Marine peptides and their anti-infective activities

A review on endophytic fungi: a potent reservoir of bioactive metabolites with special emphasis on blight disease management

Phytopathogenic microorganisms have caused blight diseases that present significant challenges to global agriculture. These diseases result in substantial crop losses and have a significant economic impact. Due to the limitations of conventional chemical treatments in effectively and sustainably managing these diseases, there is an increasing interest in exploring alternative and environmentally friendly approaches for disease control. Using endophytic fungi as biocontrol agents has become a promising strategy in recent years. Endophytic fungi live inside plant tissues, forming mutually beneficial relationships, and have been discovered to produce a wide range of bioactive metabolites. These metabolites demonstrate significant potential for fighting blight diseases and provide a plentiful source of new biopesticides. In this review, we delve into the potential of endophytic fungi as a means of biocontrol against blight diseases. We specifically highlight their significance as a source of biologically active compounds. The review explores different mechanisms used by endophytic fungi to suppress phytopathogens. These mechanisms include competing for nutrients, producing antifungal compounds, and triggering plant defense responses. Furthermore, this review discusses the challenges of using endophytic fungi as biocontrol agents in commercial applications. It emphasizes the importance of conducting thorough research to enhance their effectiveness and stability in real-world environments. Therefore, bioactive metabolites from endophytic fungi have considerable potential for sustainable and eco-friendly blight disease control. Additional research on endophytes and their metabolites will promote biotechnology solutions.

Therapeutic Potential of Marine-Derived Cyclic Peptides as Antiparasitic Agents

Parasitic diseases still compromise human health. Some of the currently available therapeutic drugs have limitations considering their adverse effects, questionable efficacy, and long treatment, which have encouraged drug resistance. There is an urgent need to find new, safe, effective, and affordable antiparasitic drugs. Marine-derived cyclic peptides have been increasingly screened as candidates for developing new drugs. Therefore, in this review, a systematic analysis of the scientific literature was performed and 25 marine-derived cyclic peptides with antiparasitic activity (1-25) were found. Antimalarial activity is the most reported (51%), followed by antileishmanial (27%) and antitrypanosomal (20%) activities. Some compounds showed promising antiparasitic activity at the nM scale, being active against various parasites. The mechanisms of action and targets for some of the compounds have been investigated, revealing different strategies against parasites.

Marine Invertebrate Antimicrobial Peptides and Their Potential as Novel Peptide Antibiotics

Marine invertebrates constantly interact with a wide range of microorganisms in their aquatic environment and possess an effective defense system that has enabled their existence for millions of years. Their lack of acquired immunity sets marine invertebrates apart from other marine animals. Invertebrates could rely on their innate immunity, providing the first line of defense, survival, and thriving. The innate immune system of marine invertebrates includes various biologically active compounds, and specifically, antimicrobial peptides. Nowadays, there is a revive of interest in these peptides due to the urgent need to discover novel drugs against antibiotic-resistant bacterial strains, a pressing global concern in modern healthcare. Modern technologies offer extensive possibilities for the development of innovative drugs based on these compounds, which can act against bacteria, fungi, protozoa, and viruses. This review focuses on structural peculiarities, biological functions, gene expression, biosynthesis, mechanisms of antimicrobial action, regulatory activities, and prospects for the therapeutic use of antimicrobial peptides derived from marine invertebrates.

The diversification of the antimicrobial peptides from marine worms is driven by environmental conditions

Antimicrobial peptides (AMPs) play a key role in the external immunity of animals, offering an interesting model for studying the influence of the environment on the diversification and evolution of immune effectors. Alvinellacin (ALV), arenicin (ARE) and polaricin (POL, a novel AMP identified here), characterized from three marine worms inhabiting contrasted habitats ('hot' vents, temperate and polar respectively), possess a well conserved BRICHOS domain in their precursor molecule despite a profound amino acid and structural diversification of the C-terminal part containing the core peptide. Data not only showed that ARE, ALV and POL display an optimal bactericidal activity against the bacteria typical of the habitat where each worm species lives but also that this killing efficacy is optimal under the thermochemical conditions encountered by their producers in their environment. Moreover, the correlation between species habitat and the cysteine contents of POL, ARE and ALV led us to investigate the importance of disulfide bridges in their biological efficacy as a function of abiotic pressures (pH and temperature). The construction of variants using non-proteinogenic residues instead of cysteines (α-aminobutyric acid variants) leading to AMPs devoid of disulfide bridges, provided evidence that the disulfide pattern of the three AMPs allows for a better bactericidal activity and suggests an adaptive way to sustain the fluctuations of the worm's environment. This work shows that the external immune effectors exemplified here by BRICHOS AMPs are evolving under strong diversifying environmental pressures to be structurally shaped and more efficient/specific under the ecological niche of their producer.

