Sesquiterpene lactone dimers from Artemisia lavandulifolia inhibit interleukin-1β production in macrophages through activating autophagy

Unusual cadinane-involved sesquiterpenoid dimers from Artemisia annua and their antihepatoma effect

Artemisia annua L. ("Qinghao" in Chinese) is a famous traditional Chinese medicinal herb and has been used to treat malaria and various tumors. Our preliminary screening indicated that the EtOAc extract of A. annua manifested activity against HepG2, Huh7, and SK-Hep-1 cell lines with inhibitory ratios of 53.2%, 52.1%, and 59.6% at 200 μg/mL, respectively. Bioassay-guided isolation of A. annua afforded 14 unusual cadinane-involved sesquiterpenoid dimers, artemannuins A‒N (1-14), of which the structures were elucidated by extensive spectral analyses, ECD calculations, and single-crystal X-ray diffraction. Structurally, these compounds were classified into five different types based on the coupled modes of two monomeric sesquiterpenoids. Among them, compounds 1-9 represented the first examples of sesquiterpenoid dimers formed via the C-3‒C-3' single bond of two 5(4 → 3)-abeo-cadinane sesquiterpenoid monomers, while compounds 13 and 14 were dimers fused by cadinane and humulane sesquiterpenoids via an ester bond. Methylated derivatives of 1, 4, 6, and 8 showed antihepatoma activity against HepG2, Huh7, and SK-Hep-1 cell lines with IC50 values ranging from 30.5 to 57.2 μM.

Artemyriantholides A-K, guaiane-type sesquiterpenoid dimers from Artemisia myriantha var. pleiocephala and their antihepatoma activity

Artemyriantholides A-K (1-11) as well as 14 known compounds (12-25) were isolated from Artemisia myriantha var. pleiocephala (Asteraceae). The structures and absolute configuration of compounds 2 and 8-9 were confirmed by the single crystal X-ray diffraction analyses, and the others were elucidated by MS, NMR spectral data and electronic circular dichroism calculations. All compounds were chemically characterized as guaiane-type sesquiterpenoid dimers (GSDs). Compound 1 was the first example of the GSD fused via C-3/C-11' and C-5/C-13' linkages, and compounds 2 and 5 were rare GSDs containing chlorine atoms. Eleven compounds showed obvious inhibitory activity in HepG2, Huh7 and SK-Hep-1 cell lines by antihepatoma assay to provide the IC50 values ranging from 7.9 to 67.1 μM. Importantly, compounds 5 and 8 exhibited the best inhibitory activity with IC50 values of 14.2 and 18.8 (HepG2), 9.0 and 11.5 (Huh7), and 8.8 and 11.3 μM (SK-Hep-1), respectively. The target of compound 5 was predicted to be MAP2K2 by a computational prediction model. The interaction between compound 5 and MAP2K2 was conducted to give docking score of -9.0 kcal/mol by molecular docking and provide KD value of 43.7 μM by Surface Plasmon Resonance assay.

Eudesmane-type sesquiterpenoids from the aerial parts of Artemisia lavandulaefolia and their anti-pancreatic cancer activities

Five undescribed eudesmane sesquiterpenoids, artemilavanins A-E, and one undescribed rearranged eudesmane sesquiterpenoid, artemilavanin F, were isolated from the 95% ethanol extract of the aerial parts of Artemisia lavandulaefolia DC., along with ten known compounds. The structures and configurations of undescribed compounds were mainly elucidated by spectroscopic analyses and single-crystal X-ray diffraction analysis. Among all isolated compounds, artemilavanin F exhibited inhibitory activity on PANC-1 pancreatic cancer cells with IC50 of 9.69 ± 2.39 μM. Artemilavanin F inhibited PANC-1 cell proliferation by induction of G2/M cell cycle arrest and apoptosis mediated by downregulation of cyclin-dependent kinases and accumulation of reactive oxygen species. Moreover, artemilavanin F inhibited the colony formation, cell migration and sphere formation of PANC-1 cells, indicating the suppression of stem-cell-like phenotype of PANC-1 cells. Further results confirmed that the expression of cancer stem cell markers such as Bmi1, CD44, CD133 were inhibited by artemilavanin F. Downregulation of epithelial-mesenchymal transition (EMT) markers such as N-cadherin and Oct-4 indicated the potential of artemilavanin F in prevention of metastasis.

