Marine natural products

Antimicrobial, antibiofilm, cytotoxicity, and anti-DNA topoisomerase activity of Streptomyces sp. 22SH with ADME and in silico study

The genus Streptomyces has been recently proven to be a valuable and rich source of producing several bioactive compounds with substantial biological activity and applications in many fields such as medicine, environmental science, food industries, and agronomy. This study highlights the importance of Streptomyces as an antimicrobial, antibiofilm, and anticancer. Out of the 75 actinobacteria isolated from both marine and soil habitats, one isolate, HG2, was selected based on its potent antimicrobial activity. The isolate has been identified morphologically by studying colony and spore chain morphology using TEM and genetically by sequencing their 16 sr RNA gene as Streptomyces sp. 22SH with Accession number OK326829.1. Bioassay-guided fractionation of the Streptomyces sp. 22SH crude extract led to the isolation and purification of Cis-9-Octadecenoic. Biological evaluation including antimicrobial and antibiofilm activity of the crude and purified compound was performed on four clinical microbes (S. aureus ATCC6538-P, B. subtilis ATCC6633, and P. aeruginosa ATCC27853). The compound showed the ability to eradicate the biofilm formation by the tested pathogens. Additionally, the antitumor activity was assessed, and the compound showed a cytotoxic effect against liver carcinoma and breast cancer cells, with IC50 values of 17.48 ± 0.94 and 88.73 ± 4.78 µg/ml, respectively. While it displayed anti-topoisomerase activity with an IC50 of 0.65 ± 0.023 µg/ml. Furthermore, the compound's ADME-related physicochemical features and docking analysis were investigated.

Harnessing marine resources for Alzheimer's therapy: A review integrating bioactivity and molecular docking

Alzheimer's disease (AD) is a neurodegenerative condition resulting in cognitive impairment and the formation of neurofibrillary tangles and plaques in the brain. The drivers of AD's molecular progression and pathology include the accumulation of amyloid β protein (Aβ); thus, Aβ is an intervention target. However, the limitations in clinical trials of Aβ-targeted medicine and the failure to intervene in disease progression have raised concerns about the use of this drug and its veracious route. In particular, we comprehensively reviewed the potential effect of marine compounds and the mechanism of isolation and extraction from marine organisms resulting in the optimization of AD treatment. Furthermore, the hub compounds were docked with Beta-secretase receptors to strengthen the extrapolation of mechanistic interactions thus inhibiting the activity of an enzyme. An extensive review revealed that marine aquaculture and its byproducts are a promising source and isolated with green methods or less investment, ensuring their sustainability. MNPs harbor specific pharmacological features that enable them to exert neuroprotective effects by minimizing events such as Aβ peptide formation and reactive oxygen species (ROS) generation.

Identification of novel cyclin-dependent kinase 4/6 inhibitors from marine natural products

Cyclin-dependent kinases 4 and 6 (CDK4/6) are crucial regulators of cell cycle progression and represent important therapeutic targets in breast cancer. This study employs a comprehensive computational approach to identify novel CDK4/6 inhibitors from marine natural products. We utilized structure-based virtual screening of the CMNPD database and MNP library, followed by rigorous filtering based on drug-likeness criteria, PAINS filter, ADME properties, and toxicity profiles. From an initial hit of 9,497 compounds, 2,344 passed drug-likeness and PAINS filters. Further ADME filtering yielded 50 compounds, of which 25 exhibited non-toxic profiles. These 25 candidates underwent consensus molecular docking using seven distinct algorithms: AutoDockTools 4.2, idock, LeDock, Qvina 2, Smina, AutoDock Vina 1.2.0, PLANTS, and rDock. Based on these results, six top-scoring compounds were selected for comprehensive 500 nanosecond all-atom molecular dynamics simulations to evaluate their structural stability and interactions with CDK4/6. Our analysis revealed that compounds CMNPD11585 and CMNPD2744 demonstrated superior stability in their interactions with CDK4/6, exhibiting lower RMSD and RMSF values, more favorable binding free energies, and persistent hydrogen bonding patterns. These compounds also showed lower Solvent Accessible Surface Area values, indicating better compatibility with the CDK4/6 active site. Subsequent in-vitro studies using MTT assays on MCF-7 breast cancer cells confirmed the cytotoxic effects of these compounds, with CMNPD11585 showing the highest potency, followed by CMNPD2744.

Halobacteria Formula Improvement of Skin Care-A Randomized, Double-Blind, Placebo-Controlled Clinical Study

BACKGROUND

Halobacteria trueperi, an extremophilic microorganism thriving in high-salt environments, produces extracellular polysaccharides with potential anti-inflammatory and anti-aging properties. However, its clinical efficacy in skin improvement remains unclear. This study focuses on H. trueperi TCI66207, isolated from the Pacific Ocean at a depth of 662 m near Hualien, and its potential to enhance skin parameters, aiming to develop a novel functional formulation for pharmaceutical and cosmetic use.

AIMS

This sudy aims to evaluate the clinical efficacy of H. trueperi TCI66207 on various skin parameters and its potential for developing new functional cosmetic formulations.

PATIENTS/METHODS

A total of 40 subjects were recruited and randomly divided into two groups: the test group applied a serum containing H. trueperi TCI66207, while the placebo group used a basic serum. Subjects were instructed to apply the serum twice daily for 4 weeks. Skin parameters, including moisture, brightness, elasticity, pigmentation (spots and UV spots), texture, wrinkles, pores, and collagen density, were assessed before and after the 4-week application period.

RESULTS

After 4 weeks of using the H. trueperi TCI66207 serum, significant improvements were observed in all measured skin parameters compared to baseline, with notable enhancements in moisture, brightness, elasticity, texture, and collagen density, along with reductions in wrinkles, spots, and pore size.

CONCLUSIONS

Halobacteria trueperi TCI66207 serum demonstrates a clear ability to improve skin conditions and delay signs of aging, making it a promising candidate for the development of new cosmetic formulations with potent anti-aging and skin-rejuvenating properties.

Secondary Metabolites from the Mangrove Ecosystem-Derived Fungi Penicillium spp.: Chemical Diversity and Biological Activity

Mangrove ecosystems have attracted widespread attention because of their high salinity, muddy or sandy soil, and low pH, as well as being partly anoxic and periodically soaked by tides. Mangrove plants, soil, or sediment-derived fungi, especially the Penicillium species, possess unique metabolic pathways to produce secondary metabolites with novel structures and potent biological activities. This paper reviews the structural diversity and biological activity of secondary metabolites isolated from mangrove ecosystem-derived Penicillium species over the past 5 years (January 2020-October 2024), and 417 natural products (including 170 new compounds, among which 32 new compounds were separated under the guidance of molecular networking and the OSMAC approach) are described. The structures were divided into six major categories, including alkaloids, polyketides, terpenoids, benzene derivatives, steroids, and other classes. Among these natural products, the plausible biosynthetic pathways of 37 compounds were also proposed; 11 compounds have novel skeleton structures, and 26 compounds contain halogen atoms. A total of 126 compounds showed biological activities, such as cytotoxic, antifungal, antibacterial, anti-inflammatory, and α-glucosidase-inhibitory activities, and 11 compounds exhibited diverse biological activities. These new secondary metabolites with novel structures and potent bioactivities will continue to guide the separation or synthesis of structurally novel and biologically active compounds and will offer leading compounds for the development and innovation of pharmaceuticals and pesticides.

Machine Learning-Driven Discovery and Database of Cyanobacteria Bioactive Compounds: A Resource for Therapeutics and Bioremediation

Cyanobacteria strains have the potential to produce bioactive compounds that can be used in therapeutics and bioremediation. Therefore, compiling all information about these compounds to consider their value as bioresources for industrial and research applications is essential. In this study, a searchable, updated, curated, and downloadable database of cyanobacteria bioactive compounds was designed, along with a machine-learning model to predict the compounds' targets of newly discovered molecules. A Python programming protocol obtained 3431 cyanobacteria bioactive compounds, 373 unique protein targets, and 3027 molecular descriptors. PaDEL-descriptor, Mordred, and Drugtax software were used to calculate the chemical descriptors for each bioactive compound database record. The biochemical descriptors were then used to determine the most promising protein targets for human therapeutic approaches and environmental bioremediation using the best machine learning (ML) model. The creation of our database, coupled with the integration of computational docking protocols, represents an innovative approach to understanding the potential of cyanobacteria bioactive compounds. This resource, adhering to the findability, accessibility, interoperability, and reuse of digital assets (FAIR) principles, is an excellent tool for pharmaceutical and bioremediation researchers. Moreover, its capacity to facilitate the exploration of specific compounds' interactions with environmental pollutants is a significant advancement, aligning with the increasing reliance on data science and machine learning to address environmental challenges. This study is a notable step forward in leveraging cyanobacteria for both therapeutic and ecological sustainability.

