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The alkaloid physostigmine is an approved anticholinergic drug and an important lead structure for the development of novel therapeutics. Using a complementary approach that merged chemical synthesis with pathway refactoring, we produced a series of physostigmine analogues with altered specificity and toxicity profiles in the heterologous host Myxococcus xanthus. The compounds that were generated by applying a simple feeding strategy include the promising drug candidate phenserine, which was previously accessible only by total synthesis.

Historically, natural products (NP’s) have played a significant role in drug discovery, not only in cancer and infectious diseases, but also in other therapeutic areas including cardiovascular diseases and multiple sclerosis. Profit and loss, Partnerships and averages, natural products also present certain challenges for drug discovery, such as technical obstacles to screening, isolation, characterization and optimization, which added to decline in their search by the pharmaceutical industry from the 1990s onwards. In recent days the applications of molecular biological techniques have increased the availability of novel compounds that can be conveniently produced in bacteria or yeast or plant sources. In addition to this, combinational chemistry approaches are being based on natural product scaffolds to create screening libraries that closely resemble drug-like compounds. Employing these technologies gives us a chance to execute research in screening new molecules by means of a software and data base to ascertain natural products as a major source for drug discovery. It lastly directs to lead structure discovery. This review discusses plant based natural product drug discovery and how innovative technologies play a role in next generation drug discovery and highlights from the published literature on plants as sources of antiinflammatory agents. GRAPHICAL ABSTRACT

Natural product congeners serve a useful role in the understanding of natural product biosynthesis and structure-activity relationships. A minor congener with superior activity, selectivity, and modifiable functional groups could serve as a more effective lead structure and replace even the original lead molecule that was used for medicinal chemistry modifications. Currently, no effective method exists to discover targeted congeners rapidly, specifically, and selectively from producing sources. Herein, a new method based on liquid-chromatography tandem-mass spectrometry combination is evaluated for targeted discovery of congeners of platensimycin and platencin from the extracts of Streptomyces platensis. By utilizing a precursor-ion searching protocol, tandem mass spectrometry not only confirmed the presence of known congeners but also provided unambiguous detection of many previously unknown congeners of platensimycin and platencin. This high-throughput and quantitative method can be rapidly and broadly applied for dereplication and congener discovery from a variety of producing sources, even when the targeted compounds are obscured by the presence of unrelated natural products.

The development of radiometal‐labelled pharmaceuticals for neuroimaging could offer great potential due to easier handling during labelling and availability through radionuclide generator systems. Nonetheless, to date, no such tracers are available for positron emission tomography, primarily owing to the challenge of crossing the blood–brain barrier (BBB) and loss of affinity through chelator attachment. We have prepared a variety of 68Ga‐labelled phenyltropanes showing that, through a simple hydrocarbon‐linker, it is possible to introduce a chelator onto the lead structure while maintaining its high affinity for hDAT (human dopamine transporter) and simultaneously achieving adequate lipophilicity. One of the candidates, [68Ga]Ga‐HBED‐hexadiyne‐tropane, showed an IC50 value of 66 nM, together with a log D 7.4 of 0.96. A μPET study in a hemi‐parkinsonian rat model showed a fast wash‐out of the tracer, and no specific uptake in the brain, thus implying an inability to penetrate the BBB., Tracer metal: Tropanes are commonly used in radiopharmacy to assess the status of the dopaminergic system. However, no suitable radiometal‐labelled tracers are available for PET, primarily owing to the challenge of crossing the blood–brain barrier and loss of affinity through chelator attachment. We have developed 68Ga‐labelled phenyltropanes showing promising affinity and lipophilicity, and conducted a first PET study.

