Fluorinated amino-derivatives of the sesquiterpene lactone, parthenolide, as (19)f NMR probes in deuterium-free environments

A novel 1-benzoazepine-derived Michael acceptor and its hetero-adducts active against MRSA

Multidrug-resistant bacterial infections continue to be a rising global health concern. Herein, we describe the development of a novel class of 3-substituted benzoazepinedione derivatives with promising antibacterial activity. The pivotal compound, benzoazepinedione carboxylate 9, represents a highly electrophilic Michael acceptor, enabling divergent access to a wide range of thia-, aza-, oxa-, and phospha-Michael adducts. Notably, most prepared compounds exhibited potent antibacterial activity against both drug-susceptible and drug-resistant strains of Staphylococcus aureus (MIC90 of up to 2 μg mL-1). The cytotoxicity assessment in the VERO6 cell line revealed that thia-adduct 10d (IC50 of 36.5 μg mL-1) exhibits lower toxicity compared to its parent electrophile 9 (IC50 of 14.3 μg mL-1), which is in agreement with the hypothesis of covalently modified prodrugs. Additionally, stability studies of the prepared compounds in CD3OD and a DMSO-PBS mixture confirmed that thia-Michael adducts 10 are stable under neutral conditions while dynamic under mildly basic conditions. Moreover, 3D reconstructed tissue models (human lung epithelial EpiAirway™ and a human small intestine model) did not exhibit a viability decrease below 80% of the untreated control at all concentrations tested, indicating tolerance to higher concentrations of potential drugs and prodrugs.

Mechanistic study of the retro-aza-Michael reaction in saccharothriolide L: identification of 2-amino-4-methylphenol as an effective protecting tool for the Michael acceptor

Saccharothriolide L (1), a derivative of saccharothriolides (STLs) produced by the rare actinomycete Saccharotrix sp. A1506, was synthesized through the precursor-directed in situ synthesis (PDSS) method. The structure of 1 was determined by 1D and 2D NMR and HR-ESI-MS data analyses. A comparison of the rate of the retro-aza-Michael reaction between saccharothriolide L (1) and saccharothriolide B (2) indicated that the 2-amino-4-methylphenol group in 1 might be an effective masking tool for highly reactive, bioactive α, β-unsaturated carbonyl compounds.

Phosphine-Catalyzed Synthesis and Cytotoxic Evaluation of Michael Adducts of the Sesquiterpene Lactone Arglabin

A general method for chemo- and diastereoselective modification of anticancer natural product arglabin with nitrogen- and carbon-centered pronucleophiles under the influence of nucleophilic phosphine catalysts was developed. The locked s-cis-geometry of α-methylene-γ-butyrolactone moiety of arglabin favors for the additional stabilization of the zwitterionic intermediate by electrostatic interaction between phosphonium and enolate oxygen centers, leading to the unprecedentedly high efficiency of the phosphine-catalyzed Michael additions to this sesquiterpene lactone. Using n-Bu3P as the catalyst, pyrazole, phthalimide, 2-oxazolidinone, 4-quinazolinone, uracil, thymine, cytosine, and adenine adducts of arglabin were obtained. The n-Bu3P-catalyzed reaction of arglabin with active methylene compounds resulted in the predominant formation of bisadducts bearing a new quaternary carbon center. All synthesized Michael adducts and previously obtained phosphorylated arglabin derivatives were evaluated in vitro against eleven cancer and two normal cell lines, and the results were compared to those of natural arglabin and its dimethylamino hydrochloride salt currently used as anticancer drugs. 2-Oxazolidinone, uracil, diethyl malonate, dibenzyl phosphonate, and diethyl cyanomethylphosphonate derivatives of arglabin exhibited more potent antiproliferative activity towards several cancer cell lines and lower cytotoxicity towards normal cell lines in comparison to the reference compounds, indicating the feasibility of the developed methodology for the design of novel anticancer drugs with better therapeutic potential.

Expanding Natural Diversity: Tailored Enrichment of the 8,12-Sesquiterpenoid Lactone Chemical Space through Divergent Synthesis

The divergent synthesis of a non-natural 8,12-sesquiterpenoid lactone collection is described. The synthesis relies on a rationally designed guaianolide scaffold bearing a tertiary hydroxyl as the pinpoint for inducing its selective diversification. Key reactions include an unprecedented Suarez-type CH lactonization and a highly diastereoselective oxy-Cope/ene cascade that allows the introduction of three stereocenters in a single operation. Selective oxidative/reductive and redox neutral transformations follow to highlight the synthesis of naturally unpresented highly substituted 8,12-guaianolides.

