Semisynthetic Derivatives Research Articles

Identification of Novel Flavonoids and Ansa-Macrolides with Activities against Leishmania donovani through Natural Product Library Screening.

The protozoan parasite Leishmania donovani is the causative agent of visceral leishmaniasis (VL), a potentially fatal disease if left untreated. Given the limitations of current therapies, there is an urgent need for new, safe, and effective drugs. To discover novel antileishmanial compounds from previously unexplored chemical spaces, we conducted a high-throughput screening (HTS) of 2562 natural compounds, assessing their activity against L. donovani promastigotes and intracellular amastigotes. Utilizing the criteria of ≥70% parasite growth inhibition and ≥70% host cell (THP-1) viability, we selected 100 inhibitors for half-maximal inhibitory concentration (IC50) value determination. Twenty-six compounds showed activities in both forms of Leishmania with a selectivity index of over 3. Clustering analysis resulted in four chemical clusters with scaffolds of lycorine (cluster 1), 5-hydroxy-9,10-dihydro-4H,8H-pyrano[2,3-f]chromene-4,8-dione (cluster 2), and semi-synthetic derivatives of ansamycin macrolide (cluster 4). The enantiomer of lycorine, BMD-NP-00820, showed the highest anti-amastigote activity with an IC50 value of 1.74 ± 0.27 μM and a selectivity index (SI) > 29. In cluster 3, the most potent compound had an IC50 value of 2.20 ± 0.29 μM with an SI > 23, whereas in cluster 4, with compounds structurally similar to the tuberculosis drug rifapentine, BMD-NP-02085 had an IC50 value of 1.76 ± 0.28 μM, but the SI value was 7.5. Taken together, the natural products identified from this study are a potential source for the discovery of antileishmanial chemotypes for further development.

Synthesis and Phytocytogenotoxic Activity of N-Phenyl-2-phenoxyacetamides Derived from Thymol.

The excessive use of herbicides has caused a series of problems related to human health, environmental pollution, and an increase in the resistance of plants to commercial herbicides. As an alternative, natural compounds and their semisynthetic derivatives have been widely studied to obtain environmentally friendly and more effective herbicides than the usual ones. In view of these factors, the aim of this work was to synthesize new molecules with herbicidal potential using thymol as a starting material, a natural phenol that has a pronounced phytotoxic effect. Novel N-phenyl-2-thymoxyacetamides were synthesized and characterized by MS and by 1H and 13C NMR. All prepared molecules were subjected to phytotoxic and cytotoxic activity assays using Lactuca sativa L. and Sorghum bicolor L. as model plants. Molecules containing chlorine in the para position of the thymoxy group exhibited phytotoxic and cytogenotoxic effects superior to those of the commercial herbicides 2,4-D and glyphosate.

From Plant to Chemistry: Sources of Antinociceptive Non-Opioid Active Principles for Medicinal Chemistry and Drug Design.

Pain is associated with many health problems and a reduced quality of life and has been a common reason for seeking medical attention. Several therapeutics are available on the market, although side effects, physical dependence, and abuse limit their use. As the process of pain transmission and modulation is regulated by different peripheral and central mechanisms and neurotransmitters, medicinal chemistry continues to study novel ligands and innovative approaches. Among them, natural products are known to be a rich source of lead compounds for drug discovery due to their chemical structural variety and different analgesic mechanisms. Numerous studies suggested that some chemicals from medicinal plants could be alternative options for pain relief and management. Previously, we conducted a literature search aimed at identifying natural products interacting either directly or indirectly with opioid receptors. In this review, instead, we have made an excursus including active ingredients derived from plants whose mechanism of action appears from the literature to be other than the modulation of the opioid system. These substances could, either by themselves or through synthetic and/or semi-synthetic derivatives, be investigated in order to improve their pharmacokinetic characteristics and could represent a valid alternative to the opioid approach to pain therapy. They could also be the basis for the study of new mechanisms of action in the approach to this complex and disabling pathology.

