Current Status and Future Prospects of Marine Natural Products (MNPs) as Antimicrobials

Exploring marine natural products for identifying putative candidates as EBNA1 inhibitors: An insight from molecular docking, molecular dynamics, and DFT computations

Epstein-Barr virus (EBV), namely a DNA neoplasm virus, is liable for over 1 % of malignant neoplasms involving Hodgkin's and Burkitt's lymphoma as well as ventral cancer. Despite the crucial role of EBV in carcinoma evolution, no treatment has been discovered yet against EBV. Epstein-Barr nuclear antigen 1 (EBNA1), the EBV-encoded latent protein, is produced in all EBV-linked neoplasms and is the only latent protein in these cancer types. EBNA1 protein has multiple roles in the upkeep, reproduction, and EBV genome separation and can thus act as an attractive therapeutic target for treating EBV-related malignancies. In the past few decades, attempts have been made to develop specialized EBNA1 inhibitors to reduce EBNA1 expression or obstruct EBNA1-relied processes, but none has been approved yet. Marine natural products (MNPs) have garnered significant interest as potential sources of antiviral drug candidates. In seeking potent drug candidates to inhibit EBV reproduction, an MNP database containing >14,000 compounds was mined to hunt putative EBNA1 inhibitors using docking computations and molecular dynamics simulations (MDS). On the basis of binding energy (ΔGbinding) estimations over 200 ns MDS, UMHMNP351444649 and UMHMNP134128179 revealed a greater binding affinity towards EBNA1 compared to KWG, with ΔGbinding values of -35.6, -33.3, and -32.4 kcal/mol, respectively. Structural and energetical investigations of UMHMNP351444649 and UMHMNP134128179 complexed with EBNA1 were inspected, unveiling the great constancy of these inhibitors within the EBNA1 binding site. Moreover, the identified MNPs demonstrated favorable physicochemical and medicinal chemistry characteristics. Finally, density functional theory calculations were executed, and the results assured the outcomes obtained from docking computations and MDS. These findings proposed UMHMNP351444649 and UMHMNP134128179 as potential anti-EBV drug candidates that warrant further in-vitro and in-vivo assays.

Investigating the antimicrobial and antibiofilm properties of marine halophilic Bacillus species against ESKAPE pathogens

Antimicrobial resistance (AMR), known as the "silent pandemic," is exacerbated by pathogenic bacteria's ability to form biofilms. Marine compounds hold promise for novel antibacterial drug discovery. Two isolates from preliminary saltwater environment screening demonstrated antimicrobial activity and were subsequently identified as Bacillus subtilis MTUA2 and Bacillus velezensis MTUC2. Minimum inhibitory concentrations (MICs), minimum biofilm inhibition concentrations (MBICs) and minimum biofilm eradication concentrations (MBECs) required to prevent and/or disrupt bacterial growth and biofilm formation were established for MRSA, Staphylococcus aureus, Acinetobacter baumannii and Escherichia coli. The metabolic activity within biofilms was determined by the 2,3,5-triphenyltetrazolium chloride assay. Both Bacillus species exhibited unique antimicrobial effects, reducing MRSA and S. aureus planktonic cell growth by 50% and sessile cell growth for S. aureus and E. coli by 50% and 90%, respectively. No effect was observed against A. baumannii. Significant MBIC and MBEC values were achieved, with 99% inhibition and 90% reduction in MRSA and S. aureus biofilms. Additionally, 90% and 50% inhibition was observed in E. coli and A. baumannii biofilms, respectively, with a 50% reduction in E. coli biofilm. These findings suggest that the mode of action employed by B. subtilis MTUA2 and B. velezensis MTUC2 metabolites should be further characterized and could be beneficial if used independently or in combination with other treatments.

Recent advancement of novel marine fungi derived secondary metabolite fibrinolytic compound FGFC in biomedical applications: a review

For several decades, products derived from marine natural sources (PMN) have been widely identified for several therapeutic applications due to their rich sources of bioactive sub-stances, unique chemical diversity, biocompatibility and excellent biological activity. For the past 15 years, our research team explored several PMNs, especially fungi fibrinolytic compounds (FGFCs). FGFC is an isoindolone alkaloid derived from marine fungi, also known as staplabin analogs or Stachybotrys microspora triprenyl phenol (SMTP). For instance, our previous studies explored different types of FGFCs such as FGFC 1, 2, 3 and 4 from the marine fungi Stachybotrys longispora FG216 derived metabolites. The derivatives of FGFC are potentially employed in several disease treatments, mainly for stroke, cancer, ischemia, acute kidney injury, inflammation, cerebral infarction, thrombolysis and hemorrhagic activities, etc. Due to the increasing use of FGFCs in pharmaceutical and biomedical applications, it is important to understand the fundamental signaling concept of FGFCs. Hence, for the first time, this review collectively summarizes the background, types, mode of action and biological applications of FGFCs and their current endeavors for future therapies.

Injectable pH- and Ultrasound-Responsive Dual-Crosslinked Dextran/Chitosan/TiO2 Nanocomposite Hydrogels for Antibacterial Applications

Combining exogenous and endogenous antibacterial mechanisms has been demonstrated to enhance therapeutic efficacy significantly. This study constructs an innovative type of exogenous and endogenous antibacterial nanocomposite hydrogels with injectable dual-crosslinked networks and dual-stimuli responsiveness. The primary network establishes imine bonds between the functionalized dextran featuring norbornenes and aldehydes (NorAld-Dex) and the quaternized chitosan (QCS). The imine bonds provide self-healing, injectability, and pH-responsiveness to the hydrogel network. The secondary network is established by integrating thiolated mesoporous silica-coated titanium dioxide nanoparticles (TiO2@MS-SH) into the hydrogel network via an ultrasound-activated thiol-norbornene reaction with NorAld-Dex. The microstructures and properties of NorAld-Dex/QCS/TiO2@MS-SH hydrogels can be fine-tuned by adjusting the sonication time to increase the amount of thiol-norbornene crosslinks in the network. Effective antibacterial performance of NorAld-Dex/QCS/TiO2@MS-SH hydrogels at low pH has been demonstrated with the synergistic effect of the acid-induced dissociation of the hydrogel network, protonated QCS, and the reactive oxygen species (ROS) generated by TiO2@MS-SH nanoparticles under ultrasound irradiation. In summary, NorAld-Dex/QCS/TiO2@MS-SH nanocomposite hydrogel is an advanced dual stimuli-responsive antibacterial platform with customizable microstructures and properties, offering great potential for biomedical applications.

A guide to the use of bioassays in exploration of natural resources

Bioassays are the main tool to decipher bioactivities from natural resources thus their selection and quality are critical for optimal bioprospecting. They are used both in the early stages of compounds isolation/purification/identification, and in later stages to evaluate their safety and efficacy. In this review, we provide a comprehensive overview of the most common bioassays used in the discovery and development of new bioactive compounds with a focus on marine bioresources. We present a comprehensive list of practical considerations for selecting appropriate bioassays and discuss in detail the bioassays typically used to explore antimicrobial, antibiofilm, cytotoxic, antiviral, antioxidant, and anti-ageing potential. The concept of quality control and bioassay validation are introduced, followed by safety considerations, which are critical to advancing bioactive compounds to a higher stage of development. We conclude by providing an application-oriented view focused on the development of pharmaceuticals, food supplements, and cosmetics, the industrial pipelines where currently known marine natural products hold most potential. We highlight the importance of gaining reliable bioassay results, as these serve as a starting point for application-based development and further testing, as well as for consideration by regulatory authorities.

