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.

Guaianolide sesquiterpenes and their activity from Artemisia mongolica

Seven undescribed sesquiterpenes, including three dimeric guaianolide sesquiterpenes artemongolides G-I (1-3) and four sesquiterpene lactones artemanomalide D-G (16-19), along with seventeen known compounds isoabsinthin (4), absinthin (5), 11-eptabsinthin (6), 11, 11'-bis-epiabsinthin (7), 10', 11'- epiabsinthin (8), anabsinthin (9), isoanabsinthin (10), absinthin D (11), anabsin (12), caruifolin D (13), gnapholide (14), caruifolin C (15), 1β(R),10β(S)-dihydroxy-3-oxo-11β (S)H-4,11(13)-guaien-6α(S),12-olide (20), 1α,6α,8α-trihydroxy-5α,7βH-guaia-3,10(14),11(13)-trien-12-oic acid (21), 1α,6α,8α-trihydroxy-5α,7βH-guaia-3,9,11(13)-trien-12-oic acid (22), argyinolide J (23), artabsinolide A (24) were isolated from the plant Artemisia mongolica. The structures were determined by interpreting NMR, HRESIMS and ECD data. The X-ray crystal structure of 4, 7 and 8 were reported for the first time. In the anti-vitiligo activity test, compounds 2, 7, 12, 23 and 24 demonstrated activity in promoting melanogenesis at a concentration of 50 μM in B16 cells, with 8-methoxypsoralan (8-MOP) as a positive control. Further research on the mechanism revealed that artemongolides H (2) enhance the expression of MITF and TRPs by upregulating p-Akt and p-GSK-3β, leading to an increase in β-catenin content in the cell cytoplasm. Subsequently, β-catenin translocates into the nucleus, resulting in melanogenesis. The results supported the regulation of melanogenesis by artemongolide H (2) through the Akt/GSK3β/β-catenin signaling pathway. The anti-inflammatory results demonstrated that compounds 4, 5, 6, 9 and 14 can inhibit the upregulation of IL-6 mRNA and CCL2 mRNA expression. Compound 12 specifically inhibited the upregulation of IL-6 mRNA expression. These compounds exhibited significant anti-inflammatory activities. The activity results revealed that these sesquiterpene compounds have the potential to become lead compounds for the treatment of vitiligo and inflammatory diseases.

Anti-inflammatory potential of some eudesmanolide and guaianolide sesquiterpenes

Ten sesquiterpene lactones isolated from Anvillea garcinii (Burm.f.) DC ethanolic extract were assessed for their anti-inflammatory potential by myeloperoxidase (MPO) activity assignment, and mice paw swelling model. 3α,4α-10β-trihydroxy-8α-acetyloxyguaian-12,6α-olide (1), epi-vulgarin (3), 9a-hydroxyparthenolide (4), garcinamine C (7), garcinamine D (8), garcinamine E (9), and 4, 9-dihydroxyguaian-10(14)-en-12-olide (10) showed explicit anti-inflammatory activity in rodent paw edema and MPO assignment. The findings of this study showed that the α-methylene γ-lactone moiety does not always guarantee an anti-inflammatory effect, but the presence of proline at the C3 of the lactone ring improves the binding of sesquiterpene lactones with MPO isoenzymes, resulting in a more potent inhibition.

Glaucatotones A-I: Guaiane-type sesquiterpenoids from the roots of Lindera glauca with anti-inflammatory activity

Glaucatotones A - I, nine new guaiane-type sesquiterpenoids, along with two reported compounds, namely (1β,5β)-1-hydroxyguaia-4(15),11(13)-dieno-12,5-lactone (10) and pseudoguaianelactone C (11), were isolated from the roots of Lindera glauca. The structures and absolute configurations of these compounds were elucidated by extensive spectroscopic analyses, single-crystal X-ray diffraction, and comparison of experimental and calculated electronic circular dichroism (ECD) data. Structurally, glaucatotone A (1) is characterized as a dihomosesquiterpenoid with an unprecedented 5/5/7/6 ring system. A pair of enantiomers, (±)-glaucatotone B (2a/2b), represent the first rearranged norsesquiterpenoid with a (cyclopentylmethyl)cyclohexane skeleton. 3 is defined as a dinorsesquiterpenoid possessing a 5/7/5 ring system. 4-6 are three guaiane-type norsesquiterpenoids. In vitro bioactivity, 2a selectively inhibited Bcap-37 with IC50 value of 5.60 μM, and 9 selectively inhibited Du-145 with IC50 value of 5.52 μM. The anti-inflammatory activity of 1-9 were tested, and of these compounds, 1, 2a, 2b and 7 exhibited potent inhibitory effects.

In silico toxicologic profile and in vivo trypanocidal activity of estafietin, a sesquiterpene lactone isolated from Stevia alpina Griseb

Chagas disease is an infection caused by the protozoan Trypanosoma cruzi, affecting 6-8 million people worldwide. Only two drugs are available for its treatment, having a limited efficacy and adverse side-effects. Estafietin is a sesquiterpene lactone isolated from Stevia alpina with in vitro activity against T. cruzi and low cytotoxicity against mammalian cells. The aim of this work was to predict the toxicologic profile of estafietin by in silico methods and assess its in vivo activity on a murine model of Chagas disease. Estafietin showed low toxicity according to pkCSM web tool and passed the PAINS filter from PAINS-remover web server. The treatment of infected mice with 1 mg/Kg/day of estafietin for five consecutive days administrated by intraperitoneal route significatively decreased parasitemia levels and reduced inflammatory infiltrates and myocyte damage on muscle tissue. These results suggest that estafietin had effect both on acute and chronic stages of the infection.

Antiproliferative Activities of Cynaropicrin and Related Compounds against Cancer Stem Cells

Glioblastoma (GBM) has a high mortality rate despite the availability of various cancer treatment options. Although cancer stem cells (CSCs) have been associated with poor prognosis and metastasis, and play an important role in the resistance to existing anticancer drugs and radiation; no CSC-targeting drugs are currently approved in clinical practice. Therefore, the development of antiproliferative agents against CSCs is urgently required. In this study, we evaluated the antiproliferative activities of 21 sesquiterpenoids against human GBM U-251 MG CSCs and U-251 MG non-CSCs. Particularly, the guaianolide sesquiterpene lactone cynaropicrin (1) showed strong antiproliferative activity against U-251 MG CSCs (IC50 = 20.4 µM) and U-251 MG non-CSCs (IC50 = 10.9 µM). Accordingly, we synthesized six derivatives of 1 and investigated their structure-activity relationships. Most of the guaianolide sesquiterpene lactones with the α-methylene-γ-butyrolactone moiety showed antiproliferative activities against U-251 MG cells. We conclude that the 5,7,5-ring and the α-methylene-γ-butyrolactone moiety are both important for antiproliferative activities against U-251 MG cells. The results of this study suggest that the α,β-unsaturated carbonyl moiety, which has recently become a research hotspot in drug discovery, is the active center of 1. Therefore, we consider 1 as a potential lead for developing novel drugs targeting CSCs.

