Therapeutic potential of marine macrolides: An overview from 1990 to 2022

Isolation and Characterization of the Cyanobacterial Macrolide Glycoside Moorenaside, an Anti-Inflammatory Analogue of Aurisides Targeting the Keap1/Nrf2 Pathway

A new 14-membered ring brominated macrolide glycoside, named moorenaside (1), was discovered from a marine cyanobacterial sample collected from Shands Key in Florida. The structure of 1 was established by analysis of spectroscopic data including its relative configuration. The absolute configuration was inferred from optical rotation data and comparison with related compounds. The structure of 1 features an α,β-unsaturated carbonyl system, which is also found in aurisides. The presence of this motif in 1 prompted us to evaluate its effect on Keap1/Nrf2 signaling, a cytoprotective pathway culminating in the activation of antioxidant genes activated upstream by the cysteine alkylation of Keap1. Moorenaside exhibited moderate ARE luciferase activity at 32 μM. Due to the established crosstalk between Nrf2 and NF-κB pathways, we investigated the anti-inflammatory effects of 1 in LPS-induced mouse macrophages (RAW264.7 cells), a commonly used model for inflammation. Moorenaside significantly upregulated Nqo1 (Nrf2 target gene) and downregulated iNos (NF-κB target gene) at 32 μM by 5.0- and 2.5-fold, respectively, resulting in a significant reduction of nitric oxide (NO) levels. Furthermore, we performed RNA-sequencing and demonstrated the transcriptional activity of 1 on a global level and identified canonical pathways and upstream regulators involved in inflammation, immune response, and certain oxidative-stress-underlying diseases such as multiple sclerosis and chronic kidney disease.

Chimeric antigen carried by extracellular vesicles induces stronger protective immunity against Mycobacterium tuberculosis infection

Although Bacillus Calmette-Guerin (BCG) has been used in human for centuries, tuberculosis (TB) remains one of the deadliest infectious diseases.There have been remarkable successes in the field of TB vaccine research over the past decade, but the search for a better vaccine candidate is still a challenge. Extracellular vesicles (EVs) possess a multitude of properties that make them attractive candidates for the development of novel, cell-free, non-replicative, and safe vaccine system. These properties include their small size, inherent immunogenicity, ability to be taken up by immune cells, self-adjuvant capability and the comprehensive distribution of concentrated antigens. In this study, we designed a newly chimeric antigen TB vaccine (CA) with three Mycobacterium tuberculosis (M. tb) antigens that identified from extracellular vesicle derived from M. tb-infected macrophage. We confirmed that the CA stimulated a more pronounced immune response and enhanced T-cell activation, thereby providing superior protection against Mycobacterium tuberculosis infection in comparison to the bivalent antigens. Importantly, the EVs carrying CA (EVs-CA) provided enhanced protection against M. tb infection compared to unencapsulated CA antigen. Moreover, we established an EV-carried CA system (EVs-CA) and released from a transformed cell line using endogenous loading of antigen method. This method displayed the CA could efficiently package into EVs and increased concentration of this antigen. The chimeric antigen carried by EVs induced higher levels of cytokines production and specific cytotoxic T lymphocytes, resulted in enhancing antibody response and improving protective efficacy. Our findings suggested that the potential of EVs as delivery system to carry the M. tb-specific chimeric antigen for controlling Mycobacterium tuberculosis infection.

Marine-Derived Cytosine Arabinoside (Ara-C) Inhibits Biofilm Formation by Inhibiting PEL Operon Proteins (Pel A and Pel B) of Pseudomonas aeruginosa: An In Silico Approach