In Silico Analysis: Anti-Inflammatory and α-Glucosidase Inhibitory Activity of New α-Methylene-γ-Lactams

The research about α-methylene-γ-lactams is scarce; however, their synthesis has emerged in recent years mainly because they are isosters of α-methylene-γ-lactones. This last kind of compound is structurally most common in some natural products' nuclei, like sesquiterpene lactones that show biological activity such as anti-inflammatory, anticancer, antibacterial, etc., effects. In this work, seven α-methylene-γ-lactams were evaluated by their inflammation and α-glucosidase inhibition. Thus, compounds 3-methylene-4-phenylpyrrolidin-2-one (1), 3-methylene-4-(p-tolyl)pyrrolidin-2-one (2), 4-(4-chlorophenyl)-3-methylenepyrrolidin-2-one (3), 4-(2-chlorophenyl)-3-methylenepyrrolidin-2-one (4), 5-ethyl-3-methylene-4-phenylpyrrolidin-2-one (5), 5-ethyl-3-methylene-4-(p-tolyl)pyrrolidin-2-one (6) and 4-(4-chlorophenyl)-5-ethyl-3-methylenepyrrolidin-2-one (7) were evaluated via in vitro α-glucosidase assay at 1 mM concentration. From this analysis, 7 exerts the best inhibitory effect on α-glucosidase compared with the vehicle, but it shows a low potency compared with the reference drug at the same dose. On the other side, inflammation edema was induced using TPA (12-O-tetradecanoylphorbol 13-acetate) on mouse ears; compounds 1-7 were tested at 10 µg/ear dose. As a result, 1, 3, and 5 show a better inhibition than indomethacin, at the same doses. This is a preliminary report about the biological activity of these new α-methylene-γ-lactams.

Alantolactone derivatives inhibit the tumor necrosis factor α-induced nuclear factor κB pathway by a different mechanism from alantolactone

Alantolactone is a eudesmane-type sesquiterpene lactone that exerts various biological effects, including anti-inflammatory activity. In the present study, screening using the RIKEN Natural Products Depository chemical library identified alantolactone derivatives that inhibited the expression of intercellular adhesion molecule-1 (ICAM-1) on human umbilical vein endothelial cells stimulated with proinflammatory cytokines and Toll-like receptor ligands. In human lung adenocarcinoma A549 cells stimulated with tumor necrosis factor-α (TNF-α), six alantolactone derivatives inhibited ICAM-1 expression in a dose-dependent manner and at IC50 values of 13-21 μM, whereas that of alantolactone was 5 μM. Alantolactone possesses an α-methylene-γ-lactone moiety, whereas alantolactone derivatives do not. In the nuclear factor κB (NF-κB) signaling pathway, alantolactone prevented the TNF-α-induced phosphorylation and degradation of the inhibitor of NF-κB α (IκBα) protein, and its downstream signaling pathway. In contrast, alantolactone derivatives neither reduced TNF-α-induced IκBα degradation nor the nuclear translocation of the NF-κB subunit RelA, but inhibited the binding of RelA to the ICAM-1 promoter. The inhibitory activities of alantolactone and alantolactone derivatives were attenuated by glutathione. These results indicate that alantolactone derivatives inhibit the TNF-α-induced NF-κB pathway by a different mechanism from alantolactone.

Stereoelectronic Effect in the Reaction of α-Methylene Lactones with Tertiary Phosphines and Its Application in Organocatalysis

The kinetic data indicate that the addition of tertiary phosphines to α-methylene lactones in acetic acid is strongly accelerated in comparison to the reactions of related open-chain esters. Six-membered α-methylene-δ-valerolactone exhibited a more pronounced rate increase than five-membered α-methylene-γ-butyrolactone. The use of α-methylene-γ-butyrolactam as a nitrogen analogue of α-methylene-γ-butyrolactone resulted in a total loss of the reaction acceleration. The observed reactivities were rationalized by DFT calculations at the RwB97XD/6-31+G(d,p) level of theory, showing that the intramolecular interaction between phosphonium and enolate oxygen centers provided by the locked s-cis-geometry of the heterocycles plays an important role in the stabilization of intermediate zwitterions. The reactivity is also controlled by the conformational flexibility of the heterocycle. The geometries of five-membered and, especially, six-membered lactone cycles are slightly changed upon the nucleophilic attack of phosphine, leading to the stabilizing stereoelectronic effect by the Ρ···Ο interaction. The addition of phosphine to α-methylene-γ-butyrolactam significantly distorts the initial geometry of the heterocycle, making the nucleophilic attack unfavorable. The application of the stereoelectronic effect to enhance the efficiency of the phosphine-catalyzed Michael and Pudovik reactions of α-methylene lactones was demonstrated.