Synthesis of Novel Propynyl Monoterpene Analogues and their Conjugates with β-DGlucopyranosides

Abstract: Camphor and carvone exhibit a broad spectrum of biological activity, which determines the prospect of their use as a platform for functionalization to obtain the analogues as potential drugs. The functionalization of camphor and carvone often involves changes to the skeleton of the molecules or their fragmentation. Therefore, in modern medicinal chemistry, research aimed at the development of effective approaches to the synthesis of semisynthetic derivatives of camphor and carvone with preservation of the native framework, demonstrating high biological activity, is in demand. The present work is aimed at the synthesis of new propynyl analogues of camphor and carvone, as well as their conjugates with mono- and disaccharides via Cu-catalyzed cycloaddition of acetylenes and azides (Cu- AAC). Alkylation of camphor and carvone with propargyl bromide in the presence of the base KN(SiMe3)2–Et3B in 1,2-dimethoxyethane (DME) at room temperature provides the target products with yields of 69% and 47%, respectively. Glycosyl azides were obtained by the reaction of peracetylated sugars with trimethylsilyl azide in the presence of SnCl4.The synthesis of 1,2,3-triazolyl glycoconjugates of camphor and carvone with mono- and disaccharides was carried out through Cu(I)-catalyzed 1,3-dipolar cycloaddition of azides to acetylenes (CuAAC) in the presence of Cu and CuSO4·5H2O. The structures of the synthesized compounds were determined by NMR. The new propynyl-substituted camphor and carvone, as well as their 1,2,3- triazolylglycoconjugates, can be used as promising building blocks for medicine chemistry.

Formation of Trideuteromethylated Artifacts of Pyrrole-Containing Natural Products.

Pyrrole-containing natural products form a large group of structurally diverse compounds that occur in both terrestrial and marine organisms. In the present study the formation of trideuteromethylated artifacts of pyrrole-containing natural products was investigated, focusing on the discorhabdins. Three deuterated discorhabdins, 1, 3, and 5, were identified to be isolation procedure artifacts caused by the presence of DMSO-d6 during NMR sample preparation and handling. Three additional semisynthetic derivatives, 7-9, were made during the investigation of the mechanism of formation, which was shown to be driven by trideuteromethyl radicals in the presence of water, methanol, TFA, and traces of iron in the deuterated solvent. Generation of trideuteromethylated artifacts was also confirmed for other classes of pyrrole-containing metabolites, namely, makaluvamines, tambjamines, and dibromotryptamines, which had also been dissolved in DMSO-d6 during the structure elucidation process. Semisynthetic discorhabdins were assessed for antiproliferative activity against a panel of human tumor cell lines, and 14-trideuteromethyldiscorhabdin L (3) averaged low micromolar potency.

A Review on Different Analytical Techniques for Quantification of Moxidectin

Nemadectin, a macrocyclic lactone of the milbemycin class, is a fermentation by-product of the bacteria Streptomyces cyanogriseus subsp. non-Cyanogenus. Moxidectin is a semi-synthetic derivative of nemadectin. River blindness, also known as onchocerciasis, is treated with moxidectin in patients 12 years of age and older. This condition is brought on by the parasitic worm Onchocerca volvulus and is subjected to intense itching, skin conditions that are disfiguring, and impaired vision brought on by the larvae of the worm. Some of the most common internal and exterior parasites are killed by moxidectin by selectively binding to their glutamate-gated chloride ion channels. In this review article, various pieces of equipment, such as a UV spectrometer, HPLC, LC-MS, and UPLC-MS, are used to determine moxidectin as well as its related compounds. The QuEChERS method was also used in the sample preparation according to the literature survey. The report also offers an overview of the pharmacodynamics, pharmacokinetics, and medication interactions of moxidectin.

Cytotoxicity Activity of Some meso-Dihydroguaiaretic Acid Derivatives and Mode of Action of the Most Active Compound.

The aim of this study was to screen sixteen meso-1 semi-synthetic derivatives bearing ether, esther, carbamate, phosphate or aminoether functional groups against five cancer cell lines: MCF-7 (breast), A549 (lung), HepG2 (liver), HeLa (cervix), and DU145 (prostate) at 25 μM using the MTT assay. Results from the screening showed that two derivatives had the lowest percentage of cell viability at 25 μM, the aminoether derivative meso-11 and the esther derivative meso-20 against A549 (44.15±0.78 %) and MCF-7 (41.60±0.92 %), respectively. Then, it was determined the IC50 value of each compound against their most sensitive cancer cell line. Results showed that aminoether derivative meso-11 showed potent cytotoxicity against A549 (IC50 =17.11±2.11 μM), whereas it resulted more cytotoxic against the LL-47 lung normal cell line (IC50 =9.49±1.19 μM) having a Selective Index (SI) of 0.55. On the other hand, the esther derivative meso-20 exhibited potent activity against MCF-7 (IC50 =18.20±1.98 μM), whereas it displayed moderate cytotoxicity against the MCF-10 breast normal cell line (IC50 =41.22±2.17 μM) with a SI of 2.2. Finally, studies on the mechanism of action of meso-20 indicated disruption of MCF-7 plasma membrane in vitro and the AMPK activation in silico.