Design, Synthesis, and Biological Evaluation of Novel Urea-Containing Carnosic Acid Derivatives with Anticancer Activity

A series of novel carnosic acid 1 derivatives incorporating urea moieties at the C-20 position was synthesized and evaluated for their antiproliferative activity against the HCT116 colorectal cancer cell line. Most derivatives demonstrated enhanced antiproliferative activity compared to that of carnosic acid 1. The most promising derivatives were tested in other colorectal cancer cell lines (SW480, SW620, and Caco-2), melanoma (A375), and pancreatic cancer (MiaPaca-2). Derivative 14 consistently demonstrated the highest activity across all tested cancer cell lines, showing selectivity for cancer cells over normal cells. Further investigation of the mechanism of action in SW480 cells revealed that compound 14 induced cell cycle arrest at the G0/G1 phase by downregulating CDK4 and CDK6. Molecular docking studies revealed that compound 14 established several interactions with key residues in the active site of CDK6. Additionally, compound 14 also reduced ROS production. In summary, our results strongly indicate that compound 14 has potential as a lead compound in the development of innovative anticancer drugs.

Genome mining and biosynthetic pathways of marine-derived fungal bioactive natural products

Marine fungal natural products (MFNPs) are a vital source of pharmaceuticals, primarily synthesized by relevant biosynthetic gene clusters (BGCs). However, many of these BGCs remain silent under standard laboratory culture conditions, delaying the development of novel drugs from MFNPs to some extent. This review highlights recent efforts in genome mining and biosynthetic pathways of bioactive natural products from marine fungi, focusing on methods such as bioinformatics analysis, gene knockout, and heterologous expression to identify relevant BGCs and elucidate the biosynthetic pathways and enzyme functions of MFNPs. The research efforts presented in this review provide essential insights for future gene-guided mining and biosynthetic pathway analysis in MFNPs.

New Sesterterpenes from the Antarctic Sponge Suberites sp

Chemical investigation of the Antarctic sponge Suberites sp. has previously led to the identification of new suberitane derivatives, some of which show bioactivity toward respiratory syncytial virus (RSV). Our ongoing NMR-guided investigation of new specimens of the sponge resulted in the isolation of five new analogs (1-5), previously reported suberitenones A-D (6-9), and oxaspirosuberitenone (10). Suberitenone K (1) was characterized as the 8-keto derivative of 6, while three new phenols, suberitandiol (2), abeosuberitandiol (3), and furanosuberitandiol (4), and the degraded sesterterpene norsuberitenone B (5) were also found. Compound 3 displays a ring contraction while 4 has a new dihydrofuran ring. Structural characterization was achieved by a combination of NMR, HR-MS, and X-ray diffraction (XRD). Moderate activity towards RSV was reported for 9 and the new metabolite 1, with IC50 values of 15.0 μM and 39.8 μM, respectively.

Production of marine-derived bioactive peptide molecules for industrial applications: A reverse engineering approach

This review examines a wide range of marine microbial-derived bioactive peptide molecules, emphasizing the significance of reverse engineering in their production. The discussion encompasses the advancements in Marine Natural Products (MNPs) bio-manufacturing through the integration of omics-driven microbial engineering and bioinformatics. The distinctive features of non-ribosomally synthesised peptides (NRPs), and ribosomally synthesised precursor peptides (RiPP) biosynthesis is elucidated and presented. Additionally, the article delves into the origins of common peptide modifications. It highlights various genome mining approaches for the targeted identification of Biosynthetic Gene Clusters (BGCs) and novel RiPP and NRPs-derived peptides. The review aims to demonstrate the advancements, prospects, and obstacles in engineering both RiPP and NRP biosynthetic pathways.

Discovering novel Cathepsin L inhibitors from natural products using artificial intelligence

Cathepsin L (CTSL) is a promising therapeutic target for metabolic disorders. Current pharmacological interventions targeting CTSL have demonstrated potential in reducing body weight gain, serum insulin levels, and improving glucose tolerance. However, the clinical application of CTSL inhibitors remains limited. In this study, we used a combination of artificial intelligence and experimental methods to identify new CTSL inhibitors from natural products. Through a robust deep learning model and molecular docking, we screened 150 molecules from natural products for experimental validation. At a concentration of 100 µM, we found that 36 of them exhibited more than 50 % inhibition of CTSL. Notably, 13 molecules displayed over 90 % inhibition and exhibiting concentration-dependent effects. The molecular dynamics simulation on the two most potent inhibitors, Plumbagin and Beta-Lapachone, demonstrated stable interaction at the CTSL active site. Enzyme kinetics studies have shown that these inhibitors exert an uncompetitive inhibitory effect on CTSL. In conclusion, our research identifies Plumbagin and Beta-Lapachone as potential CTSL inhibitors, offering promising candidates for the treatment of metabolic disorders and illustrating the effectiveness of artificial intelligence in drug discovery.

A Lucknolide Derivative Induces Mitochondrial ROS-Mediated G2/M Arrest and Apoptotic Cell Death in B16F10 Mouse Melanoma Cells

Melanoma is an aggressive skin cancer with a high risk of cancer-related deaths, and inducing apoptosis in melanoma cells is a promising therapeutic strategy. This study investigates the anti-tumor potential of a novel lucknolide derivative LA-UC as a therapeutic candidate for melanoma. Lucknolide A (LA), a tricyclic ketal-lactone metabolite isolated from marine-derived Streptomyces sp., was chemically modified by introducing a 10-undecenoyl group to synthesize LA-UC. LA-UC preferentially inhibited the proliferation of melanoma cells, including B16F10, while exerting minimal effects on normal melanocytes or other tumor cell types, indicating the selective action of LA-UC against melanoma cells. LA-UC decreased G2/M checkpoint proteins, including cyclin B1 and Cdc2, while activating caspase-3 and caspase-9, resulting in G2/M cell cycle arrest and inducing apoptotic cell death in B16F10 cells. The addition of a pan-caspase inhibitor confirmed the caspase-dependent mechanism of LA-UC-induced cell death. Additionally, LA-UC elevated mitochondrial ROS levels, leading to mitochondrial membrane disruption, upregulation of pro-apoptotic proteins, and DNA damage in melanoma cells. The ROS scavenger N-acetylcysteine reduced LA-UC-induced mitochondrial ROS accumulation, mitochondrial membrane disruption, DNA damage, and apoptosis. Collectively, these findings suggest that LA-UC induces G2/M cell cycle arrest and caspase-dependent apoptosis in B16F10 cells through excessive mitochondrial ROS generation, membrane impairment, and DNA damage, highlighting its potential as a promising therapeutic candidate for melanoma treatment.

