Investigation on side-product formation during the synthesis of a lactoferrin-derived lactam-bridged cyclic peptide.

Bovine lactoferrin C-lobe is able to prevent both influenza virus hemagglutination and cell infection. In particular, it was demonstrated that the fragment 418SKHSSLDCVLRP429 is a potent antiviral peptide. Therefore, we tried to increase the stability of this fragment through side-chain lactam cyclization of the peptide, S[KHSSLD]CVLRP (1). However, classic strategy involving solid-supported cyclization of the linear precursor, containing orthogonal allyl/alloc-based protection for the key amino and carboxyl residues, did not provide the desired cyclic peptide. Here, we report the identification of problematic stretches during the sequence assembly process and the optimization of the different parameters involved in the construction of 1. Results indicated a significant influence of ß-protecting group of both aspartic acid and adjacent cysteine residues on the formation of side products. Therefore, the identification of suitable ß-protecting groups of these residues allowed us to optimize the synthesis of designed lactam-bridged cyclic peptide.

Ring-Fused Cyclic Aminals from Tetrahydro-ß-carboline-Based Dipeptide Compounds.

An acid- and oxidant-promoted intramolecular cyclization of a tetrahydro-ß-carboline-based dipeptide has been developed to prepare new indole-fused aminoacetals. This approach involves N-acyliminium formation from readily available precursors and cyclization under mild reaction conditions. The diastereoselectivity in the formation of the products is influenced by the specific substituents of the starting reagents, which has been rationalized analyzing the energy profile of the related reactions and the relative stability of the proposed structures based on DFT computational methods.

The effect of d-amino acid substitution on the selectivity of temporin L towards target cells: identification of a potent anti-Candida peptide.

The frog skin peptide temporin L (TL, 13-residues long) has a wide and potent spectrum of antimicrobial activity, but it is also toxic on mammalian cells at its microbicidal concentrations. Previous studies have indicated that its analogue [Pro(3)]TL has a slightly reduced hemolytic activity and a stable helical conformation along residues 6-13. Here, to expand our knowledge on the relationship between the extent/position of α-helix in TL and its biological activities, we systematically replaced single amino acids within the α-helical domain of [Pro(3)]TL with the corresponding d isomers, known as helix breakers. Structure-activity relationship studies of these analogues, by means of CD and NMR spectroscopy analyses as well as antimicrobial and hemolytic assays were performed. Besides increasing our understanding on the structural elements that are responsible for cell selectivity of TL, this study revealed that a single l to d amino acid substitution can preserve strong anti-Candida activity of [Pro(3)]TL, without giving a toxic effect towards human cells.

Novel pyrrole based CB2 agonists: New insights on CB2 receptor role in regulating neurotransmitters' tone.

The cannabinoid system is one of the most investigated neuromodulatory systems because of its involvement in multiple pathologies such as cancer, inflammation, and psychiatric diseases. Recently, the CB2 receptor has gained increased attention considering its crucial role in modulating neuroinflammation in several pathological conditions like neurodegenerative diseases. Here we describe the rational design of pyrrole-based analogues, which led to a potent and pharmacokinetically suitable CB2 full agonist particularly effective in improving cognitive functions in a scopolamine-induced amnesia murine model. Therefore, we extended our study by investigating the interconnection between CB2 activation and neurotransmission in this experimental paradigm. To this purpose, we performed a MALDI imaging analysis on mice brains, observing that the administration of our lead compound was able to revert the effect of scopolamine on different neurotransmitter tones, such as acetylcholine, serotonin, and GABA, shedding light on important networks not fully explored, so far.

Biological activity of 3-chloro-azetidin-2-one derivatives having interesting antiproliferative activity on human breast cancer cell lines.

Resveratrol (3,4',5 tri-hydroxystilbene), a natural plant polyphenol, has gained interest as a non-toxic agent capable of inducing tumor cell death in a variety of cancer types. However, therapeutic application of these beneficial effects remains very limited due to its short biological half-life, labile properties, rapid metabolism and elimination. Different studies were undertaken to obtain synthetic analogs of resveratrol with major bioavailability and anticancer activity. We have synthesized a series 3-chloro-azetidin-2-one derivatives, in which an azetidinone nucleus connects two aromatic rings. Aim of the present study was to investigate the effects of these new 3-chloro-azetidin-2-one resveratrol derivatives on human breast cancer cell lines proliferation. Our results indicate that some azetidin-based resveratrol derivatives may become new potent alternative tools for the treatment of human breast cancer.