Computational insights into potential marine natural products as selective inhibitors of Mycobacterium tuberculosis InhA: A structure-based virtual screening study

Several factors are associated with the emergence of drug resistance mechanisms, such as impermeable cell walls, gene mutations, and drug efflux systems. Consequently, bacteria acquire resistance, leading to a decrease in drug efficacy. A new and innovative strategy is required to combat drug resistance in tuberculosis (TB) effectively. Therefore, targeting the mycolic acid biosynthesis pathway, which is involved in synthesising mycolic acids (MAs), essential structural components responsible for mycobacterial pathogenicity, has garnered interest in TB research and the concept of drug resistance. In this context, InhA, which plays a crucial role in the fatty acid synthase-II (FAS-II) system of the MA biosynthetic pathway, was selected as a druggable target for screening investigation. To identify potential lead molecules against InhA, diverse marine natural products (MNPs) were collected from the comprehensive marine natural products database (CMNPD). Virtual screening studies aided in selecting potential lead molecules that best fit within the substrate-binding pocket (SBP) of InhA, forming crucial hydrogen bond interaction with the catalytic residue Tyr158. Three MNPs, CMNPD30814, CMNPD1702, and CMNPD27355, were chosen as prospective alternative molecules due to their favorable pharmacokinetic properties and lack of toxicity according to ProTox-II predictions. Additionally, improved reactivity of the MNPs was observed in the results of density functional theory (DFT) studies. Furthermore, comparative molecular dynamics simulation (MDS), principal component (PC)-based free energy landscape (FEL) analysis, and molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) were employed to show enhanced structural stability, increased H-bond potential, and high binding affinity toward the target InhA. Moreover, the hot spot residues that contributed to the high binding energy profile and anchored the stability of the complexes were revealed with their individual interaction energy. The computational insights from this study provide potential avenues to combat TB through the multifaceted mode of action of these marine lead molecules, which can be further explored in future experimental investigations.

The Chemical Space of Marine Antibacterials: Diphenyl Ethers, Benzophenones, Xanthones, and Anthraquinones

The emergence of multiresistant bacteria and the shortage of antibacterials in the drug pipeline creates the need to search for novel agents. Evolution drives the optimization of the structure of marine natural products to act as antibacterial agents. Polyketides are a vast and structurally diverse family of compounds that have been isolated from different marine microorganisms. Within the different polyketides, benzophenones, diphenyl ethers, anthraquinones, and xanthones have shown promising antibacterial activity. In this work, a dataset of 246 marine polyketides has been identified. In order to characterize the chemical space occupied by these marine polyketides, molecular descriptors and fingerprints were calculated. Molecular descriptors were analyzed according to the scaffold, and principal component analysis was performed to identify the relationships among the different descriptors. Generally, the identified marine polyketides are unsaturated, water-insoluble compounds. Among the different polyketides, diphenyl ethers tend to be more lipophilic and non-polar than the remaining classes. Molecular fingerprints were used to group the polyketides according to their molecular similarity into clusters. A total of 76 clusters were obtained, with a loose threshold for the Butina clustering algorithm, highlighting the large structural diversity of the marine polyketides. The large structural diversity was also evidenced by the visualization trees map assembled using the tree map (TMAP) unsupervised machine-learning method. The available antibacterial activity data were examined in terms of bacterial strains, and the activity data were used to rank the compounds according to their antibacterial potential. This potential ranking was used to identify the most promising compounds (four compounds) which can inspire the development of new structural analogs with better potency and absorption, distribution, metabolism, excretion, and toxicity (ADMET) properties.

Marine Algal Polyphenols as Skin Protective Agents: Current Status and Future Prospectives

The skin is the outermost anatomical barrier, which plays a vital role in the maintenance of internal homeostasis and protection against physical, chemical, and biological detractors. Direct contact with various stimuli leads to several physiological changes that are ultimately important for the growth of the cosmetic industry. Due to the consequences of using synthetic compounds in skincare and cosmeceutical-related industries, the pharmaceutical and scientific communities have recently shifted their focus to natural ingredients. The nutrient-rich value of algae, which are some of the most interesting organisms in marine ecosystems, has attracted attention. Secondary metabolites isolated from seaweeds are potential candidates for a wide range of economic applications, including food, pharmaceuticals, and cosmetics. An increasing number of studies have focused on polyphenol compounds owing to their promising biological activities against oxidation, inflammation, allergies, cancers, melanogenesis, aging, and wrinkles. This review summarizes the potential evidence of the beneficial properties and future perspectives of using marine macroalgae-derived polyphenolic compounds for advancing the cosmetic industry.

Marine-Derived Lead Fascaplysin: Pharmacological Activity, Total Synthesis, and Structural Modification

Fascaplysin is a planar structure pentacyclic alkaloid isolated from sponges, which can effectively induce the apoptosis of cancer cells. In addition, fascaplysin has diverse biological activities, such as antibacterial, anti-tumor, anti-plasmodium, etc. Unfortunately, the planar structure of fascaplysin can be inserted into DNA and such interaction also limits the further application of fascaplysin, necessitating its structural modification. In this review, the biological activity, total synthesis and structural modification of fascaplysin will be summarized, which will provide useful information for pharmaceutical researchers interested in the exploration of marine alkaloids and for the betterment of fascaplysin in particular.

Antibacterial potential of Luidia clathrata (sea star) tissue extracts against selected pathogenic bacteria

As resistance to traditional antibiotics has become a major issue, it is essential to explore natural sources for new antimicrobial agents. The marine environment offers a variety of natural bioactive compounds. In this study, we examined the antibacterial potential of Luidia clathrata, a tropical sea star species. The experiment was conducted against both gram-positive (Bacillus subtilis, Enterococcus faecalis, Staphylococcus aureus, Bacillus cereus and Mycobacterium smegmatis) and gram-negative (Proteus mirabilis, Salmonella typhimurium, Escherichia coli, Pseudomonas aeruginosa and Klebsiella pneumoniae) bacteria using disk diffusion method. Specifically, we extracted the body wall and gonad using methanol, ethyl acetate, and hexane. Our findings show that the body wall extract using ethyl acetate (1.78μg/ml) was particularly effective against all tested pathogens, while the gonad extract (0.107μg/ml) showed activity against six out of ten selected pathogens. This is a crucial and new discovery that suggests L. clathrata may be a useful source for discovering antibiotics and more research is required to pinpoint and comprehend the active ingredients.

Antifungal and Antibacterial Activities of Isolated Marine Compounds

To combat the ineffectiveness of currently available pharmaceutical medications, caused by the emergence of increasingly resistant bacterial and fungal strains, novel antibacterial and antifungal medications are urgently needed. Novel natural compounds with antimicrobial activities can be obtained by exploring underexplored habitats such as the world's oceans. The oceans represent the largest ecosystem on earth, with a high diversity of organisms. Oceans have received some attention in the past few years, and promising compounds with antimicrobial activities were isolated from marine organisms such as bacteria, fungi, algae, sea cucumbers, sea sponges, etc. This review covers 56 antifungal and 40 antibacterial compounds from marine organisms. These compounds are categorized according to their chemical structure groups, including polyketides, alkaloids, ribosomal peptides, and terpenes, and their organismal origin. The review provides the minimum inhibitory concentration MIC values and the bacterial/fungal strains against which these chemical compounds show activity. This study shows strong potential for witnessing the development of new novel antimicrobial drugs from these natural compounds isolated and evaluated for their antimicrobial activities.

