Synthesis and biological activity of analogues of batzelladine F

Guanidine dicycloamine-based analogs: green chemistry synthesis, biological investigation, and molecular docking studies as promising antibacterial and antiglycation leads

Dicyandiamide (DCD) reacted with amino acids 1a-f to produce biguanides 2 and 4 and guanidine pyrazolones 3, 5, 6, 7, and 8, according to the reaction. DCD exhibited the following reactions: imidodicarbonimidicdiamide 9, diazocan-2-ylguanidine 10, methyl biguanidylthion 11, N-carbamothioylimidodicarbonimidicdiamide 12, 2-guanidinebenzoimidazole 13a, 2-guanidinylbenzoxazole 13b, and 2-guanidinylbenzothiazol 13c. These reactions were triggered by 6-amino caproic acid, thioacetamide, thiourea, o-aminophenol, o-aminothiophenol, and anthranilic acid, respectively. Compound 2 had the least antimicrobial activity, while compound 13c demonstrated the most antibacterial impact against all bacterial strains. Furthermore, in terms of antiglycation efficacy (AGEs), 12, 11, and 7 were the most effective AGE cross-linking inhibitors. Eight and ten, which showed a considerable inhibition on cross-linking AGEs, come next. Compounds 4 and 6 on the other hand have shown the least suppression of AGE production. The most promising antiglycation scaffolds 8, 11, and 12 in the Human serum albumin (HAS) active site were shown to be able to adopt crucial binding interactions with important amino acids based on the results of in silico molecular docking. The most promising antiglycation compounds 8, 11, and 12 were also shown to have better hydrophilicity, acceptable lipophilicity, gastrointestinal tract absorption (GIT), and blood-brain barrier penetration qualities when their physicochemical properties were examined using the egg-boiled method.

Investigating the structure-activity relationship of marine polycyclic batzelladine alkaloids as promising inhibitors for SARS-CoV-2 main protease (Mpro)

Over a span of two years ago, since the emergence of the first case of the novel coronavirus (SARS-CoV-2) in China, the pandemic has crossed borders causing serious health emergencies, immense economic crisis and impacting the daily life worldwide. Despite the discovery of numerous forms of precautionary vaccines along with other recently approved orally available drugs, yet effective antiviral therapeutics are necessarily needed to hunt this virus and its variants. Historically, naturally occurring chemicals have always been considered the primary source of beneficial medications. Considering the SARS-CoV-2 main protease (M^pro) as the duplicate key element of the viral cycle and its main target, in this paper, an extensive virtual screening for a focused chemical library of 15 batzelladine marine alkaloids, was virtually examined against SARS-CoV-2 main protease (M^pro) using an integrated set of modern computational tools including molecular docking (MDock), molecule dynamic (MD) simulations and structure-activity relationships (SARs) as well. The molecular docking predictions had disclosed four promising compounds including batzelladines H–I (8–9) and batzelladines F-G (6–7), respectively according to their prominent ligand-protein energy scores and relevant binding affinities with the (M^pro) pocket residues. The best two chemical hits, batzelladines H–I (8–9) were further investigated thermodynamically though studying their MD simulations at 100 ns, where they showed excellent stability within the accommodated (M^pro) pocket. Moreover, SARs studies imply the crucial roles of the fused tricyclic guanidinic moieties, its degree of unsaturation, position of the N–OH functionality and the length of the side chain as a spacer linking between two active sites, which disclosed fundamental structural and pharmacophoric features for efficient protein-ligand interaction. Such interesting findings are greatly highlighting further in vitro/vivo examinations regarding those marine natural products (MNPs) and their synthetic equivalents as promising antivirals.

Leveraging Marine Natural Products as a Platform to Tackle Bacterial Resistance and Persistence

