Ingenane and jatrophane diterpenoids from Euphorbia kansui and their antiproliferative effects

20-Deoxyingenol ester and ether derivatives: Synthesis, properties and cytotoxicity

The C-3 and C-5 substituted 20-deoxyingenol monoesters are important active components in Euphorbiaceae plants. Nonetheless, their similar physical properties make them difficult to distinguish. The present study developed fast and efficient rules for identifying the esterification sites of 20-deoxyingenol based on a series of chemical syntheses of monoesters and literature research, utilizing NMR spectroscopy, optical rotation analysis, and chromatographic retention behavior. In addition, a series of 20-deoxyingenol ether derivatives, including 1,3,4-oxadiazole derivatives, were synthesized. The cytotoxic activities of 20-deoxyingenol derivatives were evaluated on A549 and HepG2 cell lines. Notably, 20-deoxyingenol 1,3,4-oxadiazole derivative 22 (IC50 = 8.8 μM) exhibited significant anticancer activity against HepG2 cells with low toxicity to normal cells (IC50 > 50 μM), making it a promising compound. We investigated the potential anticancer mechanism of compound 22 by examining protein expression changes in HepG2 cells using quantitative proteomics. Our findings indicated that 22 induced G1/S phase cell cycle arrest and, In a dose-dependent manner, inhibited CDK4 and CyclinD1 expression while upregulating P21. Moreover, 22 promoted the accumulation of autophagosomes and the proteins LC3 and PINK1, enhancing autophagy and mitophagy in HepG2 cells. Collectively, compound 22 might serve as a novel autophagy agonist with anticancer properties.

Two O-acyltransferases from the diterpene biosynthetic gene cluster of Euphorbia lathyris contribute to the structural diversity of medicinal macrocyclic diterpenoid esters biosynthesis

Macrocyclic diterpenoid esters from Euphorbiaceae plants hold significant medicinal value owing to their structural diversity and for attributing structural uniqueness and biological efficacy. However, the responsible enzymes for the acylation of macrocyclic diterpenoids remain unknown. We identified two macrocyclic diterpenoid O-acyltransferases, ElBAHD16 and ElBAHD35, from the diterpene biosynthetic gene cluster of Euphorbia lathyris. ElBAHD16 and ElBAHD35 were characterized both in vitro (using Escherichia coli) and in vivo (using Nicotiana benthamiana and E. lathyris) and exhibited mono-acylation activities toward the hydroxy groups of their substrates, 7-hydroxylathyrol and lathyrol. ElBAHD16 showed not only regioselectivity toward the 7-OH group of 7-hydroxylathyrol but also donor promiscuity, thereby producing three different mono-acylation products. Conversely, ElBAHD35 demonstrated specific recognition for the 5-OH group of 7-hydroxylathyrol and lathyrol, thereby mediating mono-acetylation reactions with acetyl-CoA, showing donor specificity. Site-directed mutagenesis revealed that residues H154 and T363 in ElBAHD16 are critical for its catalytic activity. Notably, the Q35 residue enhanced the efficiency of ElBAHD16, while the M296, N292, and F394 residues were crucial for its donor promiscuity. These findings elucidate the last step in the biosynthesis of macrocyclic diterpenoid esters and highlight the contribution of acyltransferases to the structural diversity of diterpenoids.

An Ingenane-Type Diterpene from Euphorbia kansui Promoted Cell Apoptosis and Macrophage Polarization via the Regulation of PKC Signaling Pathways

Euphorbia kansui, a toxic Chinese medicine used for more than 2000 years, has the effect of "purging water to promote drinking" and "reducing swelling and dispersing modules". Diterpenes and triterpenes are the main bioactive components of E. kansui. Among them, ingenane-type diterpenes have multiple biological activities as a protein kinase C δ (PKC-δ) activator, which have previously been shown to promote anti-proliferative and pro-apoptotic effects in several human cancer cell lines. However, the activation of PKC subsequently promoted the survival of macrophages. Recently, we found that 13-hydroxyingenol-3-(2,3-dimethylbutanoate)-13-dodecanoate (compound A) from E. kansui showed dual bioactivity, including the inhibition of tumor-cell-line proliferation and regulation of macrophage polarization. This study identifies the possible mechanism of compound A in regulating the polarization state of macrophages, by regulating PKC-δ-extracellular signal regulated kinases (ERK) signaling pathways to exert anti-tumor immunity effects in vitro, which might provide a new treatment method from the perspective of immune cell regulation.

