Structure-activity relationship study of sesquiterpene lactones and their semi-synthetic amino derivatives as potential antitrypanosomal products

Bioelectronics for bitterness-based phytocompound detection using human bitter taste receptor nanodiscs

Various organisms produce several products to defend themselves from the environment and enemies. These natural products have pharmacological and biological activities and are used for therapeutic purposes, retaining bitter taste because of chemical defense mechanisms. Cnicin is a plant-derived bitter sesquiterpene lactone with pharmacological characteristics such as anti-bacterial, anti-myeloma, anti-cancer, anti-tumor, anti-oxidant, anti-inflammatory, allelopathic, and cytotoxic properties. Although many studies have focused on cnicin detection, they have limitations and novel cnicin-detecting strategies are required. In this study, we developed the bioelectronics for screening cnicin using its distinct taste. hTAS2R46 was produced using an Escherichia coli expression system and reconstituted into nanodiscs (NDs). The binding sites and energy between hTAS2R46 and cnicin were investigated using biosimulations. hTAS2R46-NDs were combined with a side-gated graphene micropatterned field-effect transistor (SGMFET) to construct hTAS2R46-NDs bioelectronics. The construction was examined by chemical and electrical characterization. The developed system exhibited unprecedented performance, 10 fM limit of detection, rapid response time (within 10 s), 0.1354 pM-1 equilibrium constant, and high selectivity. Furthermore, the system was stable as the sensing performance was maintained for 15 days. Therefore, the hTAS2R46-NDs bioelectronics can be utilized to screen cnicin from natural products and applied in the food and drug industries.

Bioassay-guided isolation of dehydrocostus lactone from Echinops kebericho as a leishmanicidal drug

Several strains of Leishmania parasite are involved in the occurrence of leishmaniasis infections, which makes its prevention and treatment very challenging. Currently, all forms of leishmaniasis are being treated with chemical drugs, which have limitations and adverse effects. Discovering antileishmanial agents from natural sources can lead to novel drugs against this dreadful disease. The essential oils and nonpolar solvent extracts of the roots of E. kebericho exhibit antileishmanial activity. Thus, the isolation of the leishmanicidal compounds from the roots of E. kebericho through a bioassay-guided technique was carried out in this study. The present finding showed that the essential oil and hexane fraction of crude extract from the roots of E. kebericho possessed significant leishmanicidal activity against L. major and L. tropica. Dehydrocostus lactone (1), one of the major constituents of the essential oil and hexane fraction, was more active than the standard drug miltefosine against L. major and L. tropica promastigotes. The presence of α-methylene, γ-lactone is the responsible moiety of dehydrocostus lactone towards the leishmanicidal activity against the tested Leishmania species. The MTT assay of dehydrocostus lactone showed inactive toxicity against the human cervical carcinoma HeLa cells. In addition, dehydrocostus lactone exhibits a broad spectrum of antibiotic activities. Based on this interesting finding, dehydrocostus lactone was identified as a potential lead for treating infections caused by Leishmania.

Arnicolide D: a multi-targeted anticancer sesquiterpene lactone-preclinical efficacy and mechanistic insights

Arnicolide D, a potent sesquiterpene lactone from Centipeda minima, has emerged as a promising anticancer candidate, demonstrating significant efficacy in inhibiting cancer cell proliferation, inducing apoptosis, and suppressing metastasis across various cancer models. This comprehensive study delves into the molecular underpinnings of Arnicolide D's anticancer actions, emphasizing its impact on key signaling pathways such as PI3K/AKT/mTOR and STAT3, and its role in modulating cell cycle and survival mechanisms. Quantitative data from preclinical studies reveal Arnicolide D's dose-dependent cytotoxicity against cancer cell lines, including nasopharyngeal carcinoma, triple-negative breast cancer, and human colon carcinoma, showcasing its broad-spectrum anticancer potential. Given its multifaceted mechanisms and preclinical efficacy, Arnicolide D warrants further investigation in clinical settings to validate its therapeutic utility against cancer. The evidence presented underscores the need for rigorous pharmacokinetic and toxicological studies to establish safe dosing parameters for future clinical trials.