Synthesis and cytotoxic activity evaluation of 2,3-thiazolidin-4-one derivatives on human breast cancer cell lines.

It is well known that resveratrol (RSV) displayed cancer-preventing and anticancer properties but its clinical application is limited because of a low bioavailability and a rapid clearance from the circulation. Aim of this work was to synthesize pharmacologically active resveratrol analogs with an enhanced structural rigidity and bioavailability. In particular, we have synthesized a library of 2,3-thiazolidin-4-one derivatives in which a thiazolidinone nucleus connects two aromatic rings. Some of these compounds showed strong inhibitory effects on breast cancer cell growth. Our results indicate that some of thiazolidin-based resveratrol derivatives may become a new potent alternative tool for the treatment of human breast cancer.

Design, Synthesis, and Pharmacological Characterization of a Potent Soluble Epoxide Hydrolase Inhibitor for the Treatment of Acute Pancreatitis.

Acute pancreatitis (AP) is a potentially life-threatening illness characterized by an exacerbated inflammatory response with limited options for pharmacological treatment. Here, we describe the rational development of a library of soluble epoxide hydrolase (sEH) inhibitors for the treatment of AP. Synthesized compounds were screened in vitro for their sEH inhibitory potency and selectivity, and the results were rationalized by means of molecular modeling studies. The most potent compounds were studied in vitro for their pharmacokinetic profile, where compound 28 emerged as a promising lead. In fact, compound 28 demonstrated a remarkable in vivo efficacy in reducing the inflammatory damage in cerulein-induced AP in mice. Targeted metabololipidomic analysis further substantiated sEH inhibition as a molecular mechanism of the compound underlying anti-AP activity in vivo. Finally, pharmacokinetic assessment demonstrated a suitable profile of 28 in vivo. Collectively, compound 28 displays strong effectiveness as sEH inhibitor with potential for pharmacological AP treatment.

Discovery and Optimization of Indoline-Based Compounds as Dual 5-LOX/sEH Inhibitors: In Vitro and In Vivo Anti-Inflammatory Characterization.

The design of multitarget drugs represents a promising strategy in medicinal chemistry and seems particularly suitable for the discovery of anti-inflammatory drugs. Here, we describe the identification of an indoline-based compound inhibiting both 5-lipoxygenase (5-LOX) and soluble epoxide hydrolase (sEH). In silico analysis of an in-house library identified nine compounds as potential 5-LOX inhibitors. Enzymatic and cellular assays revealed the indoline derivative 43 as a notable 5-LOX inhibitor, guiding the design of new analogues. These compounds underwent extensive in vitro investigation revealing dual 5-LOX/sEH inhibitors, with 73 showing the most promising activity (IC50s of 0.41 ± 0.01 and 0.43 ± 0.10 µM for 5-LOX and sEH, respectively). When challenged in vivo in zymosan-induced peritonitis and experimental asthma in mice, compound 73 showed remarkable anti-inflammatory efficacy. These results pave the way for the rational design of 5-LOX/sEH dual inhibitors and for further investigation of their potential use as anti-inflammatory agents.

Identification of a dual acting SARS-CoV-2 proteases inhibitor through in silico design and step-by-step biological characterization.

COVID-19 pandemic, starting from the latest 2019, and caused by SARS-CoV-2 pathogen, led to the hardest health-socio-economic disaster in the last century. Despite the tremendous scientific efforts, mainly focused on the development of vaccines, identification of potent and efficient anti-SARS-CoV-2 therapeutics still represents an unmet need. Remdesivir, an anti-Ebola drug selected from a repurposing campaign, is the only drug approved, so far, for the treatment of the infection. Nevertheless, WHO in later 2020 has recommended against its use in COVID-19. In the present paper, we describe a step-by-step in silico design of a small library of compounds as main protease (Mpro) inhibitors. All the molecules were screened by an enzymatic assay on Mpro and, then, cellular activity was evaluated using Vero cells viral infection model. The cellular screening disclosed compounds 29 and 34 as in-vitro SARS-CoV-2 replication inhibitors at non-toxic concentrations (0.32 < EC50 < 5.98 µM). To rationalize these results, additional in-vitro assays were performed, focusing on papain like protease (PLpro) and spike protein (SP) as potential targets for the synthesized molecules. This pharmacological workflow allowed the identification of compound 29, as a dual acting SARS-CoV-2 proteases inhibitor featuring micromolar inhibitory potency versus Mpro (IC50 = 1.72 µM) and submicromolar potency versus PLpro (IC50 = 0.67 µM), and of compound 34 as a selective SP inhibitor (IC50 = 3.26 µM).