Pseudomonas aeruginosa (P. aeruginosa) is a gram-negative biofilm-forming opportunistic human pathogen whose vital mechanism is biofilm formation for better survival. PelA and PelB proteins of the PEL operon are essential for bacterial-synthesized pellicle polysaccharide (PEL), which is a vital structural component of the biofilm. It helps in adherence of biofilm on the surface and maintenance of cell-to-cell interactions and with other matrix components. Here, in-silico molecular docking and simulation studies were performed against PelA and PelB using ten natural bioactive compounds, individually [podocarpic acids, ferruginol, scopadulcic acid B, pisiferic acid, metachromin A, Cytarabine (cytosine arabinoside; Ara-C), ursolic acid, oleanolic acid, maslinic acid, and betulinic acid], those have already been established as anti-infectious compounds. The results obtained from AutoDock and Glide-Schordinger stated that a marine-derived cytosine arabinoside (Ara-C) among the ten compounds binds active sites of PelA and PelB, exhibiting strong binding affinity [Trp224 (hydrogen), Ser219 (polar), Val234 (hydrophobic) for PelA; Leu365 and Glu389 (hydrogen), Gln366 (polar) for PelB] with high negative binding energy - 5.518 kcal/mol and - 6.056 kcal/mol, respectively. The molecular dynamic and simulation studies for 100 ns showed the MMGBSA binding energy scores are - 16.4 kcal/mol (Ara-C with PelA), and - 22.25 kcal/mol (Ara-C with PelB). Further, ADME/T studies indicate the IC50 values of AraC are 6.10 mM for PelA and 18.78 mM for PelB, which is a comparatively very low dose. The zero violation of Lipinski's Rule of Five further established that Ara-C is a good candidate for drug development. Thus, Ara-C could be considered a potent anti-biofilm compound against PEL operon-dependent biofilm formation of P. aeruginosa.

Irpetones A and B, Anti-Osteoclastic Heptaketides from a Marine Mesophotic Zone Ircinia Sponge-Associated Fungus Irpex sp. NBUF088

Chemical investigation of Irpex sp. NBUF088, associated with an Ircinia sp. sponge located at an 84 m deep mesophotic zone, led to the discovery of two new heptaketides, named irpetones A (1) and B (2). Their structures were identified by analysis of spectroscopic data and quantum-chemical calculations. Compound 1 exhibited inhibition against the receptor activator of NF-κB ligand-induced osteoclastogenesis in bone marrow monocytes with an IC50 of 6.3 ± 0.2 μM, causing no notable cytotoxicity. It was also determined that 1 inhibited the phosphorylation of ERK1/2-JNK1/2-p38 MAPKs and the nuclear translocation of NF-κB, consequently suppressing the activation of MAPK and NF-κB signaling pathways induced by the NF-κB ligand.

Synthesis of the C13-C27 Fragment of Madeirolide A Using Visible-Light-Promoted Radical Cyclization

The convergent synthesis of a fully elaborated C13-C27 fragment of madeirolide A has been achieved. The key features of the synthesis include the stereocontrolled construction of both the THF and THP rings via visible-light-induced iridium-catalyzed radical cyclization and the late-stage union of the two oxacyclic subunits through nickel-catalyzed decarboxylative cross-coupling.

Natural Products and Pharmacological Properties of Symbiotic Bacillota (Firmicutes) of Marine Macroalgae

The shift from the terrestrial to the marine environment to discover natural products has given rise to novel bioactive compounds, some of which have been approved for human medicine. However, the ocean, which makes up nearly three-quarters of the Earth's surface, contains macro- and microorganisms whose natural products are yet to be explored. Among these underexplored marine organisms are macroalgae and their symbiotic microbes, such as Bacillota, a phylum of mostly Gram-positive bacteria previously known as Firmicutes. Macroalgae-associated Bacillota often produce chemical compounds that protect them and their hosts from competitive and harmful rivals. Here, we summarised the natural products made by macroalgae-associated Bacillota and their pharmacological properties. We discovered that these Bacillota are efficient producers of novel biologically active molecules. However, only a few macroalgae had been investigated for chemical constituents of their Bacillota: nine brown, five red and one green algae. Thus, Bacillota, especially from the marine habitat, should be investigated for potential pharmaceutical leads. Moreover, additional diverse biological assays for the isolated molecules of macroalgae Bacillota should be implemented to expand their bioactivity profiles, as only antibacterial properties were tested for most compounds.