The Effects of Sesquiterpene Lactones on the Differentiation of Human or Animal Cells Cultured In-Vitro: A Critical Systematic Review

Cellular differentiation is pivotal in health and disease. Interfering with the process of differentiation, such as inhibiting the differentiation of adipocytes and inducing the differentiation of cancer cells, is considered a therapeutic approach. Sesquiterpene lactones, primarily found in plants, have been attracted attention as differentiating/dedifferentiating agents tested on various human or animal cells. However, a consensus on sesquiterpene lactones’ effects and their mechanism of action is required. In this sense, through a systematic review, we have investigated the differentiating/dedifferentiating effects of sesquiterpene lactones on human or animal cells. 13 different cell lines originated from humans, mice, and rats, in addition to the effects of a total of 21 sesquiterpene lactones, were evaluated in the included studies. These components had either inducing, inhibiting, or no effect on the cells, mediating their effects through JAK-STAT, PI3K-Akt, mitogen-activated protein kinases, NFκB, PPARγ pathways. Although nearly all inducing and inhibiting effects were attributed to cancerous and normal cells, respectively, this is likely a result of a biased study design. Few studies reported negative results along with others, and no study was found reporting only negative results. As a result, not only are the effects and mechanism of action of sesquiterpene lactones not vivid but our knowledge and decisions are also misconducted. Moreover, there is a significant knowledge gap regarding the type of evaluated cells, other sesquiterpene lactones, and the involved signaling pathways. In conclusion, sesquiterpene lactones possess significant effects on differentiation status, leading to potentially efficient therapy of obesity, osteoporosis, and cancer. However, reporting negative results and further investigations on other cells, sesquiterpene lactones, and signaling pathways are highly suggested to pave the path of sesquiterpene lactones to the clinic more consciously.

Total synthesis of cynaropicrin

Cynaropicrin is found in artichoke (Cynara scolymus) and is the source of its bitter taste and it is a sesquiterpene lactone with a 5-7-5 tricyclic skeleton, six chiral centers, and four exo-olefins. This natural product has numerous attractive biological activities including the inhibition of NF-κB activation, antihepatitis C activity, and antitrypanosomal activity. In this study, the first total synthesis of cynaropicrin was achieved starting from (S)-α-pinene. The synthesis involved a stereoselective Favorskii rearrangement and an indium-promoted diastereoselective Barbier reaction.

Phylobioactive hotspots in plant resources used to treat Chagas disease

Globally, more than six million people are infected with Trypanosoma cruzi, the causative protozoan parasite of the vector-borne Chagas disease (CD). We conducted a cross-sectional ethnopharmacological field study in Bolivia among different ethnic groups where CD is hyperendemic. A total of 775 extracts of botanical drugs used in Bolivia in the context of CD and botanical drugs from unrelated indications from the Mediterranean De Materia Medica compiled by Dioscorides two thousand years ago were profiled in a multidimensional assay uncovering different antichagasic natural product classes. Intriguingly, the phylobioactive anthraquinone hotspot matched the antichagasic activity of Senna chloroclada, the taxon with the strongest ethnomedical consensus for treating CD among the Izoceño-Guaraní. Testing common 9,10-anthracenedione derivatives in T. cruzi cellular infection assays demarcates hydroxyanthraquinone as a potential antichagasic lead scaffold. Our study systematically uncovers in vitro antichagasic phylogenetic hotspots in the plant kingdom as a potential resource for drug discovery based on ethnopharmacological hypotheses.

Cynaropicrin Shows Antitumor Progression Potential in Colorectal Cancer Through Mediation of the LIFR/STATs Axis

BACKGROUND

Colorectal cancer (CRC) is the second deadliest malignant disease in the world and the leukemia inhibitory factor receptor/signal transducers and activators of transcriptions (LIFR/STATs) signaling axis plays an important role in the molecular biology of CRC.

METHODS

Cell function tests were performed to observe the inhibitory effect of cynaropicrin on human CRC cells (RKO, HCT116, and DLD-1). Expression levels of LIFR, P-STAT3, P-STAT4, and apoptotic proteins were detected by Western blotting. Immunoprecipitation confirmed the presence of LIFR/STAT3/STAT4 complex. Cell immunofluorescence assay was used to observe the subcellular localization of STAT3 and STAT4. In vivo efficacy of cynaropicrin was evaluated by a xenotransplantation model in nude mice.

RESULTS

Cynaropicrin significantly reduced the survival ability of human CRC cells and promoted apoptosis in a dose-dependent manner. Western blotting results suggested that the antitumor effects of cynaropicrin might be mediated by inhibition of the LIFR/STATs axis. Cynaropicrin reduced the formation of STAT3/STAT4 heterodimers and blocked their entry into the nucleus. Cynaropicrin also suppressed tumor growth in the xenograft model.