Chetomin, a SARS-CoV-2 3C-like Protease (3CLpro) Inhibitor: In Silico Screening, Enzyme Docking, Molecular Dynamics and Pharmacokinetics Analysis

The emergence of the Coronavirus Disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has led to over 6 million deaths. The 3C-like protease (3CLpro) enzyme of the SARS-CoV-2 virus is an attractive druggable target for exploring therapeutic drug candidates to combat COVID-19 due to its key function in viral replication. Marine natural products (MNPs) have attracted considerable attention as alternative sources of antiviral drug candidates. In looking for potential 3CLpro inhibitors, the MNP database (>14,000 molecules) was virtually screened against 3CLpro with the assistance of molecular docking computations. The performance of AutoDock and OEDocking software in anticipating the ligand-3CLpro binding mode was first validated according to the available experimental data. Based on the docking scores, the most potent MNPs were further subjected to molecular dynamics (MD) simulations, and the binding affinities of those molecules were computed using the MM-GBSA approach. According to MM-GBSA//200 ns MD simulations, chetomin (UMHMNP1403367) exhibited a higher binding affinity against 3CLpro than XF7, with ΔGbinding values of −55.5 and −43.7 kcal/mol, respectively. The steadiness and tightness of chetomin with 3CLpro were evaluated, revealing the high stabilization of chetomin (UMHMNP1403367) inside the binding pocket of 3CLpro throughout 200 ns MD simulations. The physicochemical and pharmacokinetic features of chetomin were also predicted, and the oral bioavailability of chetomin was demonstrated. Furthermore, the potentiality of chetomin analogues −namely, chetomin A-D− as 3CLpro inhibitors was investigated. These results warrant further in vivo and in vitro assays of chetomin (UMHMNP1403367) as a promising anti-COVID-19 drug candidate.

Seaweeds in the Oncology Arena: Anti-Cancer Potential of Fucoidan as a Drug—A Review

Marine natural products are a discerning arena to search for the future generation of medications to treat a spectrum of ailments. Meanwhile, cancer is becoming more ubiquitous over the world, and the likelihood of dying from it is rising. Surgery, radiation, and chemotherapy are the mainstays of cancer treatment worldwide, but their extensive side effects limit their curative effect. The quest for low-toxicity marine drugs to prevent and treat cancer is one of the current research priorities of researchers. Fucoidan, an algal sulfated polysaccharide, is a potent therapeutic lead candidate against cancer, signifying that far more research is needed. Fucoidan is a versatile, nontoxic marine-origin heteropolysaccharide that has received much attention due to its beneficial biological properties and safety. Fucoidan has been demonstrated to exhibit a variety of conventional bioactivities, such as antiviral, antioxidant, and immune-modulatory characteristics, and anticancer activity against a wide range of malignancies has also recently been discovered. Fucoidan inhibits tumorigenesis by prompting cell cycle arrest and apoptosis, blocking metastasis and angiogenesis, and modulating physiological signaling molecules. This review compiles the molecular and cellular aspects, immunomodulatory and anticancer actions of fucoidan as a natural marine anticancer agent. Specific fucoidan and membranaceous polysaccharides from Ecklonia cava, Laminaria japonica, Fucus vesiculosus, Astragalus, Ascophyllum nodosum, Codium fragile serving as potential anticancer marine drugs are discussed in this review.

Natural Products of Marine Origin for the Treatment of Colorectal and Pancreatic Cancers: Mechanisms and Potential

Gastrointestinal cancer refers to malignancy of the accessory organs of digestion, and it includes colorectal cancer (CRC) and pancreatic cancer (PC). Worldwide, CRC is the second most common cancer among women and the third most common among men. PC has a poor prognosis and high mortality, with 5-year relative survival of approximately 11.5%. Conventional chemotherapy treatments for these cancers are limited due to severe side effects and the development of drug resistance. Therefore, there is an urgent need to develop new and safe drugs for effective treatment of PC and CRC. Historically, natural sources—plants in particular—have played a dominant role in traditional medicine used to treat a wide spectrum of diseases. In recent decades, marine natural products (MNPs) have shown great potential as drugs, but drug leads for treating various types of cancer, including CRC and PC, are scarce. To date, marine-based drugs have been used against leukemia, metastatic breast cancer, soft tissue sarcoma, and ovarian cancer. In this review, we summarized existing studies describing MNPs that were found to have an effect on CRC and PC, and we discussed the potential mechanisms of action of MNPs as well as future prospects for their use in treating these cancers.

Marine Actinomycetes Associated with Stony Corals: A Potential Hotspot for Specialized Metabolites

Microbial secondary metabolites are an important source of antibiotics currently available for combating drug-resistant pathogens. These important secondary metabolites are produced by various microorganisms, including Actinobacteria. Actinobacteria have a colossal genome with a wide array of genes that code for several bioactive metabolites and enzymes. Numerous studies have reported the isolation and screening of millions of strains of actinomycetes from various habitats for specialized metabolites worldwide. Looking at the extent of the importance of actinomycetes in various fields, corals are highlighted as a potential hotspot for untapped secondary metabolites and new bioactive metabolites. Unfortunately, knowledge about the diversity, distribution and biochemistry of marine actinomycetes compared to hard corals is limited. In this review, we aim to summarize the recent knowledge on the isolation, diversity, distribution and discovery of natural compounds from marine actinomycetes associated with hard corals. A total of 11 new species of actinomycetes, representing nine different families of actinomycetes, were recovered from hard corals during the period from 2007 to 2022. In addition, this study examined a total of 13 new compounds produced by five genera of actinomycetes reported from 2017 to 2022 with antibacterial, antifungal and cytotoxic activities. Coral-derived actinomycetes have different mechanisms of action against their competitors.

Two New Alkaloids from the Marine-Derived Fungus Penicillium sp. LSH-3-1

Two new alkaloids, peniokaramine (1) and penipyranopyridine (6), along with seven known compounds, were isolated from the marine-derived fungus Penicillium sp. LSH-3-1. Their structures were elucidated from UV, IR, MS, 1D and 2D NMR spectroscopic data. The anti-inflammatory potential of compounds 1-8 in LPS-induced RAW264.7 cells was detected, revealing that compounds 3 and 5 significantly decreased LPS-induced production of pro-inflammatory mediators, including NO, IL-6 and TNF-α. Compounds 1-8 were also screened for their cytotoxic activity against A549 cells and compound 1 showed moderate activity.

Discovery of Anti-MRSA Secondary Metabolites from a Marine-Derived Fungus Aspergillus fumigatus

Methicillin-resistant Staphylococcus aureus (MRSA), a WHO high-priority pathogen that can cause great harm to living beings, is a primary cause of death from antibiotic-resistant infections. In the present study, six new compounds, including fumindoline A-C (1-3), 12β, 13β-hydroxy-asperfumigatin (4), 2-epi-tryptoquivaline F (17) and penibenzophenone E (37), and thirty-nine known ones were isolated from the marine-derived fungus Aspergillus fumigatus H22. The structures and the absolute configurations of the new compounds were unambiguously assigned by spectroscopic data, mass spectrometry (MS), electronic circular dichroism (ECD) spectroscopic analyses, quantum NMR and ECD calculations, and chemical derivatizations. Bioactivity screening indicated that nearly half of the compounds exhibit antibacterial activity, especially compounds 8 and 11, and 33-38 showed excellent antimicrobial activities against MRSA, with minimum inhibitory concentration (MIC) values ranging from 1.25 to 2.5 μM. In addition, compound 8 showed moderate inhibitory activity against Mycobacterium bovis (MIC: 25 μM), compound 10 showed moderate inhibitory activity against Candida albicans (MIC: 50 μM), and compound 13 showed strong inhibitory activity against the hatching of a Caenorhabditis elegans egg (IC50: 2.5 μM).

Bixa orellana L. (Achiote, Annatto) as an antimicrobial agent: A scoping review of its efficiency and technological prospecting

ETHNOPHARMACOLOGICAL RELEVANCE

Bixa orellana L. is reported to have numerous applications in traditional medicine and pharmacological properties such as wound healing, analgesic, hemostatic, and antioxidant activities. Recently, the literature has shown scientific interest of its antimicrobial properties aiming the development of cost-effective phytotherapeutic agents. However, no literature are available in witch the antimicrobial and technological prospecting are summarized.