Covalent targeting the LAS1-NOL9 axis for selective treatment in NPM1 mutant acute myeloid leukemia

Patients with NPM1 gene mutation-associated acute myeloid leukemia (AML), particularly those over the age of 60, have no viable targeted therapeutic choices. In this study, we identified HEN-463, a sesquiterpene lactone derivative specific targets AML with this gene mutation. This compound inhibits the interaction of LAS1-NOL9 by covalently binding to the C264 site of the ribosomal biogenesis-related protein LAS1, which translocates the LAS1 to the cytoplasm, thereby inhibiting the maturation of 28 S rRNA. This has a profound effect on the NPM1-MDM2-p53 pathway and ultimately results in the stabilization of p53. Combining this treatment with the XPO1 inhibitor Selinexor (Sel) can ideally preserve the stabilized p53 in the nucleus, considerably enhancing the efficacy of HEN-463 and addressing Sel's drug resistance. Patients with AML over the age of 60 who possess the NPM1 mutation have an unusually elevated level of LAS1, which has a significant impact on their prognosis. In NPM1-mutant AML cells, decreased LAS1 expression promotes proliferation inhibition, apoptosis, cell differentiation, and cell cycle arrest. This suggests that it may be a therapeutic target for this kind of blood cancer, especially in patients over the age of 60.

Targeting proteases involved in the viral replication of SARS-CoV-2 by sesquiterpene lactones from chicory (Cichorium intybus L.)

SARS-CoV-2 is a highly transmissible and pathogenic coronavirus causing a respiratory disease that emerged in 2019, leading to a public health emergency situation which continues to date. The treatment options are still very limited and vaccines available are less effective against new variants. SARS-CoV-2 enzymes, namely main protease (Mpro) and papain-like protease (PLpro), play a pivotal role in the viral life cycle, making them a putative drug target. Here, we described for the first time the potential inhibitory activity of chicory extract against both proteases. Besides, we have identified that the four most abundant sesquiterpene lactones in chicory inhibited these proteases, showing an effective binding in the active sites of Mpro and PLpro. This paper provides new insight for further drug development or food-based strategies for the prevention of SARS-CoV-2 by targeting viral proteases.

13-amino derivatives of dehydrocostus lactone display greatly enhanced selective toxicity against breast cancer cells and improved binding energies to protein kinases in silico

The biological activities of dehydrocostus lactone and its analogues are suggested to be mediated by the lactone ring and α,β-methylene-γ-lactone. However, few studies exist on the structure-activity relationship of 13-amino derivatives of dehydrocostus latone. In this study new 13-amino derivatives of dehydrocostus lactone DHLC (1–4) were synthesized through Michael addition reactions, and were screened against three different breast cancer cell lines, namely hormone receptor positive breast cancer (MCF-7), triple-negative breast cancer (HCC70), and non-tumorigenic mammary epithelial (MCF-12A) cell lines. Dehydrocostus lactone (DHLC) exhibited IC₅₀ values of 1.11 (selectivity index (SI) = 0.06), 24.70 (SI = 0.01) and 0.07 μM against HCC70, MCF-7 and MCF-12A cells, respectively. All the amino derivatives, except DHLC-3 displayed low micromolar IC₅₀ values (ranging from 0.07–4.24 μM) against both breast cancer cell lines, with reduced toxicity towards MCF-12A non-tumorigenic mammary epithelial cells (SI values ranging from 6.00–126.86). DHLC-1 and DHLC-2 demonstrated the greatest selectivity for the MCF-7 cells (with SI of 121 and 126.86 respectively) over the MCF-12A cells. This reveals that, overall, the derivatives display greatly improved selectivity for breast cancer over non-tumorigenic mammary epithelial cells, with between 100-fold and 12 000-fold higher SI values. The improved docking scores were recorded for all the 13-amino dehydrocostus lactone derivatives for the enzymes analyzed. Compounds DHLC-4, and DHLC-3 recorded higher docking scores of -7.33 and -5.97 Kca/mol respectively, compared to the parent structure, dehydrocostus lactone (-5.34 Kca/mol) for protein kinase (PKC) theta (1XJD) and -6.22 and -5.88 Kca/mol, respectively for protein kinase iota (1RZR). The compounds further showed promising predicted adsorption, distribution, metabolisms and excretion (ADME) properties. Predicting the ADME properties of these derivatives is of importance in evaluating their drug-likeness, which could in turn be developed into potential drug candidates.