Artemongolins A-K, undescribed germacrane-guaiane sesquiterpenoid dimers from Artemisia mongolica and their antihepatoma activities

Artemongolins A-K (1-11), which are undescribed sesquiterpenoid dimers, were obtained from Artemisia mongolica and characterized through comprehensive spectral data, including HRESIMS, IR, 1D and 2D NMR, and ECD calculations. The absolute configurations of compounds 1, 4, and 7 were undoubtedly determined by a single-crystal X-ray crystallography. Artemongolins A-K (1-11) featured a rare 5/7/5/5/5/10 hexacyclic system composed of a germacrene and a guaianolide by a fused 2-oxaspiro[4,4]nonane-1-one ring system. Antihepatoma evaluation against three human hepatoma cell lines demonstrated that the most active compounds 5 and 6 displayed inhibitory activity with IC50 values of 88.6 and 57.0 (HepG2), 59.1 and 26.4 (Huh7), and 67.5 and 32.5 (SK-Hep-1) µM, respectively.

Artemongolides A-F, undescribed sesquiterpenoid dimers from Artemisia mongolica and their antihepatic fibrosis activities

Artemongolides A-E (1-5), an unusual class of diseco-guaianolides featuring a rare fused 7-methylbicyclo[2.2.1]-2-ene-7-heptanol ring system, and artemongolide F (6), the first example of [4 + 2] Diels-Alder type adducts presumably incorporating a chain farnesane sesquiterpene and a guaianolide diene, were isolated from the whole plant of Artemisia mongolica. Their structures were elucidated based on the spectroscopic analyses of UV, IR, MS, and 1D and 2D NMR spectra. The absolute configurations of artemongolides A (1) and F (6) were determined by single-crystal X-ray crystallography, and those of artemongolides B-E (2-5) were established by ECD calculations. Cytotoxicity evaluation suggested that compound 1 exhibited activity against HSC-LX2 cells with an IC₅₀ value of 165.0 μM, equivalent to that of the positive control silybin (IC₅₀, 146.4 μM). Preliminary mechanism studies revealed that compound 1 could inhibit the deposition of human collagen type I (Col I), human hyaluronic acid (HA), and human laminin (HL) with IC₅₀ values of 123.8, 160.4, and 139.20 μM.

Artemidubolides A-T, cytotoxic unreported guaiane-type sesquiterpenoid dimers against three hepatoma cell lines from Artemisia dubia

A random bioassay revealed that the EtOH extract and EtOAc fraction of Artemisia dubia Wall. (Asteraceae) exhibited cytotoxic activity against HepG2 cells with inhibitory ratios of 57.1% and 84.2% at a concentration of 100.0 μg/mL. Bio-guided isolation combined by LC-MS-IT-TOF analyses of the active fractions led to the isolation of 20 previously undescribed guaiane-type sesquiterpenoid dimers named artemidubolides A-T (1-20). Their structures and the absolute configurations were determined by comprehensive spectral analyses, comparison of the experimental and calculated ECD spectra, and seven compounds (artemidubolides A, B, D, F, K, O and R) were confirmed unequivocally by single crystal X-ray diffraction analysis. Structurally, artemidubolides A-Q were [4 + 2] Diels-Alder adducts of two monomeric guaianolides, and artemidubolides R-T were linked though an ester bond. All the isolated compounds were evaluated for their hepatomatic cytotoxicity against HepG2, Huh7, and SK-Hep-1 cell lines to demonstrate that 18 compounds exhibited obvious cytotoxicity against three tested hepatoma cell lines with IC₅₀ values in the range of 5.4-87.6 μM. Importantly, artemidubolides B, D, and M exhibited hepatoma cytotoxicity with IC₅₀ values of 5.4, 5.7, and 9.7 (HepG2), 8.2, 4.3, and 12.2 (Huh7), and 13.4, 8.4, and 12.9 μM (SK-Hep-1), respectively. Mechanism investigation in HepG2 cells suggested the most active artemidubolide D dose-dependently inhibited cell migration and invasion, induced G1/M cell cycle arrest by down-regulating proteins CDK4, CDK6 and CyclinD1 and up-regulating the level of protein P21; and induced apoptosis by down-regulated of PARP-1 and BCL-2 expression and up-regulating Bax and cleaved PARP-1 levels.