AIM OF STUDY

This study aimed to systematically review articles and patents related to the antimicrobial activity of B. orellana.

METHODS

The review followed the guidelines proposed by The Joanna Briggs Institute and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. Two reviewers performed a literature search up to November 2021 in eight databases: Medline (PubMed), Scopus, Scifinder, Web of Science, Cochrane, Embase, Scielo, and Biblioteca Virtual em Saúde. The following databases for the patent search were analyzed: United States Patent and Trademark Office (USPTO), Google Patents, National Institute of Industrial Property (INPI), World Intellectual Property Organization (WIPO), and Espacenet (European Patent Office, EPO). The grey literature was searched using the ProQuest Dissertations and Periódicos Capes Theses database. The methodological quality and risk of bias in the included studies were carried out using Review Manager (RevMan) 5.3.5.

RESULTS

After analyzing the 47 studies and five patents fulfilled all the criteria and were included in the present investigation. The evidence suggests that this herbal medicine is effective against several fungi, Gram-positive and Gram-negative bacteria, being more effective to Gram-negative bacteria. Regarding the risk of bias and methodological quality analysis, most studies a high risk of bias related to random sequence generation and allocation concealment.

CONCLUSION

Up to now, the evidence in the literature suggests that the use of B. orellana preparations for antimicrobial preparations has some effectiveness. However, further research is needed using standard B. orellana preparations to determine their effectiveness as antimicrobial agents and expanding their application at an industrial level, in addition in vivo studies are needed for this confirmation.

Antibacterial Molecules from Marine Microorganisms against Aquatic Pathogens: A Concise Review

Antibiotic resistance and residues in aquaculture are a growing concern worldwide and consequently identifying favorable antibacterial compounds against aquatic pathogenic bacteria are gained more attention. Active compounds derived from marine microorganisms have shown great promise in this area. This review is aimed to make a comprehensive survey of anti-aquatic pathogenic bacterial compounds that were produced by marine microorganisms. A total of 79 compounds have been reported, covering literature from 1997 to 2021. The compounds are included in different structural classes such as polyketides, terpenoids, nitrogen compounds and others, and some of them present the potential to be developed into agents for the treatment of aquatic pathogenic bacteria.

Role of microalgal metabolites in controlling quorum-sensing-regulated biofilm

Bacterial infections are primarily caused due to the formation of biofilms on the surfaces. The formation of bacterial biofilms results in 60-70% of nosocomial infections in hospital-acquired infections for multidrug-resistant bacteria. Quorum-sensing (QS) is the process of cell-cell communications among bacterial cells. The formation and regulation of biofilm-producing signaling molecules, competence for DNA uptake and factors responsible for virulence occur. When the bacterial cell population density increases, auto-inducers bind with QS receptors and induce gene expression. To suppress the expression of the virulence genes, certain antibiotics and small molecules are used against the pathogenic bacteria. Since the microorganisms are becoming resistant to antibiotics, there is a need of new compounds or molecules which can suppress or inhibit the expression or regulation of virulence genes. Microalgae are an important and rich source of bioactive compounds which have the antimicrobial property. Microalgae have various antibacterial metabolites, such as Portoamides (peptides), flavonoids, eicosapentaenoic acid, alkaloids, peptides and many other secondary metabolites. This review focuses on the signaling molecule-regulated QS mechanism, biofilm formation, and microalgae compounds' effects against pathogenic bacteria. Consequently, most of the compounds have made it to the different levels of clinical trials, even some of the compounds are used therapeutically. Despite the promising applications of antibacterial peptides and the importance of searching for new natural sources of antibiotics, limitations persist for their pharmaceutical applications. However, given due research impetus, these marine metabolites might emerge as a new wave of promising drugs.

Promising antiparasitic agents from marine sponges

Parasitic diseases especially those prevail in tropical and subtropical regions severely threaten the lives of people due to available drugs found to be ineffective as several resistant strains have been emerged. Due to the complexity of the marine environment, researchers considered it as a new field to search for compounds with therapeutic efficacy, marine sponges represents the milestone in the discovery of unique compounds of potent activities against parasitic infections. In the present article, literatures published from 2010 until March 2021 were screened to review antiparasitic potency of bioactive compounds extracted from marine sponges. 45 different genera of sponges have been studied for their antiparasitic activities. The antiparasitic activity of the crude extract or the compounds that have been isolated from marine sponges were assayed in vitro against Plasmodium falciparum, P. berghei, Trypanosoma brucei rhodesiense, T. b. brucei, T. cruzi, Leishmania donovani, L. tropica, L. infantum, L. amazonesis, L. major, L. panamesis, Haemonchus contortus and Schistosoma mansoni. The majority of antiparastic compounds extracted from marine sponges were related to alkaloids and peroxides represent the second important group of antiparasitic compounds extracted from sponges followed by terpenoids. Some substances have been extracted and used as antiparasitic agents to a lesser extent like steroids, amino acids, lipids, polysaccharides and isonitriles. The activities of these isolated compounds against parasites were screened using in vitro techniques. Compounds' potent activity in screened papers was classified in three categories according to IC₅₀: low active or inactive, moderately active and good potent active.

Whole-genome sequence and broad-spectrum antibacterial activity of Chryseobacterium cucumeris strain MW-6 isolated from the Arabian Sea

In the current study, Chryseobacterium cucumeris strain MW-6 isolated from Arabian seawater exhibited broad-spectrum antibacterial activity against indicator bacterial pathogens. The partially extracted antibacterial metabolites with ethyl acetate revealed promising activity against Escherichia coli, Pseudomonas aeruginosa, Salmonella typhimurium, Listeria monocytogenes, and Staphylococcus aureus. The minimum inhibitory concentrations (MICs) were determined against indicator strains that ranged from 65-90 µg/ml. The genome size of C. cucumeris MW-6 is 4.81 Mbs containing 4227 coding DNA sequences, 74 tRNAs, 3 rRNAs, and 3 ncRNAs genes with 36.90% GC contents. The genome harbors nine putative biosynthetic gene clusters (BGCs) involved in the biosynthesis of lanthipeptide, NRPS-like, RiPPs-like, terpene, microviridin, T1PKS (hg1E-KS), resorcinol, and siderophore. Additionally, the strain encodes genes for sodium/proton antiporter, glutathione, superoxide dismutase, and cold shock protein to survive under stress conditions such as osmotic, oxidative, and cold shock. These putative BGCs and stress-related genes can be associated with in-vitro antibacterial activities and adaptation of this strain to the marine environment.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-03039-5.

Antibacterial activity of four recombinant carbohydrate recognition domain proteins identified from the kuruma shrimp Marsupenaeus japonicus

The carbohydrate recognition domain (CRD) is the key component of C-type lectins (CTLs) with the capacity to recognize and eliminate invading pathogens. Herein, the recombinant proteins of four CRDs identified from the kuruma shrimp, Marsupenaeus japonicus, were produced and purified by an Escherichia coli expression system and affinity chromatography. Bacterial binding and antibacterial assays showed that the four CRDs displayed various bacterial binding and antibacterial activities against different bacteria. Among the four recombinant CRDs, His-CRD2-3 exhibited the broadest spectrum of bacterial binding and antibacterial activities against gram-negative bacteria (Vibrio parahaemolyticus, V. alginolyticus and V. harveyi) and gram-positive bacteria (Staphylococcus aureus and Micrococcus lysodeikticus). Moreover, the four recombinant CRDs showed different capacities to regulate the expression of several immune effector genes (MjCTL3, MjCTL4, MjCTL, Mjily and Mjsty), among which His-CRD2-3 displayed broader and stronger inductive effects on these immune effector genes. This study indicated that the four CRDs participated in immune defense by binding and killing bacteria and regulating the transcription of other immune effector genes. In addition, our results suggested that His-CRD2-3 might be a promising agent for the prevention and treatment of bacteriosis.