Behandeling van opioïdverslaafde zwangere vrouwen met buprenorfine: invloed op de foetus en de pasgeborene

Treatment of opioid addiction in pregnancy with buprenorphine: implications for the fetus and newborn The aim of this article is to summarize the actual knowledge on the use of buprenorphine for the treatment of opioid addiction in pregnancy. Buprenorphine is a semisynthetic thebaine derivative, increasingly used instead of methadone for the treatment of opioid-dependent pregnant women. Fetuses exposed to buprenorphine have a more favorable biophysical profile compared to methadone. The neonatal abstinence syndrome (NAS) occurs less in comparison to methadone-exposed neonates. Treatment is not always indicated and, if necessary, morphine is administered. Buprenorphine is a promising alternative to methadone in the treatment of pregnant women with opioid addiction.

Predicting environmental biodegradability using initial rates: mineralization of cellulose, guar and their semisynthetic derivatives in wastewater and soil

Microplastic pollution is a growing concern, and natural materials are being increasingly sought as plastic alternatives. Semisynthetic biopolymers occupy a grey area between natural and synthetic materials and are often presented as green alternatives to conventional plastic. They can be water-soluble or insoluble, and are ubiquitous in commercial products as thickeners, films, filters, viscosity modifiers and coatings. This work compares the mineralization kinetics of cellulose, guar and several of their commercialized derivatives using a simple pseudo first-order kinetic model to extrapolate half-lives and lifetimes, while identifying the levers that influence the mineralization rates of these ubiquitous materials. Industrial composting rates were consistently faster than those of wastewater. While partially substituted biopolymers exhibited measurable degradation, kinetic analysis revealed this effect could be entirely accounted for by the fraction of unsubstituted biopolymer. Surprisingly, the initial rates of highly substituted biopolymers exhibited persistence on par with conventional plastics over the experimental durations studied.

Curcumin and Its Semisynthetic Derivative F-Curcumin Ameliorate the Expression of Cytokines in Autoimmune Encephalomyelitis Mouse Models of Multiple Sclerosis.

Multiple sclerosis (MS) is an inflammatory disorder impacting the central nervous system, with cytokines significantly influencing its pathogenesis. This study investigates the effect of curcumin and its semisynthetic derivative F-curcumin on cytokine gene expression in autoimmune encephalomyelitis (EAE) mouse models of MS. We assessed the expression levels of specific cytokines including interleukin (IL)-1β, IL-4, IL-10, IL-17, interferon-γ (IFN-γ), and transforming growth factor-β (TGF-β), alongside key transcription factors for helper T cells (T-bet, GATA-3, RORγt, and FoxP3) in both the spinal cord and spleen. Treatment with curcumin and F-curcumin significantly ameliorated the severity and onset of EAE. Notably, mice administered with either compound showed a substantial decrease in the expression of genes encoding IL-1 (2 folds), IFN-γ (2 and 4 folds), and IL-17 (2.5 and 3.5 folds), alongside a marked increase in TGF-β (7 folds) and IL-10 (4 and 6 folds) levels. Additionally, the gene expression of T cell-derived transcription factors nearly mirrored the changes observed in pro-inflammatory and anti-inflammatory cytokines across the groups. The F-curcumin-treated group exhibited more pronounced results. In conclusion, curcumin and F-curcumin significantly modulate cytokine gene expression during EAE induction, potentially alleviating inflammation in MS, with F-curcumin showing a more substantial effect.

In vitro anthelmintic activity and in silico analysis of monoterpenes, sesquiterpenes, and semisynthetic derivatives against Eisenia foetida

Helminthiases remain a worldwide public health problem, mainly in not-developed countries. Available drugs are scarce, and the risk of developing resistance by the parasites is always present. Natural products remain a valid alternative in the search for new antiparasitic drugs. Among them are monoterpenes and sesquiterpenes, standard components of essential oils. This work evaluated the in vitro activity of monoterpenes, sesquiterpenes, and semi-synthetic derivatives against Eisenia foetida using albendazole as a positive control. Gas chromatography coupled with mass spectrometry was used to determine the structure of the derivatives. In silico analysis was also performed on probable molecular targets such as β-tubulin, acetylcholinesterase (AChE), and γ-aminobutyric acid B (GABA B) receptor. The compounds with hydroxyl groups in their structure, such as linalool and (S)-cis-verbenol, showed better biological activity, superior to the reference drug. The binding affinity of these compounds was also found in silico with AChE, GABA B receptor, and β-tubulin. These results demonstrate that natural products may constitute lead compounds for developing new anthelmintic drugs.

