Cephalostatins and ritterazines: Distinctive dimeric marine-derived steroidal pyrazine alkaloids with intriguing anticancer activities.

Cephalostatins and ritterazines represent fascinating classes of dimeric marine derived steroidal alkaloids with unique chemical structures and promising biological activities. Originally isolated from marine tube worms and the tunicate Ritterella tokioka collected off the coast of Japan, cephalostatins and ritterazines display potent anticancer effects by inducing apoptosis, disrupting cell cycle progression, and targeting multiple molecular pathways. This review covers the chemistry and bioactivities of 45 cephalostatins and ritterazines from 1988 to 2024, highlighting their complex structures and medicinal contributions. With insights into their structure activity relationships (SAR). Key structural elements, such as the pyrazine ring and 5/6 spiroketal moieties, are found crucial for their biological effects, suggesting interactions with lipid membranes or hydrophobic protein domains. Additionally, the formation of oxocarbenium ions from spiroketal cleavage may enhance their potency by covalently modifying DNA. The pharmacokinetics, ADMET and Drug likeness properties of these steroidal alkaloids are thoroughly addressed. Drug likeness analysis shows that these compounds fit well with the Rule of 4 (Ro4) for Protein-Protein Interaction Drugs (PPIDs), underscoring their potential in this area. Ten compounds (20, 27, 33, 34, 39, 40, 41, 42, 43, and 45) have demonstrated favourable pharmacokinetic and ADMET profiles, making them promising candidates for further research. Future efforts should focus on alternative administration routes, structural modifications, and innovative delivery systems, such as prodrugs and nanoparticles, to improve bioavailability and therapeutic effects. Advances in synthetic chemistry, mechanistic insights, and interdisciplinary collaborations will be essential for translating cephalostatins and ritterazines into effective anticancer therapies.

Unlocking saponin biosynthesis in soapwort.

Soapwort (Saponaria officinalis) is a flowering plant from the Caryophyllaceae family with a long history of human use as a traditional source of soap. Its detergent properties are because of the production of polar compounds (saponins), of which the oleanane-based triterpenoid saponins, saponariosides A and B, are the major components. Soapwort saponins have anticancer properties and are also of interest as endosomal escape enhancers for targeted tumor therapies. Intriguingly, these saponins share common structural features with the vaccine adjuvant QS-21 and, thus, represent a potential alternative supply of saponin adjuvant precursors. Here, we sequence the S. officinalis genome and, through genome mining and combinatorial expression, identify 14 enzymes that complete the biosynthetic pathway to saponarioside B. These enzymes include a noncanonical cytosolic GH1 (glycoside hydrolase family 1) transglycosidase required for the addition of D-quinovose. Our results open avenues for accessing and engineering natural and new-to-nature pharmaceuticals, drug delivery agents and potential immunostimulants.

Complete biosynthesis of QS-21 in engineered yeast.

QS-21 is a potent vaccine adjuvant and remains the only saponin-based adjuvant that has been clinically approved for use in humans1,2. However, owing to the complex structure of QS-21, its availability is limited. Today, the supply depends on laborious extraction from the Chilean soapbark tree or on low-yielding total chemical synthesis3,4. Here we demonstrate the complete biosynthesis of QS-21 and its precursors, as well as structural derivatives, in engineered yeast strains. The successful biosynthesis in yeast requires fine-tuning of the host's native pathway fluxes, as well as the functional and balanced expression of 38 heterologous enzymes. The required biosynthetic pathway spans seven enzyme families-a terpene synthase, P450s, nucleotide sugar synthases, glycosyltransferases, a coenzyme A ligase, acyl transferases and polyketide synthases-from six organisms, and mimics in yeast the subcellular compartmentalization of plants from the endoplasmic reticulum membrane to the cytosol. Finally, by taking advantage of the promiscuity of certain pathway enzymes, we produced structural analogues of QS-21 using this biosynthetic platform. This microbial production scheme will allow for the future establishment of a structure-activity relationship, and will thus enable the rational design of potent vaccine adjuvants.

Synthesis and Molecular Docking of some new Thiazolidinone and Thiadiazole Derivatives as Anticancer Agents.