Chemical Evaluation, Antioxidant, Antiproliferative, Anti-Inflammatory and Antibacterial Activities of Organic Extract and Semi-Purified Fractions of the Adriatic Sea Fan, Eunicella cavolini

Due to sedentary lifestyle and harsh environmental conditions, gorgonian coral extracts are recognized as a rich source of novel compounds with various biological activities, of interest to the pharmaceutical and cosmetic industries. The presented study aimed to perform chemical screening of organic extracts and semi-purified fractions obtained from the common Adriatic gorgonian, sea fan, Eunicella cavolini (Koch, 1887) and explore its abilities to exert different biological effects in vitro. Qualitative chemical evaluation revealed the presence of several classes of secondary metabolites extended with mass spectrometry analysis and tentative dereplication by using Global Natural Product Social Molecular Networking online platform (GNPS). Furthermore, fractions F4 and F3 showed the highest phenolic (3.28 ± 0.04 mg GAE/g sample) and carotene (23.11 ± 2.48 mg β-CA/g sample) content, respectively. The fraction F3 inhibited 50% of DPPH (2,2-diphenyl-1-picryl-hydrazyl-hydrate) and ABTS (2,2′-azino-bis (3-ethylbenzthiazolin-6-yl) sulfonic acid) radicals at the concentrations of 767.09 ± 11.57 and 157.16 ± 10.83 µg/mL, respectively. The highest anti-inflammatory potential was exhibited by F2 (IC₅₀ = 198.70 ± 28.77 µg/mL) regarding the inhibition of albumin denaturation and F1 (IC₅₀ = 254.49 ± 49.17 µg/mL) in terms of soybean lipoxygenase inhibition. In addition, the most pronounced antiproliferative effects were observed for all samples (IC₅₀ ranging from 0.82 ± 0.14–231.18 ± 46.13 µg/mL) against several carcinoma cell lines, but also towards non-transformed human fibroblasts pointing to a generally cytotoxic effect. In addition, the antibacterial activity was tested by broth microdilution assay against three human pathogenic bacteria: Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. The latter was the most affected by fractions F2 and F3. Finally, further purification, isolation and characterization of pure compounds from the most active fractions are under investigation.

Marine Bacterial Secondary Metabolites: A Treasure House for Structurally Unique and Effective Antimicrobial Compounds

The prevalence of antimicrobial resistance reduces the effectiveness of antimicrobial drugs in preventing and treating infectious diseases caused by pathogenic organisms, such as bacteria, fungi, and viruses. Because of the burgeoning growth of microbes with antimicrobial-resistant traits, there is a dire need to identify and develop novel and effective antimicrobial agents to treat infections from antimicrobial-resistant strains. The marine environment is rich in ecological biodiversity and can be regarded as an untapped resource for prospecting novel bioactive compounds. Therefore, exploring the marine environment for antimicrobial agents plays a significant role in drug development and biomedical research. Several earlier scientific investigations have proven that bacterial diversity in the marine environment represents an emerging source of structurally unique and novel antimicrobial agents. There are several reports on marine bacterial secondary metabolites, and many are pharmacologically significant and have enormous promise for developing effective antimicrobial drugs to combat microbial infections in drug-resistant pathogens. In this review, we attempt to summarize published articles from the last twenty-five years (1996–2020) on antimicrobial secondary metabolites from marine bacteria evolved in marine environments, such as marine sediment, water, fauna, and flora.

A Thermotolerant Marine Bacillus amyloliquefaciens S185 Producing Iturin A5 for Antifungal Activity against Fusarium oxysporum f. sp. cubense

Fusarium wilt of banana (also known as Panama disease), is a severe fungal disease caused by soil-borne Fusarium oxysporum f. sp. cubense (Foc). In recent years, biocontrol strategies using antifungal microorganisms from various niches and their related bioactive compounds have been used to prevent and control Panama disease. Here, a thermotolerant marine strain S185 was identified as Bacillus amyloliquefaciens, displaying strong antifungal activity against Foc. The strain S185 possesses multiple plant growth-promoting (PGP) and biocontrol utility properties, such as producing indole acetic acid (IAA) and ammonia, assimilating various carbon sources, tolerating pH of 4 to 9, temperature of 20 to 50 °C, and salt stress of 1 to 5%. Inoculation of S185 colonized the banana plants effectively and was mainly located in leaf and root tissues. To further investigate the antifungal components, compounds were extracted, fractionated, and purified. One compound, inhibiting Foc with minimum inhibitory concentrations (MICs) of 25 μg/disk, was identified as iturin A5 by high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) and nuclear magnetic resonance (NMR). The isolated iturin, A5, resulted in severe morphological changes during spore germination and hyphae growth of Foc. These results specify that B. amyloliquefaciens S185 plays a key role in preventing the Foc pathogen by producing the antifungal compound iturin A5, and possesses potential as a cost-effective and sustainable biocontrol strain for Panama disease in the future. This is the first report of isolation of the antifungal compound iturin A5 from thermotolerant marine B. amyloliquefaciens S185.

Metabolites with Antioxidant Activity from Marine Macroalgae

Reactive oxygen species (ROS) attack biological molecules, such as lipids, proteins, enzymes, DNA, and RNA, causing cellular and tissue damage. Hence, the disturbance of cellular antioxidant homeostasis can lead to oxidative stress and the onset of a plethora of diseases. Macroalgae, growing in stressful conditions under intense exposure to UV radiation, have developed protective mechanisms and have been recognized as an important source of secondary metabolites and macromolecules with antioxidant activity. In parallel, the fact that many algae can be cultivated in coastal areas ensures the provision of sufficient quantities of fine chemicals and biopolymers for commercial utilization, rendering them a viable source of antioxidants. This review focuses on the progress made concerning the discovery of antioxidant compounds derived from marine macroalgae, covering the literature up to December 2020. The present report presents the antioxidant potential and biogenetic origin of 301 macroalgal metabolites, categorized according to their chemical classes, highlighting the mechanisms of antioxidative action when known.

Marine Antitumor Peptide Dolastatin 10: Biological Activity, Structural Modification and Synthetic Chemistry

Dolastatin 10 (Dol-10), a leading marine pentapeptide isolated from the Indian Ocean mollusk Dolabella auricularia, contains three unique amino acid residues. Dol-10 can effectively induce apoptosis of lung cancer cells and other tumor cells at nanomolar concentration, and it has been developed into commercial drugs for treating some specific lymphomas, so it has received wide attention in recent years. In vitro experiments showed that Dol-10 and its derivatives were highly lethal to common tumor cells, such as L1210 leukemia cells (IC50 = 0.03 nM), small cell lung cancer NCI-H69 cells (IC50 = 0.059 nM), and human prostate cancer DU-145 cells (IC50 = 0.5 nM), etc. With the rise of antibody-drug conjugates (ADCs), milestone progress was made in clinical research based on Dol-10. A variety of ADCs constructed by combining MMAE or MMAF (Dol-10 derivatives) with a specific antibody not only ensured the antitumor activity of the drugs themself but also improved their tumor targeting and reduced the systemic toxicity. They are currently undergoing clinical trials or have been approved for marketing, such as Adcetris®, which had been approved for the treatment of anaplastic large T-cell systemic malignant lymphoma and Hodgkin lymphoma. Dol-10, as one of the most medically valuable natural compounds discovered up to now, has brought unprecedented hope for tumor treatment. It is particularly noteworthy that, by modifying the chemical structure of Dol-10 and combining with the application of ADCs technology, Dol-10 as a new drug candidate still has great potential for development. In this review, the biological activity and chemical work of Dol-10 in the advance of antitumor drugs in the last 35 years will be summarized, which will provide the support for pharmaceutical researchers interested in leading exploration of antitumor marine peptides.