Toxicologic Profile and Anti-Nociceptive Effect of Two Semi-Synthetic Triterpene Derivatives from Combretum Leprosum in Mice

Abstract Background and aim: Combretum leprosum Mart. serves as a medicinal plant in traditional Brazilian medicine. The beneficial effects of C. leprosum Mart. are attributed to the triterpene, 3β,6β,16β-trihydroxylup-20(29)-ene (CL-1). Herein we evaluate the toxicity of two semi-synthetic derivatives from CL-1 (CL-P2 and CL-P2A) in vitro and in vivo, and determine the efficacy in zymosan-induced writhing response and the putative mechanism of action. Experimental procedure: Toxicity prediction was assessed using the PROTOX-II and ADMETlab 2.0 prediction tools, and SMILES codes for structure identification. In vitro cytotoxicity of the derivatives was tested using the sulforhodamine B assay in L929 and HaCaT cells at 24, 48, and 72 h. Mice received (oral gavage) CL-P2 or CL-P2A (10 mg/kg/d) for 14 days in in vivo toxicity assays. Blood samples and organs (stomach, liver, and kidneys) were collected for AST/ALT level determination and H&E staining, respectively. The anti-nociceptive effect of CL-P2 and CL-P2A (0.1, 1, or 10 mg/kg) was evaluated in the zymosan-induced writhing response. The peritoneal exudate was collected to determine myeloperoxidase (MPO) and superoxide dismutase (SOD) activity, and nitrite concentration. Results: CL-P-2 and CL-P2A derivatives exhibited low cytotoxicity and did not change body mass, AST/ALT levels, or organ weight. The histopathologic analysis did not reveal significant changes in organs. Both derivatives inhibited the writhing response in a dose-dependent manner. In addition, both derivatives failed to reduce MPO activity. However, CL-P2A increased SOD activity and CL-P2 decreased nitrite/nitrate levels. Conclusion: CL-P2 and CL-P2A were shown to exhibit anti-nociceptive effects without toxicity. Our data suggest that CL-P2 and CL-P2A efficacy is mediated, at least in part, via antioxidant activity by modulating nitrite/nitrate levels and SOD activity, respectively.

Semisynthetic phytochemicals in cancer treatment: a medicinal chemistry perspective.

Cancer is the uncontrolled proliferation of abnormal cells that invade other areas, spread to other organs, and cause metastases, which is the most common cause of death. A review of all FDA-approved new molecular entities (NMEs) shows that natural products and derivatives account for over one-third of all NMEs. Before 1940, unmodified products and derivatives accounted for 43% and 14% of NME registrations, respectively. Since then, the share of unmodified products has decreased to 9.5% of all approved NMEs, while the share of derivatives has increased to 28%. Since the 1940s, semi-synthetic and synthetic derivatives of natural substances have gained importance, and this trend continues to date. In this study, we have discussed in detail isolated phytoconstituents with chemical modifications that are either FDA-approved or under clinical trials, such as podophyllotoxin, Taxol (paclitaxel, docetaxel), vinca alkaloids (vincristine, vinblastine), camptothecin, genistein, cephalotaxine, rohitukine, and many more, which may act as essential leads to the development of novel anticancer agents. Furthermore, we have also discussed recent developments in the most potent semisynthetic phytoconstituents, their unique properties, and their importance in cancer treatment.

In-Silico Evaluation of Deoxyvasicinone and Semi Synthetic derivatives of Justicia adhatoda against Coronavirus

Novel coronavirus disease (COVID-19) is the major health crisis in the world. World Health Organization has declared COVID-19 as a global pandemic. There are no effective drugs to treat COVID-19 infection. Some drugs include remdesivir, umifenovir, favipiravir, lopinavir/ ritonavir, ribavirin, hydroxychloroquine, etc are used to treat this disease. There is an urgent need for public health measures to implement preventive approaches to control severe COVID-19 disease. Justica adhatoda is a well-known plant drug in Ayurvedic and Unani medicines. Various phytochemical constituents have been isolated from J. adhatoda which possesses activities like antitussive, abortifacient, antimicrobial, cardiovascular protection, anticholinesterase, anti-inflammatory and other important activities. The alkaloids from leaf extracts of J. adhatoda possess anti-viral activity. Molecular docking interaction study against 6W63 showed that molecule 4d showed maximum docking interaction with dock score of (-) 8.1 kcal/mol. MD simulation data reflected the stable ligand-receptor interaction. Maximum and minimum energy gap were showed by 7 and 4d, respectively. The order of stability of the synthesized molecules were 4d>2>3>5>4c>4a>4b>1>6>7. The order of ionization potential and electron affinity of the synthesized molecules were 3>4c>4b>4a>1>6>7>4d>5>2. These data confirmed that molecule 4d would be a boon for society.