This Letter presents a novel RF ground lead structure for surface-mount-type optical modules that enables RF crosstalk reduction and bandwidth enhancements. Conventional RF lead-pins of a surface-mount-type optical module have a bent shape that affects on RF ground stability and RF crosstalk between channels. The authors introduced an enhanced ground lead with an optimised shape for RF ground scheme enhancement. They prepared two types of high-bandwidth coherent driver modulator packages for demonstrating RF performance difference, one with the conventional bent ground lead and the other with the optimum-shaped ground lead. The measured results of the package with the enhanced ground lead successfully exhibited adjacent far-end crosstalk reduction of about 5 dB at 50 GHz, and the crosstalk of −30 dB or less up to 58 GHz was confirmed. Moreover, they obtained the improvement in the insertion loss of 1 dB at 54 GHz and the 3-dB electrical bandwidth enhancement of 2 GHz. These RF performances are sufficient for a high-bandwidth coherent driver modulator package that allows 96-GBd class operations.

Optimization of lead structures is crucial for drug discovery. However, the accuracy of such a prediction using the traditional molecular docking approach remains a major concern. Our study demonstrates that the employment of quantum crystallographic approach-counterpoise corrected kernel energy method (KEM-CP) can improve the accuracy by and large. We select human aldose reductase at 0.66 Å, cyclin dependent kinase 2 at 2.0 Å and estrogen receptor β at 2.7 Å resolutions with active site environment ranging from highly hydrophilic to moderate to highly hydrophobic and several of their known ligands. Overall, the use of KEM-CP alongside the GoldScore resulted superior prediction than the GoldScore alone. Unlike GoldScore, the KEM-CP approach is neither environment-specific nor structural resolution dependent, which highlights its versatility. Further, the ranking of the ligands based on the KEM-CP results correlated well with that of the experimental IC50 values. This computationally inexpensive yet simple approach is expected to ease the process of virtual screening of potent ligands, and it would advance the drug discovery research.

The increasing drug resistance of malaria parasites challenges the treatment of this life-threatening disease. Consequently, the development of innovative and effective antimalarial drugs is inevitable. O-tigloylcyclovirobuxeine-B, a nor-cycloartane alkaloid from Buxussempervirens L., has shown promising and selective in vitro activity in previous studies against Plasmodiumfalciparum (Pf), causative agent of Malaria tropica. For further investigations, it is indispensable to develop an advanced and efficient isolation procedure of this valuable natural product. Accordingly, we used liquid&ndash, liquid chromatography including centrifugal partition chromatography (CPC) to obtain the pure alkaloid on a semi-preparative scale. Identification and characterization of the target compound was accomplished by UHPLC/+ESI-QqTOF-MS/MS, 1H NMR and 13C NMR. In conclusion, this work provides a new and efficient method to obtain O-tigloylcyclovirobuxeine-B, a valuable natural product, as a promising antiplasmodial lead structure for the development of innovative and safe medicinal agents.

Background: 1,2,3-triazoles are five-membered heterocyclic scaffold; their broad-spectrum biological activities are known. Researchers around the world are increasingly being interested in this emerging area, owing to its immense pharmacological scope. Objective: This work summarizes the synthesis of 1,2,3-triazoles and the significance of this pattern as a lead structure for new drug molecules discovery. Methods: 1,2,3-triazoles can be obtained on a multigram scale through “click chemistry” under ambient conditions. Results: Sixteen compounds were synthesized and evaluated on five microbial strains E. coli, E. faecalis, P. aeruginosa, S. aureus and C. albicans. NMR, MS and IR were used to characterize all compounds. They were evaluated with their Minimum Inhibitory Concentrations (MICs) and interesting results were obtained with compounds 12a, 12b, 3, 2a and 2c, with MIC 0.14 μM (P. aeruginosa), 1.08 μM (E. coli), 1.20 μM (E. faecalis and C. albicans), 3.5 μM (E. faecalis) and 4.24 μM (C. albicans), respectively. P. aeruginosa and C. albicans were the most sensitive among all the strains. Conclusion: The synthesized compounds were found as potential antimicrobial agents against Gram (+), Gram (-) strains and fungi.