CONCLUSION

The results showed that cynaropicrin exerted a strong inhibitory effect on CRC in vitro and in vivo. Our study concluded that cynaropicrin has potential application prospects in the field of anti-CRC therapy.

Sesquiterpene Lactones from Calea pinnatifida: Absolute Configuration and Structural Requirements for Antitumor Activity

This work describes the chromatographic fractionation of the aerial parts of Calea pinnatifida and the structural characterization and determination of the absolute configuration of the isolated compounds as well as their antitumor potential. The HPLC fractionation of the CH₂Cl₂ phase of the MeOH extract from the leaves of C. pinnatifida led to the isolation of two related sesquiterpene lactones (STLs): calein C (1) and calealactone B (2). Additionally, during the purification process, a derivative of calein C (3) was formed as a product of the Michael addition of MeOH. The structures of Compounds 1–3 were established based on spectroscopic and spectrometric data, while the absolute stereochemistry was established by vibrational circular dichroism. In order to evaluate the effect of the conjugated double bonds on the cytotoxic activity of STLs, Compounds 1–3 were tested against anaplastic (KTC-2) and papillary (TPC-1) thyroid carcinoma cells. Calein C was the most active of the STLs, and displayed activity against both KTC-2 and TPC-1. On the other hand, the calein C derivative (3) was the least cytotoxic of all the compounds tested. These results are promising and suggest the importance of studying sesquiterpene lactones isolated from C. pinnatifida in terms of antitumor activity, especially considering the effects of α,β-unsaturated carbonyl systems.

Applications of Sesquiterpene Lactones: A Review of Some Potential Success Cases

Sesquiterpene lactones, a vast range of terpenoids isolated from Asteraceae species, exhibit a broad spectrum of biological effects and several of them are already commercially available, such as artemisinin. Here the most recent and impactful results of in vivo, preclinical and clinical studies involving a selection of ten sesquiterpene lactones (alantolactone, arglabin, costunolide, cynaropicrin, helenalin, inuviscolide, lactucin, parthenolide, thapsigargin and tomentosin) are presented and discussed, along with some of their derivatives. In the authors’ opinion, these compounds have been neglected compared to others, although they could be of great use in developing important new pharmaceutical products. The selected sesquiterpenes show promising anticancer and anti-inflammatory effects, acting on various targets. Moreover, they exhibit antifungal, anxiolytic, analgesic, and antitrypanosomal activities. Several studies discussed here clearly show the potential that some of them have in combination therapy, as sensitizing agents to facilitate and enhance the action of drugs in clinical use. The derivatives show greater pharmacological value since they have better pharmacokinetics, stability, potency, and/or selectivity. All these natural terpenoids and their derivatives exhibit properties that invite further research by the scientific community.

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.

N-substituted noscapine derivatives as new antiprotozoal agents: Synthesis, antiparasitic activity and molecular docking study

Novel N-substituted noscapine derivatives were synthesized by a three-component Strecker reaction of cyclic ether of N-nornoscapine with varied aldehydes, in the presence of cyanide ion. Moreover, the corresponding amides were synthesized by the oxidation of cyanide moieties in good yields. The in vitro antiprotozoal activity of the products was also investigated. Interestingly, some analogues did put on display promising antiparasitic activity against Trypanosoma brucei rhodesiense with IC₅₀ values between 2.5 and 10.0 µM and selectivity index (SI) ranged from 0.8 to 13.2. Eight compounds exhibited activity against Plasmodium falciparum K1 strain with IC₅₀ ranging 1.7-6.4 µM, and SI values between 2.8 and 10.5 against L6 rat myoblast cell lines. Molecular docking was carried out on trypanothione reductase (TbTR, PDB ID: 2WOW) and UDP-galactose 4' epimerase (TbUDPGE PDB: 1GY8) as targets for studying the envisaged mechanism of action. Compounds 6j₂ and 6b₂ displayed excellent docking scores with -8.59 and -8.86 kcal/mol for TbTR and TbUDPGE, respectively.

Primary targets of the sesquiterpene lactone deoxymikanolide on Trypanosoma cruzi

BACKGROUND

Deoxymikanolide is a sesquiterpene lactone isolated from Mikania micrantha and M. variifolia which, has previously demonstrated in vitro activity on Trypanosoma cruzi and in vivo activity on an infected mouse model.