Diversity and Antimicrobial Activity of Vietnamese Sponge-Associated Bacteria

This study aimed to assess the diversity and antimicrobial activity of cultivable bacteria associated with Vietnamese sponges. In total, 460 bacterial isolates were obtained from 18 marine sponges. Of these, 58.3% belonged to Proteobacteria, 16.5% to Actinobacteria, 18.0% to Firmicutes, and 7.2% to Bacteroidetes. At the genus level, isolated strains belonged to 55 genera, of which several genera, such as Bacillus, Pseudovibrio, Ruegeria, Vibrio, and Streptomyces, were the most predominant. Culture media influenced the cultivable bacterial composition, whereas, from different sponge species, similar cultivable bacteria were recovered. Interestingly, there was little overlap of bacterial composition associated with sponges when the taxa isolated were compared to cultivation-independent data. Subsequent antimicrobial assays showed that 90 isolated strains exhibited antimicrobial activity against at least one of seven indicator microorganisms. From the culture broth of the isolated strain with the strongest activity (Bacillus sp. M1_CRV_171), four secondary metabolites were isolated and identified, including cyclo(L-Pro-L-Tyr) (1), macrolactin A (2), macrolactin H (3), and 15,17-epoxy-16-hydroxy macrolactin A (4). Of these, compounds 2-4 exhibited antimicrobial activity against a broad spectrum of reference microorganisms.

Are propolis extracts potential pharmacological agents in human oral health? - A scoping review and technology prospecting

ETHNOPHARMACOLOGICAL RELEVANCE

The antimicrobial potential of propolis - a honey bee product - was correlated with its traditional use as a natural medicine, mainly known for antimicrobial and antioxidant properties. Moreover, research on natural products in dentistry has increased in recent years in the search for products with greater therapeutic activity, lower toxicity, better biocompatibility, and more affordable cost to the population.

OBJECTIVE

Considering that the beneficial effect of propolis is acknowledged for several oral conditions, this study aimed to synthesize the research and technological forecasts of existing evidence on the use of propolis extract as a potential antimicrobial agent in dentistry.

METHODS

Studies were identified through an investigation in the PubMed, Web of Science, Scopus, and Scielo electronic databases. Additionally, the following patent databases were screened: Google Patents, WIPO, INPI, Espacenet, and Questel Orbit. The data were tabulated and analyzed using Microsoft Office Excel 2013 and Questel Orbit.

RESULTS

A total of 174 scientific articles and 276 patents fulfilled all the criteria and were included in the investigation. The highest number of patents (n = 144) was produced by China. Additionally, the most prevalent studies were performed on an experimental basis (72%), followed by clinical studies (n = 27) and review articles (n = 21). The effect of using propolis has been extensively observed in oral care products, periodontics, pathology, and cariology, among other dental specialties.

CONCLUSION

It was possible to identify the current scientific and technological scenario of the application of propolis in dentistry, with the number of patents increasing in recent years. However, all studies related to the use of propolis in dentistry have shown a potentially safe antimicrobial agent in an extensive field of application.

Computational Simulations Identified Marine-Derived Natural Bioactive Compounds as Replication Inhibitors of SARS-CoV-2

The rapid spread of COVID-19, caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is a worldwide health emergency. Unfortunately, to date, a very small number of remedies have been to be found effective against SARS-CoV-2 infection. Therefore, further research is required to achieve a lasting solution against this deadly disease. Repurposing available drugs and evaluating natural product inhibitors against target proteins of SARS-CoV-2 could be an effective approach to accelerate drug discovery and development. With this strategy in mind, we derived Marine Natural Products (MNP)-based drug-like small molecules and evaluated them against three major target proteins of the SARS-CoV-2 virus replication cycle. A drug-like database from MNP library was generated using Lipinski's rule of five and ADMET descriptors. A total of 2,033 compounds were obtained and were subsequently subjected to molecular docking with 3CLpro, PLpro, and RdRp. The docking analyses revealed that a total of 14 compounds displayed better docking scores than the reference compounds and have significant molecular interactions with the active site residues of SARS-CoV-2 virus targeted proteins. Furthermore, the stability of docking-derived complexes was analyzed using molecular dynamics simulations and binding free energy calculations. The analyses revealed two hit compounds against each targeted protein displaying stable behavior, binding affinity, and molecular interactions. Our investigation identified two hit compounds against each targeted proteins displaying stable behavior, higher binding affinity and key residual molecular interactions, with good in silico pharmacokinetic properties, therefore can be considered for further in vitro studies.

Antimicrobials from Seaweeds for Food Applications

The exponential growth of emerging multidrug-resistant microorganisms, including foodborne pathogens affecting the shelf-life and quality of foods, has recently increased the needs of the food industry to search for novel, natural and eco-friendly antimicrobial agents. Macroalgae are a bio-diverse group distributed worldwide, known to produce multiple compounds of diverse chemical nature, different to those produced by terrestrial plants. These novel compounds have shown promising health benefits when incorporated into foods, including antimicrobial properties. This review aims to provide an overview of the general methods and novel compounds with antimicrobial properties recently isolated and characterized from macroalgae, emphasizing the molecular pathways of their antimicrobial mechanisms of action. The current scientific evidence on the use of macroalgae or macroalgal extracts to increase the shelf-life of foods and prevent the development of foodborne pathogens in real food products and their influence on the sensory attributes of multiple foods (i.e., meat, dairy, beverages, fish and bakery products) will also be discussed, together with the main challenges and future trends of the use of marine natural products as antimicrobials.

Current innovations in nutraceuticals and functional foods for intervention of non-alcoholic fatty liver disease

As innovations in global agricultural production and food trading systems lead to major dietary shifts, high morbidity rates from non-alcoholic fatty liver disease (NAFLD), accompanied by elevated risk of lipid metabolism-related complications, has emerged as a growing problem worldwide. Treatment and prevention of NAFLD and chronic liver disease depends on the availability of safe, effective, and diverse therapeutic agents, the development of which is urgently needed. Supported by a growing body of evidence, considerable attention is now focused on interventional approaches that combines nutraceuticals and functional foods. In this review, we summarize the pathological progression of NAFLD and discuss the beneficial effects of nutraceuticals and the active ingredients in functional foods. We also describe the underlying mechanisms of these compounds in the intervention of NAFLD, including their effects on regulation of lipid homeostasis, activation of signaling pathways, and their role in gut microbial community dynamics and the gut-liver axis. In order to identify novel targets for treatment of lipid metabolism-related diseases, this work broadly explores the molecular mechanism linking nutraceuticals and functional foods, host physiology, and gut microbiota. Additionally, the limitations in existing knowledge and promising research areas for development of active interventions and treatments against NAFLD are discussed.

Potentials of marine natural products against malaria, leishmaniasis, and trypanosomiasis parasites: a review of recent articles

Background

Malaria and neglected communicable protozoa parasitic diseases, such as leishmaniasis, and trypanosomiasis, are among the otherwise called diseases for neglected communities, which are habitual in underprivileged populations in developing tropical and subtropical regions of Africa, Asia, and the Americas. Some of the currently available therapeutic drugs have some limitations such as toxicity and questionable efficacy and long treatment period, which have encouraged resistance. These have prompted many researchers to focus on finding new drugs that are safe, effective, and affordable from marine environments. The aim of this review was to show the diversity, structural scaffolds, in-vitro or in-vivo efficacy, and recent progress made in the discovery/isolation of marine natural products (MNPs) with potent bioactivity against malaria, leishmaniasis, and trypanosomiasis.

Main text

We searched PubMed and Google scholar using Boolean Operators (AND, OR, and NOT) and the combination of related terms for articles on marine natural products (MNPs) discovery published only in English language from January 2016 to June 2020.