Highly oxygenated guaiane-type sesquiterpene lactones from Artemisia sacrorum and their antihepatoma activity

The ethanol and EtOAc extracts of Artemisia sacrorum exhibited inhibitory effect against HepG2, Huh7, and SK-Hep-1 cell lines with inhibitory ratios of 65.5%, 28.1%, 84.6%, and 93.5%, 82.0%, 89.0% at 200 μg/mL. Twenty-three undescribed guaiane-type sesquiterpene lactones, artemisacrolides A‒W, were isolated from A. sacrorum under the guidance of antihepatoma activity. Their structures were elucidated by spectral data (HRESIMS, IR, UV, 1D and 2D NMR), ECD calculations, and a single-crystal X-ray diffraction. Artemisacrolides A‒U were guaiane-type sesquiterpene lactones possessing α-methylene-γ-lactone and containing acetoxyl groups at C-8, and artemisacrolides V and W represented the first report from the genus Artemisia with a 1,10-rearranged guaiane-type sesquiterpene lactone. Antihepatoma assay suggested that artemisacrolides A‒U demonstrated better inhibitory activity in Huh7 and SK-Hep-1 cells than those of HepG2 cells. Among them, nine compounds exhibited significant inhibitory activity against Huh7 cells with IC50 values of 8.2-14.3 μM, superior or equal to that of sorafenib; seven compounds demonstrated obvious activity against SK-Hep-1 cells with IC50 values of 13.5-19.2 μM, which were equivalent to that of sorafenib. Artemisacrolides B and E were the most active ones in three human hepatoma cell lines with IC50 values of 21.9, 8.2, 16.9 and 22.6, 9.0, 17.3 μM.

Six undescribed guaianolide-type sesquiterpenes from the aerial parts of Daphne penicillata

Six undescribed guaianolide sesquiterpenes (1-6) were obtained from the aerial parts of Daphne penicillata. Their structures and absolute configuration were elucidated by HRESIMS, NMR analyses, ECD calculations and single-crystal X-ray diffraction analysis. Structurally, all compounds possess the typical 5,7-fused system of 8,12-guaianolides and this guaianolide-type was first reported to be isolated from Daphne penicillata. All compounds (1-6) were evaluated for anti-inflammatory and cytotoxic activity. Among them, compounds 1 and 5 showed moderate inhibitory effects on LPS-induced NO production in BV2 cells and 4 displayed potential inhibition against Hep3B cells with an IC50 value of 7.33 μM.

Micheliolide prevents estrogen deficiency-induced bone loss via inhibiting osteoclast bone resorption

Osteoporosis is one of the major health problems characterized by decreased bone density and increased risk of fractures. Nowadays, the treating strategies against osteoporosis are efficient, but still have some drawbacks. Micheliolide, a guaianolide sesquiterpene lactone isolated from Michelia compressa and Michelia champac, has been reported to have anti-inflammatory effects. Here, our data suggest that Micheliolide could protect mice from ovariectomy induced bone loss. According to the Micro-CT scan and histomorphometry quantification data, Micheliolide treatment inhibits excessive osteoclast bone resorption without affecting bone formation in estrogen deficiency mice. Consistently, our data suggest that Micheliolide could inhibit osteoclastogenesis in vitro. Additionally, we confirmed that Micheliolide inhibits osteoclasts formation via inhibiting P38 MAPK signaling pathway, and P79350 (a P38 agonist) could rescue this effect. In summary, our data suggest that Micheliolide could ameliorate estrogen deficiency-induced bone loss via attenuating osteoclastogenesis. Hence, Micheliolide could be used as a novel anti-resorptive agent against osteoporosis.

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.

Guaianolide Derivatives from the Invasive Xanthium spinosum L.: Evaluation of Their Allelopathic Potential

Ziniolide, xantholide B (11α-dihydroziniolide), and 11β-dihydroziniolide, three sesquiterpene lactones with 12,8-guaianolide skeletons, were identified as volatile metabolites from the roots of Xanthium spinosum L., an invasive plant harvested in Corsica. Essential oil, as well as hydrosol and hexane extracts, showed the presence of guaianolide analogues. The study highlights an analytical strategy involving column chromatography, GC-FID, GC-MS, NMR (1D and 2D), and the hemi-synthesis approach, to identify compounds with incomplete or even missing spectral data from the literature. Among them, we reported the 1H- and 13C-NMR data of 11β-dihydroziniolide, which was observed as a natural product for the first time. As secondary metabolites were frequently involved in the dynamic of the dispersion of weed species, the allelopathic effects of X. spinosum root's volatile metabolites were assessed on seed germination and seedling growth (leek and radish). Essential oil, as well as hydrosol- and microwave-assisted extracts inhibited germination and seedling growth; root metabolite phytotoxicity was demonstrated. Nevertheless, the phytotoxicity of root metabolites was demonstrated with a more marked selectivity to the benefit of the monocotyledonous species compared to the dicotyledonous species. Ziniolide derivatives seem to be strongly involved in allelopathic interactions and could be the key to understanding the invasive mechanisms of weed.

Benzobicyclic ketones, cycloheptenone oxide derivatives, guaiane-type sesquiterpenes, and alkaloids isolated from Taraxacum mongolicum Hand.-Mazz

Ten previously undescribed compounds, including two benzobicyclic ketones, one cycloheptenone oxide derivative, three guaiane-type sesquiterpenes, and four alkaloids, along with one known cycloheptenone oxide derivative, were isolated from the whole plants of Taraxacum mongolicum Hand.-Mazz. Their structures were elucidated by UV, IR, HR-ESI-MS, 1D and 2D NMR spectroscopy, ECD spectroscopy, or X-ray diffraction analysis. Notably, benzobicyclic ketones have never been isolated from nature before. The 70% EtOH-H₂O extract of T. mongolicum displayed a significant inhibitory activity (33%) against croton oil-induced mouse ear edema. The two cycloheptenone oxide derivatives exhibited anti-inflammatory activities at 10 μM and significantly reduced the nitric oxide (NO) and interleukin-6 (IL-6) levels in RAW 264.7 macrophages induced by lipopolysaccharide (LPS), with inhibitory rates of 26.4-64.4%.

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.

Guaiazulene derivative 1,2,3,4-tetrahydroazuleno[1,2-b] tropone reduces the production of ATP by inhibiting electron transfer complex II

Molecularly targeted therapy has been used for treatment of various types of cancer. However, cancer cells often acquire resistance to molecularly targeted drugs that inhibit specific molecular abnormalities, such as constitutive activation of kinases. Even in cancer cells that have acquired resistance, enhanced anabolism, including the synthesis of nucleotides, amino acids and lipids, is common to normal cancer cells. Therefore, there is a renewed interest in effectively eliminating cancer cells by specifically targeting their abnormal energy metabolism. Multiple strategies are currently being developed for mitochondrial-targeted cancer therapy, with agents targeting oxidative phosphorylation, glycolysis, the tricarboxylic acid cycle and apoptosis. In this study, we found that one of the guaiazulene derivatives, namely, 1,2,3,4-tetrahydroazuleno[1,2-b] tropone (TAT), inhibited the proliferation of cancer cell lines stronger than that of normal cells. In addition, we showed that TAT inhibited energy production in cancer cell lines, resulting in apoptosis. Analyses done in cancer cell lines and in the animal model Caenorhabditis elegans suggested that TAT acts on the mitochondrial electron transfer complex II and suppresses cellular energy production by inhibiting oxidative phosphorylation across species. These results suggest that TAT could represent a novel anticancer agent that selectively targets mitochondria.

