression of inducible nitric oxide synthase, cyclooxygenase-2 and TNF-α mRNA, respectively, through the down-regulation of NF-κB binding activity. The isolation of structurally-related analogues allowed us to perform SAR studies, which gave information on the key pharmacophoric elements of these new classes of promising drugs.

Paraliane and pepluane diterpenes as anti-inflammatory agents: First insights in structure–activity relationships

Two new diterpenes, named paralianone (2) and pepluene (3), based, respectively, on rare paraliane and pepluane skeletons, have been isolated from Euphorbia paralias, together with two known analogues (4 and 5), and their stereostructure determined by spectroscopic methods. The isolated compounds were tested as anti-inflammatory agents in vitro for evaluating their ability to inhibit the nitric oxide production in LPS-stimulated J774 murine macrophages. Compound 4 showed the highest anti-inflammatory activity comparable to those recently discovered for pepluanone (1). The data obtained provided first insights towards the structure-activity relationship of this class of compounds highlighting the key role of D-ring structure.

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.

Guyonianin A and B, Two Polyester Diterpenes from Algerian Euphorbia guyoniana

The dichloromethane extract of the aerial parts of Euphorbia guyoniana afforded two new polyester diterpenes, named guyonianin A and B, a rare class of bicyclic diterpenes. Their structures were established by high-field NMR spectroscopic methods, including DEPT, COSY, NOESY, HMQC and HMBC.

Evaluation of some medicinal plant extracts for antidiarrhoeal activity

The antidiarrhoeal effect of seven plant extracts namely: the aerial parts of Euphorbia paralias L. (EP), Bidens bipinnata L. (BB), Cynachum acutum L. (CyAc), Diplotaxis acris (Forssk.) Boiss (DA), Convolvulus fatmensis (CF) and Schouwia thebaica Webb (ST) and the leaves of Plantago major L. (PM), was evaluated on castor oil-induced diarrhoea, gastrointestinal movement in rats (charcoal meal) and on the motility of duodenum isolated from freshly slaughtered rabbits. A significant antidiarrhoeal effect of the tested plant extracts against castor oil-induced diarrhoea in rats was achieved by 200 and 400 mg/kg. The tested plant extracts decreased the gastrointestinal movement as indicated by the significantly (p<0.05 to 0.001) decreased distance travelled by the charcoal meal. The large dose of the tested plant extracts was slightly more effective than the small one. The antidiarrhoeal effect was confirmed by the reported dose dependent inhibition of the motility of duodenum isolated from freshly slaughtered rabbits. The EP and PM methanol extract produced a transient stimulation followed by inhibition in doses of less than 0.05 and 1.6 mg/kg, respectively. Higher concentrations caused rapid muscle relaxation. Tannins, flavonoids, unsaturated sterols/triterpenes, carbohydrates, lactones and proteins/amino acids were reported as major active constituents of the tested plants.