Bioactive Compounds Isolated from Marine Bacterium Vibrio neocaledonicus and Their Enzyme Inhibitory Activities

Polyketides from the marine-derived fungus Aspergillus falconensis: In silico and in vitro cytotoxicity studies

Fermentation of the marine-derived fungus Aspergillus falconensis, isolated from sediment collected from the Red Sea, Egypt on solid rice medium containing 3.5% NaCl yielded a new dibenzoxepin derivative (1) and a new natural isocoumarin (2) along with six known compounds (3-8). Changes in the metabolic profile of the fungus were induced by replacing NaCl with 3.5% (NH₄)₂SO₄ that resulted in the accumulation of three further known compounds (9-11), which were not detected when the fungus was cultivated in the presence of NaCl. The structures of the new compounds were elucidated by HRESIMS and 1D/2D NMR as well as by comparison with the literature. Molecular docking was conducted for all isolated compounds on crucial enzymes involved in the formation, progression and metastasis of cancer which included human cyclin-dependent kinase 2 (CDK-2), human DNA topoisomerase II (TOP-2) and matrix metalloproteinase 13 (MMP-13). Diorcinol (7), sulochrin (9) and monochlorosulochrin (10) displayed notable stability within the active pocket of CDK-2 with free binding energy (ΔG) equals to -25.72, -25.03 and -25.37 Kcal/mol, respectively whereas sulochrin (9) exerted the highest fitting score within MMP-13 active center (ΔG = -33.83 Kcal/mol). In vitro cytotoxic assessment using MTT assay showed that sulochrin (9) exhibited cytotoxic activity versus L5178Y mouse lymphoma cells with an IC₅₀ value of 5.1 µM and inhibition of migration of MDA-MB 231 breast cancer cells at a concentration of 70 µM.

Weak Microbial Metabolites: a Treasure Trove for Using Biomimicry to Discover and Optimize Drugs

For decades, traditional drug discovery has used natural product and synthetic chemistry approaches to generate libraries of compounds, with some ending as promising drug candidates. A complementary approach has been to adopt the concept of biomimicry of natural products and metabolites so as to improve multiple drug-like features of the parent molecule. In this effort, promiscuous and weak interactions between ligands and receptors are often ignored in a drug discovery process. In this Emerging Concepts article, we highlight microbial metabolite mimicry, whereby parent metabolites have weak interactions with their receptors that then have led to discrete examples of more potent and effective drug-like molecules. We show specific examples of parent-metabolite mimics with potent effects in vitro and in vivo. Furthermore, we show examples of emerging microbial ligand-receptor interactions and provide a context in which these ligands could be improved as potential drugs. A balanced conceptual advance is provided in which we also acknowledge potential pitfalls-hyperstimulation of finely balanced receptor-ligand interactions could also be detrimental. However, with balance, we provide examples of where this emerging concept needs to be tested. SIGNIFICANCE STATEMENT: Microbial metabolite mimicry is a novel way to expand on the chemical repertoire of future drugs. The emerging concept is now explained using specific examples of the discovery of therapeutic leads from microbial metabolites.

Mycotoxins from Fusarium proliferatum: new inhibitors of papain-like cysteine proteases

Papain-like cysteine proteases (PLCPs) in plants are essential to prevent phytopathogen invasion. In order to search for cysteine protease inhibitors and to investigate compounds that could be associated to pineapple Fusarium disease, a chemistry investigation was performed on Fusarium proliferatum isolated from Ananas comosus (pineapple) and cultivated in Czapek medium. From F. proliferatum extracts, nine secondary metabolites were isolated and characterized by nuclear magnetic resonance spectroscopy and mass spectrometry experiments: beauvericin (1), fusaric acid (2), N-ethyl-3-phenylacetamide (3), N-acetyltryptamine (4), cyclo(L-Val-L-Pro) cyclodipeptide (5), cyclo(L-Leu-L-Pro) cyclodipeptide (6), cyclo(L-Leu-L-Pro) diketopiperazine (7), 2,4-dihydroxypyrimidine (8), and 1H-indole-3-carbaldehyde (9). Compounds 1, 3, and 6 showed significant inhibition of papain, with IC50 values of 25.3 ± 1.9, 39.4 ± 2.5, and 7.4 ± 0.5 μM, respectively. Compound 1 also showed significant inhibition against human cathepsins V and B with IC50 of 46.0 ± 3.0 and 6.8 ± 0.7 μM, respectively. The inhibition of papain by mycotoxins (fusaric acid and beauvericin) may indicate a mechanism of Fusarium in the roles of infection process.