Cytotoxic Guaianolide Sesquiterpenoids from Ainsliaea fragrans

Twelve guaianolide-type sesquiterpene oligomers with diverse structures were isolated from the whole plants of Ainsliaea fragrans, including a novel trimer (1) and two new dimers (2, 3). The chemical structures of the new compounds were elucidated through spectroscopic data interpretation and computational calculations. Ainsfragolide (1) is an unusual guaianolide sesquiterpene trimer generated with a novel C-C linkage at C_2'-C_15″, which may be biosynthesized prospectively through a further Michael addition. Cytotoxicity results showed that ainsfragolide (1) was the most potent compound against five cancer cell lines with IC₅₀ values in the range of 0.4-8.3 μM.

(-)-Englerin-A Has Analgesic and Anti-Inflammatory Effects Independent of TRPC4 and 5

Recently, we found that the deletion of TRPC5 leads to increased inflammation and pain-related behaviour in two animal models of arthritis. (-)-Englerin A (EA), an extract from the East African plant Phyllanthus engleri has been identified as a TRPC4/5 agonist. Here, we studied whether or not EA has any anti-inflammatory and analgesic properties via TRPC4/5 in the carrageenan model of inflammation. We found that EA treatment in CD1 mice inhibited thermal hyperalgesia and mechanical allodynia in a dose-dependent manner. Furthermore, EA significantly reduced the volume of carrageenan-induced paw oedema and the mass of the treated paws. Additionally, in dorsal root ganglion (DRG) neurons cultured from WT 129S1/SvIm mice, EA induced a dose-dependent cobalt uptake that was surprisingly preserved in cultured DRG neurons from 129S1/SvIm TRPC5 KO mice. Likewise, EA-induced anti-inflammatory and analgesic effects were preserved in the carrageenan model in animals lacking TRPC5 expression or in mice treated with TRPC4/5 antagonist ML204.This study demonstrates that while EA activates a sub-population of DRG neurons, it induces a novel TRPC4/5-independent analgesic and anti-inflammatory effect in vivo. Future studies are needed to elucidate the molecular and cellular mechanisms underlying EA's anti-inflammatory and analgesic effects.

Dimeric guaianes from leaves of Xylopia vielana as snail inhibitors identified by high content screening

The transcriptional repressor Snail trriggers epithelial-mesenchymal transition (EMT), the process allowing cancer cells with invasive and metastasis properties. In this study, we screened medicinal plants for the Snail inhibitory active components by high content screen (HCS) and found that the crude extract of Xylopia vielana leaves showed potential activity. Subsequently, bioassay-guided isolation of the extract of Xylopia vielana was performed to obtain twenty-four dimeric guaianes (1-24), including 16 new analogues (1-5, 8-11, 13-15, 17, 18, 21, and 22). Their structures were elucidated by the comprehensive application of multiple spectroscopic methods. Compounds 1, 11, 12, and 16 were initially identified as the active compounds. Wound healing assay, transwell migration assay and western blot experiments verified that compounds 1 and 12 inhibited the expression of Snail in a concentration-dependent manner, and compound 12 was verified as a potent tumor migration inhibitory agent. This work showed a practical strategy for the discovery of new Snail inhibitors from natural products and provided potential insights for dimeric guaianes as anticancer lead compounds specifically targeting Snail protein.

Ambrosin sesquiterpene lactone exerts selective and potent anticancer effects in drug-resistant human breast cancer cells (MDA-MB-231) through mitochondrial mediated apoptosis, ROS generation and targeting Akt/β-Catenin signaling pathway

PURPOSE

Breast cancer accounts for a significant proportion of cancer burden among women world over. Concerning breast cancer treatment, there are only few chemotherapeutic agents available, which also have serious side effects. The present study was thus designed to explore in vitro the antitumor effects of ambrosin sesquiterpene lactone against human drug-resistant breast cancer cells (MDA-MB-231).

METHODS

WST-1 assay was used to determine cell viability. The fact that ambrosin induced apoptosis was studied through acridine orange (AO)/ethidium bromide (EB) staining using fluorescence microscopy as well as using flow cytometry in association with annexin-v/propidium iodide (PI) staining. Furthermore, western blot assay was used to study effects of ambrosin on apoptosis-related protein expressions including Bax and Bcl-2, as well as to study the effects on numerous caspases and Akt/β-Catenin Signaling Pathway. The effects on reactive oxygen species (ROS) and mitochondrial membrane potential (MMP) were evaluated by flow cytometry.

RESULTS

The results showed that ambrosin with an IC50 value of 25 µM decreased the viability of the MDA-MB-231 cells. The cytotoxicity of ambrosin was also investigated on the MCF-12A normal breast cells which showed that it exerted very low toxic effects on these cells. Ambrosin also caused remarkable changes in the morphology and suppressed the colony forming potential of MDA-MB-231 cells. The AO/EB staining assay showed that ambrosin inhibits the viability of cancer cells via induction of apoptotic cell death which was associated with increase in Bax and reduction in Bcl-2 levels. The apoptotic cells increased from 3.5% in the controls to around 56% at 50 µM concentration in the MDA-MB-231 cells. It was also seen that ambrosin treatment to these cancer cells resulted in substantial suppression in MMP and remarkable rise in ROS in a dose-dependent manner. This molecule also significantly inhibited the Akt/β-catenin signalling pathway by reducing the expressions of phosphorylated GSK-3β and Akt.

CONCLUSIONS

Taken all together, the results of our study indicate that ambrosin sesquiterpene may be developed as a promising anticancer agent in human breast cancer provided further in-depth studies are performed.

Anti-inflammatory Activity of Absinthin and Derivatives in Human Bronchoepithelial Cells

Bitter taste receptors (hTAS2R) are expressed ectopically in various tissues, raising the possibility of a pharmacological exploitation. This seems of particular relevance in airways, since hTAS2Rs are involved in the protection of the aerial tissues from infections and in bronchodilation. The bis-guaianolide absinthin (1), one of the most bitter compounds known, targets the hTAS2R46 bitter receptor. Absinthin (1), an unstable compound, readily turns into anabsinthin (2) with substantial retention of the bitter properties, and this compound was used as a starting material to explore the chemical space around the bis-guaianolide bitter pharmacophore. Capitalizing on the chemoselective opening of the allylic lactone ring, the esters 3 and 4, and the nor-azide 6 were prepared and assayed on human bronchoepithelial (BEAS-2B) cells expressing hTAS2R46. Anti-inflammatory activity was evaluated by measuring the expression of MUC5AC, iNOS, and cytokines, as well as the production of superoxide anion, qualifying the methyl ester 3 as the best candidate for additional studies.