Unprecedented synthesis of a novel amino quinone ring system via oxidative decarboxylation of quinone-based alpha,alpha-amino esters.

An unusual and efficient method for the synthesis of new quinone-based amine and its derivatives from the corresponding alpha,alpha-amino ester is described. The procedure involves the quinone-based system's oxidative decarboxylation via hydride transfer throughout basic hydrolysis. This synthetic method provides, with good yields, rapid access to new potentially cytotoxic quinones.

Synthesis and Pharmacological Characterization of Conformationally Restricted Retigabine Analogues as Novel Neuronal Kv7 Channel Activators.

Kv7 K+ channels represent attractive pharmacological targets for the treatment of different neurological disorders, including epilepsy. In this paper, 42 conformationally restricted analogues of the prototypical Kv7 activator retigabine have been synthesized and tested by electrophysiological patch-clamp experiments as Kv7 agonists. When compared to retigabine (0.93 ± 0.43 µM), the EC50s for Kv7.2 current enhancements by compound 23a (0.08 ± 0.04 µM) were lower, whereas no change in potency was observed for 24a (0.63 ± 0.07 µM). In addition, compared to retigabine, 23a and 24a showed also higher potency in activating heteromeric Kv7.2/Kv7.3 and homomeric Kv7.4 channels. Molecular modeling studies provided new insights into the chemical features required for optimal interaction at the binding site. Stability studies evidenced improved chemical stability of 23a and 24a in comparison with retigabine. Overall, the present results highlight that the N5-alkylamidoindole moiety provides a suitable pharmacophoric scaffold for the design of chemically stable, highly potent and selective Kv7 agonists.

Identification of an indol-based multi-target kinase inhibitor through phenotype screening and target fishing using inverse virtual screening approach.

A series of 1,3,5-substituted indole derivatives was prepared to explore the anti-proliferative activity against a panel of human tumour cell lines. A 5-carboxamide derivative (27) emerged as the most potent compound of this series, inhibiting the HeLa cell growth at sub-micromolar concentrations. Target fishing of 27 using a combination of inverse virtual screening (IVS) approach and ligand-based shape similarity study identified the top-ranked targets for 27 as belonging to kinome. These results were further confirmed by in vitro binding assays, leading to the identification of 27 as multi-target kinase inhibitor. The compound 27 was further characterized for its antiproliferative activity by in cell studies, showing a mechanism of action involving modification of the cell cycle, increase in ROS release and caspase 3-expression and decrease in ERK expression.

An Efficient Approach to Aromatic Aminomethylation Using Dichloromethane as Methylene Source.

Ultrasound-promoted N-aminomethylation of indoles can be achieved in basic medium using sodium hydride and dichloromethane (DCM) as C1 donor source. This innovative amino methylation protocol results in good to excellent yields of multifunctional indole derivatives. The procedure is also applicable to other aza-heterocyclic compounds and, interestingly, affords direct access to aminomethyl-substituted aryl alcohols.

Design, Synthesis, Biological Activity, and Structural Analysis of Lactam-Constrained PTPRJ Agonist Peptides.

PTPRJ is a receptor-like protein tyrosine phosphatase mainly known for its antiproliferative and tumor-suppressive functions. PTPRJ dephosphorylates several growth factors and their receptors, negatively regulating cell proliferation and migration. We recently identified a disulfide-bridged nonapeptide, named PTPRJ-19 (H-[Cys-His-His-Asn-Leu-Thr-His-Ala-Cys]-OH), which activates PTPRJ, thereby causing cell growth inhibition and apoptosis of both cancer and endothelial cells. With the aim of replacing the disulfide bridge by a chemically more stable moiety, we have synthesized and tested a series of lactam analogues of PTPRJ-19. This replacement led to analogues with higher activity and greater stability than the parent peptide.