Seaweeds and Corals from the Brazilian Coast: Review on Biotechnological Potential and Environmental Aspects

Brazil has a megadiversity that includes marine species that are distributed along 800 km of shoreline. This biodiversity status holds promising biotechnological potential. Marine organisms are important sources of novel chemical species, with applications in the pharmaceutical, cosmetic, chemical, and nutraceutical fields. However, ecological pressures derived from anthropogenic actions, including the bioaccumulation of potentially toxic elements and microplastics, impact promising species. This review describes the current status of the biotechnological and environmental aspects of seaweeds and corals from the Brazilian coast, including publications from the last 5 years (from January 2018 to December 2022). The search was conducted in the main public databases (PubChem, PubMed, Science Direct, and Google Scholar) and in the Espacenet database (European Patent Office-EPO) and the Brazilian National Property Institute (INPI). Bioprospecting studies were reported for seventy-one seaweed species and fifteen corals, but few targeted the isolation of compounds. The antioxidant potential was the most investigated biological activity. Despite being potential sources of macro- and microelements, there is a literature gap regarding the presence of potentially toxic elements and other emergent contaminants, such as microplastics, in seaweeds and corals from the Brazilian coast.

Antimicrobial Peptides from Photosynthetic Marine Organisms with Potential Application in Aquaculture

Aquaculture production is at a record level and is estimated to increase in the coming years. However, this production can be negatively affected by infectious diseases produced by viruses, bacteria, and parasites, causing fish mortality and economic losses. Antimicrobial peptides (AMPs) are small peptides that may be promising candidates to replace antibiotics because they are the first line of defense in animals against a wide variety of pathogens and have no negative effects; they also show additional activities such as antioxidant or immunoregulatory functions, which makes them powerful alternatives for use in aquaculture. Moreover, AMPs are highly available in natural sources and have already been used in the livestock farming and food industries. Photosynthetic marine organisms can survive under all kinds of environmental conditions and under extremely competitive environments thanks to their flexible metabolism. For this reason, these organisms represent a powerful source of bioactive molecules as nutraceuticals and pharmaceuticals, including AMPs. Therefore, in this study we reviewed the present knowledge about AMPs from photosynthetic marine organism sources and analyzed whether they could be suitable for use in aquaculture.

Isolation and Characterization of NpCI, a New Metallocarboxypeptidase Inhibitor from the Marine Snail Nerita peloronta with Anti-Plasmodium falciparum Activity

Metallocarboxypeptidases are zinc-dependent peptide-hydrolysing enzymes involved in several important physiological and pathological processes. They have been a target of growing interest in the search for natural or synthetic compound binders with biomedical and drug discovery purposes, i.e., with potential as antimicrobials or antiparasitics. Given that marine resources are an extraordinary source of bioactive molecules, we screened marine invertebrates for new inhibitory compounds with such capabilities. In this work, we report the isolation and molecular and functional characterization of NpCI, a novel strong metallocarboxypeptidase inhibitor from the marine snail Nerita peloronta. NpCI was purified until homogeneity using a combination of affinity chromatography and RP-HPLC. It appeared as a 5921.557 Da protein with 53 residues and six disulphide-linked cysteines, displaying a high sequence similarity with NvCI, a carboxypeptidase inhibitor isolated from Nerita versicolor, a mollusc of the same genus. The purified inhibitor was determined to be a slow- and tight-binding inhibitor of bovine CPA (Ki = 1.1·× 10^-8 mol/L) and porcine CPB (Ki = 8.15·× 10^-8 mol/L) and was not able to inhibit proteases from other mechanistic classes. Importantly, this inhibitor showed antiplasmodial activity against Plasmodium falciparum in an in vitro culture (IC₅₀ = 5.5 μmol/L), reducing parasitaemia mainly by inhibiting the later stages of the parasite's intraerythrocytic cycle whilst having no cytotoxic effects on human fibroblasts. Interestingly, initial attempts with other related proteinaceous carboxypeptidase inhibitors also displayed similar antiplasmodial effects. Coincidentally, in recent years, a metallocarboxypeptidase named PfNna1, which is expressed in the schizont phase during the late intraerythrocytic stage of the parasite's life cycle, has been described. Given that NpCI showed a specific parasiticidal effect on P. falciparum, eliciting pyknotic/dead parasites, our results suggest that this and related inhibitors could be promising starting agents or lead compounds for antimalarial drug discovery strategies.