Two Disaccharide-Bearing Polyethers, K-41B and K-41Bm, Potently Inhibit HIV-1 via Mechanisms Different from That of Their Precursor Polyether, K-41A

The screening of novel antiviral agents from marine microorganisms is an important strategy for new drug development. Our previous study found that polyether K-41A and its analog K-41Am, derived from a marine Streptomyces strain, exhibit anti-HIV activity by suppressing the activities of HIV-1 reverse transcriptase (RT) and its integrase (IN). Among the K-41A derivatives, two disaccharide-bearing polyethers-K-41B and K-41Bm-were found to have potent anti-HIV-1IIIB activity in vitro. This study aimed to clarify whether K-41B and K-41Bm have inhibitory effects on different HIV-1 strains or whether these two derivatives have mechanisms of action different from that of their precursor, K-41A. An anti-HIV-1 assay indicated that K-41B and K-41Bm have potent anti-HIV-1BaL activity, with low 50% inhibitory concentrations (IC50s) (0.076 and 0.208 μM, respectively) and high selective indexes (SIs) (58.829 and 31.938, respectively) in the peripheral blood mononuclear cell (PBMC)-HIV-1BaL system. The time-of-addition (TOA) assay indicated that K-41B and K-41Bm may exert antiviral effects by activating multiple stages of HIV-1 replication. A cell protection assay indicated that the pretreatment of cells with K-41B or K-41Bm has almost no inhibitory effect on HIV-1 infection. A virus inactivation assay indicated that pretreatment of the virus with K-41B or K-41Bm inhibits HIV-1 infection by 60%. A cell-cell fusion assay showed that K-41B and K-41Bm blocked the cell fusion mediated by viral envelope proteins. The HIV-1 key enzyme experiment also indicated that both compounds have certain inhibitory effects on HIV-1 IN. Furthermore, molecular docking showed that K-41B and K-41Bm interact with several viral and host proteins, including HIV-1 IN, an envelope protein (gp120), a transmembrane protein (gp41), and cell surface receptors (CD4, CCR5, and CXCR4). Overall, in addition to having a similar anti-HIV-1 mechanism of inhibiting HIV-1 IN like the precursor polyether K-41A, the disaccharide-bearing polyether derivatives K-41B and K-41Bm may also inhibit viral entry. This suggests that they display anti-HIV-1 mechanisms that are different from those of their precursor polyethers.

Biodiversity and antifouling activity of microbes associated with gorgonian corals Leptogorgia rigida and Menella kanisa from the South China Sea

Recently, coral-associated microorganisms have attracted widespread attention, and most of these studies have focused on stony and soft corals. However, our knowledge of the diversity and bioactivity of microorganisms in gorgonian corals is still limited. In this study, the biodiversity of microbes in two gorgonian corals (Leptogorgia rigida and Menella kanisa) from the South China Sea was investigated by combining traditional culture method with molecular biology technique (bacterial 16S or fungal internal transcribed spacer (ITS) rRNA gene sequences). A total of 216 bacterial and 98 fungal isolates were obtained using 4 different isolation media. These isolates were identified and belonged to 31 bacterial and 12 fungal species, suggesting an unexpectedly diverse microbial community harbored in the South China Sea gorgonian corals L. rigida and M. kanisa. Furthermore, 56% of the tested microbial isolates displayed various antifouling activities against four biofouling organisms (including two microfouling bacteria Micrococcus luteus and Shewanella onedensis, and two macrofouling organisms Bugula neritina and Balanus amphitrite). Among the microbial isolates with antifouling activity, Bacillus firmus SCAU-038 and Streptomyces parvulus SCAU-062 displayed moderate or strong antifouling activity against all tested biofouling organisms. This is the first study on the biodiversity and antifouling activity of microorganisms associated with gorgonians L. rigida and M. kanisa from the South China Sea. These results contribute to the further understanding of microorganisms associated with gorgonian corals and provide potential resources for new natural antifouling agents.

Unveiling the bioactive potential of Actinomycetota from the Tagus River estuary

The increase in global travel and the incorrect and excessive use of antibiotics has led to an unprecedented rise in antibiotic resistance in bacterial and fungal populations. To overcome these problems, novel bioactive natural products must be discovered, which may be found in underexplored environments, such as estuarine habitats. In the present work, estuarine actinomycetotal strains were isolated with conventional and iChip techniques from the Tagus estuary in Alcochete, Portugal, and analysed for different antimicrobial bioactivities. Extracts were produced from the isolated cultures and tested for bioactivity against Staphylococcus aureus ATCC 29213, Escherichia coli ATCC 25922, Aspergillus fumigatus ATCC 240305, Candida albicans ATCC 10231 and Trichophyton rubrum FF5. Furthermore, bioactive extracts were subjected to dereplication by high-performance liquid chromatography (HPLC) and high-resolution mass spectrometry (HRMS) to putatively identify their chemical components. In total, 105 isolates belonging to 3 genera were obtained. One which was isolated, MTZ3.1 T, represents a described novel taxon for which the name Streptomyces meridianus was proposed. Regarding the bioactivity testing, extracts from 12 strains proved to be active against S. aureus, 2 against E. coli, 4 against A. fumigatus, 3 against C. albicans and 10 against T. rubrum. Dereplication of bioactive extracts showed the presence of 28 known bioactive molecules, 35 hits have one or more possible matches in the DNP and 18 undescribed ones. These results showed that the isolated bacteria might be the source of new bioactive natural products.

A comprehensive review to assess the potential, health benefits and complications of fucoidan for developing as functional ingredient and nutraceutical

Polysaccharides from seaweeds or macroalgae are garnering significant interest from pharmaceutical and food industries due to their bioactivities and promising therapeutic effects. Among the diverse agal polysaccharides, fucoidan is a well-documented and stands out as a well-researched sulphated heteropolysaccharide found in brown seaweeds. It primarily consists of l-fucose and sulfate ester groups, along with other monosaccharides like xylose, mannose, uronic acid, rhamnose, arabinose, and galactose. Recent scientific investigations have unveiled the formidable inhibitory prowess of fucoidan against SARS-CoV-2, offering a promising avenue for therapeutic intervention in our current landscape. Moreover, fucoidan has demonstrated remarkable abilities in safeguarding the gastrointestinal tract, regulating angiogenesis, mitigating metabolic syndrome, and fortifying bone health. Despite the abundance of studies underscoring fucoidan's potential as a vital component sourced from nature, its exploitation remains constrained by inherent limitations. Thus, the primary objective of this article is to furnish a comprehensive discourse on the structural attributes, health-enhancing properties, safety parameters, and potential toxicity associated with fucoidan. Furthermore, the discourse extends to elucidating the practical applications and developmental prospects of fucoidan as a cornerstone in the realm of functional foods and nutraceuticals.

Seagrass Meadows: Prospective Candidates for Bioactive Molecules

Seagrass meadows consist of angiosperms that thrive fully submerged in marine environments and form distinct ecosystems. They provide essential support for many organisms, acting as nursery grounds for species of economic importance. Beyond their ecological roles, seagrasses and their associated microbiomes are rich sources of bioactive compounds with the potential to address numerous human healthcare challenges. Seagrasses produce bioactive molecules responding to physical, chemical, and biological environmental changes. These activities can treat microbe-borne diseases, skin diseases, diabetes, muscle pain, helminthic diseases, and wounds. Seagrasses also offer potential secondary metabolites that can be used for societal benefits. Despite numerous results on their presence and bioactive derivatives, only a few studies have explored the functional and therapeutic properties of secondary metabolites from seagrass. With the increasing spread of epidemics and pandemics worldwide, the demand for alternative drug sources and drug discovery has become an indispensable area of research. Seagrasses present a reliable natural source, making this an opportune moment for further exploration of their pharmacological activities with minimal side effects. This review provides a comprehensive overview of the biochemical, phytochemical, and biomedical applications of seagrasses globally over the last two decades, highlighting the prospective areas of future research for identifying biomedical applications.

α-Arbutin ameliorates UVA-induced photoaging through regulation of the SIRT3/PGC-1α pathway

Owing to its tyrosinase inhibitory activity, α-arbutin has been added to several skin care products as a skin-lightening agent. However, the protective effect of α-arbutin against ultraviolet A (UVA)-induced photoaging has not been well investigated. The present study was designed to investigate the photoprotective effect and mechanism of α-arbutin against UVA-induced photoaging. In vitro experiments, HaCaT cells were treated with UVA at a dose of 3 J/cm2 to evaluate the anti-photoaging effect of α-arbutin. α-Arbutin was found to exhibit a strong antioxidant effect by increasing glutathione (GSH) level and inhibiting reactive oxygen species (ROS) production. Meanwhile, α-arbutin markedly improved the expression of sirtuin 3 (SIRT3) and peroxisome proliferator-activated receptor γ coactivator 1 α (PGC-1α) proteins, initiating downstream signaling to increase mitochondrial membrane potential and mediate mitochondrial biogenesis, and improve mitochondrial structure significantly. In vivo analysis, the mice with shaved back hair were irradiated with a cumulative UVA dose of 10 J/cm2 and a cumulative ultraviolet B (UVB) dose of 0.63 J/cm2. The animal experiments demonstrated that α-arbutin increased the expression of SIRT3 and PGC-1α proteins in the back skin of mice, thereby reducing UV-induced skin damage. In conclusion, α-arbutin protects HaCaT cells and mice from UVA damage by regulating SIRT3/PGC-1α signaling pathway.