Targeting the NLRP3 Inflammasome in Severe COVID-19

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a member of the genus Betacoronavirus within the family Coronaviridae. It is an enveloped single-stranded positive-sense RNA virus. Since December of 2019, a global expansion of the infection has occurred with widespread dissemination of coronavirus disease 2019 (COVID-19). COVID-19 often manifests as only mild cold-like symptomatology, but severe disease with complications occurs in 15% of cases. Respiratory failure occurs in severe disease that can be accompanied by a systemic inflammatory reaction characterized by inflammatory cytokine release. In severe cases, fatality is caused by the rapid development of severe lung injury characteristic of acute respiratory distress syndrome (ARDS). Although ARDS is a complication of SARS-CoV-2 infection, it is not viral replication or infection that causes tissue injury; rather, it is the result of dysregulated hyperinflammation in response to viral infection. This pathology is characterized by intense, rapid stimulation of the innate immune response that triggers activation of the Nod-like receptor family, pyrin domain-containing 3 (NLRP3) inflammasome pathway and release of its products including the proinflammatory cytokines IL-6 and IL-1β. Here we review the literature that describes the pathogenesis of severe COVID-19 and NLRP3 activation and describe an important role in targeting this pathway for the treatment of severe COVID-19.

Anti-neuroinflammatory effects of dimethylaminomylide (DMAMCL, i.e., ACT001) are associated with attenuating the NLRP3 inflammasome in MPTP-induced Parkinson disease in mice

Parthenolide (PTL) is a natural compound with anti-inflammatory and antioxidant properties and is an active ingredient extracted from the medicinal plant Tanacetum parthenium. ACT001 is derived from parthenolide and is a fumarate form of dimethylaminomylide (DMAMCL). Its effect is equivalent to that of PTL, but it is more stable in plasma and has lower acquisition costs. Related reports indicate that NLRP3-mediated neuroinflammation is involved in the progression of Parkinson's disease (PD). In our research, we explored whether ACT001 alleviates NLRP3-mediated neuroinflammation in PD mice induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Our results revealed that ACT001 reduces movement impairment and cognitive deficit in PD mice. In addition, it alleviates dopaminergic neurodegeneration in the nigrostriatal pathway and inhibits oxidative stress, the inflammatory response and activation of the NLRP3 inflammasome in the midbrain of MPTP-induced PD mice. Moreover, it attenuates microglial activation in the nigrostriatal pathway. Overall, our study showed that ACT001 alleviates NLRP3-mediated neuroinflammation in PD mice induced by MPTP.

Antitumor effects of helenalin in doxorubicin-resistant leukemia cells are mediated via mitochondrial mediated apoptosis, loss of mitochondrial membrane potential, inhibition of cell migration and invasion and downregulation of PI3-kinase/AKT/m-TOR signalling pathway

PURPOSE

The main purpose of the current study was to investigate the antitumor effects of helenalin - a plant derived sesquiterpene lactone, against doxorubicin-resistant acute myeloid leukemia HL60 cells, along with evaluating its effects on apoptosis induction, mitochondrial membrane potential (MMP), cell migration and inhibition and PI3K/AKT/M-TOR signalling pathway.

METHODS

Antiproliferative effects were evaluated with CCK8 cell viability assay and colony formation assay. Cell apoptotic effects were studied by (acridine orange) AO/ethidium bromide (EB) staining assay. To further estimate the extent of apoptosis, flow cytometry using annexin V assay was used. Effects on MMP were estimated by flow cytometry, while transwell migration assay was used to study the effects on cell migration and invasion. Protein expression was estimated by western blot method.

RESULTS

The results showed that helenalin inhibits the growth of the HL60 cells significantly and exhibited an IC50 of 23.5 µM. In addition, it was observed that the anticancer effects of helenalin are due to induction of mitochondrial-mediated apoptosis which was also associated with enhancement of the expression of Bax and decrease in the expression of Bcl-2. Helenalin also caused loss of MMP in the doxorubicin-resistant HL-60 cells and also inhibited their migratory and invasive properties via modulation of the PI3K/AKT/M-TOR signalling pathway.

CONCLUSIONS

In conclusion, the present study reveals that helenalin sesquiterpene lactone exhibits significant antitumor activity in doxorubicin-resistant acute myeloid leukemia HL60 cells by targeting some key pathways and as such this molecule could prove to be a potential drug candidate for future investigations.

Guaianolides from Ormenis mixta: Structural Insights and Evaluation of Their Anti-inflammatory Profile

In this paper, the isolation of five new guaianolides (1:  - 5: ) and four (6:  - 9: ) known sesquiterpenes from Ormenis mixta aerial parts is reported. The structural determination of the guaianolides was obtained by NMR spectroscopic data, as well as MS experiments. Their relative configurations were assigned by a combined quantum mechanical/NMR approach, comparing the experimental ¹³C/¹H NMR chemical shift data and ¹ J _H-H homonuclear coupling constants with the related predicted values. The isolates were assayed for their anti-inflammatory potential evaluating nitric oxide release and cyclooxygenase-2 expression in J774A.1 macrophages treated with lipopolysaccharide from Escherichia coli. Our results indicated that, among the tested compounds, 1:  - 3: , and 7: were able to inhibit nitric oxide release, while all were able to inhibit cyclooxygenase-2 expression with different potencies.

Ambrosin, a potent NF-κβ inhibitor, ameliorates lipopolysaccharide induced memory impairment, comparison to curcumin

Despite its poor bioavailability, curcumin is a promising natural polyphenol targeting NF-κβ. NF-κβ is a target for new therapeutics because it plays a pivotal role in the pathophysiology of Alzheimer disease (AD). In contrast, ambrsoin, a sesquiterpene lactone which is a potent NF-κβ inhibitor, is scarcely studied in AD models. The current work aims to assess the efficacy of ambrosin as a possible remedy for AD. In silico studies showed that bioavailability and BBB permeability could be favorable for ambrosin over curcumin. Memory impairment was induced in mice by single intraperitoneal injection of LPS (0.4 mg/kg). Treated groups received curcumin (100 mg/kg) or ambrosin at doses (5 or 10 mg/kg) for 7 days. Mice in treated groups showed a significant improvement in memory functions during Morris water maze and object recognition tests. Curcumin and ambrosin (10 mg/kg) inhibited the upsurge of NF-κβp65 transcript and protein levels. Consequently, downstream pro-inflammatory and nitrosative mediators were inhibited, namely, TNF-α, IL-1β, COX-2 and iNOS. BACE1 was inhibited, thereby reducing amyloid plaques (Aβ) deposition and eventually reducing inflammation and apoptosis of neurons as revealed by immunohistopathological examination. In conclusion, ambrosin can be repurposed as AD remedy after further pharmacokinetic/pharamacodynamic assessments. It could serve as an additional lead drug for AD therapeutics.