Syntheses Based on 3,4α-Epoxy-1,5,7α,6β(H)-guai-10(14),11(13)-dien-6,12-olide

The sesquiterpene γ-lactone estafiatin 1, the molecule of which has a structure of 3,4α-epoxy-1,5,7α,6β(H)-guai-10(14),11(13)-dien-6,12-olide, is characteristic of plants of the genera Achillea L. and Artemisia L. of the Asteraceae family. This article presents the results of chemical modification for three reaction centers of the estafiatin molecule 1: epoxy cycle, exomethylene group conjugated with γ-lactone carbonyl, and exomethylene group in position C10=C14; and at the same time 33 new derivatives were synthesized, the structures of which were established based on physicochemical constants, spectral data (IR-, PMR-, ¹³C-NMR), and X-ray diffraction analysis. The stereo- and regiospecificity, as well as the chemoselectivity of the reaction based on estafiatin molecule 1, are discussed. The reactivity of the substrate is significantly influenced by the stereochemistry of its molecule, the nature of the reagent, and the reaction medium. Based on the results of in silico screening, derivatives of estafiatin with high binding energies for both DNA-topoisomerase I and DNA-topoisomerase II were identified. The values of the inhibitory dose of IC₅₀ for estafiatin 1 and its derivatives were determined on cell lines of eight types of tumors. in vivo experiments of the samples made it possible to establish that estafiatin 1 and its derivatives have pronounced antitumor activity against Pliss lymphosarcoma, Walker’s carcinosarcoma, sarcoma 45, sarcoma-180, alveolar liver cancer PC-1, leukemia P-388 and L-1210, and sarcoma-45 resistant to 5-fluorouracil.

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.

A multifunctional divergent scaffold to access the formal syntheses of various sesquiterpenoids

The development of a divergent scaffold able to access an array of diverse natural sesquiterpenoids is described. The route unifies the scope of previously reported plans of our group to allow the scalable synthesis of 8,12-furo and lactone sesquiterpenoid carbocyclic cores of elemanes, germacranes, guaianes, cadinanes, lindenanes and myliols. The formal syntheses of furogermenone, methyl-curdionolide, zedoarol, qweicurculactone, lindenene and sarcandralactone A are reported.

Retro-aza-Michael reaction of an o-aminophenol adduct in protic solvents inspired by natural products

α,β-Unsaturated carbonyls are reactive group often found in bioactive small molecules. Their non-specific reaction with biomolecules can be the cause of the low efficacy and unexpected side-effects of the molecule. Accordingly, unprotected α,β-unsaturated carbonyls are not often found in drugs. Here, we report that o-aminophenol is a new masking group of α,β-unsaturated ketone, which is inspired by natural products saccharothriolides. o-Aminophenol adduct of α,β-unsaturated ketone, but not those of α,β-unsaturated amide or ester, undergoes a retro-Michael reaction to yield o-aminophenol and the Michael acceptor. This reaction was observed only in protic solvents, such as MeOH and aqueous MeOH. In contrast, o-anisidine was not eliminated from its Michael adduct. o-Aminophenol may be a promising masking tool of highly-reactive bioactive α,β-unsaturated carbonyl compounds.

What dominates the changeable pharmacokinetics of natural sesquiterpene lactones and diterpene lactones: a review focusing on absorption and metabolism

Sesquiterpene lactones (STLs) and diterpene lactones (DTLs) are two groups of common phytochemicals with similar structures. It's frequently reported that both exhibit changeable pharmacokinetics (PK) in vivo, especially the unstable absorption and extensive metabolism. However, the recognition of their PK characteristics is still scattered. In this review, representative STLs (atractylenolides, alantolactone, costunolide, artemisinin, etc.) and DTLs (ginkgolides, andrographolide, diosbulbins, triptolide, etc.) as typical cases are discussed in detail. We show how the differences of treatment regimens and subjects alter the PK of STLs and DTLs, with emphasis on the effects from absorption and metabolism. These compounds tend to be quite permeable in intestinal epithelium, but gastrointestinal pH and efflux transporters (represented by P-glycoprotein) have great impact and result in the unstable absorption. As the only characteristic functional moiety, the metabolic behavior of lactone ring is not dominant. The α, β-unsaturated lactone moiety has the strongest metabolic activity. While with the increase of low-activity saturated lactone moieties, the metabolism is led by other groups more easily. The phase I (oxidation, reduction and hydrolysis reaction) and II metabolism (conjugation reaction) are both extensive. CYP450s, mainly CYP3A4, are largely involved in biotransformation. However, only UGTs (UGT1A3, UGT1A4, UGT2B4 and UGT2B7) has been mentioned in studies about phase II metabolic enzymes. Our work offers a beneficial reference for promoting the safety evaluation and maximizing the utilization of STLs and DTLs.