Identification of potential NUDT5 inhibitors from marine bacterial natural compounds via molecular dynamics and free energy landscape analysis

NUDIX hydrolase 5 (NUDT5) is an enzyme involved in the hydrolysis of nucleoside diphosphates linked to other moieties, such as ADP-ribose. This cofactor is vital in redox reactions and is essential for the activity of sirtuins and poly(ADP-ribose) polymerases, which are involved in DNA repair and genomic stability. It has been shown that NUDT5 activity can also influence NAD+ homeostasis, thereby affecting cancer cell metabolism and survival. In this regard, the discovery of NUDT5 inhibitors has emerged as a potential therapeutic approach in cancer treatment. In this study, we conducted a high-throughput virtual screening of marine bacterial compounds against the NUDT5 enzyme and four molecules were selected based on their docking scores. These compounds established strong interactions within the NUDT5 active site, with molecular analysis highlighting the key role of Trp28A and Trp46B residues. Molecular dynamics simulations over 200 ns indicated a stable behavior, in association with root mean square deviation values always below 3 Å, suggesting conformational stability. Free energy landscape analysis further supported their potential as NUDT5 inhibitors, offering avenues for novel therapeutic strategies against NUDT5-associated breast cancer.

Induced production of defensive secondary metabolites from Aspergillus fumigatiaffinis by co-culture with Aspergillus alabamensis

Seven previously undescribed compounds, including four diketomorpholine alkaloids (1‒4), one indole diketopiperazine alkaloid (9), one chromone (10), and one benzoic acid derivative (13), and nine known compounds (5-8, 11, 12, and 14-16) were isolated from two different fungal sources. Nine of these metabolites (1-9) were obtained from a seagrass-derived Aspergillus alabamensis SYSU-6778, while the others were obtained from a mixed culture of A. alabamensis SYSU-6778 and a co-isolated fungus A. fumigatiaffinis SYSU-6786. The chemical structures of the compounds were deduced via spectroscopic techniques (including HRESIMS, 1D and 2D NMR), chemical reactions, and ECD calculations. It is worth noting that compound 10 was identified as a defensive secondary metabolite of strain SYSU-6786, produced through the induction of compound 8 under co-culture conditions. Compounds 3 and 4 possessed a naturally rare isotryptophan core. Moreover, compounds 1 and 2 exhibited potent inhibitory activities against fish pathogenic bacterium Edwardsiella ictalurid, with minimum inhibitory concentration values of 10.0 μg/mL for both compounds.

Design and Synthesis of Marine Polybrominated Diphenyl Ether Derivatives as Potential Anti-Inflammatory Agents

Natural polybrominated diphenyl ethers are generally isolated from sponges and possess a broad range of biological activities. Through screening of our marine natural product library, we discovered that polybrominated diphenyl ethers 5 and 6 exhibit considerable anti-inflammatory activity. In order to expand our repertoire of derivatives for further biological activity studies, we designed and synthesized a series of 5-related polybrominated diphenyl ethers. Importantly, compound 5a showed comparable anti-inflammatory activity while much lower cytotoxicity on lipopolysaccharide (LPS)-induced RAW264.7 cells. Additionally, western blotting analysis showed that 5a reduced the expression of phosphorylated extracellular signal-regulated kinase (p-ERK). Besides, molecular docking experiments were conducted to predict and elucidate the potential mechanisms underlying the varying anti-inflammatory activities exhibited by compounds 5a, 5, and 6.

Halenaquinol Blocks Staphylococcal Protein A Anchoring on Cell Wall Surface by Inhibiting Sortase A in Staphylococcus aureus

Sortase A (SrtA) is a cysteine transpeptidase that binds to the periplasmic membrane and plays a crucial role in attaching surface proteins, including staphylococcal protein A (SpA), to the peptidoglycan cell wall. Six pentacyclic polyketides (1-6) were isolated from the marine sponge Xestospongia sp., and their structures were elucidated using spectroscopic techniques and by comparing them to previously reported data. Among them, halenaquinol (2) was found to be the most potent SrtA inhibitor, with an IC50 of 13.94 μM (4.66 μg/mL). Semi-quantitative reverse transcription PCR data suggest that halenaquinol does not inhibit the transcription of srtA and spA, while Western blot analysis and immunofluorescence microscopy images suggest that it blocks the cell wall surface anchoring of SpA by inhibiting the activity of SrtA. The onset and magnitude of the inhibition of SpA anchoring on the cell wall surface in S. aureus that has been treated with halenaquinol at a value 8× that of the IC50 of SrtA are comparable to those for an srtA-deletion mutant. These findings contribute to the understanding of the mechanism by which marine-derived pentacyclic polyketides inhibit SrtA, highlighting their potential as anti-infective agents targeting S. aureus virulence.

The Identification of Peptide Inhibitors of the Coronavirus 3CL Protease from a Fucus ceranoides L. Hydroalcoholic Extract Using a Ligand-Fishing Strategy

Brown seaweeds of the Fucus genus represent a rich source of natural antiviral products. In this study, a Fucus ceranoides hydroalcoholic extract (FCHE) was found to inhibit 74.2 ± 1.3% of the proteolytic activity of the free SARS-CoV-2 3CL protease (3CLpro), an enzyme that plays a pivotal role in polyprotein processing during coronavirus replication and has been identified as a relevant drug discovery target for SARS- and MERS-CoVs infections. To purify and identify 3CLpro ligands with potential inhibitory activity using a one-step approach, we immobilized the enzyme onto magnetic microbeads (3CLpro-MPs), checked that the enzymatic activity was maintained after grafting, and used this bait for a ligand-fishing strategy followed by a high-resolution mass spectrometry analysis of the fished-out molecules. Proof of concept for the ligand-fishing capacity of the 3CLpro-MPs was demonstrated by doping the FCHE extract with the substrate peptide TSAVLQ-pNA, resulting in the preferential capture of this high-affinity peptide within the macroalgal complex matrix. Ligand fishing in the FCHE alone led to the purification and identification via high-resolution mass spectrometry (HRMS) of seven hepta-, octa-, and decapeptides in an eluate mix that significantly inhibited the free 3CLpro more than the starting FCHE (82.7 ± 2.2% inhibition). Molecular docking simulations of the interaction between each of the seven peptides and the 3CLpro demonstrated a high affinity for the enzyme's proteolytic active site surpassing that of the most affine peptide ligand identified so far (a co-crystallographic peptide). Testing of the corresponding synthetic peptides demonstrated that four out of seven significantly inhibited the free 3CLpro (from 46.9 ± 6.4 to 76.8 ± 3.6% inhibition at 10 µM). This study is the first report identifying peptides from Fucus ceranoides with high inhibitory activity against the SARS-CoV-2 3CLprotease which bind with high affinity to the protease's active site. It also confirms the effectiveness of the ligand-fishing strategy for the single-step purification of enzyme inhibitors from complex seaweed matrices.