Vielanin P enhances the cytotoxicity of doxorubicin via the inhibition of PI3K/Nrf2-stimulated MRP1 expression in MCF-7 and K562 DOX-resistant cell lines

BACKGROUND

Cancer cells that are resistant to structurally and mechanically unrelated anticancer drugs are said to have multidrug resistance (MDR). The overexpression of the ATP-binding cassette (ABC) transporter is one of the most important mechanisms of MDR. Vielanin P (VP), a dimeric guaiane from the leaves of Xylopia vielana, has the potential to reverse multidrug resistance.

PURPOSE

To evaluate the meroterpenoid compound VP as a low cytotoxicity MDR regulator and the related mechanisms.

METHODS

Cell viability was determined by CCK-8 and MTT assays. Apoptosis and the accumulation of doxorubicin (DOX) and 5(6)-carboxyfluorescein diacetate (CFDA) were determined by flow cytometry. We determined mRNA levels by quantitative real-time polymerase chain reaction (qRT-PCR). Protein levels were analyzed by Western blotting and immunofluorescence.

RESULTS

In the MCF-7 and K562 DOX-resistant cell lines, VP treatment (10 μM or 20 μM) enhanced the activity of chemotherapeutic agents. We found that VP selectively inhibited MRP1 mRNA but not MDR1 mRNA. VP enhanced DOX-induced apoptosis and reduced colony formation in the presence of DOX in drug-resistant cells. Moreover, VP increased the accumulation of DOX and the MRP1-specific substrate CFDA. In addition, VP reversed MRP1 protein levels and the accumulation of DOX and CFDA in MRP1-overexpressing MCF-7 and K562 cells. Thus, the mechanism of MDR reversal by VP is MRP1-dependent. Furthermore, we found that the inhibitory effect of VP on MRP1 is PI3K/Nrf2-dependent.

CONCLUSION

These results support the potential therapeutic value of VP as an MDR-reversal agent by inhibiting MRP1 via PI3K/Nrf2 signaling.

Vieloplains A-G, seven new guaiane-type sesquiterpenoid dimers from Xylopia vielana

Seven new guaiane-type sesquiterpene dimers vieloplains A-G, connecting patterns through three different direct CC bonds compounds 1-5 (C-3 to C-3', C-4 to C-1'), compound 6 (C-2 to C-3', C-4 to C-2') and compound 7 (C-2 to C-1', C-4 to C-2') were isolated from the roots of Xylopia vielana. Their absolute configurations were established by NOESY analysis, the Cu Kα X-ray crystallographic the experiment circular dichroism (ECD) and the calculated ECD. Among them, only compound 6 showed a considerable cytotoxicity against DU145 cells with IC₅₀ values of 9.5 μM. Flow cytometry analysis confirmed that 6 caused death of DU145 cells via apoptosis induction.

Activity of Estafietin and Analogues on Trypanosoma cruzi and Leishmania braziliensis

Sesquiterpene lactones are naturally occurring compounds mainly found in the Asteraceae family. These types of plant metabolites display a wide range of biological activities, including antiprotozoal activity and are considered interesting structures for drug discovery. Four derivatives were synthesized from estafietin (1), isolated from Stevia alpina (Asteraceae): 11βH,13-dihydroestafietin (2), epoxyestafietin (3a and 3b), 11βH,13-methoxyestafietin, (4) and 11βH,13-cianoestafietin. The antiprotozoal activity against Trypanosoma cruzi and Leishmania braziliensis of these compounds was evaluated. Epoxyestafietin was the most active compound against T. cruzi trypomastigotes and amastigotes (IC₅₀ values of 18.7 and 2.0 µg/mL, respectively). Estafietin (1) and 11βH,13-dihydroestafietin (2) were the most active and selective compounds on L. braziliensis promastigotes (IC₅₀ values of 1.0 and 1.3 μg/mL, respectively). The antiparasitic activity demonstrated by estafietin and some of its derivatives make them promising candidates for the development of effective compounds for the treatment of Chagas disease and leihsmaniasis.

Micheliolide inhibits gastric cancer growth in vitro and in vivo via blockade of the IL-6/STAT3 pathway

Upregulation of pro-inflammatory cytokine interleukin (IL)-6 is observed in gastric cancer tissue, and high IL-6 serum levels predict a poor prognosis of gastric cancer patients. The IL-6/STAT3 pathway has been confirmed to play essential roles in the process of carcinogenesis, including gastric cancer. Thus, blockade of the IL-6/STAT3 pathway may be a potentially effective therapeutic option for gastric cancer. Micheliolide (MCL), a guaianolide sesquiterpene lactone, possesses anti-inflamma tory properties and can attenuate the IL-6 level. In addition, MCL has been widely reported to possess anti-tumor activity. But the anti-cancer effect of MCL on gastric cancer is unclear. In this study, we detected the effects of MCL on gastric cancer cell proliferation and apoptosis by performing MTT, colony formation, TUNEL and western blot assays, and found that MCL inhibited gastric cancer cell proliferation and promoted apoptosis in vitro. We further investigated the molecular mechanism by which MCL played an efficient role against gastric cancer, and found that the IL-6/STAT3 pathway is involved in the anti-cancer effect of MCL on gastric cancer. In vivo experiments further confirmed this conclusion. Taken together, MCL inhibits gastric cancer growth in vitro and in vivo via blockade of IL-6/STAT3 pathway.

Review: Warburg effect and renal cancer caused by errs in fumarate hydratase encoding gene

The several types of heterogeneous kidney cancers are interrelated by their primary sites of pathology. Despite its origin in the kidney, renal cell carcinoma (RCC) is associated with its varying genetic basis. Von Hippel-Lindau (VHL) syndrome is the earliest and, thus the most highly, characterized of genetic forms of kidney cancer, which is associated with alterations in the Von Hippel-Lindau (VHL) gene. As a result of his studies and investigations, Otto Warburg reached the conclusion that cancer's fundamental cause is altered mechanism. But this theory was disdained because of the discovery of tumor suppressor genes and oncogenes. Lately, the breakthrough finding about the tumor suppressing role of gene coding for enzymes involved in Krebs cycle has revived the interest in Warburg's hypothesis. This effect has led to the uncovering of the links between metabolic alterations, mitochondrial dysfunction and cancer. One such metastatic cancer characterized by the germ-line inactivating mutation of the gene coding for fumarate hydratase (FH), a Krebs cycle's enzyme, is hereditary leiomyomatosis and renal cell carcinoma (HLRCC). In this review paper, we have discussed the background of this carcinoma, the metabolic dysfunction causing it and its therapeutic solutions.