New sets of functionalized thiazolidinone and thiadiazole derivatives were synthesized, and their cytotoxicity was evaluated on HepG2, MCF-7, HTC-116, and WI38 cells. The synthetic approach is based on the preparation of 4-(4-acetamidophenyl)thiosemicarbazide (4) and their thiosemicarbazones 5 a-e, which are converted to the corresponding thiazoldin-4-one compounds 6 a-e upon cyclization with ethyl bromoacetate. The thiadiazole compounds 9 and 12 were obtained by reacting 4-(4-acetamidophenyl)thiosemicarbazide with isothiocyanates and/or ethyl 2-cyano-3,3-bis(methylthio)acrylate, respectively. The thiazolidinone compounds 6 c and 6 e exhibited strong cytotoxicity against breast cancer cells, with an IC50 (6.70±0.5 µM) and IC50 (7.51±0.8 µM), respectively, very close to that of doxorubicin (IC50: 4.17±0.2 µM). In addition, the anti-cancer properties of the tested thiazolidinone and thiadiazole scaffolds were further explored by the molecular docking program (MOE)-(PDB Code-1DLS). Compounds 5 d, 5 e, 6 d, 6 e, and 7 have the best binding affinity, ranging from -8.5386 kcal.mol-1 to -8.2830 kcal.mol-1.

Synthesis of Some Novel Thiophene Analogues as Potential Anticancer Agents.

The aim of this study involves the synthesis novel thiophene analogues that can be used as anticancer medications through a strategic multicomponent reaction connecting ethyl 4-chloroacetoacetate (1), phenyl isothiocyanate, and a series of active methylene reagents, including ethyl acetoacetate (2), malononitrile, ethyl cyanoacetate, cyanoacetamide 6a-c, N-phenyl cyanoacetamide derivatives 13a-c, and acetoacetanilide derivatives 18. This reaction was facilitated by dry dimethylformamide with a catalytic quantity of K2CO3. The resultant thiophene derivatives were identified as 4, 8a-b, 9, 12a-d, 15a-c, and 20a-b. Further reaction of compound 4 with hydrazine hydrate yielded derivative 5, respectively. When compound 1 was refluxed with ethyl 3-mercapto-3-(phenylamino)-2-(p-substituted phenyldiazenyl)acrylate 10a-e in the presence of sodium ethoxide, it produced thiophene derivatives 12a-d. Comprehensive structural elucidation of these newly synthesized thiophene-analogues was accomplished via elemental and spectral analysis data. Furthermore, the study delves into the cytotoxicity of the newly synthesized thiophenes was evaluated using the HepG2, A2780, and A2780CP cell lines. The amino-thiophene derivative 15b exhibited an increased growth inhibition of A2780, and A2780CP with IC50 values 12±0.17, and 10±0.15 µM, respectively compared to Sorafenib with IC50 values 7.5±0.54 and 9.4±0.14. This research opens new avenues for developing thiophene-based anticancer agents.

Complete biosynthesis of the potent vaccine adjuvant QS-21.

QS-21 is a potent vaccine adjuvant currently sourced by extraction from the Chilean soapbark tree. It is a key component of human vaccines for shingles, malaria, coronavirus disease 2019 and others under development. The structure of QS-21 consists of a glycosylated triterpene scaffold coupled to a complex glycosylated 18-carbon acyl chain that is critical for immunostimulant activity. We previously identified the early pathway steps needed to make the triterpene glycoside scaffold; however, the biosynthetic route to the acyl chain, which is needed for stimulation of T cell proliferation, was unknown. Here, we report the biogenic origin of the acyl chain, characterize the series of enzymes required for its synthesis and addition and reconstitute the entire 20-step pathway in tobacco, thereby demonstrating the production of QS-21 in a heterologous expression system. This advance opens up unprecedented opportunities for bioengineering of vaccine adjuvants, investigating structure-activity relationships and understanding the mechanisms by which these compounds promote the human immune response.

Discovery of isoflavone phytoalexins in wheat reveals an alternative route to isoflavonoid biosynthesis.

Isoflavones are a group of phenolic compounds mostly restricted to plants of the legume family, where they mediate important interactions with plant-associated microbes, including in defense from pathogens and in nodulation. Their well-studied health promoting attributes have made them a prime target for metabolic engineering, both for bioproduction of isoflavones as high-value molecules, and in biofortification of food crops. A key gene in their biosynthesis, isoflavone synthase, was identified in legumes over two decades ago, but little is known about formation of isoflavones outside of this family. Here we identify a specialized wheat-specific isoflavone synthase, TaCYP71F53, which catalyzes a different reaction from the leguminous isoflavone synthases, thus revealing an alternative path to isoflavonoid biosynthesis and providing a non-transgenic route for engineering isoflavone production in wheat. TaCYP71F53 forms part of a biosynthetic gene cluster that produces a naringenin-derived O-methylated isoflavone, 5-hydroxy-2',4',7-trimethoxyisoflavone, triticein. Pathogen-induced production and in vitro antimicrobial activity of triticein suggest a defense-related role for this molecule in wheat. Genomic and metabolic analyses of wheat ancestral grasses further show that the triticein gene cluster was introduced into domesticated emmer wheat through natural hybridization ~9000 years ago, and encodes a pathogen-responsive metabolic pathway that is conserved in modern bread wheat varieties.