Assessment of antimicrobial activity and GC-MS using culture filtrate of local marine Bacillus strains

Secondary metabolites produced by Bacillus species from marine sources encompass a variety of compounds such as lipopeptides, isocoumarins, polyketides, macrolactones, polypeptides and fatty acids. These bioactive substances exhibit various biological activities, including antibiotic, antifungal, antiviral, and antitumor properties. This study aimed to isolate and identify a particular species of Bacillus from marine water and organisms that can produce bioactive secondary metabolites. Among the 73 Bacillus isolates collected, only 5 exhibited antagonistic activity against various viral and bacterial pathogens. The active isolates were subjected to 16S rRNA sequencing to determine their taxonomical affiliation. Among them, Bacillus tequilensis CCASU-2024-66 strain no. 42, with the accession number ON 054302 in GenBank, exhibited the highest inhibitory potential. It displayed an inhibition zone of 21 mm against Bacillus cereus while showing a minimum zone of inhibition of 9 mm against Escherichia coli and gave different inhibition against pathogenic fungi, the highest inhibition zone 15 mm against Candida albicans but the lowest inhibition zone 10 mm was against Botrytis cinerea, Fusarium oxysporum. Furthermore, it demonstrated the highest percentage of virucidal effect against the Newcastle virus and influenza virus, with rates of 98.6% and 98.1%, respectively. Furthermore, GC-MS analysis was employed to examine the bioactive substance components, specifically focusing on volatile and polysaccharide compounds. Based on these results, Bacillus tequilensis strain 42 may have the potential to be employed as an antiviral agent in poultry cultures to combat Newcastle and influenza, two extremely destructive viruses, thus reducing economic losses in the poultry production sector. Bacteria can be harnessed for the purpose of preserving food and controlling pathogenic fungi in both human and plant environments. Molecular docking for the three highly active derivatives 2,3-Butanediol, 2TMS, D-Xylopyranose, 4TMS, and Glucofuranoside, methyl 2,3,5,6-tetrakis-O-(trimethylsilyl) was carried out against the active sites of Bacillus cereus, Listeria monocytogenes, Candida albicans, Newcastle virus and influenza virus. The data obtained from molecular docking is highly correlated with that obtained from biology. Moreover, these highly active compounds exhibited excellent proposed ADMET profile.

Natural Product-Derived Phytochemicals for Influenza A Virus (H1N1) Prevention and Treatment

Influenza A (H1N1) viruses are prone to antigenic mutations and are more variable than other influenza viruses. Therefore, they have caused continuous harm to human public health since the pandemic in 2009 and in recent times. Influenza A (H1N1) can be prevented and treated in various ways, such as direct inhibition of the virus and regulation of human immunity. Among antiviral drugs, the use of natural products in treating influenza has a long history, and natural medicine has been widely considered the focus of development programs for new, safe anti-influenza drugs. In this paper, we focus on influenza A (H1N1) and summarize the natural product-derived phytochemicals for influenza A virus (H1N1) prevention and treatment, including marine natural products, flavonoids, alkaloids, terpenoids and their derivatives, phenols and their derivatives, polysaccharides, and derivatives of natural products for prevention and treatment of influenza A (H1N1) virus. We further discuss the toxicity and antiviral mechanism against influenza A (H1N1) as well as the druggability of natural products. We hope that this review will facilitate the study of the role of natural products against influenza A (H1N1) activity and provide a promising alternative for further anti-influenza A drug development.

Microwave-assisted synthesis of highly sulfated mannuronate glycans as potential inhibitors against SARS-CoV-2

Algae-based marine carbohydrate drugs are typically decorated with negative ion groups such as carboxylate and sulfate groups. However, the precise synthesis of highly sulfated alginates is challenging, thus impeding their structure-activity relationship studies. Herein we achieve a microwave-assisted synthesis of a range of highly sulfated mannuronate glycans with up to 17 sulfation sites by overcoming the incomplete sulfation due to the electrostatic repulsion of crowded polyanionic groups. Although the partially sulfated tetrasaccharide had the highest affinity for the receptor binding domain (RBD) of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant, the fully sulfated octasaccharide showed the most potent interference with the binding of the RBD to angiotensin-converting enzyme 2 (ACE2) and Vero E6 cells, indicating that the sulfated oligosaccharides might inhibit the RBD binding to ACE2 in a length-dependent manner.

Aurantoside L, a New Tetramic Acid Glycoside with Anti-Leishmanial Activity Isolated from the Marine Sponge Siliquariaspongia japonica

A new tetramic acid glycoside, aurantoside L (1), was isolated from the sponge Siliquariaspongia japonica collected at Tsushima Is., Nagasaki Prefecture, Japan. The structure of aurantoside L (1) composed of a tetramic acid bearing a chlorinated polyene system and a trisaccharide part was elucidated using spectral analysis. Aurantoside L (1) showed anti-parasitic activity against L. amazonensis with an IC50 value of 0.74 µM.

Investigation on the chemical constituents of the marine-derived fungus strain Aspergillus brunneoviolaceus MF180246

Aspergillus have been proven to be excellent resources for new natural products. During our systematic biodiversifying new compounds from marine derived fungi, one novel compound, asperbrunneo acid (1), along with seven bistetrahydroxanthone analogues, secalonic acid D (2), secalonic acid F (3), secalonic acid F1 (4), secalonic acid H (5), penicillixanthone A (6), chrysoxanthone C (7), and asperdichrome (8), one ketodivinyllactonic steroid, herbarulide (9), as well as one tyrosine-derived compound, aspergillusol A (10), were isolated from the marine-derived fungus Aspergillus brunneoviolaceus MF180246. These structures were elucidated by HRMS, 1 D and 2 D NMR analysis. Compound 1 possessed the first reported new carbon skeleton natural product. Compounds 1, 4, 5, 6, 7 and 8 showed antibacterial activity against Staphylococcus aureus with minimum inhibitory concentration values of 200, 25, 50, 6.25, 50, and 25 µg/ml, respectively.

A Noble Extract of Pseudomonas sp. M20A4R8 Efficiently Controlling the Influenza Virus-Induced Cell Death

Epidemic diseases that arise from infectious RNA viruses, particularly influenza viruses, pose a constant threat to the global economy and public health. Viral evolution has undermined the efficacy of acquired immunity from vaccines and the antiviral effects of FDA-approved drugs. As such, there is an urgent need to develop new antiviral lead agents. Natural compounds, owing to their historical validation of application and safety, have become a promising solution. In this light, a novel marine bacterium, Pseudomonas sp. M20A4R8, has been found to exhibit significant antiviral activity [half maximal inhibitory concentration (IC50) = 1.3 µg/mL, selectivity index (SI) = 919.4] against influenza virus A/Puerto Rico/8/34, surpassing the activity of chloroquine. The antiviral response via M20A4R8 extract was induced during post-entry stages of the influenza virus, indicating suitability for post-application after the establishment of viral infection. Furthermore, post-treatment with M20A4R8 extract protected the host from virus-induced apoptosis, suggesting its potential use in acute respiratory disease complexes resulting from immune effectors' overstimulation and autophagy-mediated self-apoptosis. The extract demonstrated an outstanding therapeutic index against influenza virus A/Wisconsin/15/2009 (IC50 = 8.1 µg/mL, SI = 146.2) and B/Florida/78/2015 Victoria lineage (IC50 = 3.5 µg/mL, SI = 343.8), indicating a broad anti-influenza virus activity with guaranteed safety and effectiveness. This study provides a new perspective on mechanisms for preventing a broad spectrum of viral infections through antiviral agents from novel and natural origins. Future studies on a single or combined compound from the extract hold promise, encouraging its use in preclinical challenge tests with various influenza virus strains.

Studies on Secondary Metabolites and In vitro and In silico Anticholinesterases Activities of the Sea Urchin Echinometra mathaei Crude Venoms from the Persian Gulf-Bushehr

Background:

Echinoderms are a unique source of amazing secondary metabolites with a wide spectrum of biological activities. Several species of sea urchins contain various toxins and biologically active metabolites. One of the most attractive approaches to treat Alzheimer's disease is searching for effective marine natural products with cholinesterase inhibitory activities.

Objective:

The current study is designed to investigate the in vitro and in silico acetylcholinesterase and butyrylcholinesterase inhibitory activities of the Persian Gulf echinoderm sea urchin Echinometra mathaei venom and related chemical compounds.

Methods:

The experiments for LD50, total protein, protein bands, in vitro cholinesterase inhibitory activities, the identity of secondary metabolites, and the in silico evaluations, respectively, were performed by Spearman-Karber, Lowry, SDS-PAGE, Ellman's spectroscopic, GC-MS, and docking methods.