Monomeric and Dimeric Cytotoxic Guaianolide-Type Sesquiterpenoids from the Aerial Parts of Chrysanthemum indicum

Twelve new guaianolide-type sesquiterpenoids (1-12) and five known guaianolide derivatives (13-17) were isolated from an aqueous ethanol extract of the aerial parts of Chrysanthemum indicum. Their structures were determined through spectroscopic data analysis. The absolute configurations of the new compounds were assigned by X-ray crystallography and electronic circular dichroism. Compound 5 shows multiple cytotoxic activities against four human naso-pharyngeal carcinoma (NPC) cell lines (CNE1, CNE2, SUNE-1, and HONE-1) and one human intestinal epithelial cell line (HT-29) with IC₅₀ values of 4.6, 6.0, 3.5, 4.3, and 9.6 μM, respectively. Compound 16 exhibits weak cytotoxicity against four NPC cell lines, CNE1 (IC₅₀ = 7.3 μM), CNE2 (IC₅₀ = 7.4 μM), HONE-1 (IC₅₀ = 7.6 μM), and SUNE-1 (IC₅₀ = 5.6 μM), but no cytotoxicity against HT-29 (IC₅₀ > 10 μM).

Rare dimeric guaianes from Xylopia vielana and their multidrug resistance reversal activity

Thirteen undescribed dimeric guaianes were isolated from the leaves of Xylopia vielana Pierre. Their structures were elucidated by NMR spectroscopy and mass spectrometry, and the absolute configurations of vielanins G-Q were determined by a combination of the circular dichroism (CD) exciton chirality method, chemical conversion, and electronic CD (ECD) spectroscopy analysis. Vielaninors A and B are the first examples of trinor-guaiane-dimers. Multidrug resistance reversal activity assay of the isolates was evaluated in doxorubicin-resistant human breast cancer cells. Vielanins H, K-M, P, and Q were noncytotoxic and enhanced the cytotoxicity of doxorubicin by 2.1-41.6-fold at 10 μM.

Absolute Configurations and Bioactivities of Guaiane-Type Sesquiterpenoids Isolated from Pogostemon cablin

Seven novel guaiane sesquiterpenoids (1-7) and three known seco-guaianes were isolated from the volatile oil of Pogostemon cablin. Their structures including absolute configurations were determined by spectroscopic analyses, a modified Mosher's method, and X-ray diffraction and ECD data. The results indicated that the ECD Cotton effects arising from one or two nonconjugated olefinic chromophores could be applied to define the absolute configurations of guaiane sesquiterpenoids. Compounds 3 and 6 exhibited significant vasorelaxant activity against phenylephrine-induced and KCl-induced contractions of rat aorta rings [half-maximal effective concentration (EC₅₀) of 3 against PHE-induced contraction, 5.4 μM; EC₅₀ of 6 against PHE- and KCl-induced contractions, 1.6 and 24.2 μM, respectively]. They also showed antifungal activity against Candida albicans (minimum inhibitory concentrations, 500 and 300 μM, respectively). In addition, 2 and 7-9 displayed a neuroprotective effect against glutamate-induced injury in PC12 cells.

Two new guaiane sesquiterpene lactones from the aerial parts of Artemisia vulgaris

Two new guaiane sesquiterpene lactones, vulgarolides A and B (1 and 2), were isolated from Artemisia vulgaris aerial parts using various chromatographic separations. The structure elucidation was performed by combination of spectroscopic experiments including 1D and 2D NMR, HR ESI MS, and CD. Their in vitro cytotoxic activities against five human cancer cell lines were also evaluated using SRB method.

1,10-Secoguaianolides from Artemisia austro-yunnanensis and Their Anti-Inflammatory Effects

Seven 1,10-secoguaianolides 1⁻7, including a new one (compound 1), were isolated from Artemisia austro-yunnanensis and identified by HRESIMS and other spectroscopic methods. Their anti-inflammatory effects were evaluated by the model of LPS-induced RAW264.7 cells in vitro. Bioassay results showed that six of them (1⁻4, 6 and 7), with the exception of 5, produce some cytotoxicity on RAW264.7 cells at its high dosage, can significantly decrease the release of NO, TNF-α, IL-1β, IL-6 and PGE2 in a dose dependent manner, and down-regulate the expression of proteins iNOS and COX-2. The mechanism study indicated they regulated the NF-κB dependent transcriptional activity through decreasing the phosphorylation of NF-κB. Further, the relationship between their structures and cytokines to anti-inflammatory were studied by PCA and discussed.

Natural Product Micheliolide (MCL) Irreversibly Activates Pyruvate Kinase M2 and Suppresses Leukemia

Metabolic reprogramming of cancer cells is essential for tumorigenesis in which pyruvate kinase M2 (PKM2), the low activity isoform of pyruvate kinase, plays a critical role. Herein, we describe the identification of a nature-product-derived micheliolide (MCL) that selectively activates PKM2 through the covalent binding at residue cysteine424 (C424), which is not contained in PKM1. This interaction promotes more tetramer formation, inhibits the lysine433 (K433) acetylation, and influences the translocation of PKM2 into the nucleus. In addition, the pro-drug dimethylaminomicheliolide (DMAMCL) with similar properties as MCL significantly suppresses the growth of leukemia cells and tumorigenesis in a zebrafish xenograft model. Cell-based assay with knock down PKM2 expression verifies that the effects of MCL are dependent on PKM2 expression. DMAMCL is currently in clinical trials in Australia. Our discovery may provide a valuable pharmacological mechanism for clinical treatment and benefit the development of new anticancer agents.

Micheliolide alleviates hepatic steatosis in db/db mice by inhibiting inflammation and promoting autophagy via PPAR-γ-mediated NF-кB and AMPK/mTOR signaling

The anti-inflammatory, immunomodulatory, and anticancer effects of micheliolide (MCL) isolated from Michelia champaca were previously reported, but its role and underlying mechanisms in relieving liver steatosis remain unclear. Herein, we investigated the effects of MCL on hepatic steatosis using a db/db mouse model and lipid mixture (LM)-induced AML12 and LO2 cells. The body and liver weights, food consumption, lipid content and liver aminotransferase levels in serum, the lipid content and inflammatory cytokine levels in liver tissue, and the extent of hepatic steatosis in db/db mice were increased compared with those in db/m mice, and these increases were reversed by MCL treatment. Similarly, MCL also attenuated the inflammatory responses and lipid accumulation in LM-treated AML12 and L02 cells by upregulating PPAR-γ and decreasing p-IкBα and p-NF-κB/p65, thereby inhibiting the NF-κB pathway and reducing lipotoxicity. Furthermore, MCL administration increased LC3B, Atg7 and Beclin-1 expression and the LC3B-II/I ratio in db/db mouse livers and LM-treated AML12 and L02 cells, and these MCL-induced increases were mediated by the activation of PPAR-γ and p-AMPK and inhibition of p-mTOR and induce autophagy. These effects were blocked by PPAR-γ and AMPK inhibitors. Our findings suggest that MCL ameliorates liver steatosis by upregulating PPAR-γ expression, thereby inhibiting NF-κB-mediated inflammation and activating AMPK/mTOR-dependent autophagy.

Three new elemanolides from the seeds of Vernonia anthelmintica

Three new elemanolides, named vernonilides D (1), E (2), and F (3), along with four known sesquiterpenoids, including two elemanolides (4, 5), a guaianolide (6), and a germacranolide (7) were isolated from the seeds of Vernonia anthelmintica. The structures of them were elucidated based on 1D and 2D NMR experiments and comparison with published data. Cytotoxicity of the compounds against four human tumor cell lines was assayed. 6 showed strongly inhibitory effect against HCT-15 and PC-3 cell lines with IC₅₀ values of 0.56 and 0.69 μM, respectively. The new compounds showed moderate cytotoxicity against four cell lines with IC₅₀ values ranging from 9.1 to 28.1 μM.