PURPOSE

Based on these promising findings, the aim of this study was to investigate the mechanism of action of this compound on different parasite targets.

METHODS

The interaction of deoxymikanolide with hemin was examined under reducing and non- reducing conditions by measuring modifications in the Soret absorption band of hemin; the thiol interaction was determined spectrophotometrically through its reaction with 5,5'-dithiobis-2-nitrobenzoate in the presence of glutathione; activity on the parasite antioxidant system was evaluated by measuring the activity of the superoxide dismutase and trypanothione reductase enzymes, together with the intracellular oxidative state by flow cytometry. Superoxide dismutase and trypanothione reductase activities were spectrophotometrically tested. Cell viability, phosphatidylserine exposure and mitochondrial membrane potential were assessed by means of propidium iodide, annexin-V and rhodamine 123 staining, respectively; sterols were qualitatively and quantitatively tested by TLC; ultrastructural changes were analyzed by transmission electron microscopy. Autophagic cells were detected by staining with monodansylcadaverine.

RESULTS

Deoxymikanolide decreased the number of reduced thiol groups within the parasites, which led to their subsequent vulnerability to oxidative stress. Treatment of the parasites with the compound produced a depolarization of the mitochondrial membrane even though the plasma membrane permeabilization was not affected. Deoxymikanolide did not affect the intracellular redox state and so the mitochondrial dysfunction produced by this compound could not be attributed to ROS generation. The antioxidant defense system was affected by deoxymikanolide at twenty four hours of treatment, when both an increased oxidative stress and decreased activity of superoxide dismutase and trypanothione reductase (40 and 60% respectively) were observed. Both the oxidative stress and mitochondrial dysfunction induce parasite death by apoptosis and autophagy.

CONCLUSION

Based on our results, deoxymikanolide would exert its anti-T cruzi activity as a strong thiol blocking agent and by producing mitochondrial dysfunction.

Antiparasitic activity of chicory (Cichorium intybus) and its natural bioactive compounds in livestock: a review

Increasing drug resistance in gastrointestinal (GI) parasites of livestock and concerns about chemical residues in animal products and the environment are driving the development of alternative control strategies that are less reliant on the use of synthetic drugs. An increasingly investigated approach is the use of bioactive forages with antiparasitic properties as part of the animal's diet (nutraceuticals) or as potential sources of novel, natural parasiticides. Chicory (Cichorium intybus) is a multi-purpose crop and one of the most promising bioactive forages in temperate regions, and numerous in vivo trials have explored its potential against parasitic nematodes in livestock. However, it is unclear whether chicory can induce a direct and broad activity against various GI parasites in different livestock species, and the levels of chicory in the diet that are required to exert an efficient antiparasitic effect. Moreover, the mechanisms leading to the reported parasiticidal activity of chicory are still largely unknown, and its bioactive phytochemicals have only recently been investigated. In this review, we summarise the progress in the study of the antiparasitic activity of chicory and its natural bioactive compounds against GI parasites in livestock, through examination of the published literature. The available evidence indicates that feeding chicory can reduce faecal egg counts and/or worm burdens of abomasal nematodes, but not infections with intestinal worms, in ruminants. Highly chicory-rich diets (≥ 70% of chicory dry matter in the diet) may be necessary to directly affect abomasal parasitism. Chicory is known to synthesise several bioactive compounds with potential antiparasitic activity, but most research has been devoted to the role of sesquiterpene lactones (SL). Recent in vitro studies have confirmed direct and potent activity of SL-rich extracts from chicory against different GI helminths of livestock. Chicory SL have also been reported to exhibit antimalarial properties and its potential antiprotozoal activity in livestock remains to be evaluated. Furthermore, the detailed identification of the main antiparasitic metabolites of chicory and their pharmacokinetics need further confirmation. Research gaps and perspectives on the potential use of chicory as a nutraceutical forage and a source of bioactive compounds for parasite control in livestock are discussed.