Antimicrobial resistance to existing antibiotics represents one of the greatest threats to human health and is growing at an alarming rate. To further complicate treatment of bacterial infections, many chronic infections are the result of bacterial biofilms that are tolerant to treatment with antibiotics because of the presence of metabolically dormant persister cell populations. Together these threats are creating an increasing burden on the healthcare system, and a "preantibiotic" age is on the horizon if significant action is not taken by the scientific and medical communities. While the golden era of antibiotic discovery (1940s-1960s) produced most of the antibiotic classes in clinical use today, followed by several decades of limited development, there has been a resurgence in antibiotic drug discovery in recent years fueled by the academic and biotech sectors. Historically, great success has been achieved by developing next-generation variants of existing classes of antibiotics, but there remains a dire need for the identification of novel scaffolds and/or antimicrobial targets to drive future efforts to overcome resistance and tolerance. In this regard, there has been no more valuable source for the identification of antibiotics than natural products, with 69-77% of approved antibiotics either being such compounds or being derived from them.Our group has developed a program centered on the chemical synthesis and chemical microbiology of marine natural products with unusual structures and promising levels of activity against multidrug-resistant (MDR) bacterial pathogens. As we are motivated by preparing and studying the biological effects of these molecules, we are not initially pursuing a biological question but instead are allowing the observed phenotypes and activities to guide the ultimate project direction. In this Account, our recent efforts on the synoxazolidinone, lipoxazolidinone, and batzelladine natural products will be discussed and placed in the context of the field's greatest challenges and opportunities. Specifically, the synoxazolidinone family of 4-oxazolidinone-containing natural products has led to the development of several chemical methods to prepare antimicrobial scaffolds and has revealed compounds with potent activity as adjuvants to treat bacterial biofilms. Bearing the same 4-oxazolidinone core, the lipoxazolidinones have proven to be potent single-agent antibiotics. Finally, our synthetic efforts toward the batzelladines revealed analogues with activity against a number of MDR pathogens, highlighted by non-natural stereochemical isomers with superior activity and simplified synthetic access. Taken together, these studies provide several distinct platforms for the development of novel therapeutics that can add to our arsenal of scaffolds for preclinical development and can provide insight into the biochemical processes and pathways that can be targeted by small molecules in the fight against antimicrobial-resistant and -tolerant infections. We hope that this work will serve as inspiration for increased efforts by the scientific community to leverage synthetic chemistry and chemical microbiology toward novel antibiotics that can combat the growing crisis of MDR and tolerant bacterial infections.

Batzella, Crambe and Monanchora: Highly Prolific Marine Sponge Genera Yielding Compounds with Potential Applications for Cancer and Other Therapeutic Areas

Pyrroloquinoline and guanidine-derived alkaloids present distinct groups of marine secondary metabolites with structural diversity that displayed potentialities in biological research. A considerable number of these molecular architectures had been recorded from marine sponges belonging to different marine genera, including Batzella, Crambe, Monanchora, Clathria, Ptilocaulis and New Caledonian starfishes Fromia monilis and Celerina heffernani. In this review, we aim to comprehensively cover the chemodiversity and the bioactivities landmarks centered around the chemical constituents exclusively isolated from these three marine genera including Batzella, Crambe and Monanchora over the period 1981-2017, paying a special attention to the polycyclic guanidinic compounds and their proposed biomimetic landmarks. It is concluded that these marine sponge genera represent a rich source of novel compounds with potential applications for cancer and other therapeutic areas.

Analogues of Marine Guanidine Alkaloids Are in Vitro Effective against Trypanosoma cruzi and Selectively Eliminate Leishmania (L.) infantum Intracellular Amastigotes

Synthetic analogues of marine sponge guanidine alkaloids showed in vitro antiparasitic activity against Leishmania (L.) infantum and Trypanosoma cruzi. Guanidines 10 and 11 presented the highest selectivity index when tested against Leishmania. The antiparasitic activity of 10 and 11 was investigated in host cells and in parasites. Both compounds induced depolarization of mitochondrial membrane potential, upregulation of reactive oxygen species levels, and increased plasma membrane permeability in Leishmania parasites. Immunomodulatory assays suggested an NO-independent effect of guanidines 10 and 11 on macrophages. The same compounds also promoted anti-inflammatory activity in L. (L.) infantum-infected macrophages cocultived with splenocytes, reducing the production of cytokines MCP-1 and IFN-γ. Guanidines 10 and 11 affect the bioenergetic metabolism of Leishmania, with selective elimination of parasites via a host-independent mechanism.

The chemistry and biology of guanidine natural products

The present review discusses the isolation, structure determination, synthesis, biosynthesis and biological activities of secondary metabolites bearing a guanidine group.

Syntheses of Cyclic Guanidine-Containing Natural Products

Naturally occurring guanidine derivatives frequently display medicinally useful properties. Among them, the higher order pyrrole-imidazole alkaloids, the dragmacidins, the crambescidins/batzelladines, and the saxitoxins/tetradotoxins have stimulated the development of many new synthetic methods over the past decades. We provide here an overview of the syntheses of these cyclic guanidine-containing natural products.

Guanidine Motif in Biologically Active Peptides

In the past decade, guanidines have attracted attention as valuable hydrogen bond-based catalysts while they have long been considered as organic superbases with a broad scope of synthetic applicability. Their easy modification has also expanded their capacity to form complexes with a wide range of metal salts as effective metal scavengers. All these attractive aspects have promoted a huge growth in the field of organic synthesis involving guanidines and examples of such reactions have been collected in numerous reviews and some books. Moreover, this structural motif is also present in a large number of natural products and biologically active compounds that exhibit appealing properties and play important roles in medicinal chemistry. In this highlight, we will only cover the synthesis and properties of biologically active guanidine-containing peptides reported in the past 3 years.