Synthesis and antihepatoma activity of guaianolide dimers derived from lavandiolide I

Guaianolide dimers represent a unique class of natural products with anticancer activities, but their low content in plants has limited in-depth pharmacological studies. Lavandiolide I is a guaianolide dimer isolated from Artemisia species, and had been synthesized on a ten-gram scale in four steps with 60 % overall yield, which showed potent antihepatoma activity on the HepG2, Huh7, and SK-Hep-1 cell lines with IC50 values of 12.1, 18.4, and 17.6 µM, respectively. To explore more active dimers, 33 lavandiolide I derivatives were designed, synthesized, and evaluated for their inhibitory activity on human hepatoma cell lines. Among them, 10 derivatives were more active than lavandiolide I and sorafenib on the three cell lines. The primary structure-activity relationship concluded that the introduction of aldehyde, ester, azide, amide, carbamate and urea functional groups at C-14' of the guaianolide dimer significantly enhanced the antihepatoma activity. Among these compounds, derivatives 25, 27, and 33 enhanced antihepatoma activity more than 1.2-5.8 folds than that of lavandiolide I, and demonstrated low toxicity to the human liver cell lines (THLE-2) and good safety profiles with selective index ranging from 1.3 to 3.4, while lavandiolide I was more toxic to THLE-2 cells. This work provides new insights into enhancing the antihepatoma efficacy and reducing the toxicity of sesquiterpenoid dimers.

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.

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.

Design, synthesis, and biological evaluation of artemyrianolide H derivatives as potential antihepatoma agents

Artemyrianolide H (AH) is a germacrene-type sesquiterpenolid isolated from Artemisia myriantha, and showed potent cytotoxicity against three human hepatocellular carcinoma cell lines HepG2, Huh7, and SK-Hep-1 with IC₅₀ values of 10.9, 7.2, and 11.9 µM, respectively. To reveal structure-activity relationship, 51 artemyrianolide H derivatives including 19 dimeric analogs were designed, synthesized, and assayed for their cytotoxicity against three human hepatoma cell lines. Among them, 34 compounds were more active than artemyrianolide H and sorafenib on the three cell lines. Especially, compound 25 exhibited the most promising activity with IC₅₀ values of 0.7 (HepG2), 0.6 (Huh7), and 1.3 µM (SK-Hep-1), which were 15.5, 12.0, and 9.2-fold higher than that of AH and 16.4, 16.3 and 17.5-fold higher than that of sorafenib. Cytotoxicity evaluation on normal human liver cell lines (THLE-2) demonstrated good safety profile of compound 25 with SI of 1.9 (HepG2), 2.2 (Huh 7) and 1.0 (SK-Hep1). Further studies revealed that compound 25 dose-dependently arrested cells at G2/M phase which was correlated with the up-regulation of both cyclin B1 and p-CDK1, and induced apoptosis through the activation of mitochondrial pathways in HepG2 cells. In addition, the migratory and invasive abilities in HepG2 cells after treatment with 1.5 μM of compound 25 were decreased by 89% and 86% with the increase of E-cadherin expression accompanied by the decrease of N-cadherin, vimentin expression. Bioinformatics analysis based on machine learning predicted that PDGFRA and MAP2K2 might be acting targets of compound 25, and SPR assays demonstrated compound 25 were bound with PDGFRA and MAP2K2 with K_D value of 0.168 nM, and 8.49 µM, respectively. This investigation proposed that compound 25 might be considered as a promising lead compound for the development of antihepatoma candidate.

Artemiprinolides A-M, thirteen undescribed sesquiterpenoid dimers from Artemisia princeps and their antihepatoma activity

Bioassay-guided investigation of the active fraction of Artemisia princeps led to 13 undescribed sesquiterpenoid dimers, artemiprinolides A-M (1-13), together with 11 known ones (14-24). Their structures were elucidated by comprehensive spectroscopic data and absolute configurations were assigned based on single crystal X-ray diffraction data and ECD calculations. Structurally, all compounds were postulated to be derived from the Diels-Alder cycloaddition. The isolated dimers except 11 and 15 were assayed for their cytotoxicity against HepG2, Huh7, and SK-Hep-1 cell lines, of which four compounds (3, 13, 17, 18) exhibited obvious cytotoxicity with IC₅₀ values ranging from 8.8 to 20.1 μM. Interestingly, the most active compounds 1 and 16 manifested significant cytotoxicity on the three tested hepatoma cell lines with IC₅₀ values of 5.4, 4.1 (HepG2), 7.7, 5.6 (Huh7), and 11.8, 15.7 μM (SK-Hep-1), respectively, which were better than sorafenib. Compound 1 dose-dependently inhibited cell migration and invasion, and significantly induced the HepG2 cell arrest in G2/M phase by downregulating cdc2 and pcdc2 and upregulating cyclinB1; and induced apoptosis by downregulating Bcl-2 expression and upregulating Bax level. The molecular docking study implied that the carbonyl at the C-12' of 1 had a strong binding affinity with PRKACA.