Alkylamides from Zanthoxylum armatum DC. and their neuroprotective activity

Zanthoxylum armatum DC. is an important medicinal plant, and its pericarps are commonly used as a natural spice in Asian countries. In this study, fifteen alkylamides were isolated and elucidated from the pericarps of Z. armatum, including five undescribed alkylamides (1-5) and ten known compounds (6-15). The molecular structures of all compounds were elucidated by 1D and 2D NMR spectroscopic analysis and mass spectrometry, among which the absolute configuration of compound 15 was determined by the Mo₂(OAc)₄-induced circular dichroism method. Moreover, all compounds were screened for their neuroprotective activity against H₂O₂-induced oxidative stress in human neuroblastoma SH-SY5Y cells for the evaluation of their neuroprotective activity. Especially, compounds 2-4 expressed potential neuroprotective activity, and further research showed that the cell viability was significantly enhanced in a concentration dependent manner when the cells were treated for 6 h. Moreover, compounds 2-4 could decrease reactive oxygen species accumulation. This paper enriched structure types of alkylamides in Zanthoxylum armatum.

Offline two-dimensional normal-phase × reversed-phase liquid chromatography coupled with high-resolution mass spectrometry for comprehensive analysis of chemical constituents in Euphorbia kansui

Euphorbia kansui is the dried root of Euphorbia kansui T. N. Liou ex T.P. Wang. Its main chemical components are diterpenoids, triterpenes, and volatile oil. In this study, an offline two-dimensional (2D) normal-phase × reversed-phase liquid chromatography method coupled with quadrupole time-of-flight mass spectrometry was established to comprehensively analyze the chemical constituents in E. kansui. A total of 240 compounds were identified from the E. kansui extract, including 218 diterpenoids (77 known, 141 new), 16 known volatile oils, and six known triterpenes. The relationship between the structural characteristics and tandem mass spectroscopy fragments of diterpenoids was further analyzed. Based on the characteristic fragment ions, 141 new diterpenoids were determined as 118 ingenane diterpenoids and 23 jatrophane diterpenoids. The newly identified diterpenoids may provide lead compounds for drug discovery, improving the medicinal value of E. kansui.

Triterpenoids, steroids and other constituents from Euphorbia kansui and their anti-inflammatory and anti-tumor properties

Six undescribed triterpenoids (euphokanols A-F), two undescribed C21-steroidal glycosides (euphokanosides A and B), together with fifty-four known compounds were isolated from the roots of Euphorbia kansui. Their structures were demonstrated by extensive spectroscopic data (1D, 2D NMR and HR-ESI-MS), and the absolute configuration of euphokanol A was elucidated based on electronic circular dichroism (ECD) calculation. Among them, euphokanol A was a tetracyclic triterpenoid with a 5,10-epoxy moiety and concurrent rearrangement of Me-19(10 → 9) and Me-30 (14 → 8), while euphokanols B and C were rare 19(10 → 9) abeo-tirucallane-type triterpenoids with Δ5(10) double bonds and 7,8-epoxy moieties. In addition, ten C21-steroidal glycosides were isolated from Euphorbia plants for the first time. Moreover, cynotophylloside B, caudatin, 5α,8α-epidioxy-22E-ergosta-6,22-diene-3β-ol, 6β,7β-epoxy-3β,4β,5β-trihydroxyl-20-deoxyingenol, 13-hydroxyingenol-3-(2,3- dimethylbutanoate)-13-dodecanoate, ingenol, 3-O-benzoyl-13-O-dodecanoateingenol, 3-O-(2'E,4'Z-decadienoyl)-20-O-acetylingenol, 20-O-acetylingenol and 20- deoxyingenol exhibited significant inhibition on NO production with IC50 values of 9.10, 17.38, 1.71, 0.55, 0.57, 12.22, 0.56, 0.30, 11.21 and 2.98 μM, respectively. Furthermore, wilfoside KIN, cynsaccatol L, kanesulone A, and 3β,7β,15β-triacetyloxy-5α-benzoyloxy-2α,8α-dihydroxyjatropha-6(17),11E-diene-9, 14-dione showed cytotoxicity against HepG2 cell line, with IC50 values of 12.55, 12.61, 18.24 and 18.26 μM, respectively. 13-Hydroxyingenol-3-(2,3-dimethylbutanoate)-13- dodecanoate exhibited anti-proliferation activity on MCF-7 cell line with an IC50 value of 17.12 μM. Specifically, euphol selectively inhibited the growth of human glioma stem cells (GSC-3# and GSC-12#), with IC50 values of 8.89 and 13.00 μM, respectively.