Investigating the hepatoprotective potentiality of marine-derived steroids as promising inhibitors of liver fibrosis.

It has been reported that organic extracts derived from soft corals belonging to the genus Sarcophyton have exhibited a wide range of therapeutic characteristics. Based on biochemical and histological techniques, we aimed to assess the hepatoprotective role of the organic extract and its principal steroidal contents derived from the Red Sea soft coral Sarcophyton glaucum on acetaminophen-induced liver fibrosis in rats. Serum liver function parameters (ALT, AST, ALP and total bilirubin) were quantified using a spectrophotometer, and both alpha-fetoprotein (AFP) and carcinoembryonic antigen (CEA) levels were determined by using enzyme-linked immunosorbent assay (ELISA) kits while transformed growth factor beta (TGF-ß) and tumor necrosis factor α (TNF-α) in liver tissue homogenate were determined using ELISA, and TGF-ß and TNF-α gene expression in liver tissue was determined using real-time PCR following extraction and purification. Histopathological alterations in hepatic tissue were also examined under a microscope. In order to prioritize the isolation and characterization of the most promising marine steroids from the organic extract of the Red Sea soft coral Sarcophyton glaucum as hepatoprotective agents, a computational approach was employed. This approach involved molecular docking (MDock) and analysis of the structure-activity relationship (SAR) against glutathione-S-transferase (GST) and Cu-Zn human superoxide dismutase (Cu-ZnSOD) enzymes. Although the major role in the detoxification of foreign chemicals and toxic metabolites of GST and SOD enzymes is known, there is a lack of knowledge about the mode of action of the hepatoprotective process and those of the targets involved. The present study investigated the multiple interactions of a series of marine steroids with the GST and SOD enzymes, in order to reveal insights into the process of hepatoprotection.

Investigating the antiviral therapeutic potentialities of marine polycyclic lamellarin pyrrole alkaloids as promising inhibitors for SARS-CoV-2 and Zika main proteases (Mpro).

The new coronavirus variant (SARS-CoV-2) and Zika virus are two world-wide health pandemics. Along history, natural products-based drugs have always crucially recognized as a main source of valuable medications. Considering the SARS-CoV-2 and Zika main proteases (Mpro) as the re-production key element of the viral cycle and its main target, herein we report an intensive computer-aided virtual screening for a focused list of 39 marine lamellarins pyrrole alkaloids, against SARS-CoV-2 and Zika main proteases (Mpro) using a set of combined modern computational methodologies including molecular docking (MDock), molecule dynamic simulations (MDS) and structure-activity relationships (SARs) as well. Indeed, the molecular docking studies had revealed four promising marine alkaloids including [lamellarin H (14)/K (17)] and [lamellarin S (26)/Z (39)], according to their notable ligand-protein energy scores and relevant binding affinities with the SARS-CoV-2 and Zika (Mpro) pocket residues, respectively. Consequentially, these four chemical hits were further examined thermodynamically though investigating their MD simulations at 100 ns, where they showed prominent stability within the accommodated (Mpro) pockets. Moreover, in-deep SARs studies suggested the crucial roles of the rigid fused polycyclic ring system, particularly aromatic A- and F- rings, position of the phenolic -OH and δ-lactone functionalities as essential structural and pharmacophoric features. Finally, these four promising lamellarins alkaloids were investigated for their in-silico ADME using the SWISS ADME platform, where they displayed appropriated drug-likeness properties. Such motivating outcomes are greatly recommending further in vitro/vivo examinations regarding those lamellarins pyrrole alkaloids (LPAs).Communicated by Ramaswamy H. Sarma.

Elucidation of the pathway for biosynthesis of saponin adjuvants from the soapbark tree.