Results:

The LD50 (IV rat) of the spine, gonad, and coelomic fluid from sea urchin samples were 2.231 ± 0.09, 1.03 ± 0.05, and 1.12 ± 0.13 mg/ml, respectively. The SDS-PAGE and total protein studies showed that at least a portion of the venom is protein in nature. GC-MS analysis of the identified samples revealed 12, 23, and 21 compounds with different chemical types, including alkaloids, terpenes, and steroids, respectively. According to the results, all samples act as significant inhibitors of both enzymes. In silico data for the identified compounds also confirmed the experimental results.

Conclusion:

The alkaloid compound 6H-Indolo[3,2,1-de] [1,5] naphthyridine-6-one,1,2,3a,4,5- hexahydro-8-hydroxy-3-methyl (C7) had the highest affinity for both enzymes. Further research is needed to determine whether C7 could be a therapeutic candidate for Alzheimer's disease.

Marine natural products

Covering: January to the end of December 2022This review covers the literature published in 2022 for marine natural products (MNPs), with 645 citations (633 for the period January to December 2022) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, the submerged parts of mangroves and other intertidal plants. The emphasis is on new compounds (1417 in 384 papers for 2022), together with the relevant biological activities, source organisms and country of origin. Pertinent reviews, biosynthetic studies, first syntheses, and syntheses that led to the revision of structures or stereochemistries, have been included. An analysis of NP structure class diversity in relation to biota source and biome is discussed.

Marine Brown Algae-Derived Compounds as Potential Inhibitors of Japanese Encephalitis Virus RNA-Dependent RNA Polymerase

The Japanese encephalitis virus (JEV) is a mosquito-borne flavivirus that primarily affects people in Asia and seriously threatens public health. Considering the rising occurrence rates and lack of targeted antiviral treatments, it is essential to comprehend and tackle obstacles related to JEV in order to lessen its influence on world health. This investigation explores compounds derived from marine brown algae (Phaeophyceae) as potential inhibitors of JEV RNA-dependent RNA polymerase (RdRp), a critical enzyme in the virus's replication cycle. Employing the computational virtual screen approach, four compounds, i.e., CMNPD16749, CMNPD2606, CMNPD27817, and CMNPD23662, with favorable binding energies ranging from -15.7 Kcal/mol to -13.9 kcal/mol were identified. Subsequently, through molecular docking analysis, the interactions responsible for the binding stability between the target protein and hit molecules compared to the reference molecule Galidesvir were studied. Further, through extensive molecular dynamic (MD) simulation studies at 200 ns, it was confirmed that each docked complex showed acceptable dynamic stability compared to the reference molecule. These findings were further validated using MM/PBSA free binding energy calculations, PCA analysis and free energy landscape construction. These computational findings suggested that the brown algae-derived compounds may act as an antiviral drug against JEV infection and lay a crucial foundation for future experimental studies against JEV.

Cytotoxic metabolites from Sinularia levi supported by network pharmacology

The in-vitro anti-proliferative evaluation of Sinularia levi total extract against three cell lines revealed its potent effect against Caco-2 cell line with IC50 3.3 μg/mL, followed by MCF-7 and HepG-2 with IC50 6.4 μg/mL and 8.5 μg/mL, respectively, in comparison to doxorubicin. Metabolic profiling of S. levi total extract using liquid chromatography coupled with high-resolution electrospray ionization mass spectrometry (LC-HR-ESI-MS) revealed the presence of phytoconstituents clusters consisting mainly of steroids and terpenoids (1-20), together with five metabolites 21-25, which were additionally isolated and identified through the phytochemical investigation of S. levi total extract through various chromatographic and spectroscopic techniques. The isolated metabolites included one sesquiterpene, two steroids and two diterpenes, among which compounds prostantherol (21) and 12-hydroperoxylsarcoph-10-ene (25) were reported for the first time in Sinularia genus. The cytotoxic potential evaluation of the isolated compounds revealed variable cytotoxic effects against the three tested cell lines. Compound 25 was the most potent with IC50 value of 2.13 ± 0.09, 3.54 ± 0.07 and 5.67 ± 0.08 μg/mL against HepG-2, MCF-7 and Caco-2, respectively, followed by gorgosterol (23) and sarcophine (24). Additionally, network analysis showed that cyclin-dependent kinase 1 (CDK1) was encountered in the mechanism of action of the three cancer types. Molecular docking analysis revealed that CDK1 inhibition could possibly be the reason for the cytotoxic potential.

Study of marine microorganism metabolites: new resources for bioactive natural products

The marine environment has remained a source of novel biological molecules with diversified applications. The ecological and biological diversity, along with a unique physical environment, have provided the evolutionary advantage to the plant, animals and microbial species thriving in the marine ecosystem. In light of the fact that marine microorganisms frequently interact symbiotically or mutualistically with higher species including corals, fish, sponges, and algae, this paper intends to examine the potential of marine microorganisms as a niche for marine bacteria. This review aims to analyze and summarize modern literature data on the biotechnological potential of marine fungi and bacteria as producers of a wide range of practically valuable products (surfactants, glyco-and lipopeptides, exopolysaccharides, enzymes, and metabolites with different biological activities: antimicrobial, antitumor, and cytotoxic). Hence, the study on bioactive secondary metabolites from marine microorganisms is the need of the hour. The scientific novelty of the study lies in the fact that for the first time, the data on new resources for obtaining biologically active natural products - metabolites of marine bacteria and fungi - were generalized. The review investigates the various kinds of natural products derived from marine microorganisms, specifically focusing on marine bacteria and fungi as a valuable source for new natural products. It provides a summary of the data regarding the antibacterial, antimalarial, anticarcinogenic, antibiofilm, and anti-inflammatory effects demonstrated by marine microorganisms. There is currently a great need for scientific and applied research on bioactive secondary metabolites of marine microorganisms from the standpoint of human and animal health.

Total Synthesis of the Reported Structure of Cahuitamycin A: Insights into an Elusive Natural Product Scaffold

In a 2016 screen of natural product extracts, a new family of natural products, the cahuitamycins, was discovered and found to inhibit biofilm formation in the human pathogen Acinetobacter baumannii. The proposed molecular structures contained an unusual piperazic acid residue, which piqued interest related to their structure/function and biosynthesis. Herein we disclose the first total synthesis of the proposed structure of cahuitamycin A in a 12-step longest linear sequence and 18% overall yield. Comparison of spectral and biological data of the authentic natural product and synthetic compound revealed inconsistentancies with the isolated metabolite. We therefore executed the diverted total synthesis of three isomeric compounds, which were also found to be disparate from the isolated natural product. This work sets the stage for future synthetic and biochemical investigations of an important class of natural products.

Progress and challenges in exploring aquatic microbial communities using non-targeted metabolomics

Advances in bioanalytical technologies are constantly expanding our insights into complex ecosystems. Here, we highlight strategies and applications that make use of non-targeted metabolomics methods in aquatic chemical ecology research and discuss opportunities and remaining challenges of mass spectrometry-based methods to broaden our understanding of environmental systems.

Antibacterial and Anti-HIV Metabolites from Marine Streptomyces albus MAB56 Isolated from Andaman and Nicobar Islands, India

Marine-derived actinobacteria have tremendous potential to produce novel metabolites with diverse biological activities. The Andaman coast of India has a lot of microbial diversity, but it is still a relatively unknown ecology for isolating novel actinobacteria with beneficial bioactive compounds. We have isolated 568 actinobacterial strains from mangrove rhizosphere sediments and sponge samples. Crude extracts from 75 distinct strains were produced by agar surface fermentation and extracted using ethyl acetate. In the disc diffusion method, 25 actinobacterial strains showed antimicrobial activity; notably, the strain MAB56 demonstrated promising broad-spectrum activity. Strain MAB56 was identified as Streptomyces albus by cultural, microscopic, and molecular methods. Conditions for bioactive metabolites from MAB56 were optimized and produced in a lab-scale fermenter. Three active metabolites (C1, C2, and C3) that showed promising broad-spectrum antimicrobial activity were isolated through HPLC-based purification. Based on the UV, FT-IR, NMR, and LC-MS analysis, the chemical nature of the active compounds was confirmed as 12-methyltetradecanoic acid (C1), palmitic acid (C2), and tridecanoic acid (C3) with molecular formulae C14H28O2, C16H32O2, and C13H26O2, respectively. Interestingly, palmitic acid (C2) also exhibited anti-HIV activity with an IC50 value of < 1 µg/ml. Our findings reveal that the actinobacteria from the Andaman marine ecosystems are promising for isolating anti-infective metabolites.