Phytochemical and pharmacological review of diterpenoids from the genus Euphorbia Linn (2012-2021)

ETHNOPHARMACOLOGICAL RELEVANCE

Euphorbia is one of the major genera in angiosperms, which is widely distributed all over the world, including Asia, Africa and Central and South America. The roots or tubers of Euphorbia are famous for medicinal purposes, especially in China. Many of them, such as Euphorbia pekinensis Rupr, Euphorbia fischeriana Steud and Euphorbia Kansui S.L.Liou ex S.B.Ho. . are used as Chinese herbal medicines.

AIM OF THE STUDY

This paper reviews the diterpenoids isolated from the genus Euphorbia species and the pharmacological activities of these compounds to evaluate its traditional use and potential future development.

MATERIALS AND METHODS

Information on the studies of the genus Euphorbia Linn was collected from scientific journals, books and reports via library and electronic data search (Scifinder, Web of Science, PubMed, Elsevier, Scopus, Google Scholar, Springer, Science Direct, Wiley, ACS, CNKI and Kew Plants of the Word Online). Meanwhile, it was also obtained from published works of material medica, folk records, ethnophmacological literatures, Ph.D. and Masters dissertations.

RESULTS

Known as the main constituents of the genus Euphorbia Linn, Diterpenoids possess many pharmacological properties such as anti-inflammation, antiviral activities and cytotoxicity. To date, various types of diterpenoids were identified from this genus, including isopimarane, rosane, abietane, ent-kaurane, ent-atisane. cembrane, casbane, lathyrane, myrsinane, jatropholane, tigliane, ingenane, jatrophane, paraliane, pepluane, and euphoractin.

CONCLUSIONS

This review describes 14 types of diterpenoid isolated from 45 Euphorbia species from 2012 to 2021, a total of 615 compounds. Among them, mainly include jatrophane (171), lathyrane (92), myrsinane (62), abietane (70), ent-atisane (36), ent-kaurane (7), tigliane (26) and ingenane (19). The possible biological pathways of these compounds were presumed. At the same time, more than 10 biological activities of these compounds were summarized, such as anti-inflammation, antiviral activities and cytotoxicity.

Euphorfiatnoids A-I: Diterpenoids from the roots of Euphorbia fischeriana with cytotoxic effects

Nine previously undescribed diterpenoids, euphorfiatnoids A-I, together with seven known diterpenoids, were isolated from the roots of wild Euphorbia fischeriana. Their structures were elucidated by the interpretation of HRESIMS, UV, and NMR data. Their configurations were determined by electronic circular dichroism (ECD) spectroscopy analysis and the structure of euphorfiatnoid A was confirmed by X-ray crystallography. To further understand the antitumor effects of E. fischeriana, we tested the cytotoxicity of these compounds against H460, HepG2, and MCF-7 cell lines in vitro using MTT assays. Euphorfiatnoid B exhibited the most promising inhibitory effect against H460 cells with an IC₅₀ value of 9.97 μM. Euphorfiatnoid A and C also exhibited moderate cytotoxicity against HepG2 cells with IC₅₀ values of 11.64 and 13.10 μM, respectively.

Euphorbia diterpenoids: isolation, structure, bioactivity, biosynthesis, and synthesis (2013-2021)

Covering: 2013 to 2021As the characteristic metabolites of Euphorbia plants, Euphorbia diterpenoids have always been a hot topic in related science communities due to their intriguing structures and broad bioactivities. In this review, we intent to provide an in-depth and extensive coverage of Euphorbia diterpenoids reported from 2013 to the end of 2021, including 997 new Euphorbia diterpenoids and 78 known ones with latest progress. Multiple aspects will be summarized, including their occurrences, chemical structures, bioactivities, and syntheses, in which the structure-activity relationship and biosynthesis of this class will be discussed for the first time.

New Diterpenes with Potential Antitumoral Activity Isolated from Plants in the Years 2017-2022

Diterpenes represent a wider class of isoprenoids, with more than 18,000 isolated compounds, and are present in plants, fungi, bacteria, and animals in both terrestrial and marine environments. Here, we report on the fully characterised structures of 251 new diterpenes, isolated from higher plants and published from 2017, which are shown to have antitumoral activity. An overview on the most active compounds, showing IC50 < 20 μM, is provided for diterpenes of different classes. The most active compounds were extracted from 29 different plant families; particularly, Euphorbiaceae (69 compounds) and Lamiaceae (54 compounds) were the richest sources of active compounds. A better activity than the positive control was obtained with 33 compounds against the A549 cell line, 28 compounds against the MCF-7 cell line, 9 compounds against the HepG2 cell line, 8 compounds against the Hep3B cell line, 19 compounds against the SMMC-7721 cell line, 9 compounds against the HL-60 cell line, 24 compounds against the SW480 cell line, and 19 compounds against HeLa.