Lactoferrin-derived Peptides Active towards Influenza: Identification of Three Potent Tetrapeptide Inhibitors.

Bovine lactoferrin is a biglobular multifunctional iron binding glycoprotein that plays an important role in innate immunity against infections. We have previously demonstrated that selected peptides from bovine lactoferrin C-lobe are able to prevent both Influenza virus hemagglutination and cell infection. To deeper investigate the ability of lactoferrin derived peptides to inhibit Influenza virus infection, in this study we identified new bovine lactoferrin C-lobe derived sequences and corresponding synthetic peptides were synthesized and assayed to check their ability to prevent viral hemagglutination and infection. We identified three tetrapeptides endowed with broad anti-Influenza activity and able to inhibit viral infection in a concentration range femto- to picomolar. Our data indicate that these peptides may constitute a non-toxic tool for potential applications as anti-Influenza therapeutics.

Development and Identification of a Novel Anti-HIV-1 Peptide Derived by Modification of the N-Terminal Domain of HIV-1 Integrase.

The viral enzyme integrase (IN) is essential for the replication of human immunodeficiency virus type 1 (HIV-1) and represents an important target for the development of new antiretroviral drugs. In this study, we focused on the N-terminal domain (NTD), which is mainly involved into protein oligomerization process, for the development and synthesis of a library of overlapping peptide sequences, with specific length and specific offset covering the entire native protein sequence NTD IN 1-50. The most potent fragment, VVAKEIVAH (peptide 18), which includes a His residue instead of the natural Ser at position 39, inhibits the HIV-1 IN activity with an IC50 value of 4.5 µM. Amino acid substitution analysis on this peptide revealed essential residues for activity and allowed us to identify two nonapeptides (peptides 24 and 25), that show a potency of inhibition similar to the one of peptide 18. Interestingly, peptide 18 does not interfere with the dynamic interplay between IN subunits, while peptides 24 and 25 modulated these interactions in different manners. In fact, peptide 24 inhibited the IN-IN dimerization, while peptide 25 promoted IN multimerization, with IC50 values of 32 and 4.8 µM, respectively. In addition, peptide 25 has shown to have selective anti-infective cell activity for HIV-1. These results confirmed peptide 25 as a hit for further development of new chemotherapeutic agents against HIV-1.

Identification of an indol-based derivative as potent and selective varicella zoster virus (VZV) inhibitor.

We report the synthesis and antiviral activity of a new family of non-nucleoside antivirals, derived from the indole nucleus. Modifications of this template through Mannich and Friedel-Crafts reactions, coupled with nucleophilic displacement and reductive aminations led to 23 final derivatives, which were pharmacologically tested. Tryptamine derivative 17a was found to have a selective inhibitory activity against human varicella zoster virus (VZV) replication in vitro, being inactive against a variety of other DNA and RNA viruses. A structure-activity relationship (SAR) study showed that the presence of a biphenyl ethyl moiety and the acetylation at the amino group of tryptamine are a prerequisite for anti-VZV activity. The novel compound shows the same activity against thymidine kinase (TK)-competent (TK+) and TK-deficient (TK-) VZV strains, pointing to a novel mechanism of antiviral action.

Dihydrithieno[2,3-b]naphto-4,9-dione analogues as anticancer agents: Synthesis and in cell pharmacological studies.

The synthesis of a series of highly functionalized DNTQ-based derivatives is described. In vitro, most of the compounds exerted a cytotoxic effect against several tumour cell lines comparable to or greater than that of doxorubicin. Here we demonstrate that compound 14, the less cardiotoxic compound of this series, induced cell differentiation and was distributed mainly in the cytoplasm in the human glioblastoma LN229 cell line. Moreover, compound 14 reduced both cellular glucose uptake and serine/threonine kinase AKT expression, and triggered cell apoptosis. These findings suggest that highly functionalized DTNQ-based derivatives are promising pharmacological tools for the study of human solid tumours.