Ergot alkaloids as pharmaceuticals: Status and prospects of commercial cultivation of ergot crop for natural alkaloids

Ergot is a plant disease symptom induced by a fungal pathogen of the genus Claviceps in grains of cereal crops, wherein the ergot alkaloids are produced in the cereal grains which are transformed into ergot sclerotia. The natural occurrence of ergot grains in cereal crops is dependent on the environmental factors conducive to ergot development. Under natural fungal infection, the ergot percent varies from 1.2 to 3.3 in the infected crops which hamper the yield or recovery of natural ergot alkaloids. Ergot alkaloids are specific pharmaceutical alkaloids used to treat certain ailments like migraines, induction of childbirth, and the control of postpartum bleeding in humans. Ergot sclerotia contain about 0.15% to 0.5% alkaloids, with medicinally useful compounds. Annual world production of ergot alkaloids has been estimated at 5,000-8,000 kg of all ergopeptines (peptide ergot alkaloids) and 10,000-15,000 kg of lysergic acid, the latter being mainly used in the manufacture of semisynthetic derivatives. The greater part of this production occurs as a result of fermentation (around 60%) while field cultivation of triticale (a hybrid of wheat and rye) accounts for the balance. This is because the artificial cultivation of ergot sclerotia on a host crop plant is lacking as a business module. Due to the low recovery of ergot grains and ergot alkaloids under natural crop production conditions, commercial cultivation for ergot grains is discussed in this paper.

Statins-From Fungi to Pharmacy.

Statins have been used in the treatment of hyperlipidemia, both as monotherapy and in combination therapy. Natural fermentation processes of fungi such as Monascus spp., Penicillium spp., Aspergillus terreus, and Pleurotus ostreatus have given rise to natural statins. Compactin (mevastatin), the original naturally occurring statin, is the primary biotransformation substrate in the manufacturing process of marketed drugs. Statins are classified into natural, semi-synthetic derivatives of natural statins, and synthetic ones. Synthetic statins differ from natural statins in their structural composition, with the only common feature being the HMG-CoA-like moiety responsible for suppressing HMG-CoA reductase. Statins do not differ significantly regarding their pleiotropic and adverse effects, but their characteristics depend on their pharmacokinetic parameters and chemical properties. This paper focuses on describing the processes of obtaining natural statins, detailing the pharmacokinetics of available statins, divided into natural and synthetic, and indicating their pleiotropic effects.

Recent Applications of Protoberberines as Privileged Starting Materials for the Development of Novel Broad-Spectrum Antiviral Agents: A Concise Review (2017-2023).

Berberine is a well-known phytochemical with significant antiviral activity against a wide range of viruses. Due to having a unique backbone consisting of four interconnected rings, it can be used as a platform for the design and development of novel semisynthetic antiviral agents. The question here is whether novel broad-spectrum antiviral drugs with enhanced activity and toxicity potential can be obtained by attempting to modify the structure of this privileged lead compound. The present study aims to review the results of recent studies in which berberine and its close analogues (protoberberine alkaloids) have been used as starting materials for the production of new semisynthetic antiviral structures. For this purpose, relevant studies published in high-quality journals indexed in databases such as Scopus, Web of Science, PubMed, etc. in the time frame of 2017 to 2023 were collected. Our selection criterion in the current review focuses on the studies in which protoberberines were used as starting materials for the production of semisynthetic agents with antiviral activity during the indicated time period. Correspondingly, studies were identified in which semisynthetic derivatives with significant inhibitory activity against a wide range of viruses including human immunodeficiency virus (HIV), enterovirus 71 (EV71), zika virus (ZIKV), influenza A/B, cytomegalovirus (CMV), respiratory syncytial virus (RSV), and coxsackieviruses were designed and synthesized. Our conclusion is that, despite the introduction of diverse semisynthetic derivatives of berberine with improved activity profiles compared to the parent natural leads, sufficient derivatization has not been done yet and more studies are needed.