Stonefish (Synanceia spp.) Ichthyocrinotoxins: An ecological review and prospectus for future research and biodiscovery

Marine organisms possess a diverse array of unique substances, many with wide ranging potential for applications in medicine, industry, and other sectors. Stonefish (Synanceia spp.), a bottom-dwelling fish that inhabit shallow and intertidal waters throughout the Indo-Pacific, harbour two distinct substances, a venom, and an ichthyocrinotoxin. Stonefish are well-known for the potent venom associated with their dorsal spines as it poses a significant risk to public health. Consequently, much of the research on stonefish focusses on the venom, with the aim of improving outcomes in cases of envenomation. However, there has been a notable lack of research on stonefish ichthyocrinotoxins, a class of toxin that is synthesised within specialised epithelial cells (i.e., tubercles) and exuded onto the skin. This has resulted in a substantial knowledge gap in our understanding of these animals. This review aims to bridge this gap by consolidating literature on the ecological functions and biochemical attributes of ichthyocrinotoxins present in various fish species and juxtaposing it with the current state of knowledge of stonefish ecology. We highlight the roles of ichthyocrinotoxins in predator defence, bolstering innate immunity, and mitigating integumentary interactions with parasites and detrimental fouling organisms. The objective of this review is to identify promising research avenues that could shed light on the ecological functions of stonefish ichthyocrinotoxins and their potential practical applications as therapeutics and/or industrial products.

Marine indole alkaloid diversity and bioactivity. What do we know and what are we missing?

Covering: marine indole alkaloids (n = 2048) and their reported bioactivities up to the end of 2021Despite increasing numbers of marine natural products (MNPs) reported each year, most have only been examined for cytotoxic, antibacterial, and/or antifungal biological activities with the majority found to be inactive in these assays. In this context, why are natural products continuing to be examined in assays they are unlikely to show significant activity in, and what targets might be more useful for expanding knowledge of their biologically relevant chemical space? We have undertaken a meta-analysis of the biological activities for 2048 marine indole alkaloids (MIAs), a diverse sub-class of MNPs reported up to the end of 2021, and this has highlighted that the bioactivity potentials for up to 86% of published MIAs remains underexplored and/or undefined. Although most published MIAs are not cytotoxic or antimicrobial, there is a continued focus on using these assays to evaluate new structurally related analogues. Using cheminformatics analyses, the chemical diversity of the 2048 MIAs were clustered using fragment based fingerprints and their reported bioactivity potency towards specific disease targets was assessed for structure activity trends. These analyses showed that there are groups of MIAs that possess potent and diverse activities and that many analogues, previously tested only in cellular toxicity assays, could be better exploited to generate structure activity relationships associated with leads to treat emerging diseases. A collection of indole drug and drug-lead structures from non-natural sources were also incorporated into the dataset providing complementary bioactivity profiles that were further used to predict underexplored areas of potential new activity and to better direct future testing of MIAs. Our findings clearly suggest the biological evaluation of MIAs continues to be conducted on a narrow range of bioassays and disease targets, and that shifting the focus to non-toxic disease targets should provide expanded knowledge of biologically relevant chemical space aimed at maximising the potential of MIAs for drug discovery.

Peptides from Marine-Derived Fungi: Chemistry and Biological Activities

Marine natural products are well-recognized as potential resources to fill the pipeline of drug leads to enter the pharmaceutical industry. In this circumstance, marine-derived fungi are one of the unique sources of bioactive secondary metabolites due to their capacity to produce diverse polyketides and peptides with unique structures and diverse biological activities. The present review covers the peptides from marine-derived fungi reported from the literature published from January 1991 to June 2023, and various scientific databases, including Elsevier, ACS publications, Taylor and Francis, Wiley Online Library, MDPI, Springer, Thieme, Bentham, ProQuest, and the Marine Pharmacology website, are used for a literature search. This review focuses on chemical characteristics, sources, and biological and pharmacological activities of 366 marine fungal peptides belonging to various classes, such as linear, cyclic, and depsipeptides. Among 30 marine-derived fungal genera, isolated from marine macro-organisms such as marine algae, sponges, coral, and mangrove plants, as well as deep sea sediments, species of Aspergillus were found to produce the highest number of peptides (174 peptides), followed by Penicillium (23 peptides), Acremonium (22 peptides), Eurotium (18 peptides), Trichoderma (18 peptides), Simplicillium (17 peptides), and Beauveria (12 peptides). The cytotoxic activity against a broad spectrum of human cancer cell lines was the predominant biological activity of the reported marine peptides (32%), whereas antibacterial, antifungal, antiviral, anti-inflammatory, and various enzyme inhibition activities ranged from 7% to 20%. In the first part of this review, the chemistry of marine peptides is discussed and followed by their biological activity.

Tandocyclinones A and B, Ether Bridged C-Glycosyl Benz[a]anthracenes from an Intertidal Zone Streptomyces sp

Two new proton-deficient metabolites, tandocyclinones A and B (1 and 2), were discovered via the chemical profiling of the Streptomyces sp. strain TDH03, which was isolated from a marine sediment sample collected from the intertidal mudflat in Tando Port, the Republic of Korea. The structures of 1 and 2 were elucidated as new ether-bridged C-glycosyl benz[a]anthracenes by using a combination of spectroscopic analyses of ultraviolet (UV) and mass spectrometry (MS) data, along with nuclear magnetic resonance (NMR) spectra, which were acquired in tetrahydrofuran (THF)-d8 selected after an extensive search for a solvent, resulting in mostly observable exchangeable protons in the 1H NMR spectrum. Their configurations were successfully assigned by applying a J-based configuration analysis, rotating-frame Overhauser enhancement spectroscopy (ROESY) NMR correlations, chemical derivatization methods based on NMR (a modified version of Mosher's method) and circular dichroism (CD) (Snatzke's method using Mo2(OAc)4-induced CD), as well as quantum-mechanics-based computational methods, to calculate the electronic circular dichroism (ECD). Tandocyclinones A and B (1 and 2) were found to have weak antifungal activity against Trichophyton mentagrophytes IFM40996 with an MIC value of 128 μg/mL (244 and 265 μM for 1 and 2, respectively). A further biological evaluation revealed that tandocyclinone A (1) displayed inhibitory activity against Mycobacterium avium (MIC50 = 40.8 μM) and antiproliferative activity against SNU638 and HCT116 cancer cells, with IC50 values of 31.9 µM and 49.4 µM, respectively.

Dictyota and Canistrocarpus Brazilian Brown Algae and Their Bioactive Diterpenes-A Review

Dictyotaceae algae have gained recognition as prolific producers of diterpenes, which are molecules with significant biotechnological potential. These diterpenes hold immense promise as potential active drug components, making the algae a compelling area of study. The present review aims to present the latest advancements in understanding the biopotential of Brazilian Dictyota and Canistrocarpus brown algae, shedding light on the remarkable diversity and the biological and pharmacological potential of the secondary metabolites they produce. A total of 78 articles featuring 26 distinct diterpenes are reported in this review, with their antiviral potential being the mosthighlighted biological activity. Despite considerable research on these algae and their diterpenes, significant knowledge gaps persist. Consequently, the present review is poised to serve as a pivotal resource for researchers who are actively engaged in the pursuit of active diterpenes beyond the immediate purview. Furthermore, it holds the potential to catalyze an increase in research endeavors centered around these algal species within the geographical confines of the Brazilian coastline. Also, it assumes a critical role in directing future scientific explorations toward a better comprehension of these compounds and their ecological implications.