Ecological and biotechnological importance of secondary metabolites produced by coral-associated bacteria

Symbiotic relationships between corals and their associated micro-organisms are essential to maintain host homeostasis. Coral-associated bacteria (CAB) can have different beneficial roles in the coral metaorganism, such as metabolizing essential nutrients for the coral host and protecting the coral from pathogens. Many CAB exert these functions via secondary metabolites, which include antibacterial, antifouling, antitumour, antiparasitic and antiviral compounds. This review describes how analysis of CAB has led to the discovery of secondary metabolites with potential biotechnological applications. The most commonly found types of secondary metabolites, antimicrobial and antibiofilm compounds, are emphasized and described. Recently developed methods that can be applied to enhance the culturing of CAB from shallow-water reefs and the less-studied deep-sea coral reefs are also discussed. Last, we suggest how the combined use of meta-omics and innovative growth-diffusion techniques can vastly improve the discovery of novel compounds in coral environments.

Combining in silico and in vitro approaches to identification of potent inhibitor against phospholipase A2 (PLA2)

Phospholipase A2 (PLA2) is the main constituent of snake venom. PLA2 enzymes catalyze the Ca²⁺ dependent hydrolysis of 2-acyl ester bonds of 3-sn-phospholipids, releasing fatty acids and lysophospholipids. Inside the body of the victim, PLA2 from snake venom induces either direct or indirect pathophysiological effects, including anticoagulant, inflammatory, neurotoxic, cardiotoxic, edematogenic, and myotoxic activities. Therefore, there is a need to find the potential inhibitors against PLA2 responsible for snakebite. In this study, we employed in silico and in vitro methods to identify the potential inhibitor against PLA2. Virtual screening and molecular docking studies were performed to find potent inhibitor against PLA2 using Traditional Chinese Medicine Database (TCM). Based on these studies, Scutellarin (TCM3290) was selected and calculated by density functional theory calculation at B3LYP/6-31G**⁺⁺ level to explore the stereo-electronic features of the molecule. Further, molecular docking and DFT of Minocycline was carried out. Quantum polarized ligand docking was performed to optimize the geometry of the protein-ligand complexes. The protein-ligand complexes were subjected to molecular dynamics simulation and binding free energy calculations. The residence time of a protein-ligand complex is a critical parameter affecting natural influences in vitro. It is nonetheless a challenging errand to expect, regardless of the accessibility of incredible PC assets and a large variety of computing procedures. In this metadynamics situation, we used the conformational flooding technique to deal with rank inhibitors constructions. The systematic free energy perturbation (FEP) protocol and calculate the energy of both complexes. Finally, the selected compound of TCM3290 was studied in vitro analysis such as inhibition of PLA2 activity, hyaluronidase activity and fibrinogenolytic activity. The TCM3290 had a more binding affinity compare to Minocycline, and interacted with the key residues of TYR63 and GLY31. DFT represented the highest HOMO and LUMO energy of 0.15146 eV. MD simulation with 100 ns proved that an inhibitor binding mode is more stable inside the binding site of PLA2. In vitro analysis shows that TCM3290 significantly neutralized by PLA2. The above observations confirmed that Scutellarin (TCM3290) had a potent snake venom neutralizing capacity and could hypothetically be used for therapeutic drives of snakebite envenomation.