Enhanced Cytotoxicity and Antimelanoma Activity of Novel Semisynthetic Derivatives of Betulinic Acid with Indole Conjugation.

The prevalence and severity of skin cancer, specifically malignant melanoma, among Caucasians remains a significant concern. Natural compounds from plants have long been explored as potential anticancer agents. Betulinic acid (BI) has shown promise in its therapeutic properties, including its anticancer effects. However, its limited bioavailability has hindered its medicinal applications. To address this issue, two recently synthesized semisynthetic derivatives, N-(2,3-indolo-betulinoyl)diglycylglycine (BA1) and N-(2,3-indolo-betulinoyl)glycylglycine (BA2), were compared with previously reported compounds N-(2,3-indolo-betulinoyl)glycine (BA3), 2,3-indolo-betulinic acid (BA4), and BI. These compounds were evaluated for their effects on murine melanoma cells (B164A5) using various in vitro assays. The introduction of an indole framework at the C2 position of BI resulted in an increased cytotoxicity. Furthermore, the cytotoxicity of compound BA4 was enhanced by conjugating its carboxylic group with an amino acid residue. BA2 and BA3, with glycine and glycylglycine residues at C28, exhibited approximately 2.20-fold higher inhibitory activity compared to BA4. The safety assessment of the compounds on human keratinocytes (HaCaT) has revealed that concentrations up to 10 µM slightly reduced cell viability, while concentrations of 75 µM resulted in lower cell viability rates. LDH leakage assays confirmed cell membrane damage in B164A5 cells when exposed to the tested compounds. BA2 and BA3 exhibited the highest LDH release, indicating their strong cytotoxicity. The NR assay revealed dose-dependent lysosome disruption for BI and 2,3-indolo-betulinic acid derivatives, with BA1, BA2, and BA3 showing the most cytotoxic effects. Scratch assays demonstrated concentration-dependent inhibition of cell migration, with BA2 and BA3 being the most effective. Hoechst 3342 staining revealed that BA2 induced apoptosis, while BA3 induced necrosis at lower concentrations, confirming their anti-melanoma properties. In conclusion, the semisynthetic derivatives of BI, particularly BA2 and BA3, show promise as potential candidates for further research in developing effective anti-cancer therapies.

Expanding Diterpene Complexity and Diversity via Photoinduced Ring Distortions.

Natural products and their semi-synthetic derivatives undoubtedly constitute an important source of therapeutic agents. Their importance lies in their own origin and evolution, since they have great chemical diversity, biochemical specificity, and pharmacological properties. Currently, there is a renewed interest in the development of methodologies capable of efficiently modifying the chemical structure of these bioactive platforms. In this work, the photoderivatization of the diterpene solidagenone was performed using a complexity-to-diversity-oriented approach. By exploring [2+2]-photocycloaddition, photoinduced-hydrogen abstraction, and photoxygenation reactions, a set of solidagenone derivatives was obtained, showing different ring fusions, side chain rearrangements, and modifications of the original furan ring's substitution pattern. The derivatives obtained were characterised by NMR methodologies. To evaluate the structural diversity of the labdane-derived compounds, their physicochemical properties, structural similarity, and chemical space were analysed. These results suggest that photochemical reactions are a useful tool for performing ring distortion transformations, generating derivatives of natural compounds with wide diversity, structural complexity, and with potential biological properties.

Structure of Staphylococcus aureus ClpP Bound to the Covalent Active‐Site Inhibitor Cystargolide A

AbstractThe caseinolytic protease is a highly conserved serine protease, crucial to prokaryotic and eukaryotic protein homeostasis, and a promising antibacterial and anticancer drug target. Herein, we describe the potent cystargolides as the first natural β‐lactone inhibitors of the proteolytic core ClpP. Based on the discovery of two clpP genes next to the cystargolide biosynthetic gene cluster in Kitasatospora cystarginea, we explored ClpP as a potential cystargolide target. We show the inhibition of Staphylococcus aureus ClpP by cystargolide A and B by different biochemical methods in vitro. Synthesis of semisynthetic derivatives and probes with improved cell penetration allowed us to confirm ClpP as a specific target in S. aureus cells and to demonstrate the anti‐virulence activity of this natural product class. Crystal structures show cystargolide A covalently bound to all 14 active sites of ClpP from S. aureus, Aquifex aeolicus, and Photorhabdus laumondii, and reveal the molecular mechanism of ClpP inhibition by β‐lactones, the predominant class of ClpP inhibitors.