Natural products as inhibitors of Leishmania major dihydroorotate dehydrogenase

The flavoenzyme dihydroorotate dehydrogenase (DHODH) catalyzes the fourth reaction of the de novo pyrimidine biosynthetic pathway, which exerts vital functions in the cells, especially within DNA and RNA biosynthesis. Thus, this enzyme stands out as a new key molecular target for parasites causing Neglected Diseases (NDs). Focused on contributing to the development of new therapeutic alternatives for NDs, in this study, for the first time, a screening of 57 natural products for in vitro inhibition of Leishmania major DHODH (LmDHODH) was carried out, including cross validation against the human DHODH (HsDHODH). A subset of natural products consisting of 21 sesquiterpene lactones (STLs) was submitted to QSAR studies. Additionally, thermostability studies by differential scanning fluorimetry (DSF) were performed to determine whether the STLs are effectively or not binding to the enzyme. The IC₅₀ values against LmDHODH varied from 27 to 1200 μM; only irrelevant inhibition was obtained on HsDHODH. DSF assays confirmed binding of STLs to LmDHODH; moreover, it is suggested that such inhibitors might act in a different site other than the active site. A reliable QSAR model based on molecular descriptors was obtained (R²: 0.83; Q²_CV: 0.69 and Q²_EXT/F2: 0.66) indicating that stronger inhibition requires a balanced distribution of the hydrophobic regions across the molecular surface, as well as higher width and lower hydrophobicity of the molecules. A pharmacophore-based 3D-QSAR approach also afforded a useful model (R²: 0.72; Q²_CV: 0.50 and Q²_EXT/F2: 0.62), which confirmed the importance of proper orientation of the ligands, molecular surface features and shape for stronger inhibition, reflecting properties of a putative common binding site. These data indicated for the first time that natural products can actually inhibit LmDHODH and highlighted some metabolites as potentially interesting starting points for the discovery of more potent LmDHODH inhibitors, ultimately aiming at new effective therapeutic alternatives for leishmaniasis and, possibly, other NDs caused by trypanosomatids.

Acid-Induced Rearrangement of Epoxygermacranolides: Synthesis of Furanoheliangolides and Cadinanes from Nobilin

The acid-induced rearrangement of three epoxyderivatives of nobilin 1, the most abundant sesquiterpene lactone in Anthemisnobilis flowers, was investigated. From the 1,10-epoxyderivative 2, furanoheliangolide 5 was obtained, while the 4,5-epoxy group of 3 did not react. Conversely, when the 3-hydroxy function of nobilin was acetylated (12), the 4,5-epoxy derivative did cyclize into cadinanes (15 and 16) under Lewis acid catalysis. The reactivity of the 4,5- and 1,10-epoxy derivatives of nobilin (2 and 3) was compared with that of parthenolide, and rationalized on the basis of quantum chemical calculations. All isolated reaction products were fully characterized by spectroscopic and computational methods, and their in vitro anti-protozoal activity was evaluated. The paper could provide new insights into the biosynthesis of this class of natural products.

Improving anti-trypanosomal activity of alkamides isolated from Achillea fragrantissima

In previous studies the aerial parts of Achillea fragrantissima were found to have substantial antileishmanial and antitrypanosomal activity. A bioassay-guided fractionation of a dichloromethane extract yielded the isolation of the essential anti-trypanosomal compounds of the plant. Seven sesquiterpene lactones (including Achillolide-A), two flavonoids, chrysosplenol-D and chrysosplenetine, and four alkamides (including pellitorine) were identified. This is the first report for the isolation of the sesquiterpene lactones 3 and 4, chrysosplenetine and the group of alkamides from this plant. Bioevaluation against Trypanosoma brucei brucei TC221 (T.b brucei) using the Alamar-Blue assay revealed the novel alkamide 13 to have an IC₅₀ value of 40.37μM. A compound library, derived from the alkamide pellitorine (10), was synthesized and bioevaluated in order to find even more active substances. The most active compounds 26 and 27 showed activities in submicromolar concentrations and selectivity indices of 20.1 and 45.6, respectively, towards macrophage cell line J774.1. Toxicity of 26 and 27 was assessed using the greater wax moth Galleria mellonella larvae as an in vivo model. No significant toxicity was observed for the concentration range of 1.25-20mM.

Antiprotozoal Activity-Based Profiling of a Dichloromethane Extract from Anthemis nobilis Flowers

A dichlomethane extract of Anthemis nobilis flower cones showed promising in vitro antiprotozoal activity against Trypanosoma brucei rhodesiense and Leishmania donovani, with IC₅₀ values of 1.43 ± 0.50 and 1.40 ± 0.07 μg/mL, respectively. A comprehensive profiling of the most active fractions afforded 19 sesquiterpene lactones, including 15 germacranolides, two seco-sesquiterpenes, one guaianolide sesquiterpene lactone, and one cadinane acid. Of these, 13 compounds were found to be new natural products. The compounds were characterized by extensive spectroscopic data analysis (1D and 2D NMR, HRMS, circular dichroism) and computational methods, and their in vitro antiprotozoal activity was evaluated. The furanoheliangolide derivative 15 showed high potency and selectivity in vitro against T. b. rhodesiense bloodstream forms (IC₅₀ 0.08 ± 0.01 μM; SI 63). In silico calculations were consistent with the drug-like properties of 15.