Absolute Stereochemistry Determination of Bioactive Marine-Derived Cyclopeptides by Liquid Chromatography Methods: An Update Review (2018-2022)

Cyclopeptides are considered as one of the most important classes of compounds derived from marine sources, due to their structural diversity and a myriad of their biological and pharmacological activities. Since marine-derived cyclopeptides consist of different amino acids, many of which are non-proteinogenic, they possess various stereogenic centers. In this respect, the structure elucidation of new molecular scaffolds obtained from natural sources, including marine-derived cyclopeptides, can become a very challenging task. The determination of the absolute configurations of the amino acid residues is accomplished, in most cases, by performing acidic hydrolysis, followed by analyses by liquid chromatography (LC). In a continuation with the authors' previous publication, and to analyze the current trends, the present review covers recently published works (from January 2018 to November 2022) regarding new cyclopeptides from marine organisms, with a special focus on their biological/pharmacological activities and the absolute stereochemical assignment of the amino acid residues. Ninety-one unreported marine-derived cyclopeptides were identified during this period, most of which displayed anticancer or antimicrobial activities. Marfey's method, which involves LC, was found to be the most frequently used for this purpose.

A Review: The Antiviral Activity of Cyclic Peptides

In the design and development of therapeutic agents, macromolecules with restricted structures have stronger competitive edges than linear biological entities since cyclization can overcome the limitations of linear structures. The common issues of linear peptides include susceptibility to degradation of the peptidase enzyme, off-target effects, and necessity of routine dosing, leading to instability and ineffectiveness. The unique conformational constraint of cyclic peptides provides a larger surface area to interact with the target at the same time, improving the membrane permeability and in vivo stability compared to their linear counterparts. Currently, cyclic peptides have been reported to possess various activities, such as antifungal, antiviral and antimicrobial activities. To date, there is emerging interest in cyclic peptide therapeutics, and increasing numbers of clinically approved cyclic peptide drugs are available on the market. In this review, the medical significance of cyclic peptides in the defence against viral infections will be highlighted. Except for chikungunya virus, which lacks specific antiviral treatment, all the viral diseases targeted in this review are those with effective treatments yet with certain limitations to date. Thus, strategies and approaches to optimise the antiviral effect of cyclic peptides will be discussed along with their respective outcomes. Apart from isolated naturally occurring cyclic peptides, chemically synthesized or modified cyclic peptides with antiviral activities targeting coronavirus, herpes simplex viruses, human immunodeficiency virus, Ebola virus, influenza virus, dengue virus, five main hepatitis viruses, termed as type A, B, C, D and E and chikungunya virus will be reviewed herein.

Graphical Abstract

Application of antimicrobial, potential hazard and mitigation plans

The tremendous rise in the consumption of antimicrobial products had aroused global concerns, especially in the midst of pandemic COVID-19. Antimicrobial resistance has been accelerated by widespread usage of antimicrobial products in response to the COVID-19 pandemic. Furthermore, the widespread use of antimicrobial products releases biohazardous substances into the environment, endangering the ecology and ecosystem. Therefore, several strategies or measurements are needed to tackle this problem. In this review, types of antimicrobial available, emerging nanotechnology in antimicrobial production and their advanced application have been discussed. The problem of antimicrobial resistance (AMR) due to antibiotic-resistant bacteria (ARB)and antimicrobial resistance genes (AMG) had become the biggest threat to public health. To deal with this problem, an in-depth discussion of the challenges faced in antimicrobial mitigations and potential alternatives was reviewed.