Synthesis and biological evaluation of semi-synthetic albocycline analogs

Albocycline (ALB) is a unique macrolactone natural product with potent, narrow-spectrum activity against methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-intermediate (VISA), and vancomycin-resistant S. aureus (VRSA) strains (MIC = 0.5-1.0 μg/mL). Described herein is the synthesis and evaluation of a novel series analogs derived from albocycline by functionalization at three specific sites: the C2-C3 enone, the tertiary carbinol at C4, and the allylic C16 methyl group. Exploration of the structure-activity relationships (SAR) by means of minimum inhibitory concentration assays (MICs) revealed that C4 ester analog 6 was twice as potent as ALB, which represents a class of lead compound that can be further studied to address multi-drug resistant pathogens.

Synthesis, Crystallography, and Anti-Leukemic Activity of the Amino Adducts of Dehydroleucodine

Dehydroleucodine is a bioactive sesquiterpene lactone. Herein, four dehydroleucodine amino derivatives were synthesized using the amines proline, piperidine, morpholine, and tyramine, and spectroscopic methods and single-crystal X-ray diffraction unambiguously established their structures. The cytotoxic activity of these compounds was evaluated against eight acute myeloid leukemia cell lines, and their toxicity to peripheral blood mononuclear cells was also determined. The proline adduct was the most active compound, it showed anti-leukemic activity, upregulated heme oxygenase 1 (HMOX1) and the primary stress-inducible isoform of the heath shock 70 kDa protein 1 (HSPA1A), and downregulated NFkB1 transcription, it was also found to be about 270 times more water soluble than dehydroleucodine.

Chemical modification of ovatodiolide revealed a promising amino-prodrug with improved pharmacokinetic profile

Stepwise modification of ovatodiolide revealed a prodrug, NMP-diepoxyovatodiolide, which can provide sustained release of an active compound, substantial metabolic stability and a unique accumulation profile in the liver. Besides, NMP-diepoxyovatodiolide demonstrated therapeutic benefits in an acute autoimmune hepatitis mouse model and a broad safety window. Therefore, NMP-diepoxyovatodiolide is a very promising candidate for further development of liver-related drugs.

Potential antidiabetic and antioxidant activities of a heliangolide sesquiterpene lactone isolated from Helianthus annuus L. leaves

Heliangolide is a naturally occurring sesquiterpene lactone and its derivatives are biologically active compounds present in most medicinal plants. This study evaluated the antioxidant and antidiabetic properties of a heliangolide sesquiterpene lactone isolated from Helianthus annuus L. leaves. The heliangolide sesquiterpene lactone was isolated through a combination of solvent-solvent partitioning, column chromatography, thin layer chromatography and high-performance liquid chromatography techniques. The antioxidant activity of the compound was evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and nitric oxide radical scavenging assays while the antidiabetic effects were investigated in alloxan-induced diabetic rats. The heliangolide derivative at the concentration of 954.2 µmol L-1 showed 23.7 % DPPH and 26 % nitric oxide radical inhibitions compared with 96.6 and 50.9 %, resp., displayed by the controls (2,271.2 µmol L-1). It also reduced the fasting blood glucose (FBG) levels in a time-dependent manner. The highest activity was recorded within 6 h post-treatment at 0.2 mmol kg-1 bm. The heliangolide derivative exhibited significant (p < 0.05) antioxidant and antidiabetic properties and provides a basis for further development of constituents of Helianthus annuus leaves for the management of such diseases.

Natural product-based semisynthesis and biological evaluation of thiol/amino-Michael adducts of xanthatin derived from Xanthium strumarium as potential pesticidal agents

Xanthatin, a natural sesquiterpene lactone, occurs as one of the major constituents of Xanthium plants (Compositae) and exhibits many important biological properties. To discover natural products-based pesticides, forty-nine Michael-type thiol/amino adducts of xanthatin were synthesized and characterized, while their pesticidal activities were investigated. Among them, compounds 2c, 2h, 2i, and 2t exhibited more potent antifungal activity against Botrytis cinerea (IC₅₀ = 0.96, 0.38, 6.33, and 7.21 µg/mL, respectively) than xanthatin and the two commercial fungicides. Compounds 2t and 2u displayed broad-spectrum and excellent antifungal effects against all tested phytopathogenic fungi, while their IC₅₀ values ranged from 7.21 to 75.88 µg/mL. Compounds 2a, 2f, 2l, 2m, 2v, 7c, 7e, 7h, 7i, and 7j showed moderate larvicidal activity against Plutella xylostella Linnaeus. Furthermore, compounds 2b, 7g, and 7h demonstrated significant ovicidal activity against P. xylostella with the LC₅₀ values of 14.04, 10.00, and 11.95 mg/L, respectively. These findings suggest that thiol/amino appended in the C-13 position of xanthatin may improve antifungal and ovicidal activities for the derivatives. It was also noticed that the exocyclic double bond of xanthatin is crucial for its larvicidal activity. This work also provides some important hints for further design, synthesis, and structural modification of the xanthanolides sesquiterpene lactones toward development of the new environmentally friendly pesticides for sustainable agricultural production.