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.

Cynaropicrin: A Comprehensive Research Review and Therapeutic Potential As an Anti-Hepatitis C Virus Agent

The different pharmacologic properties of plants-containing cynaropicrin, especially artichokes, have been known for many centuries. More recently, cynaropicrin exhibited a potential activity against all genotypes of hepatitis C virus (HCV). Cynaropicrin has also shown a wide range of other pharmacologic properties such as anti-hyperlipidemic, anti-trypanosomal, anti-malarial, antifeedant, antispasmodic, anti-photoaging, and anti-tumor action, as well as activation of bitter sensory receptors, and anti-inflammatory properties (e.g., associated with the suppression of the key pro-inflammatory NF-κB pathway). These pharmacological effects are very supportive factors to its outstanding activity against HCV. Structurally, cynaropicrin might be considered as a potential drug candidate, since it has no violations for the rule of five and its water-solubility could allow formulation as therapeutic injections. Moreover, cynaropicrin is a small molecule that can be easily synthesized and as the major constituent of the edible plant artichoke, which has a history of safe dietary use. In summary, cynaropicrin is a promising bioactive natural product that, with minor hit-to-lead optimization, might be developed as a drug for HCV.

Natural Sesquiterpene Lactones as Potential Trypanocidal Therapeutic Agents: A Review

Chagas’ disease and Human African Trypanosomiasis are parasitic diseases that remain major health problems, mainly among the poorest and the most marginalized communities from Latin America and Africa. The scarcity of effective chemotherapy, due to the low investment in the research and development (R&D) of new drugs, together with a high incidence of side effects, and the emergence of drug resistance phenomena emphasize the urgent need for new prophylactic and therapeutic agents. Over the ages, humans have employed natural products to treat a wide spectrum of diseases. Recently, the pharmaceutical industry has focused on plant research and a large body of evidence has been collected to demonstrate the immense potential of medicinal plants as a source of bioactive compounds and lead molecules. In the field of parasitic diseases, drug development from plants has been successful for the sesquiterpene lactone (STL) artemisinin, which is employed as an antimalarial agent. STLs are a large group of naturally occurring terpenoids derived from plants that mostly belong to the Asteraceae family which exhibit a variety of skeletal arrangements and are the largest and most diverse category of natural products with an α-methylene-λ-lactone motif. STLs display a broad spectrum of biological activities such as antitumor, cytotoxic, antibacterial, anthelmintic, uterus contracting, antimalarial, neurotoxic, antiprotozoal and allergic (contact dermatitis) activities. In this context, the purpose of the present review is to provide an overview of the trypanocidal activity reported for STLs against Trypanosoma cruzi and T. brucei rhodesiense over the period 1993–2015.

The role of glutathione reductase and related enzymes on cellular redox homoeostasis network

In this review article we examine the role of glutathione reductase in the regulation, modulation and maintenance of cellular redox homoeostasis. Glutathione reductase is responsible for maintaining the supply of reduced glutathione; one of the most abundant reducing thiols in the majority of cells. In its reduced form, glutathione plays key roles in the cellular control of reactive oxygen species. Reactive oxygen species act as intracellular and extracellular signalling molecules and complex cross talk between levels of reactive oxygen species, levels of oxidised and reduced glutathione and other thiols, and antioxidant enzymes such as glutathione reductase determine the most suitable conditions for redox control within a cell or for activation of programmed cell death. Additionally, we discuss the translation and expression of glutathione reductase in a number of organisms including yeast and humans. In yeast and human cells, a single gene expresses more than one form of glutathione reductase, destined for residence in the cytoplasm or for translocation to different organelles; in plants, however, two genes encoding this protein have been described. In general, insects and kinetoplastids (a group of protozoa, including Plasmodia and Trypanosoma) do not express glutathione reductase or glutathione biosynthetic enzymes. Instead, they express either the thioredoxin system or the trypanothione system. The thioredoxin system is also present in organisms that have the glutathione system and there may be overlapping functions with cross-talk between the two systems. Finally we evaluate therapeutic targets to overcome oxidative stress associated cellular disorders.