New cytotoxic sesquiterpene lactones from Achillea cretica L. growing in Tunisia

The phytochemical study of Achillea cretica growing in Tunisia led to the isolation of two novel sesquiterpene lactones, which have been designated achicretin 1 and achicretin 2. Their chemical structures were further confirmed by mass spectroscopy (ESI-MS) and by extensive application of one- and two-dimensional NMR spectroscopy. The isolated compounds were tested for their cytotoxic activity against four human cancer cell lines, IGROV-1, OVCAR-3, MCF-7, and HCT-116 using the MTT assay. It has been found that achicretin 2 exhibited more potent inhibitory activity with IC₅₀ = values of 14.0 ± 1.0 and 16.0 ± 2.0 μM against OVCAR-3 and HCT-116 cells, respectively.

Identification of an (-)-englerin A analogue, which antagonizes (-)-englerin A at TRPC1/4/5 channels

BACKGROUND AND PURPOSE

(-)-Englerin A (EA) is a potent cytotoxic agent against renal carcinoma cells. It achieves its effects by activation of transient receptor potential canonical (TRPC)4/TRPC1 heteromeric channels. It is also an agonist at channels formed by the related protein, TRPC5. Here, we sought an EA analogue, which might enable a better understanding of these effects of EA.

EXPERIMENTAL APPROACH

An EA analogue, A54, was synthesized by chemical elaboration of EA. The effects of EA and A54 on the activity of human TRPC4 or TRPC5 channels overexpressed on A498 and HEK 293 cells were investigated, firstly, by measuring intracellular Ca²⁺ and, secondly, current using whole-cell patch clamp recordings.

KEY RESULTS

A54 had weak or no agonist activity at endogenous TRPC4/TRPC1 channels in A498 cells or TRPC4 or TRPC5 homomeric channels overexpressed in HEK 293 cells. A54 strongly inhibited EA-mediated activation of TRPC4/TRPC1 or TRPC5 and weakly inhibited activation of TRPC4. Studies of TRPC5 showed that A54 shifted the EA concentration-response curve to the right without changing its slope, consistent with competitive antagonism. In contrast, Gd³⁺ -activated TRPC5 or sphingosine-1-phosphate-activated TRPC4 channels were not inhibited but potentiated by A54. A54 did not activate TRPC3 channels or affect the activation of these channels by the agonist 1-oleoyl-2-acetyl-sn-glycerol.

CONCLUSIONS AND IMPLICATIONS

This study has revealed a new tool compound for EA and TRPC1/4/5 channel research, which could be useful for characterizing endogenous TRPC1/4/5 channels and understanding EA-binding sites and their physiological relevance.

Highly Oxidized Guaianolide Sesquiterpenoids with Potential Anti-inflammatory Activity from Chrysanthemum indicum

Ten new highly oxidized monomeric (1-8) and dimeric guaianolides (9 and 10), along with two known guaianolide derivatives (11 and 12), were isolated from the aerial parts of Chrysanthemum indicum using a bioassay-guided fractionation procedure. The new compounds were characterized by the basic analysis of the spectroscopic data obtained, and the absolute configurations were determined by both empirical approaches and ECD calculations. Inhibitory effects of 1-12 on nitric oxide production were investigated in lipopolysaccaride (LPS)-mediated RAW 264.7 cells, and most of them (1-8 and 11) displayed IC₅₀ values in the range 1.4-9.7 μM. Moreover, a mechanistic study revealed that the potential anti-inflammatory activity of compound 1 appears to be mediated via suppression of an LPS-induced NF-κB pathway and down-regulation of MAPK activation.

The natural sesquiterpene lactones arglabin, grosheimin, agracin, parthenolide, and estafiatin inhibit T cell receptor (TCR) activation

Inhibition of the T cell receptor (TCR) pathway represents an effective strategy for the treatment of T cell-mediated inflammatory and autoimmune diseases. To identify natural compounds that could inhibit inflammatory T cell responses, we screened 13 sesquiterpene lactones, including achillin, arglabin, argolide, argracin, 3β-hydroxyarhalin, artesin, artemisinin, estafiatin, grosheimin, grossmisin, leucomisine, parthenolide, and taurine, for their ability to modulate activation-induced Ca²⁺ mobilization in Jurkat T cells. Five of the compounds (arglabin, grosheimin, argracin, parthenolide, and estafiatin) inhibited anti-CD3-induced mobilization of intercellular Ca²⁺ ([Ca²⁺]_i) in Jurkat cells, with the most potent being parthenolide and argacin (IC₅₀ = 5.6 and 6.1 μM, respectively). Likewise, phosphorylation of extracellular signal-regulated kinase (ERK) 1/2 in activated Jurkat cells was inhibited by these five compounds, with the most potent being parthenolide and estafiatin (IC₅₀ = 13.8 and 15.4 μM, respectively). These compounds also inhibited ERK1/2 phosphorylation in primary human T cells and depleted intracellular glutathione. In contrast, none of the sesquiterpene lactones inhibited ERK1/2 phosphorylation in HL60 cells transfected with N-formyl peptide receptor 2 (FPR2) and stimulated with the FPR2 peptide agonist WKYMVM, indicating specificity for T cell activation. Estafiatin, a representative sesquiterpene lactone, was also profiled in a cell-based phosphokinase array for 43 kinase phosphorylation sites, as well as in a cell-free competition binding assay for its ability to compete with an active-site directed ligand for 95 different protein kinases. Besides inhibition of ERK1/2 phosphorylation, estafiatin also inhibited phosphorylation of p53, AMPKα1, CREB, and p27 elicited by TCR activation in Jurkat cells, but it did not bind to any of 95 kinases evaluated. These results suggest that arglabin, grosheimin, agracin, parthenolide, and estafiatin can selectively inhibit initial phases of TCR activation and may be natural compounds with previously undescribed immunotherapeutic properties.

Guaianolide sesquiterpene lactones and aporphine alkaloids from the stem bark of Guatteria friesiana

Three guaianolide sesquiterpenes, denoted guatterfriesols A-C, and four aporphine alkaloid derivatives were isolated from the stem bark of the Amazonian plant Guatteria friesiana. Thus far, sesquiterpene lactones have not been described in Annonaceae. Structures of the previously undescribed compounds were established by using 1D and 2D NMR spectroscopy in combination with MS. The absolute stereochemistry was assigned via NOE NMR experiments, ECD spectroscopy, and theoretical calculations using the TDDFT approach. Among the isolated compounds, the alkaloid guatterfriesidine showed anti-glycation activity by inhibiting the formation of advanced glycation end-products (AGEs) through the prevention of oxidation in both BSA/methylglyoxal and BSA/fructose systems.