Phosphine-catalyzed Michael additions to α-methylene-γ-butyrolactones

The highly efficient addition of phosphorus and carbon pronucleophiles to α-methylene-γ-butyrolactones (tulipalin A and arglabin) under n-Bu3P catalysis is reported. Kinetic experiments indicate that the unprecedentedly high reactivity of α-methylene-γ-butyrolactones results from the rigid s-cis geometry of the 1-oxa-1,3-butadiene moiety that favors generation of zwitterionic intermediate stabilized by interaction between the phosphonium center and adjacent carbonyl oxygen. The presented strategy offers an economical and practical method for functionalization of natural biologically active α-methylene-γ-butyrolactones with high levels of chemo- and stereoselectivity.

A Novel Heterocyclic System Based on Natural Epoxyalantolactone

Natural sesquiterpene lactones which contain an exocyclic methylene group in the β-position of the lactone ring react readily with N-nucleophiles. When studying the reaction of the natural epoxyalantolactone with the primary amines we demonstrate the formation of a new heterocyclic system—the hydrogenated benzo[g]furo[4,3,2-cd]indol-3(1H)-one. Spectral data on the characteristics of the synthesized compounds are presented. The data on the reaction mechanisms and its applicability for the preparation are discussed.

Derivatisation of parthenolide to address chemoresistant chronic lymphocytic leukaemia

Parthenolide is a natural product that exhibits anti-leukaemic activity, however, its clinical use is limited by its poor bioavailability. It may be extracted from feverfew and protocols for growing, extracting and derivatising it are reported. A novel parthenolide derivative with good bioavailability and pharmacological properties was identified through a screening cascade based on in vitro anti-leukaemic activity and calculated "drug-likeness" properties, in vitro and in vivo pharmacokinetics studies and hERG liability testing. In vitro studies showed the most promising derivative to have comparable anti-leukaemic activity to DMAPT, a previously described parthenolide derivative. The newly identified compound was shown to have pro-oxidant activity and in silico molecular docking studies indicate a prodrug mode of action. A synthesis scheme is presented for the production of amine 7 used in the generation of 5f.

Synthesis of novel 1,2,3-triazole-substituted tomentosins

A series of 1,2,3-triazole-containing tomentosin scaffolds was obtained from tomentosin 1. The synthesis involved a Michael addition of trimethylsilylazide on the α-methylene-γ-lactone function of the natural sesquiterpene lactone 1 to give the diastereoisomers 2 and 3, which were readily separated by column chromatography. These compounds underwent copper-catalyzed Huisgen 1,3-dipolar cycloaddition with various terminal alkynes to provide compounds 4a–h and 5a–h in good yields.

Pd(ii)/Zn co-catalyzed chemo-selective hydrogenation of α-methylene-γ-keto carboxylic acids

Divergent synthesis of α-methyl-γ-keto carboxylic acids, α-methylcarboxylic acids, and lactones from α-methylene-γ-keto carboxylic acids.

Development of covalent NLRP3 inflammasome inhibitors: Chemistry and biological activity

The NOD-like receptor family, pyrin domain-containing 3 (NLRP3) inflammasome is the best recognized and most widely implicated regulator of caspase-1 activation. It is a key regulator of innate immune response and is involved in many pathophysiological processes. Recent evidences for its inappropriate activation in autoinflammatory, autoimmune, as well as in neurodegenerative diseases attract a growing interest toward the development of small molecules NLRP3 inhibitors. Based on the knowledge of biochemical and structural aspects of NLRP3 activation, one successful strategy in the identification of NLRP3 inhibitors relies on the development of covalent irreversible inhibitors. Covalent inhibitors are reactive electrophilic molecules able to alkylate nucleophiles in the target protein. These inhibitors could ensure good efficacy and prolonged duration of action both in vitro and in vivo. In spite of these advantages, effects on other signalling pathways, prone to alkylation, may occur. In this review, we will illustrate the chemistry and the biological action of the most studied covalent NLRP3 inhibitors developed so far. A description of what we know about their mechanism of action will address the reader toward a critical understanding of NLRP3 inhibition by electrophilic compounds.