Background and objectives To evaluate tau PET using C-pyridinyl-butadienyl-benzothiazole 3 (C-PBB3) in the 4-repeat (4R)-tauopathies progressive supranuclear palsy (PSP) and corticobasal syndrome (CBS). Methods Retrospective analysis of C-PBB3 PET in 2, 7, and 2 patients with CBS, PSP, and Alzheimer dementia (AD), respectively. Normalized C-PBB3 uptake in clusters with significant hypometabolism on F-FDG-PET and corresponding atlas-based volumes of interest was compared between diagnostic groups. Results In accordance with visually appreciable group differences, C-PBB3 uptake was significantly higher in dorsolateral frontal and motor cortex in CBS patients and frontal and temporal cortices in AD patients as compared with PSP patients. Patients with PSP showed mildly but significantly higher uptake in midbrain compared with AD patients. Conclusions In line with known neuropathological changes, the spatial pattern and magnitude of C-PBB3 tau binding differ between CBS, PSP, and AD, which may be of diagnostic utility. Thus, C-PBB3 offers a promising lead structure for development of ligands for tau imaging, including 4R-tauopathies.

Lead structure discovery mainly focuses on the identification of noncovalently binding ligands. Covalent linkage, however, is an essential binding mechanism for a multitude of successfully marketed drugs, although discovered by serendipity in most cases. We present a concept for the design of fragments covalently binding to proteases. Covalent linkage enables fragment binding unrelated to affinity to shallow protein binding sites and at the same time allows differentiated targeted hit verification and binding location verification through mass spectrometry. We describe a systematic and rational computational approach for the identification of covalently binding fragments from compound collections inhibiting enteroviral 3C protease, a target with high therapeutic potential. By implementing reactive groups potentially forming covalent bonds as a chemical feature in our 3D pharmacophore methodology, covalent binders were discovered by high-throughput virtual screening. We present careful experimental validation of the virtual hits using enzymatic assays and mass spectrometry unraveling a novel, previously unknown irreversible inhibition of the 3C protease by phenylthiomethyl ketone-based fragments. Subsequent synthetic optimization through fragment growing and reactivity analysis against catalytic and noncatalytic cysteines revealed specific irreversible 3C protease inhibition.

Herein, we describe the synthesis and structure–activity relationships of cyclic peptides designed to target heat shock protein 90 (Hsp90). Generating 19 compounds and evaluating their binding affinity reveals that increasing electrostatic interactions allows the compounds to bind more effectively with Hsp90 compared to the lead structure. Exchanging specific residues for lysine improves binding affinity for Hsp90, indicating some residues are not critical for interacting with the target, whereas others are essential. Replacing l- for d-amino acids produced compounds with decreased binding affinity compared to the parent structure, confirming the importance of conformation and identifying key residues most important for binding. Thus, a specific conformation and electrostatic interactions are required in order for these inhibitors to bind to Hsp90.

The structure of wondonin marine natural products was renovated to attain new drug-like scaffolds. Wondonins have novel antiangiogenic properties without overt cytotoxicity. However, the chemical instability and synthetic complexity of wondonins have hindered their development as a new type of antiangiogenesis agent. Using a structure-based bioisosterism, the benzodioxole moiety was changed to benzothiazole, and the imidazole moiety was replaced by 1,2,3-triazole. Our efforts resulted in a new scaffold with enhanced antiangiogenic activity and minimized cytotoxicity. One compound with this scaffold effectively inhibited hyaloid vessel formation in diabetic retinopathy mimic zebrafish model. The biological findings together suggested the potential of the scaffold as a lead structure for development of antiangiogenic drugs with novel functions and as a probe to elucidate new biological mechanisms associated with angiogenesis.