Molecular mechanisms of endocrine and metabolic disruption: An in silico study on antitrypanosomal natural products and some derivatives

The VirtualToxLab is an in silico technology for estimating the toxic potential - endocrine and metabolic disruption, as well as aspects of carcinogenicity and cardiotoxicity - of drugs, chemicals and natural products. The technology is based on an automated protocol that simulates and quantifies the binding of small molecules towards a series of currently 16 proteins, known or suspected to trigger adverse effects. The simulations are conducted at the atomic level and explicitly allow for a mechanistic interpretation of the results (in real-time 3D/4D), thereby complying with the Setubal principles put forward in 2002 for computational approaches to toxicology. Moreover, the underlying "ab-initio" protocol is independent from any training data and makes the approach universal with respect to the applicability domain. The VirtualToxLab runs in client-server mode and is freely available to academic and non-profit organizations. As the underlying technology yields a thermodynamic estimate of the binding affinity, the associated ligand-protein complexes have been challenged by molecular-dynamics simulations to probe their kinetic stability. Human African trypanosomiasis is a neglected tropical disease caused by two subspecies of Trypanosoma brucei. The control of this parasitic infection relies on a few chemotherapeutic agents, most of which were discovered decades ago and pose many challenges including adverse side effects, poor efficacy, and the occurrence of drug resistances. Natural products, on the other hand, offer a high potential for the discovery of new drug leads due to their chemical diversity. In this in silico study, we analyze a series of 89 natural products and derivatives displaying anti-trypanosomal activity for their potential to trigger adverse effects. Our results indicate a moderate potential for a number of those compounds to bind to nuclear receptors and thereby ease the development of endocrine disregulation. A few others would seem to inhibit enzymes of the cytochrome P450 family and, hence, sustain drug-drug interactions.

Pan-genotypic Hepatitis C Virus Inhibition by Natural Products Derived from the Wild Egyptian Artichoke

Hepatitis C virus (HCV) infection is the leading cause of chronic liver diseases. Water extracts of the leaves of the wild Egyptian artichoke (WEA) [Cynara cardunculus L. var. sylvestris (Lam.) Fiori] have been used for centuries in the Sinai Peninsula to treat hepatitis symptoms. Here we isolated and characterized six compounds from the water extracts of WEA and evaluated their HCV inhibition capacities in vitro. Importantly, two of these compounds, grosheimol and cynaropicrin, inhibited HCV with half-maximal effective concentrations (EC50s) in the low micromolar range. They inhibited HCV entry into target cells and were active against both cell-free infection as well as cell-cell transmission. Furthermore, the antiviral activity of both compounds was pan-genotypic as HCV genotypes 1a, 1b, 2b, 3a, 4a, 5a, 6a, and 7a were inhibited. Thus, grosheimol and cynaropicrin are promising candidates for the development of new pan-genotypic entry inhibitors of HCV infection.

IMPORTANCE

Because there is no preventive HCV vaccine available today, the discovery of novel anti-HCV cell entry inhibitors could help develop preventive measures against infection. The present study describes two compounds isolated from the wild Egyptian artichoke (WEA) with respect to their structural elucidation, absolute configuration, and quantitative determination. Importantly, both compounds inhibited HCV infection in vitro. The first compound was an unknown molecule, and it was designated "grosheimol," while the second compound is the known molecule cynaropicrin. Both compounds belong to the group of sesquiterpene lactones. The mode of action of these compounds occurred during the early steps of the HCV life cycle, including cell-free and cell-cell infection inhibition. These natural compounds present promising candidates for further development into anti-HCV therapeutics.

Synthesis of cynaropicrin-d(4)

Cynaropicrin is a guaianolide sesquiterpene lactone, which has potent in vitro and in vivo inhibitory activity against Trypanosoma brucei, the protozoan parasite that causes human African trypanosomiasis (HAT; sleeping sickness). Herein, we describe the synthesis of cynaropicrin's deuterated derivative, cynaropicrin-d4, by the replacement of the side chain of natural cynaropicrin. The synthesized cynaropicrin-d4 could be employed as an internal standard for liquid chromatography-mass spectrometry (LC-MS) analysis, in the pharmacokinetic study of cynaropicrin. This could potentially advance the study of this therapeutic lead.