Synthesis and anticancer studies of Michael adducts and Heck arylation products of sesquiterpene lactones, zaluzanin D and zaluzanin C from Vernonia arborea

Sesquiterpene lactones containing α-methylene-γ-lactones, zaluzanin D 1 and zaluzanin C 2 were isolated from the leaves of Vernonia arborea. Several diverse Michael adducts (3-22) and Heck arylation analogs (23-34) of 1 have been synthesized by reacting with various amines and aryl iodides, respectively and were assayed for their in vitro anticancer activities against human breast cancer cell lines MCF7 and MDA-MB-231. Among all the synthesized analogs, Michael adducts 9 and 10 showed better anticancer activities as compared to 1. However, among these compounds, only 10 has minimal cytotoxic effect on normal breast epithelial MCF10A cells. Our detailed mechanistic studies reveal that compounds 9 and 10 execute their antiproliferative activity through induction of apoptosis and thereby inhibit the cancer cells proliferation and compound 10 could be a lead compound for designing potential anti-cancer compound.

Sesquiterpene lactones from the methanol extracts of twenty-eight Hieracium species from the Balkan Peninsula and their chemosystematic significance

Four sesquiterpene lactones (SLs), including three undescribed proline-SL conjugates, the guaianolides calophyllamine A and 8-epiixerisamine A, and the eudesmanolide calophyllamine B, were isolated from the methanol extract of Hieracium calophyllum R. Uechtr. (Compositae) flowering heads. Another known guaianolide, crepiside E, was detected in Hieracium L. species for the first time. Their structures were elucidated using extensive 1D and 2D NMR spectroscopy in combination with HRMS. The isolated SLs were used as external standards for qualitative and quantitative LC-MS analysis of the dry methanol extracts of the flowering aerial parts of 28 Hieracium species from the Balkan Peninsula. Guaianolides were the dominant SLs in 27 species studied. The chemosystematic significance of detected SLs was evaluated using multivariate statistics (PCA, nMDS and UPGMA). Differentiation between the main groups was well supported. All four compounds significantly and equally contributed to the differences between the species. In addition, the eudesmanolide calophyllamine B could be a significant chemosystematic marker for H. sect. Villosa (Griseb.) Gremli s.l. and Glauciformia (Freyn) Zahn-Italica (Fr.) Av. Touv.

Application of sesquiterpene lactone: A new promising way for cancer therapy based on anticancer activity

Cancer is one of the most dangerous diseases that are rapidly increasing globally. After heart disease, it is the second leading cause of death, accounting for seven million deaths each year. Chemotherapy is the use of cytotoxic drugs on cancer cells. But the use of common chemotherapy drugs poses a problem due their high side effects and low efficacy. As a result, efforts are on to find new potent compounds with low side effects. The compounds extracted from plants have been studied in this regard due to their prevalence. Sesquiterpene lactones are a group of natural compounds that were first detected in Asteraceae dark plants. These compounds exercise their effects by reacting with functional groups available on proteins and enzymes, especially the thiol group. Owing to the high side effects as an antitumor synthetic drugs, efforts are being made to find drugs with high efficiency and low side effects. Their high structural ranges have attracted the attention of many researchers as a potential source of new anticancer drugs.

Induction of G 2 /M arrest and apoptosis through mitochondria pathway by a dimer sesquiterpene lactone from Smallanthus sonchifolius in HeLa cells

Dimer sesquiterpene lactones (SLs), uvedafolin and enhydrofolin, against four monomer SLs isolated from yacon, Smallanthus sonchifolius, leaf were the most cytotoxic substances on HeLa cells (IC₅₀ values 2.96–3.17 μM at 24 hours). However, the cytotoxic mechanism of dimer SL has not been elucidated yet. Therefore, in this study, we clarified the in vitro cytotoxic mechanism of uvedafolin on the HeLa cells, and evaluated the cytotoxicity against NIH/3T3 cells which were used as normal cells. In consequence, the dimer SLs had low toxicity for the NIH/3T3 cells (IC₅₀ 4.81–4.98 μM at 24 hours) and then the uvedafolin mediated cell cycle arrest at the G₂/M phase and induced apoptosis on the HeLa cells evidenced by appearance of a subG1 peak. Uvedafolin induced apoptosis was attributed to caspase-9 and caspase-3/7 activities. An effectively induced apoptosis pathway was demonstrated from mitochondria membrane potential change and cytochrome c release to cytosol. These results reveal that uvedafolin induced apoptosis via the mitochondria pathway. The present results indicate the potential of uvedafolin as a leading compound of new anticancer agents.