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.

Sesquiterpenoids and triterpenoids with anti-inflammatory effects from Artemisia vulgaris L

In this study, eight undescribed sesquiterpenoids (artemvulactone A-G and artemvulemdiol A), and two undescribed triterpenoids, (3S)-dammar-20,25-diene-3-hydroxy-24-one and (3S,23E)-dammar-20,23-diene-25- methoxy-3-ol were isolated from the leaves of Artemisia vulgaris L., together with ten known sesquiterpenoids and three known triterpenoids. The structures of these undescribed terpenoids were determined by extensive spectroscopy methods, including 1D and 2D-NMR, HRESIMS, IR, UV, X-ray diffraction, and ECD. The absolute configurations of artemvulactone A, artemvulactone D, and artemvulactone E were determined by X-ray diffraction (Cu Kα). All isolates were evaluated for their anti-inflammatory efficacy by detecting the expression of inflammatory mediator NO in LPS-induced RAW264.7 cells, and the results indicated that artemvulactone E exhibited significant anti-inflammatory effect with an IC50 value of 0.9 ± 0.2 μM. Furthermore, artemvulactone E could reduce LPS-induced COX-2 protein expression dose-dependently by western blotting experiments.

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.

Design and synthesis of ludartin derivatives as potential anticancer agents against hepatocellular carcinoma

Our previous study demonstrated that guaiane-type sesquiterpenoid ludartin showed potent antihepatoma activity against two human hepatocellular carcinoma cell lines, HepG2 and Huh7, with IC₅₀ values of 32.7 and 34.3 μM, respectively. In this study, 34 ludartin derivatives were designed, synthesized and evaluated for their cytotoxic activities against HepG2 and Huh7 cell lines using an MTT assay in vitro. As a result, 17 compounds increased the activity against HepG2 cells, and 20 compounds enhanced the activity against Huh7 cells; 14 derivatives 2, 4-7, 9, 11, 17, 24, 28-30 and 32-33 were superior to ludartin on both HepG2 and Huh7 cells. In particular, dimeric derivative 33 as the most active compound showed 20-fold and 17-fold enhancement of cytotoxicity against HepG2 and Huh7 cells compared to that of ludartin. These results suggested that compound 33 could serve as a promising lead compound against liver cancer.

Artemyrianosins A-J, cytotoxic germacrane-type sesquiterpene lactones from Artemisia myriantha

Ten new germacrane-type sesquiterpenoids, artemyrianosins A-J (1-10), were isolated from the aerial parts of Artemisia myriantha. Their structures were elucidated by spectral analyses including UV, IR, HRESIMS, 1D and 2D NMR, ECD and the absolute configurations of compounds 1 and 7-9 were characterized using X-ray crystallography. All isolates were tested their cytotoxicity against three human hepatoma cell lines (HepG2, Huh7, and SK-Hep-1), and compounds 1-3, 7, and 10 showed cytotoxicity with IC₅₀ values ranging from 43.7 to 89.3 μM. Among them, the most active compound 3 exhibited activity against three human hepatoma cell lines with IC₅₀ values of 43.7 μM (HepG2), 47.9 μM (Huh7), and 44.9 μM (SK-Hep-1).

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.

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).

Artematrovirenins A-P, guaiane-type sesquiterpenoids with cytotoxicities against two hepatoma cell lines from Artemisia atrovirens

Random screening revealed that the EtOH extract of Artemisia atrovirens showed significant cytotoxicity against two human hepatoma cell lines (HepG2 and Huh7) with the inhibitory ratio of 98.9% and 99.7% at the concentration of 100 μg/mL. Further bioactivity-guided isolation of active fraction led to 16 new guaiane-type sesquiterpenoids, artematrovirenins A-P (1-16). Their structures were elucidated by extensive spectroscopic data. The absolute stereochemistry of compounds 1 and 14 was determined by single-crystal X-ray diffraction analyses. Pharmacological evaluation suggested that five compounds (3, 5, 8, 10, and 15) exhibited cytotoxicity, compounds 3 and 5 displayed cytotoxicity against HepG2 cell line with an IC₅₀ values of 8.0 and 16.0 μM, as well as against Huh7 cell line with values of 18.2 and 32.2 μM.

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.

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