Dammarane triterpenoids with rare skeletons from Gynostemma pentaphyllum and their cytotoxic activities

Three unreported dammarane-type triterpenoids with rare skeletons (1-3), along with one undescribed gypenoside (4), were isolated from the aerial parts of Gynostemma pentaphyllum using diverse chromatographic materials and pre-HPLC. Their structures were elucidated on the basis of spectroscopic and spectrometric data, while the absolute configurations of 1-3 were assessed via electronic circular dichroism (ECD) analyses. Notably, compounds 1-3 possess a 3,19-hemiketal bridge in the A ring. Saponin 4 possesses an unreported 20,25-oxa structural moiety. Their antiproliferative effects against HepG2, MCF-7, and DU145 cell lines were screened. Compounds 1-3 displayed moderate cytotoxicity with IC₅₀ values ranging from 13.7 ± 0.2 to 32.0 ± 1.7 μM.

Diterpenoids with Rearranged 9(10→11)-abeo-10,12-Cyclojatrophane Skeleton and the First (15S)-Jatrophane from Euphorbia helioscopia: Structural Elucidation, Biomimetic Conversion, and Their Immunosuppressive Effects

Two novel diterpenoids, one with a rearranged trans,trans-fused tricyclo[10.3.0.04,6]pentadecane framework (1) and the other with an unprecedented 15S configuration (2), were isolated from Euphorbia helioscopia. Their structures were elucidated by extensive analysis of HR-ESI-MS, NMR, quantum-chemical calculation, and X-ray crystallographic data. Biosynthetically, 1 has a unique "cyclopropane-shift-like" biogenesis involving an oxa-di-π-methane (ODPM) rearrangement, which inspired us to accomplish the biomimetic conversion of 3 to 1. Moreover, compound 1 displayed a potent immunosuppressive effect by inhibiting Kv1.3 voltage-gated channels.

Jolkinolide B inhibits proliferation or migration and promotes apoptosis of MCF-7 or BT-474 breast cancer cells by downregulating the PI3K-Akt pathway

ETHNOPHARMACOLOGICAL RELEVANCE

The diterpenoids extracted from Euphorbia kansui S.L. Liou ex S.B.Ho, Euphorbia fischeriana Steud. have good antitumor effects. Jolkinolide B has anti-breast cancer effect, but it is unclear whether it has different therapeutic effects between luminal A subtype and luminal B subtype breast cancer.

AIM OF THE STUDY

This study investigated the Jolkinolide B has different therapeutic, important targets and pathways effects between luminal A subtype and luminal B subtype breast cancer.

MATERIALS AND METHODS

We used bioinformatics to predict the biological process and molecular mechanism of Jolkinolide B in treating two types of breast cancer. Then, in vitro, cultured MCF-7 cells and BT-474 cells were divided into control group, PI3K inhibitor + control group, Jolkinolide B group and PI3K inhibitor + Jolkinolide B group. The CCK-8 assay, Flow cytometric analysis and Transwell cell migration assay was used to detect the cell proliferation, apoptosis, and migration in each group, respectively. ELISA was used to measure the content of Akt and phosphorylated Akt (p-Akt) in cell lysis buffer.

RESULTS

Compared to luminal A breast cancer, Jolkinolide B had more targets, proliferation, migration processes and KEGG pathways when treating luminal B subtype breast cancer. Jolkinolide B significantly prolonged the survival time of luminal B subtype breast cancer patients. Compared to the control group, the cell proliferation absorbance value (A value) and migration number of the two kinds of breast cancer cells in the Jolkinolide B group were decreased (P < 0.01, n = 6), and the number of apoptotic cells was increased (P < 0.01, n = 6). Compared to the Jolkinolide B group, the A value and migration number of the two types of breast cancer cells were significantly decreased in the PI3K inhibitor + Jolkinolide B group (P < 0.01, n = 6), and the number of apoptotic cells was significantly increased (P < 0.01, n = 6). In addition, compared to MCF-7 cells, the A value and migration number of BT-474 cells stimulated with Jolkinolide B were significantly decreased (P < 0.01, n = 6), and the number of apoptotic cells was significantly increased (P < 0.01, n = 6). Akt and p-Akt protein levels in the two breast cancer cell lines in the Jolkinolide B group were all decreased (P < 0.01, n = 6), especially in BT-474 cells stimulated by Jolkinolide B.

CONCLUSION

Jolkinolide B regulates the luminal A and luminal B subtypes of breast cancer through PI3K-Akt, EGFR and other pathways. Jolkinolide B has more significant therapeutic effect on luminal B subtype breast cancer. In vitro, experiments verified that Jolkinolide B significantly inhibited the proliferation and migration activity of BT-474 breast cancer cells by downregulating the PI3K-Akt pathway.