The biotechnological potential of Aeromonas: a bird's eye view

The genus Aeromonas comprises Gram-negative bacilli widely distributed in aquatic habitats that can also be found in the terrestrial environment and in close association with humans and animals. Aeromonas spp. are particularly versatile bacteria, with high genomic plasticity and notable capacity to adapt to different environments and extreme conditions. On account of being mostly associated with their pathogenic potential, research on the biotechnological potentialities of Aeromonas spp. is considerably scarce when compared to other bacterial groups. Nonetheless, studies over the years have been hinting at several interesting hidden potentialities in this bacterial group, especially with the recent advances in whole-genome sequencing, unveiling Aeromonas spp. as interesting candidates for the discovery of novel industrial biocatalysts, bioremediation strategies, and biopolyester production. In this context, the present study aims to provide an overview of the main biotechnological applications reported in the genus Aeromonas and provide new insights into the further exploration of these frequently overlooked, yet fascinating, bacteria.

Marine-Derived Components: Can They Be a Potential Therapeutic Approach to Parkinson's Disease?

The increase in the life expectancy average has led to a growing elderly population, thus leading to a prevalence of neurodegenerative disorders, such as Parkinson's disease (PD). PD is the second most common neurodegenerative disorder and is characterized by a progressive degeneration of the dopaminergic neurons in the substantia nigra pars compacta (SNpc). The marine environment has proven to be a source of unique and diverse chemical structures with great therapeutic potential to be used in the treatment of several pathologies, including neurodegenerative impairments. This review is focused on compounds isolated from marine organisms with neuroprotective activities on in vitro and in vivo models based on their chemical structures, taxonomy, neuroprotective effects, and their possible mechanism of action in PD. About 60 compounds isolated from marine bacteria, fungi, mollusk, sea cucumber, seaweed, soft coral, sponge, and starfish with neuroprotective potential on PD therapy are reported. Peptides, alkaloids, quinones, terpenes, polysaccharides, polyphenols, lipids, pigments, and mycotoxins were isolated from those marine organisms. They can act in several PD hallmarks, reducing oxidative stress, preventing mitochondrial dysfunction, α-synuclein aggregation, and blocking inflammatory pathways through the inhibition translocation of NF-kB factor, reduction of human tumor necrosis factor α (TNF-α), and interleukin-6 (IL-6). This review gathers the marine natural products that have shown pharmacological activities acting on targets belonging to different intracellular signaling pathways related to PD development, which should be considered for future pre-clinical studies.

Modified Atmosphere Packaging (MAP) for Seaweed Conservation: Impact on Physicochemical Characteristics and Microbiological Activity

Conventional conservation techniques such as drying, salting or freezing do not allow for preserving the original characteristics of seaweeds. The present work aims to study the impact of minimal processing, in particular "Modified Atmosphere Packaging" (MAP), on the physicochemical characteristics and food safety of two seaweed species, "laver" (Porphyra umbilicalis) and "sea-lettuce" (Ulva lactuca), stored at 6 °C for 15 days. Different parameters were evaluated using analytical methods, namely the composition of headspace gases, color, texture, microorganisms, and volatile organic compounds (VOCs). The main findings of this study were that the MAP treatment was able to inhibit the respiration rate of minimally processed seaweeds, also preserving their color and texture. There was a remarkable reduction in the microbial load for P. umbilicalis treated under modified and vacuum atmospheres, and U. lactuca exhibited relatively steady values with no notable differences between the treatments and the control. Therefore, during the 15-day study period, both seaweeds met the requirements for food safety. GC-TOF-MS allowed to conclude that both MAP and vacuum treatments were more efficient in maintaining the odor characteristics of U. lactuca compared to P. umbilicalis with no significant differences throughout the storage days. Metabolic responses to diverse sources of abiotic stress seemed to account for most of the changes observed.

Exploration of Bis-Cinnamido-Polyamines as Intrinsic Antimicrobial Agents and Antibiotic Enhancers

The marine natural product ianthelliformisamine C is a bis-cinnamido substituted spermine derivative that exhibits intrinsic antimicrobial properties and can enhance the action of doxycycline towards the Gram-negative bacterium Pseudomonas aeruginosa. As part of a study to explore the structure-activity requirements of these activities, we have synthesized a set of analogues that vary in the presence/absence of methoxyl group and bromine atoms and in the polyamine chain length. Intrinsic antimicrobial activity towards Staphylococcus aureus, methicillin-resistant S. aureus (MRSA) and the fungus Cryptococcus neoformans was observed for only the longest polyamine chain examples of non-brominated analogues while all examples bearing either one or two bromine atoms were active. Weak to no activity was typically observed towards Gram-negative bacteria, with exceptions being the longest polyamine chain examples 13f, 14f and 16f against Escherichia coli (MIC 1.56, 7.2 and 5.3 µM, respectively). Many of these longer polyamine-chain analogues also exhibited cytotoxic and/or red blood cell hemolytic properties, diminishing their potential as antimicrobial lead compounds. Two of the non-toxic, non-halogenated analogues, 13b and 13d, exhibited a strong ability to enhance the action of doxycycline against P. aeruginosa, with >64-fold and >32-fold enhancement, respectively. These results suggest that any future efforts to optimize the antibiotic-enhancing properties of cinnamido-polyamines should explore a wider range of aromatic ring substituents that do not include bromine or methoxyl groups.

Shifting archetype to nature's hidden gems: from sources, purification to uncover the nutritional potential of bioactive peptides

Contemporary scientific findings revealed that our daily food stuffs are enriched by encrypted bioactive peptides (BPs), evolved by peptide linkage of amino acids or encrypted from the native protein structures. Remarkable to these BPs lies in their potential health benefiting biological activities to serve as nutraceuticals or a lead addition to the development of functional foods. The biological activities of BPs vary depending on the sequence as well as amino acid composition. Existing database records approximately 3000 peptide sequences which possess potential biological activities such as antioxidants, antihypertensive, antithrombotic, anti-adipogenics, anti-microbials, anti-inflammatory, and anti-cancerous. The growing evidences suggest that BPs have very low toxicity, higher accuracy, less tissue accretion, and are easily degraded in the disposed environment. BPs are nowadays evolved as biologically active molecules with potential scope to reduce microbial contamination as well as ward off oxidation of foods, amend diverse range of human diseases to enhance the overall quality of human life. Against the clinical and health perspectives of BPs, this review aimed to elaborate current evolution of nutritional potential of BPs, studies pertaining to overcome limitations with respect to special focus on emerging extraction, protection and delivery tools of BPs. In addition, the nano-delivery mechanism of BP and its clinical significance is detailed. The aim of current review is to augment the research in the field of BPs production, identification, characterisation and to speed up the investigation of the incredible potentials of BPs as potential nutritional and functional food ingredient.

Tolypocaibols: Antibacterial Lipopeptaibols from a Tolypocladium sp. Endophyte of the Marine Macroalga Spongomorpha arcta

Two new lipopeptaibols, tolypocaibols A (1) and B (2), and the mixed NRPS-polyketide-shikimate natural product maximiscin [(P/M)-3)] were isolated from a Tolypocladium sp. fungal endophyte of the marine alga Spongomorpha arcta. Analysis of NMR and mass spectrometry data revealed the amino acid sequences of the lipopeptaibols, which both comprise 11 residues with a valinol C-terminus and a decanoyl acyl chain at the N-terminus. The configuration of the amino acids was determined by Marfey's analysis. Tolypocaibols A (1) and B (2) showed moderate, selective inhibition against Gram-positive and acid-fast bacterial strains, while maximiscin [(P/M)-3)] showed moderate, broad-spectrum antibiotic activity.

Five Sesquiterpenes from Paraconiothyrium sp. and Their Anti-inflammatory Activity

Five eremophilane sesquiterpenes including three new ones, named paraconions A-C (1-3), were isolated from an endophytic fungus, Paraconiothyrium sp. from Artemisia selengensis. The structures of these new compounds were established based on spectroscopic methods, including nuclear magnetic resonance (NMR), ultraviolet (UV), and infrared (IR) spectroscopy, as well as high resolution electrospray ionization mass spectrometry (HR-ESI-MS). An anti-inflammatory assay indicated that paraconion B (2) inhibited lipopolysaccharide-induced nitric oxide (NO) production in RAW 264.7 cells, with an IC50 value of 51.7 μM. The compounds discovered in this study will enrich the structural types of secondary metabolites of the endophytic fungus Paraconiothyrium sp.