Twenty nine articles reported the isolation, identification and antiparasitic activity of the isolated compounds from marine environment. A total of 125 compounds were reported to have been isolated, out of which 45 were newly isolated compounds. These compounds were all isolated from bacteria, a fungus, sponges, algae, a bryozoan, cnidarians and soft corals. In recent years, great progress is being made on anti-malarial drug discovery from marine organisms with the isolation of these potent compounds. Comparably, some of these promising antikinetoplastid MNPs have potency better or similar to conventional drugs and could be developed as both antileishmanial and antitrypanosomal drugs. However, very few of these MNPs have a pharmaceutical destiny due to lack of the following: sustainable production of the bioactive compounds, standard efficient screening methods, knowledge of the mechanism of action, partnerships between researchers and pharmaceutical industries.

Conclusions

It is crystal clear that marine organisms are a rich source of antiparasitic compounds, such as alkaloids, terpenoids, peptides, polyketides, terpene, coumarins, steroids, fatty acid derivatives, and lactones. The current and future technological innovation in natural products drug discovery will bolster the drug armamentarium for malaria and neglected tropical diseases.

Miharadienes A–D with unique cyclic skeletons from a marine-derived Streptomyces miharaensis

A new type of natural products, miharadienes A–D (1–4), was isolated from the marine-derived Streptomyces miharaensis 151KO-143.

Marine-Derived Compounds and Prospects for Their Antifungal Application

The introduction of antifungals in clinical practice has an enormous impact on the provision of medical care, increasing the expectancy and quality of life mainly of immunocompromised patients. However, the emergence of pathogenic fungi that are resistant and multi-resistant to the existing antifungal therapy has culminated in fungal infections that are almost impossible to treat. Therefore, there is an urgent need to discover new strategies. The marine environment has proven to be a promising rich resource for the discovery and development of new antifungal compounds. Thus, this review summarizes more than one hundred marine natural products, or their derivatives, which are categorized according to their sources—sponges, bacteria, fungi, and sea cucumbers—as potential candidates as antifungal agents. In addition, this review focus on recent developments using marine antifungal compounds as new and effective approaches for the treatment of infections caused by resistant and multi-resistant pathogenic fungi and/or biofilm formation; other perspectives on antifungal marine products highlight new mechanisms of action, the combination of antifungal and non-antifungal agents, and the use of nanoparticles and anti-virulence therapy.

Chemical mining of heterotrophic Shewanella algae reveals anti-infective potential of macrocyclic polyketides against multidrug-resistant pathogens

Heterotrophic Gamma-proteobacterium Shewanella algae MTCC 12715, associated with an intertidal red algae Hypnea valentiae, presented broad-spectra of antibacterial activities against pathogenic bacteria bringing about nosocomial infection. Bioassay-guided fractionation of the bacterial crude extract resulted in two undescribed macrocyclic polyketide analogs, with anti-infective activities against methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus faecalis (MIC 3.1-5.0 µg/mL). In order to identify the polyketide biosynthetic machinery termed type-I polyketide synthase (pks-I) encoding biologically active secondary metabolites in this strain, the ketosynthase-coding regions of DNA with ≈700 bp size, were amplified, and the partial sequence was submitted in the GenBank (accession number MH157093). The titled compounds were classified under macrocyclic polyketides bearing dodecahydropyrano-trioxacyclooctadecine-dione and trioxo-octadecahydro-1H-benzo[o]tetraoxacyclopentacosine-carboxylate functionalities. Structure-activity correlation analysis displayed that hydrophobic descriptor of the studied compounds could play a prominent role in its anti-infective property against the opportunistic pathogens. Further, in silico molecular docking studies were performed in the allosteric sites of penicillin-binding protein (PBP2a) coded by mecA genes of MRSA, and the best binding pose for each compound (docking score -8.47 kcal/mol and -9.58 kcal/mol, respectively) could be correlated with their in vitro antibacterial activities. The pks-I assisted biosynthetic pathway of macrocyclic polyketides through step-wise decarboxylative condensation initiated by malonate-acyl carrier protein corroborated their structural attributes. Chemical mining of the studied macroalgae-associated heterotrophic bacterium thus revealed the promising antagonistic properties of macrocyclic polyketides isolated from Shewanella algae MTCC 12715 against multidrug-resistant pathogens.

Novel Synthesis and Antiviral Evaluation of New Benzothiazole-Bearing N-Sulfonamide 2-Pyridone Derivatives as USP7 Enzyme Inhibitors

In this article, a series of benzothiazole-bearing N-sulfonamide 2-pyridone derivatives were synthesized via the reaction of benzothiazole sulfonylhydrazide with sodium salts of both (hydroxymethylene) cycloalkanones and unsaturated ketones, as well as ethoxymethylene derivatives. The structures of the resultant compounds were confirmed using IR, ¹H NMR, ¹³C NMR, ¹H-¹H correlation spectroscopy (COSY), ¹H-¹³C heteronuclear multiple bond coherence (HMBC), and ¹H-¹³C heteronuclear multiple quantum coherence (HSQC) spectral analysis and elemental analysis. The newly synthesized compounds were evaluated in vitro for their antiviral activities against the HSV-1, HAV HM175, HCVcc genotype 4, CBV4, and HAdV7 viruses. Additionally, the compounds were examined for their cytotoxic effect on five normal cell lines. It was observed that five compounds were found to possess viral reduction of 50% or more against CBV4 with significant IC₅₀, CC₅₀, and SI values. In the case of HSV-1 and HAV HM175 viruses, three compounds have shown more than 50% reduction, while in the case of HCVcc genotype 4 and HAdV7 viruses, only two compounds demonstrated more than 50% reduction. Furthermore, the physicochemical properties of the most active compounds were evaluated. The two most potent compounds against HSV-1 virus, 7e and 13a, were evaluated for their inhibitory activity against USP7. Docking studies using Molecular Operating Environment (MOE) were used to identify the interactions between 7e and 13a compounds and the active site of the USP7 enzyme.

Bridging the Gap: Plant-Endophyte Interactions as a Roadmap to Understanding Small-Molecule Communication in Marine Microbiomes

Probing the composition of the microbiome and its association with health and disease states is more accessible than ever due to the rise of affordable sequencing technology. Despite advances in our ability to identify members of symbiont communities, untangling the chemical signaling that they use to communicate with host organisms remains challenging. In order to gain a greater mechanistic understanding of how the microbiome impacts health, and how chemical ecology can be leveraged to advance small-molecule drug discovery from microorganisms, the principals governing communication between host and symbiont must be elucidated. Herein, we review common modes of interkingdom small-molecule communication in terrestrial and marine environments, describe the differences between these environments, and detail the advantages and disadvantages for studies focused on the marine environment. Finally, we propose the use of plant-endophyte interactions as a stepping stone to a greater understanding of similar interactions in marine invertebrates, and ultimately in humans.

Recent Advancement of Ullmann Condensation Coupling Reaction in the Formation of Aryl-Oxygen (C-O) Bonding by Copper-Mediated Catalyst

Transition metal-catalyzed chemical transformation of organic electrophiles and organometallic reagents belong to the most important cross coupling reaction in organic synthesis. The biaryl ether division is not only popular in natural products and synthetic pharmaceuticals but also widely found in many pesticides, polymers, and ligands. Copper catalyst has received great attention owing to the low toxicity and low cost. However, traditional Ullmann-type couplings suffer from limited substrate scopes and harsh reaction conditions. The introduction of homogeneous copper catalyst with presence of bidentate ligands over the past two decades has totally changed this situation as these ligands enable the reaction promoted in mild condition. The reaction scope has also been greatly expanded, rendering this copper-based cross-coupling attractive for both academia and industry. In this review, we will highlight the latest progress in the development of useful homogeneous copper catalyst with presence of ligand and heterogeneous copper catalyst in Ullmann type C-O cross-coupling reaction. Additionally, the application of Ullmann type C-O cross coupling reaction will be discussed.