Euphorfinoids E-L: Diterpenoids from the roots of Euphorbia fischeriana with acetylcholinesterase inhibitory activity

Eight undescribed diterpenoids, euphorfinoids E-L, together with twelve known analogues, were isolated from the roots of wild Euphorbia fischeriana. Their structures and absolute configurations were elucidated by a combination of NMR, MS, ECD, and X-ray diffraction analyses. The plausible biosynthetic pathway of 1 was also proposed. The isolated compounds displayed moderate inhibitory activity against acetylcholinesterase (AChE) with 50% inhibiting concentration (IC₅₀) values of 6.23-192.38 μM.

Narjatamolide, an Unusual Homoguaiane Sesquiterpene Lactone from Nardostachys jatamansi

Narjatamolide (1), an unusual homoguaiane sesquiterpene lactone, was isolated from the roots and rhizomes of Nardostachys jatamansi DC. It represents the new carbon skeleton of a homoguaiane sesquiterpenoid possessing an additional acetate unit spiro-fused with C-4 and C-15 to form a cyclopropane ring. The structure of 1 was elucidated by extensive spectroscopic analyses, and the absolute configuration was confirmed by the electronic circular dichroism (ECD) calculations and X-ray single-crystal diffraction analysis. Compound 1 showed antiproliferative effects against BEL-7402 cell lines with an IC₅₀ value of 5.67 ± 1.43 μM, and the mechanism study showed that 1 induces cell cycle of BEL-7402 cell lines arrest at G2/M phase.

Euphorbia Diterpenes: An Update of Isolation, Structure, Pharmacological Activities and Structure-Activity Relationship

Euphorbia species have a rich history of ethnomedicinal use and ethnopharmacological applications in drug discovery. This is due to the presence of a wide range of diterpenes exhibiting great structural diversity and pharmacological activities. As a result, Euphorbia diterpenes have remained the focus of drug discovery investigations from natural products. The current review documents over 350 diterpenes, isolated from Euphorbia species, their structures, classification, biosynthetic pathways, and their structure-activity relationships for the period covering 2013-2020. Among the isolated diterpenes, over 20 skeletal structures were identified. Lathyrane, jatrophane, ingenane, ingenol, and ingol were identified as the major diterpenes in most Euphorbia species. Most of the isolated diterpenes were evaluated for their cytotoxicity activities, multidrug resistance abilities, and inhibitory activities in vitro, and reported good activities with significant half-inhibitory concentration (IC50) values ranging from 10-50 µM. The lathyranes, isopimaranes, and jatrophanes diterpenes were further found to show potent inhibition of P-glycoprotein, which is known to confer drug resistance abilities in cells leading to decreased cytotoxic effects. Structure-activity relationship (SAR) studies revealed the significance of a free hydroxyl group at position C-3 in enhancing the anticancer and anti-inflammatory activities and the negative effect it has in position C-2. Esterification of this functionality, in selected diterpenes, was found to enhance these activities. Thus, Euphorbia diterpenes offer a valuable source of lead compounds that could be investigated further as potential candidates for drug discovery.

Bond reactivity indices approach analysis of the [2+2] cycloaddition of jatrophane skeleton diterpenoids from Euphorbia gaditana Coss to tetracyclic gaditanone

The reaction mechanism of the intramolecular [2 + 2] cycloaddition from a jatrophane precursor to the gaditanane skeleton, an unprecedented 5/6/4/6-fused tetracyclic ring framework recently isolated from Euphorbia spp., was studied using the bond reactivity indices approach. Furthermore, six diterpenoids, including three undescribed jatrophanes isolated from E. gaditana Coss, were described. The structures of these compounds were deduced by a combination of 2D NMR spectroscopy and ECD data analysis.

Bungsteroid A: One Unusual C34 Pentacyclic Steroid Analogue from Zanthoxylum bungeanum Maxim

Bungsteroid A (1), possessing an unreported carbon skeleton, was isolated from the pericarps of Zanthoxylum bungeanum Maxim. It represents the first carbon skeleton of a C₃₄ steroid analogue featuring a unique 6/6/6/6/5-fused pentacyclic skeleton, which has been determined by spectroscopic methods, quantum-chemical ¹³C NMR, ECD calculations, and calculations of optical rotations. Bungsteroid A showed the antiproliferative effects against HepG2, MCF-7, and HeLa cell lines with the IC₅₀ values of 56.3 ± 1.1, 64.2 ± 0.9, and 74.2 ± 1.3 μM, respectively.