Chemico-pharmacological and computational studies of Ophiorrhiza fasciculata D. Don and Psychotria silhetensis Hook. f. focusing cytotoxic, thrombolytic, anti-inflammatory, antioxidant, and antibacterial properties

The current study sought to examine the pharmacological potentials of crude methanolic extracts of Ophiorrhiza fasciculata and Psychotria silhetensis, as well as their various solvent fractionates, with a focus on cytotoxic, thrombolytic, membrane stabilizing, antioxidant, and antibacterial activities via in vitro and in silico approaches. The extensive chromatographic and spectroscopic analyses confirmed and characterized two compounds as (±)-licarin B (1) and stigmasterol (2) from O. fasciculata and P. silhetensis, respectively. Petroleum ether soluble fraction of O. fasciculata and the aqueous soluble fraction of P. silhetensis showed the lowest 50% lethal concentrations (1.41 and 1.94 μg/mL, respectively) in brine shrimp bioassay. Likewise, petroleum ether soluble fraction of O. fasciculata and aqueous soluble fraction of P. silhetensis showed the highest thrombolytic activity with 46.66% and 50.10% lyses of the clot, respectively. The methanol and dichloromethane soluble fractions of O. fasciculata reduced erythrocyte hemolysis by 64.03% and 37.08%, respectively, under hypotonic and heat-induced conditions, compared to 81.97% and 42.12% for standard acetylsalicylic acid. In antioxidant activity test, aqueous soluble fraction O. fasciculata (IC50 = 7.22 μg/mL) revealed promising antioxidant potentialities in comparison to standard butylated hydroxytoluene (IC50 = 21.20 μg/mL). In antibacterial screening, chloroform, and dichloromethane soluble fractions of P. silhetensis showed a mild antibacterial activity compared with the standard drug ciprofloxacin. Additionally, the molecular docking study corroborated the current in vitro findings, and the isolated two constituents had higher binding affinities toward epidermal growth factor receptor, tissue plasminogen activator, vFLIP-IKK gamma stapled peptide dimer, glutathione reductase, and dihydrofolate reductase enzyme than their corresponding standard drugs. In addition, the both isolated compounds exerted favorable pharmacokinetics (absorption, distribution, metabolism, excretion) and toxicological profiles with drug-like qualities in computational-based ADMET and drug likeliness analyses. The current research suggests that both plants have potential as a natural treatment for treating thrombosis, inflammation, and oxidative stress. However, more thorough research is required to thoroughly screen for phytochemicals and pinpoint the precise mechanisms of action of the bioactive metabolites derived from these plants against a broad range of molecular targets.

Determination of metronidazole and clarithromycin in plasma samples using surfactant-modified amorphous carbon-based DSPE combined with DLLME followed by HPLC

This work offers preparation of surfactant-modified amorphous carbon and its application in dispersive solid phase extraction of metronidazole and clarithromycin from plasma samples. The extraction procedure was combined with dispersive liquid-liquid microextraction for further preconcentration of the analytes for sensitive determination of the analytes followed by high performance liquid chromatography-diode array detector. In this work, first, the sorbent was added to the sample and the mixture vortexed to adsorb the analytes. Then, the obtained supernatant after centrifuging is discarded and the loaded analytes onto the sorbent surface were eluted with a water-miscible organic solvent. In the following, to further enrichment of the analytes the microextraction step was done. For this purpose, the eluate is taken, mixed with a water-immiscible organic solvent, and injected into deionized water. After centrifuging, an aliquat of the sedimented phase is taken and injected into the analytical instrument for the quantitative analysis. Under the optimum extraction conditions, high extraction recoveries (79 and 89% for metronidazole and clarithromycin, respectively), low limits of detection (2.1 and 1.9 ng mL^-1 for metronidazole and clarithromycin, respectively) and quantification (7.0 and 6.3 ng mL^-1 for metronidazole and clarithromycin, respectively), good repeatability (relative standard deviations less than 4.3% for intra- and 6.3% inter-day precisions), and wide linear ranges (7.3-1000 and 6.3-1000 ng mL^-1 for metronidazole and clarithromycin, respectively) were obtained. At the end, the introduced method was applied on the plasma samples of the patients treated with metronidazole and clarithromycin successfully.

Phytochemical and pharmacological profiling of Trewia nudiflora Linn. leaf extract deciphers therapeutic potentials against thrombosis, arthritis, helminths, and insects