Guaianolide sesquiterpenoids from Ainsliaea yunnanensis

Six previously undescribed C₁₇-guaianolides, a previously undescribed guaianolide alkaloid, and two previously undescribed guaianolides as well as 10 known guaianolides were obtained from an ethanol extract of Ainsliaea yunnanensis Franch. The chemical structures of all previously reported sesquiterpenoids were determined by extensive NMR spectroscopic analysis in combination with a modified Mosher's method. All isolates were in vitro screened for inhibitory effect against nitric oxide release in RAW 264.7 macrophages stimulated by LPS. Zaluzanin C remarkably inhibited the production of nitric oxide with an IC₅₀ value of 6.54 μM.

Englerin A induces an acute inflammatory response and reveals lipid metabolism and ER stress as targetable vulnerabilities in renal cell carcinoma

Renal cell carcinoma (RCC) is among the top ten most common forms of cancer and is the most common malignancy of the kidney. Clear cell renal carcinoma (cc-RCC), the most common type of RCC, is one of the most refractory cancers with an incidence that is on the rise. Screening of plant extracts in search of new anti-cancer agents resulted in the discovery of englerin A, a guaiane sesquiterpene with potent cytotoxicity against renal cancer cells and a small subset of other cancer cells. Though a few cellular targets have been identified for englerin A, it is still not clear what mechanisms account for the cytotoxicity of englerin A in RCC, which occurs at concentrations well below those used to engage the targets previously identified. Unlike any prior study, the current study used a systems biology approach to explore the mechanism(s) of action of englerin A. Metabolomics analyses indicated that englerin A profoundly altered lipid metabolism by 24 h in cc-RCC cell lines and generated significant levels of ceramides that were highly toxic to these cells. Microarray analyses determined that englerin A induced ER stress signaling and an acute inflammatory response, which was confirmed by quantitative PCR and Western Blot analyses. Additionally, fluorescence confocal microscopy revealed that englerin A at 25 nM disrupted the morphology of the ER confirming the deleterious effect of englerin A on the ER. Collectively, our findings suggest that cc-RCC is highly sensitive to disruptions in lipid metabolism and ER stress and that these vulnerabilities can be targeted for the treatment of cc-RCC and possibly other lipid storing cancers. Furthermore, our results suggest that ceramides may be a mediator of some of the actions of englerin A. Lastly, the acute inflammatory response induced by englerin A may mediate anti-tumor immunity.

Guaiane-Type Sesquiterpenoids from Fissistigma oldhamii Inhibit the Proliferation of Synoviocytes

Three guaiane-type sesquiterpenoids, dysodensiols G-I (1-3), together with five known sesquiterpenoids (4-8) were isolated from the stems of Fissistigma oldhamii (Hemsl.) Merr. Compound 1 represents the first example of an ene(6 → 5)-abeo-14-norguaiane sesquiterpenoid derived from natural products. Their structures were elucidated by a combination of 1D and 2D NMR and MS spectra. The absolute configuration of 2 was determined by an X-ray crystallographic analysis. The inhibitory effect of all compounds on the proliferation of primary synovial cells was evaluated. Compound 3 showed a potent inhibitory effect on the proliferation of synoviocytes with an IC₅₀ value of 1.0 µM.

Unveiling (-)-Englerin A as a Modulator of L-Type Calcium Channels

The voltage-dependent L-type Ca(2+) channel was identified as a macromolecular target for (-)-englerin A. This finding was reached by using an unprecedented ligand-based prediction platform and the natural product piperlongumine as a pharmacophore probe. (-)-Englerin A features high substructure dissimilarity to known ligands for voltage-dependent Ca(2+) channels, selective binding affinity for the dihydropyridine site, and potent modulation of calcium signaling in muscle cells and vascular tissue. The observed activity was rationalized at the atomic level by molecular dynamics simulations. Experimental confirmation of this hitherto unknown macromolecular target expands the bioactivity space for this natural product and corroborates the effectiveness of chemocentric computational methods for prioritizing target-based screens and identifying binding counterparts of complex natural products.

Bioactive sesquiterpenoids from the flowers of Inula japonica

Phytochemical investigation of the flowers of Inula japonica led to isolation of nine sesquiterpenoids, inujaponins A-I, as well as eighteen known ones. These sesquiterpenoids belong to six skeletal-types, including eudesmane, 1,10-seco-eudesmane, germacrane, guaiane, 4,5-seco-guaiane, and pseudoguaiane sesquiterpenoids. Their structures were established by extensive spectroscopic analysis. The absolute configurations of inujaponin A, eupatolide, and deacetylovatifolin were determined by Cu-Kα X-ray crystallographic analysis. Most of the isolated compounds exhibited potent cytotoxicity against HL-60, SMMC-7721, A-549, MCF-7, and SW-480 cancer cell lines, with IC50 values ranging from 1.57 to 22.58 μM. Some selected compounds also possessed significant inhibitory activity against LPS-induced NO production in RAW264.7 macrophages with IC50 values ranging from 1.42 to 8.99 μM.

New sesquiterpene lactones, vernonilides A and B, from the seeds of Vernonia anthelmintica in Uyghur and their antiproliferative activities

A new guaianolide sesquiterpene lactone, vernonilide A (1), and a new elemanolide sesquiterpene lactone, vernonilide B (2), were isolated from the seeds of Vernonia anthelmintica, together with three known elemanolide sesquiterpene lactones (3-5). The structures of the isolated compounds were elucidated on the basis of physicochemical evidences. Compounds 1, 3, and 4 showed strong antiproliferative activities against three human cancer cell lines (A549, HeLa, and MDA-MB-231), with IC50 values ranging from 0.10 to 1.00μM. In addition, 5 exhibited significant antiproliferative activities against HeLa and MDA-MB-231 cells, with IC50 values ranging from 1.90 to 2.20μM. The antiproliferative activities of the acetyl derivatives 6 and 7 prepared from 4 and 3, respectively, against the three cell lines were 4-10-fold weaker than the original activities.

Synthesis of a stable and orally bioavailable englerin analogue

Synthesis of analogues of englerin A with a reduced propensity for hydrolysis of the glycolate moiety led to a compound which possessed the renal cancer cell selectivity of the parent and was orally bioavailable in mice.

Eucarobustols A-I, Conjugates of Sesquiterpenoids and Acylphloroglucinols from Eucalyptus robusta

Nine new conjugates of sesquiterpenoids and acylphloroglucinols, named eucarobustols A-I (1-9), as well as 11 known analogues were isolated from the leaves of Eucalyptus robusta. The sesquiterpenoid motifs furnishing the new conjugates included four structural types of aristolane (1 and 2), guaiane (3), eudesmane (4), and aromadendrane (5-9) moieties. Compounds 1 and 2 were found to represent the first examples of conjugates of aristolane and acylphloroglucinol units. In turn, compound 3 features a new coupling model of guaiane and acylphloroglucinol via the C-4-C-7' bond. Compounds 1, 7, and 9 showed inhibitory activities against protein tyrosine phosphatase 1B (PTP1B) with IC50 values of 1.3, 1.8, and 1.6 μM, respectively.