An overview is given of the significance of the pyridazine scaffold in crop protection chemistry. The main herbicidally, fungicidally, and insecticidally active pyridazine classes are presented, together with their synthesis routes, modes of action, and biological efficacies. In addition, the role of pyridazines as an isosteric replacement or as lead structure of other agrochemicals is reported. Also, benzannulated pyridazines, such as cinnolines and phthalazines as well as partially and fully saturated pyridazine derivatives, are covered.

1,2,3-Triazoles are important five-membered heterocyclic scaffold due to their extensive biological activities. This framework can be readily obtained in good to excellent yields on the multigram scale through click chemistry via reaction of aryl/alkyl halides, alkynes and NaN3 under ambient conditions. It has been an emerging area of interest for many researchers throughout the globe owing to its immense pharmacological scope. The present work aims to summarize the current approaches adopted for the synthesis of the 1,2,3-triazole and medicinal significance of these architectures as a lead structure for the discovery of drug molecules such as COX-1/COX-2 inhibitors (celecoxib, pyrazofurin), HIV protease inhibitors, CB1 cannabinoid receptor antagonist and much more which are in the pipeline of clinical trials. The emphasis has been given on the major advancements in the medicinal prospectus of this pharmacophore for the period during 2008-2016.

10–23 DNAzyme is an artificially selected catalytic DNA molecule. Its great potential as genetic therapeutics promoted chemical modifications for more efficient DNAzymes. Here, 10–23 DNAzyme was modified on its six deoxyadenosine residues (A5, A9, A11, A12, A15 in the catalytic domain and A0 of the recognition arm next to the cleavage site) with compound 1, an adenosine analogue with 2′-O-[N-(aminoethyl)carbamoyl]methyl group. A positive effect of compound 1 at A15 was observed (HJDS-05, kobs = 0.0111 min−1). Compared to the effect of 2′-H and 2′-OMe at A15, this result provided an approach for more efficient DNAzyme by combining 2′-substituted amino group of adenosine with A15 as the lead structure.

The 2,7-naphthyridone scaffold has been proposed as a novel lead structure of MET inhibitors by our group. To broaden the application of this new scaffold, a series of 8-amino-substituted 2-phenyl-2,7-naphthyridin-1(2H)-one derivatives were designed and synthesized. Preliminary biological screening resulted in the discovery of a new lead of c-Kit and VEGFR-2 kinase inhibitors. Compound 9k exhibited excellent c-Kit inhibitory activity, with an IC50 value of 8.5 nM, i.e., it is 38.8-fold more potent than compound 3 (IC50 of 329.6 nM). Moreover, the compounds 10l and 10r exhibited good VEGFR-2 inhibitory activity, with IC50 values of 56.5 and 31.7 nM, respectively, i.e., they are 5.0&ndash, 8.8-fold more potent than compound 3 (IC50 of 279.9 nM). Molecular docking experiments provided further insight into the binding interactions of the new lead compounds with c-Kit and VEGFR-2 kinase. In this study, an 8-amino-substituted 2-phenyl-2,7-naphthyridin-1(2H)-one scaffold was identified as the new lead structure of c-Kit and VEGFR-2 kinase inhibitors.

Target validation of current drugs remains the major challenge for target-based drug discovery, especially for agrochemical discovery. The bactericide 0 represents a novel lead structure and has shown potent efficacy against those diseases that are extremely difficult to control, such as rice bacterial leaf blight. However, no detailed target analysis of this bactericide has been reported. Here, we developed a panel of 0-derived probes 1-6, in which a conservative modification (alkyne tag) was introduced to keep the antibacterial activity of 0 and provide functionality for target identification via click chemistry. With these cell-permeable probes, we were able to discover dihydrolipoamide S-succinyltransferase (DLST) as an unprecedented target in living cells. The probes showed good preference for DLST, especially probe 1, which demonstrated distinct selectivity and reactivity. Also, we reported 0 as the first covalent DLST inhibitor, which has been used to confirm the involvement of DLST in the regulation of energy production.