The objective of the current study was to examine the phytochemical and in vitro thrombolytic, anti-arthritic, anthelmintic, and insecticidal effects of Trewia nudiflora (TN) methanolic leaf extract with its methanol (MTN), chloroform (CTN), and ethyl acetate (ETN) fractions. Pheretima posthuma and Tribolium castaneum were employed for evaluating the antihelmintic and insecticidal properties, respectively. All the tested extracts showed the presence of copious potential constituents in phytochemical analysis. Among all extracts, MTN extract exhibited the utmost clot lysis (35.95 ± 4.81%) property compared to standard streptokinase (SK) (53.77 ± 7.52%). All samples displayed striking protein denaturation activity in a dose-dependent manner (100–500 µg/mL), where the highest inhibition was observed for MTN (67.26 ± 6.39% at 500 µg/mL). Each extract demonstrated considerable anthelmintic activity at 25–75 mg/mL dose ranges. ETN showed the strongest anthelmintic activity at the highest dose. Among all samples, the CTN extract displayed the utmost mortality rate (77.22%) in the insecticidal test. The results of the study suggest that T. nudiflora leaf extracts may have potential against thrombosis, arthritis, helminths, and insects, which warrants the necessity of extensive isolation and identification of bioactive compounds to develop newer effective drugs upon preclinical and clinical investigations.

Marine Macrolides to Tackle Antimicrobial Resistance of Mycobacterium tuberculosis

Tuberculosis has become a major health problem globally. This is worsened by the emergence of resistant strains of Mycobacterium tuberculosis showing ability to evade the effectiveness of the current antimycobacterial therapies. Therefore, the efforts carried out to explore new entities from many sources, including marine, are critical. This review summarizes several marine-derived macrolides that show promising activity against M. tuberculosis. We also provide information regarding the biosynthetic processes of marine macrolides, including the challenges that are usually experienced in this process. As most of the studies reporting the antimycobacterial activities of the listed marine macrolides are based on in vitro studies, the future direction should consider expanding the trials to in vivo and clinical trials. In addition, in silico studies should also be explored for a quick screening on marine macrolides with potent activities against mycobacterial infection. To sum up, macrolides derived from marine organisms might become therapeutical options for tackling antimycobacterial resistance of M. tuberculosis.

Phenolic Constituents from Wendlandia tinctoria var. grandis (Roxb.) DC. Stem Deciphering Pharmacological Potentials against Oxidation, Hyperglycemia, and Diarrhea: Phyto-Pharmacological and Computational Approaches

Wendlandia tinctoria var. grandis (Roxb.) DC. (Family: Rubiaceae) is a semi-evergreen shrub distributed over tropical and subtropical Asia. The present research intended to explore the pharmacological potential of the stem extract of W. tinctoria, focusing on the antioxidant, hypoglycemic, and antidiarrheal properties, and to isolate various secondary metabolites as mediators of such activities. A total of eight phenolic compounds were isolated from the dichloromethane soluble fraction of the stem extract of this plant, which were characterized by electrospray ionization (ESI) mass spectrometric and 1H NMR spectroscopic data as liquiritigenin (1), naringenin (2), apigenin (3), kaempferol (4), glabridin (5), ferulic acid (6), 4-hydroxybenzoic acid (7), and 4-hydroxybenzaldehyde (8). The dichloromethane soluble fraction exhibited the highest phenolic content (289.87 ± 0.47 mg of GAE/g of dried extract) and the highest scavenging activity (IC50 = 18.83 ± 0.07 µg/mL) against the DPPH free radical. All of the isolated compounds, except 4-hydroxybenzaldehyde, exerted a higher antioxidant effect (IC50 = 6.20 ± 0.10 to 16.11 ± 0.02 μg/mL) than the standard butylated hydroxytoluene (BHT) (IC50 = 17.09 ± 0.01 μg/mL). Significant hypoglycemic and antidiarrheal activities of the methanolic crude extract at both doses (200 mg/kg bw and 400 mg/kg bw) were observed in a time-dependent manner. Furthermore, the computational modeling study supported the current in vitro and in vivo findings, and the isolated constituents had a higher or comparable binding affinity for glutathione reductase and urase oxidase enzymes, glucose transporter 3 (GLUT 3), and kappa-opioid receptor, inferring potential antioxidant, hypoglycemic, and antidiarrheal properties, respectively. This is the first report of all of these phenolic compounds being isolated from this plant species and even the first demonstration of the plant stem extract's antioxidant, hypoglycemic, and antidiarrheal potentials. According to the current findings, the W. tinctoria stem could be a potential natural remedy for treating oxidative stress, hyperglycemia, and diarrhea. Nevertheless, further extensive investigation is crucial for thorough phytochemical screening and determining the precise mechanisms of action of the plant-derived bioactive metabolites against broad-spectrum molecular targets.