Harnessing the sponge microbiome for industrial biocatalysts

Within the marine sphere, host-associated microbiomes are receiving growing attention as prolific sources of novel biocatalysts. Given the known biocatalytic potential of poriferan microbial inhabitants, this review focuses on enzymes from the sponge microbiome, with special attention on their relevant properties and the wide range of their potential biotechnological applications within various industries. Cultivable bacterial and filamentous fungal isolates account for the majority of the enzymatic sources. Hydrolases, mainly glycoside hydrolases and carboxylesterases, are the predominant reported group of enzymes, with varying degrees of tolerance to alkaline pH and growing salt concentrations being common. Prospective areas for the application of these microbial enzymes include biorefinery, detergent, food and effluent treatment industries. Finally, alternative strategies to identify novel biocatalysts from the sponge microbiome are addressed, with an emphasis on modern -omics-based approaches that are currently available in the enzyme research arena. By providing this current overview of the field, we hope to not only increase the appetite of researchers to instigate forthcoming studies but also to stress how basic and applied research can pave the way for new biocatalysts from these symbiotic microbial communities in a productive fashion. KEY POINTS: • The sponge microbiome is a burgeoning source of industrial biocatalysts. • Sponge microbial enzymes have useful habitat-related traits for several industries. • Strategies are provided for the future discovery of microbial enzymes from sponges.

The Ascidian-Derived Metabolites with Antimicrobial Properties

Among the sub-phylum of Tunicate, ascidians represent the most abundant class of marine invertebrates, with 3000 species by heterogeneous habitat, that is, from shallow water to deep sea, already reported. The chemistry of these sessile filter-feeding organisms is an attractive reservoir of varied and peculiar bioactive compounds. Most secondary metabolites isolated from ascidians stand out for their potential as putative therapeutic agents in the treatment of several illnesses like microbial infections. In this review, we present and discuss the antibacterial activity shown by the main groups of ascidian-derived products, such as sulfur-containing compounds, meroterpenes, alkaloids, peptides, furanones, and their derivatives. Moreover, the direct evidence of a symbiotic association between marine ascidians and microorganisms shed light on the real producers of many extremely potent marine natural compounds. Hence, we also report the antibacterial potential, joined to antifungal and antiviral activity, of metabolites isolated from ascidian-associate microorganisms by culture-dependent methods.

Marine Terpenoids from Polar Latitudes and Their Potential Applications in Biotechnology

Polar marine biota have adapted to thrive under one of the ocean’s most inhospitable scenarios, where extremes of temperature, light photoperiod and ice disturbance, along with ecological interactions, have selected species with a unique suite of secondary metabolites. Organisms of Arctic and Antarctic oceans are prolific sources of natural products, exhibiting wide structural diversity and remarkable bioactivities for human applications. Chemical skeletons belonging to terpene families are the most commonly found compounds, whereas cytotoxic antimicrobial properties, the capacity to prevent infections, are the most widely reported activities from these environments. This review firstly summarizes the regulations on access and benefit sharing requirements for research in polar environments. Then it provides an overview of the natural product arsenal from Antarctic and Arctic marine organisms that displays promising uses for fighting human disease. Microbes, such as bacteria and fungi, and macroorganisms, such as sponges, macroalgae, ascidians, corals, bryozoans, echinoderms and mollusks, are the main focus of this review. The biological origin, the structure of terpenes and terpenoids, derivatives and their biotechnological potential are described. This survey aims to highlight the chemical diversity of marine polar life and the versatility of this group of biomolecules, in an effort to encourage further research in drug discovery.

Antitumor and hepatoprotective activity of natural and synthetic neo steroids

In this review, steroids with a tertiary butyl group, which are usually called neo steroids, are a small group of natural lipids isolated from higher plants, fungi, marine sponges, and yeast. In addition, steroids with a tertiary butyl group have been synthesized in some laboratories in Canada, USA, Europe, and Japan and their biological activity was studied. Some natural neo steroids demonstrate antitumor or hepatoprotective activities. In addition, synthetic neo steroids exhibit anticancer and neuroprotective properties. However, to confirm the above data, both practical and clinical experimental studies are necessary. Nevertheless, the results may be useful for pharmacologists, chemists, biochemists, and the pharmaceutical industry.

Biologically active macromolecules: Extraction strategies, therapeutic potential and biomedical perspective

Marine biome exhibits an immense essence of excellence and enriched with high-value bioactive compounds of therapeutic and biomedical value. During the past several years, an array of biologically active molecules has been extracted/isolated and purified from numerous sources of marine origin with the aid of distinct techniques and methodologies for newer applications. The growing demand for bioactive molecules with unique functionalities in various industrial divisions, such as therapeutic sectors and biomedical, has endorsed the necessity for highly suitable and standardized strategies to extract these bioactive components using a state-of-the-art and inexpensive measures. This is also because many in practice conventional extraction methodologies suffer from processing limitations and low-yield issues. Besides that, other major issues include (i) decrease efficacy, (ii) excessive energy cost, (iii) low yield, (iv) lower cost-effective ratio, (v) minimal selectivity, (vi) low activity, and (vii) stability, etc. In this context, there is an urgent need for new and robust extraction strategies. The synergies of modern extraction techniques with efficient and novel pretreatment approaches, such as the integration of enzymes, accompanied by conventional extraction processes, should be the utmost goal of current research and development studies. The typical effectivity of the extraction techniques mostly relies on these points, i.e., (i) know-how about the source nature and type, (ii) understanding the structural and compositional profile, (iii) influence of the processing factors, (iv) interplay between the extraction conditions and the end-product, (v) understanding the available functional entities, (vi) reaction chemistry of the extract bioactive compounds, and (vii) effective exploitation of the end-product in the marketplace. Marine biome, among numerous naturally occurring sources, has been appeared an immense essence of excellence to isolate an array of biologically active constituents with medicinal values and related point-of-care applications. Herein, we reviewed the salient information covering various therapeutic potential and biomedical perspectives. Following a brief introduction and marine pharmacognosy, an array of high-value biomolecules of marine origin are discussed with suitable examples. From the robust extraction strategies viewpoint, a part of the review focuses on three techniques, i.e., (1) enzyme-assisted extraction (EAE), (2) supercritical-fluid extraction (SFE), and (3) microwave-assisted extraction (MAE). Each technique is further enriched with processing and workflow environment. The later part of the review is mainly focused on the therapeutic and biomedical perspectives of under-reviewed bio-active compounds or biomolecules. The previous and latest research on the anticancer, skin curative, cardio-protective, immunomodulatory and UV-protectant potentialities of marine-derived biologically active entities have been summarized with suitable examples and related pathways illustrations. Finally, the work is wrapped-up with current research challenges, future aspects, and concluding remarks.

An enumeration of natural products from microbial, marine and terrestrial sources

The discovery of a new drug is a multidisciplinary and very costly task. One of the major steps is the identification of a lead compound, i.e. a compound with a certain degree of potency and that can be chemically modified to improve its activity, metabolic properties, and pharmacokinetics profiles. Terrestrial sources (plants and fungi), microbes and marine organisms are abundant resources for the discovery of new structurally diverse and biologically active compounds. In this chapter, an attempt has been made to quantify the numbers of known published chemical structures (available in chemical databases) from natural sources. Emphasis has been laid on the number of unique compounds, the most abundant compound classes and the distribution of compounds in terrestrial and marine habitats. It was observed, from the recent investigations, that ~500,000 known natural products (NPs) exist in the literature. About 70 % of all NPs come from plants, terpenoids being the most represented compound class (except in bacteria, where amino acids, peptides, and polyketides are the most abundant compound classes). About 2,000 NPs have been co-crystallized in PDB structures.