The Chilean soapbark tree (Quillaja saponaria) produces soap-like molecules called QS saponins that are important vaccine adjuvants. These highly valuable compounds are sourced by extraction from the bark, and their biosynthetic pathway is unknown. Here, we sequenced the Q. saponaria genome. Through genome mining and combinatorial expression in tobacco, we identified 16 pathway enzymes that together enable the production of advanced QS pathway intermediates that represent a bridgehead for adjuvant bioengineering. We further identified the enzymes needed to make QS-7, a saponin with excellent therapeutic properties and low toxicity that is present in low abundance in Q. saponaria bark extract. Our results enable the production of Q. saponaria vaccine adjuvants in tobacco and open the way for new routes to access and engineer natural and new-to-nature immunostimulants.

Recent advances in the discovery, biosynthesis, and therapeutic potential of isocoumarins derived from fungi: a comprehensive update.

Microorganisms still remain the main hotspots in the global drug discovery avenue. In particular, fungi are highly prolific producers of vast structurally diverse specialized secondary metabolites, which have displayed a myriad of biomedical potentials. Intriguingly, isocoumarins is one distinctive class of fungal natural products polyketides, which demonstrated numerous remarkable biological and pharmacological activities. This review article provides a comprehensive state-of-the-art over the period 2000-2022 about the discovery, isolation, classifications, and therapeutic potentials of isocoumarins exclusively reported from fungi. Indeed, a comprehensive list of 351 structurally diverse isocoumarins were documented and classified according to their fungal sources [16 order/28 family/55 genera] where they have been originally discovered along with their reported pharmacological activities wherever applicable. Also, recent insights around their proposed and experimentally proven biosynthetic pathways are also briefly discussed.

Chemical diversity, medicinal potentialities, biosynthesis, and pharmacokinetics of anthraquinones and their congeners derived from marine fungi: a comprehensive update.

Marine fungi receive excessive attention as prolific producers of structurally unique secondary metabolites, offering promising potential as substitutes or conjugates for current therapeutics, whereas existing research has only scratched the surface in terms of secondary metabolite diversity and potential industrial applications as only a small share of bioactive natural products have been identified from marine-derived fungi thus far. Anthraquinones derived from filamentous fungi are a distinct large group of polyketides containing compounds which feature a common 9,10-dioxoanthracene core, while their derivatives are generated through enzymatic reactions such as methylation, oxidation, or dimerization to produce a large variety of anthraquinone derivatives. A considerable number of reported anthraquinones and their derivatives have shown significant biological activities as well as highly economical, commercial, and biomedical potentialities such as anticancer, antimicrobial, antioxidant, and anti-inflammatory activities. Accordingly, and in this context, this review comprehensively covers the state-of-art over 20 years of about 208 structurally diverse anthraquinones and their derivatives isolated from different species of marine-derived fungal genera along with their reported bioactivity wherever applicable. Also, in this manuscript, we will present in brief recent insights centred on their experimentally proved biosynthetic routes. Moreover, all reported compounds were extensively investigated for their in-silico drug-likeness and pharmacokinetics properties which intriguingly highlighted a list of 20 anthraquinone-containing compounds that could be considered as potential drug lead scaffolds.

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 (Mpro) 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 (Mpro) 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 (Mpro) 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 (Mpro) 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.

Cytotoxic constituents from the wheat plant pathogen Parastagonospora nodorum SN15.

Microbial natural products are continuing to be a promising platform for future drug lead discover. As a part of our ongoing research program on fungal natural product, herein we report metabolites isolated from the fungus Parastagonospora nodorum SN15 a pathogen of wheat and related cereals. Its chemical investigation led to the purification of new isoleucinic acid derivatives (1-2) along with the cis procuramine (4). Their structures were determined based on extensive NMR and the relative configuration by comparison of experimental and predicted NMR chemical shifts. All compounds were evaluated for their cytotoxic activity against a panel of human cell lines and some displayed specific feature towards cancer cells compared to normal immortalised fibroblasts.[Formula: see text].

Marine Brominated Tyrosine Alkaloids as Promising Inhibitors of SARS-CoV-2.