倍半萜内酯类治疗肠易激综合征的应用前景

肠易激综合征(irritable bowel syndrome, IBS)是常见的功能性肠道疾病, 以腹痛或腹部不适、排便习惯异常为特征, 其发病机制尚不明确. 依照罗马Ⅲ标准可将其分为腹泻型、便秘型、混合型和未定型4种亚型. 目前临床治疗原则主要是对症治疗, 迄今尚无特效药物能够有效治疗所有类型IBS. 倍半萜内酯类成分是众多药用植物的生物活性成分, 具有广泛生物学活性, 包括抗肿瘤、抗炎镇痛、抗菌等. 本文就倍半萜内酯类成分可改善IBS症状的相关生物学活性, 及其在IBS治疗中的应用前景进行简要综述.

Covalent Modifiers: A Chemical Perspective on the Reactivity of α,β-Unsaturated Carbonyls with Thiols via Hetero-Michael Addition Reactions

Although Michael acceptors display a potent and broad spectrum of bioactivity, they have largely been ignored in drug discovery because of their presumed indiscriminate reactivity. As such, a dearth of information exists relevant to the thiol reactivity of natural products and their analogues possessing this moiety. In the midst of recently approved acrylamide-containing drugs, it is clear that a good understanding of the hetero-Michael addition reaction and the relative reactivities of biological thiols with Michael acceptors under physiological conditions is needed for the design and use of these compounds as biological tools and potential therapeutics. This Perspective provides information that will contribute to this understanding, such as kinetics of thiol addition reactions, bioactivities, as well as steric and electronic factors that influence the electrophilicity and reversibility of Michael acceptors. This Perspective is focused on α,β-unsaturated carbonyls given their preponderance in bioactive natural products.

Synthesis of dual-action parthenolide prodrugs as potent anticancer agents

Cancer stem cells are responsible for the failure of a large number of cancer treatments and the re-emergence of cancer in patients. Parthenolide is a potent anticancer sesquiterpene lactone that is also able to kill cancer stem cells. The main problem with this compound is its poor solubility in water. To solve this problem, medicinal chemists have tried to prepare amino-derivatives of parthenolide, however, most amino-derivatives have less potency than that of parthenolide. In this paper, we proposed a new approach to synthesize parthenolide derivatives with better solubility and higher potency. We prepared novel parthenolide derivatives through the aza-Michael addition of nitrogen-containing anticancer drug molecules (cytarabine and melphalan) to the α-methylene-γ-lactone group of parthenolide. Different types of catalysts were used to catalyze the aza-Michael addition. Among all the used catalysts, 1,8-diazabicyclo [5.4.0] undec-7-ene (DBU) was found to have the highest catalytic activity. In addition, we examined the effects of parthenolide-anticancer drug hybrids on the growth and proliferation of three cancer cell lines (MCF-7, LNcaP, Hep G2) and CHO. The parthenolide prodrugs showed potent cytotoxic property with IC₅₀ values ranging from 0.2 to 5.2μM, higher than those of parthenolide and anticancer drugs (cytarabine and melphalan).

Peperomin E and its synthetic amino derivatives: potent agents targeting leukaemia stem cells

A series of amino derivatives of Peperomin E have been synthesized. Compound 6, derived from N-methylethanolamine, exhibited exclusive cytotoxicity against leukaemia stem cells (IC₅₀ = 0.5 μM) and low toxicity against normal bone marrow cells.

Reversibility of the thia-Michael reaction of cytotoxic C5-curcuminoid and structure-activity relationship of bis-thiol-adducts thereof

C₅-curcuminoids [a.k.a. bis(arylmethylidene)acetones] are curcumin analogues bearing a reactive cross-conjugated dienone structure essential for eliciting cytotoxicity. To gain insight into the mode of action of C₅-curcuminoids, we investigated the reversibility of the thia-Michael reaction of 1,5-bis(3,5-bis(methoxymethoxy)phenyl)-1,4-pentadiene-3-one, named GO-Y030 which is the most potent cytotoxic C₅-curcuminoid, using spectroscopic methods. A panel of GO-Y030-bis-thiol-adducts were synthesized and the structure-reactivity relationship regarding the retro thia-Michael reaction as well as the cell growth inhibitory activity against human colon cancer HCT116 were evaluated. Some C₅-curcuminoid thiol-adducts exhibited comparable cytotoxicity with GO-Y030, demonstrating their potential use as prodrugs. These results imply that C₅-curcuminoids elicit cytotoxicity by covalently interacting with various biothiols via a reversible thia-Michael reaction.