Anti-inflammatory sesquiterpenoid dimers from Artemisia atrovirens

Eight new sesquiterpenoid dimers, artatrovirenolides A-H (1-8), along with three known analogues (9-11), were isolated from Artemisia atrovirens by using the LC-MS guided isolation. Compound 1 was a compound dimerized from a guaianolide and a 1,10-seco-guaianolide unit while others were from two guaianolide units. Their structures were established by comprehensive analysis of spectroscopic data, and their absolute configurations were determined by the aid of time-dependent density functional theory electronic circular dichroism (TDDFT ECD) calculation. Compound 8 showed anti-inflammatory effect in LPS-stimulated BV-2 microglial cells at 1 μM, while compounds 1, 2, 5, and 6 inhibited microglial inflammation at 10 μM.

Semisynthesis and Non-Small-Cell Lung Cancer Cytotoxicity Evaluation of Germacrane-Type Sesquiterpene Lactones from Elephantopus scaber

Two series of germacrane-type sesquiterpene lactones were produced by semisynthetic modulation of scaberol C, which was prepared by a standard chemical transformation from an Elephantopus scaber extract. Their inhibition activities against non-small-cell lung cancer cells were screened, and preliminary structure-activity relationships were also established. Among them, monomeric analog 1u and dimeric analog 3d exhibited superior anti-non-small-cell lung cancer cytotoxic potencies with IC₅₀ values of 4.3 and 0.7 μM against A549 cells, respectively, and were more active than cisplatin and the standard sesquiterpene lactones, parthenolide and scabertopin. Further studies revealed that compounds 1u and 3d cause G2/M phase arrest and induce apoptosis through the activation of mitochondrial pathways in A549 cells. Collectively, the results obtained suggest that compounds 1u and 3d are promising anti-non-small-cell lung cancer lead compounds.

Anti-Inflammatory and Immunoregulatory Action of Sesquiterpene Lactones

Sesquiterpene lactones (SL), characterized by their high prevalence in the Asteraceae family, are one of the major groups of secondary metabolites found in plants. Researchers from distinct research fields, including pharmacology, medicine, and agriculture, are interested in their biological potential. With new SL discovered in the last years, new biological activities have been tested, different action mechanisms (synergistic and/or antagonistic effects), as well as molecular structure–activity relationships described. The review identifies the main sesquiterpene lactones with interconnections between immune responses and anti-inflammatory actions, within different cellular models as well in in vivo studies. Bioaccessibility and bioavailability, as well as molecular structure–activity relationships are addressed. Additionally, plant metabolic engineering, and the impact of sesquiterpene lactone extraction methodologies are presented, with the perspective of biological activity enhancement. Sesquiterpene lactones derivatives are also addressed. This review summarizes the current knowledge regarding the therapeutic potential of sesquiterpene lactones within immune and inflammatory activities, highlighting trends and opportunities for their pharmaceutical/clinical use.

Guaianolides from Artemisia codonocephala suppress interleukine-1β secretion in macrophages

Sesquiterpene lactones supply a variety of scaffolds for the development of anti-inflammatory drugs. In this study, eight undescribed guaianolides, i.e., lavandolides A‒H, were isolated from the whole plants of Artemisia codonocephala, together with five known analogues. Their planar structures and relative configurations were elucidated by spectroscopic measurements, and their absolute configurations were determined by electronic circulardichroism spectra and single crystal X-ray diffraction experiments. The nitric oxide inhibitory effect of all the isolates was assessed on lipopolysaccharide stimulated THP-1 macrophages. Lavandolide D showed a potent inhibitory effect on NO production, with IC₅₀ values of 3.31 ± 0.74 μM. Furthermore, lavandolide D inhibited NOD-, LRR- and pyrin domain-containing protein 3 inflammasome-mediated interleukin-1β production through activating autophagy.