There have been more than 150 million confirmed cases of SARS-CoV-2 since the beginning of the pandemic in 2019. By June 2021, the mortality from such infections approached 3.9 million people. Despite the availability of a number of vaccines which provide protection against this virus, the evolution of new viral variants, inconsistent availability of the vaccine around the world, and vaccine hesitancy, in some countries, makes it unreasonable to rely on mass vaccination alone to combat this pandemic. Consequently, much effort is directed to identifying potential antiviral treatments. Marine brominated tyrosine alkaloids are recognized to have antiviral potential. We test here the antiviral capacity of fourteen marine brominated tyrosine alkaloids against five different target proteins from SARS-CoV-2, including main protease (Mpro) (PDB ID: 6lu7), spike glycoprotein (PDB ID: 6VYB), nucleocapsid phosphoprotein (PDB ID: 6VYO), membrane glycoprotein (PDB ID: 6M17), and non-structural protein 10 (nsp10) (PDB ID: 6W4H). These marine alkaloids, particularly the hexabrominated compound, fistularin-3, shows promising docking interactions with predicted binding affinities (S-score = -7.78, -7.65, -6.39, -6.28, -8.84 Kcal/mol) for the main protease (Mpro) (PDB ID: 6lu7), spike glycoprotein (PDB ID: 6VYB), nucleocapsid phosphoprotein (PDB ID: 6VYO), membrane glycoprotein (PDB ID: 6M17), and non-structural protein 10 (nsp10) (PDB ID: 6W4H), respectively, where it forms better interactions with the protein pockets than the native interaction. It also shows promising molecular dynamics, pharmacokinetics, and toxicity profiles. As such, further exploration of the antiviral properties of fistularin-3 against SARS-CoV-2 is merited.

A unique view of SARS-CoV-2 through the lens of ORF8 protein.

Immune evasion is one of the unique characteristics of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) attributed to its ORF8 protein. This protein modulates the adaptive host immunity through down-regulation of MHC-1 (Major Histocompatibility Complex) molecules and innate immune responses by surpassing the host's interferon-mediated antiviral response. To understand the host's immune perspective in reference to the ORF8 protein, a comprehensive study of the ORF8 protein and mutations possessed by it have been performed. Chemical and structural properties of ORF8 proteins from different hosts, such as human, bat, and pangolin, suggest that the ORF8 of SARS-CoV-2 is much closer to ORF8 of Bat RaTG13-CoV than to that of Pangolin-CoV. Eighty-seven mutations across unique variants of ORF8 in SARS-CoV-2 can be grouped into four classes based on their predicted effects (Hussain et al., 2021) [1]. Based on the geo-locations and timescale of sample collection, a possible flow of mutations was built. Furthermore, conclusive flows of amalgamation of mutations were found upon sequence similarity analyses and consideration of the amino acid conservation phylogenies. Therefore, this study seeks to highlight the uniqueness of the rapidly evolving SARS-CoV-2 through the ORF8.

Comprehensive Virtual Screening of the Antiviral Potentialities of Marine Polycyclic Guanidine Alkaloids against SARS-CoV-2 (COVID-19).

The huge global expansion of the COVID-19 pandemic caused by the novel SARS-corona virus-2 is an extraordinary public health emergency. The unavailability of specific treatment against SARS-CoV-2 infection necessitates the focus of all scientists in this direction. The reported antiviral activities of guanidine alkaloids encouraged us to run a comprehensive in silico binding affinity of fifteen guanidine alkaloids against five different proteins of SARS-CoV-2, which we investigated. The investigated proteins are COVID-19 main protease (Mpro) (PDB ID: 6lu7), spike glycoprotein (PDB ID: 6VYB), nucleocapsid phosphoprotein (PDB ID: 6VYO), membrane glycoprotein (PDB ID: 6M17), and a non-structural protein (nsp10) (PDB ID: 6W4H). The binding energies for all tested compounds indicated promising binding affinities. A noticeable superiority for the pentacyclic alkaloids particularly, crambescidin 786 (5) and crambescidin 826 (13) has been observed. Compound 5 exhibited very good binding affinities against Mpro (ΔG = -8.05 kcal/mol), nucleocapsid phosphoprotein (ΔG = -6.49 kcal/mol), and nsp10 (ΔG = -9.06 kcal/mol). Compound 13 showed promising binding affinities against Mpro (ΔG = -7.99 kcal/mol), spike glycoproteins (ΔG = -6.95 kcal/mol), and nucleocapsid phosphoprotein (ΔG = -8.01 kcal/mol). Such promising activities might be attributed to the long ω-fatty acid chain, which may play a vital role in binding within the active sites. The correlation of c Log P with free binding energies has been calculated. Furthermore, the SAR of the active compounds has been clarified. The Absorption, Distribution, Metabolism, Excretion, and Toxicity (ADMET) studies were carried out in silico for the 15 compounds; most examined compounds showed optimal to good range levels of ADMET aqueous solubility, intestinal absorption and being unable to pass blood brain barrier (BBB), non-inhibitors of CYP2D6, non-hepatotoxic, and bind plasma protein with a percentage less than 90%. The toxicity of the tested compounds was screened in silico against five models (FDA rodent carcinogenicity, carcinogenic potency TD50, rat maximum tolerated dose, rat oral LD50, and rat chronic lowest observed adverse effect level (LOAEL)). All compounds showed expected low toxicity against the tested models. Molecular dynamic (MD) simulations were also carried out to confirm the stable binding interactions of the most promising compounds, 5 and 13, with their targets. In conclusion, the examined 15 alkaloids specially 5 and 13 showed promising docking, ADMET, toxicity and MD results which open the door for further investigations for them against SARS-CoV-2.