Biomimetic Synthesis of Lavandiolides H, I, and K and Artematrolide F via Diels-Alder Reaction

The biomimetic synthesis of guaianolide dimers lavandiolides H, I, and K and artematrolide F containing a spirolactone moiety has been accomplished for the first time from naturally abundant arglabin in four to six steps with an overall yield up to 60%, and a series of natural product-like guaianolide dimers, trimer, and tetramer were also successfully synthesized. Notably, the trimeric compound exhibited antihepatoma cytotoxicity more potent than that of sorafenib with IC₅₀ values of 6.2 μM (HepG2), 6.8 μM (Huh7), and 7.2 μM (SK-HEP-1).

Caesalpinaxin, a cassane-type diterpenoid with a 21-carbon core skeleton from the seeds of Caesalpinia minax possessing pro-angiogenetic property

A novel cassane-type diterpenoid, caesalpinaxin (1), was isolated from the seeds of Caesalpinia minax Hance. The structure of caesalpinaxin was established by means of spectroscopic techniques (NMR, HR-ESIMS, UV and IR). The absolute configuration of caesalpinaxin was determined by quantum chemical calculations of its theoretical electronic circular dichroism (ECD) spectrum. Caesalpinaxin is the first cassane-type diterpenoid with 21 carbons core skeleton, containing an unusual δ-lactone ring. A plausible biosynthetic pathway was proposed for compound 1. Furthermore, caesalpinaxin was tested for the pro-angiogenetic activity on human umbilical vein endothelial cells(HUVECs). The results indicated that this compound significantly stimulated migration and tuber formation through enhancing the level of vascular endothelial growth factor (VEGF). Thus, caesalpinaxin might be applied in accelerating wound healing.

New guaiane-type sesquiterpenoid dimers from Artemisia atrovirens and their antihepatoma activity

Leading by cytotoxicity against HepG2 cells, bioactivity-guided fractionation of the EtOAc fraction from Artemisia atrovirens led to the isolation of 18 new guaianolide dimers, artematrolides A–R and lavandiolides A, B, C, H, and J. Eight compounds (1, 4, 10, 12, 13, and 19–21) were unambiguously confirmed by the single-crystal X-ray diffraction analyses, and the others were elucidated based on IR, UV, HRESIMS, 1D and 2D NMR experiments, and comparison of the experimental and calculated ECD data. Structurally, all of them were [4 + 2] Diels–Alder adducts of two monomeric guaianolides. The isolates were evaluated for their cytotoxicity against three human hepatoma cell lines, and 19 compounds demonstrated cytotoxicity against HepG2, SMMC-7721, and Huh7 cell lines. Especially, compounds 1, 12, 14, and 15 exhibited cytotoxicity with IC₅₀ values of 4.4, 3.8, 7.6, and 6.7 μmol/L (HepG2), 9.6, 4.6, 6.6, and 6.0 μmol/L (SMMC-7721), and 7.6, 4.5, 6.9, and 5.6 μmol/L (Huh7), respectively. Notably, compound 12 showed the most promising activity against three human hepatoma cell lines and dose-dependently inhibited cell migration and invasion, induced G2/M cell cycle arrest and cell apoptosis in HepG2 cells, down-regulated the expression of BCL-2 and PARP-1, and activated PARP-1 to up-regulate the expression of cleaved-PARP-1.

Cytotoxic guaianolides and seco-guaianolides from Artemisia atrovirens

A phytochemical investigation of a medicinal plant Artemisia atrovirens was carried out, resulting in the characterization of a novel bis-nor seco-guaianolide, seco-atrovirenolide A (1), a new 1,10-seco-guaianolide derivative, seco-atrovirenoic acid A (2), and a new artifact 10-methanoyloxy-seco-atrovirenoic acid A (3), together with eight known guaianolide and seco-guaianolide derivatives (4-11). The structures of new compounds were fully established by extensive analysis of MS, 1D and 2D NMR spectroscopic data. The absolute configurations of the isolated compounds were confirmed by TDDFT ECD calculation, Mosher's method, and X-ray crystal diffraction experiment. All the compounds were tested in vitro for their cytotoxicity against HL-60 and A549 cell lines. Some of them showed moderate inhibitory activity against HL-60 cell lines with IC₅₀ values ranging from 5.99 to 11.74 μM.