Bioactive Bromotyrosine Derivatives from the Pacific Marine Sponge Suberea clavata (Pulitzer-Finali, 1982).

Chemical investigation of the South-Pacific marine sponge Suberea clavata led to the isolation of eight new bromotyrosine metabolites named subereins 1-8 (2-9) along with twelve known co-isolated congeners. The detailed configuration determination of the first representative major compound of this family 11-epi-fistularin-3 (11R,17S) (1) is described. Their chemical characterization was achieved by HRMS and integrated 1D and 2D NMR (nuclear magnetic resonance) spectroscopic studies and extensive comparison with literature data. For the first time, a complete assignment of the absolute configurations for stereogenic centers C-11/17 of the known members (11R,17S) 11-epi-fistularin-3 (1) and 17-deoxyfistularin-3 (10) was determined by a combination of chemical modifications, Mosher's technology, and ECD spectroscopy. Consequently, the absolute configurations of all our new isolated compounds 2-9 were determined by the combination of NMR, Mosher's method, ECD comparison, and chemical modifications. Interestingly, compounds 2-7 were obtained by chemical transformation of the major compound 11-epi-fistularin-3 (1). Evaluation for acetylcholinesterase inhibition (AChE), DNA methyltransferase 1 (DNMT1) modulating activity and antifouling activities using marine bacterial strains are also presented.

Investigating the structure-activity relationship of marine natural polyketides as promising SARS-CoV-2 main protease inhibitors.

Since its first report in December 2019, the novel coronavirus virus, SARS-CoV-2, has caused an unprecedented global health crisis and economic loss imposing a tremendous burden on the worldwide finance, healthcare system, and even daily life. Even with the introduction of different preventive vaccines, there is still a dire need for effective antiviral therapeutics. Nature has been considered as the historical trove of drug discovery and development, particularly in cases of worldwide crises. Herein, a comprehensive in silico investigation of a highly focused chemical library of 34 pederin-structurally related marine compounds, belonging to four polyketides families, was initiated against the SARS-CoV-2 main protease, Mpro, being the key replicating element of the virus and main target in many drugs development programs. Two of the most potent SARS-CoV-2 Mpro co-crystallized inhibitors, O6K and N3, were added to the tested database as reference standards. Through molecular docking simulation, promising compounds including Pederin (1), Dihydro-onnamide A (11), Onnamide C (14), Pseudo-onnamide A (17), and Theopederin G (29) have been identified from different families based on their superior ligand-protein energies and relevant binding profiles with the key Mpro pocket residues. Thermodynamic behaviors of the identified compounds were investigated through 200 ns all-atom molecular dynamics simulation illustrating their significant stability and pocket accommodation. Furthermore, structural activity preferentiality was identified for the pederin-based marine compounds highlighting the importance of the terminal guanidine and cyclic hemiacetal linker, and the length of the sidechain. Our findings highlight the challenges of targeting SARS-CoV-2 Mpro as well as recommending further in vitro and in vivo studies regarding the examined marine products either alone or in combination paving the way for promising lead molecules.

Chemical Diversity and Biological Activities of Meroterpenoids from Marine Derived-Fungi: A Comprehensive Update.

Meroterpenoids are a class of hybrid natural products, partially derived from a mixed terpenoid pathway. They possess remarkable structural features and relevant biological and pharmacological activities. Marine-derived fungi are a rich source of meroterpenoids featuring structural diversity varying from simple to complex molecular architectures. A combination of a structural variability and their myriad of bioactivities makes meroterpenoids an interesting class of naturally occurring compounds for chemical and pharmacological investigation. In this review, a comprehensive literature survey covering the period of 2009-2019, with 86 references, is presented focusing on chemistry and biological activities of various classes of meroterpenoids isolated from fungi obtained from different marine hosts and environments.