Therapeutic Potential of Marine Bioactive Peptides against Human Immunodeficiency Virus: Recent Evidence, Challenges, and Future Trends

Acquired immunodeficiency syndrome (AIDS) is a chronic and potentially fatal ailment caused by the human immunodeficiency virus (HIV) and remains a major health problem worldwide. In recent years, the research focus has shifted to a greater emphasis on complementing treatment regimens involving conventional antiretroviral (ARV) drug therapies with novel lead structures isolated from various marine organisms that have the potential to be utilized as therapeutics for the management of HIV-AIDS. The present review summarizes the recent developments regarding bioactive peptides sourced from various marine organisms. This includes a discussion encompassing the potential of these novel marine bioactive peptides with regard to antiretroviral activities against HIV, preparation, purification, and processing techniques, in addition to insight into the future trends with an emphasis on the potential of exploration and evaluation of novel peptides to be developed into effective antiretroviral drugs.

Tachyplesin and CyLoP-1 as efficient anti-mycobacterial peptides: A novel finding

Mycobacterium tuberculosis is an etiological agent of tuberculosis (TB) known to be a highly contagious disease and is the major cause of mortality from a single infectious agent worldwide. Emergence of multi-drug resistant and extremely drug resistant strains of M. tuberculosis has made TB management extremely challenging eliciting the urgent need for alternative therapeutics. Peptide based therapeutic strategies are an emerging area that can be employed as a prospective alternative to the currently existing therapeutic regime for TB treatment. Here, we are reporting the anti-mycobacterial activity of two peptides, Tachyplesin and CyLoP-1, derived from marine horseshoe crab and snake toxin respectively, with potent anti-mycobacterial activity against various mycobacterium species. Both the peptides exhibit appreciable antimicrobial and anti-biofilm activities against mycobacterium species with minimum cytotoxicity towards macrophage cells. They are also effective in eliminating mycobacterium cells from infected macrophage cells. Tachyplesin acts on mycobacterium cells in a lytic manner with outer membrane disruption confirmed by propidium iodide uptake with slight membrane depolarization and reactive oxygen species (ROS) production. CyLoP-1, on the other hand, does not rupture the mycobacterium cells even at high concentrations. It seems to follow intracellular pathway of killing mycobacterium cells by production of more ROS and membrane depolarization. Both the peptides do not lead to apoptotic way of mycobacterium cell death. These results suggest an effective peptide-based antimicrobial strategy for development of future anti-TB therapeutics.

Marine Cyclic Peptides: Antimicrobial Activity and Synthetic Strategies

Oceans are a rich source of structurally unique bioactive compounds from the perspective of potential therapeutic agents. Marine peptides are a particularly interesting group of secondary metabolites because of their chemistry and wide range of biological activities. Among them, cyclic peptides exhibit a broad spectrum of antimicrobial activities, including against bacteria, protozoa, fungi, and viruses. Moreover, there are several examples of marine cyclic peptides revealing interesting antimicrobial activities against numerous drug-resistant bacteria and fungi, making these compounds a very promising resource in the search for novel antimicrobial agents to revert multidrug-resistance. This review summarizes 174 marine cyclic peptides with antibacterial, antifungal, antiparasitic, or antiviral properties. These natural products were categorized according to their sources—sponges, mollusks, crustaceans, crabs, marine bacteria, and fungi—and chemical structure—cyclic peptides and depsipeptides. The antimicrobial activities, including against drug-resistant microorganisms, unusual structural characteristics, and hits more advanced in (pre)clinical studies, are highlighted. Nocathiacins I–III (91–93), unnarmicins A (114) and C (115), sclerotides A (160) and B (161), and plitidepsin (174) can be highlighted considering not only their high antimicrobial potency in vitro, but also for their promising in vivo results. Marine cyclic peptides are also interesting models for molecular modifications and/or total synthesis to obtain more potent compounds, with improved properties and in higher quantity. Solid-phase Fmoc- and Boc-protection chemistry is the major synthetic strategy to obtain marine cyclic peptides with antimicrobial properties, and key examples are presented guiding microbiologist and medicinal chemists to the discovery of new antimicrobial drug candidates from marine sources.

Antiviral Peptides (AVPs) of Marine Origin as Propitious Therapeutic Drug Candidates for the Treatment of Human Viruses

The marine environment presents a favorable avenue for potential therapeutic agents as a reservoir of new bioactive natural products. Due to their numerous potential pharmacological effects, marine-derived natural products—particularly marine peptides—have gained considerable attention. These peptides have shown a broad spectrum of biological functions, such as antimicrobial, antiviral, cytotoxic, immunomodulatory, and analgesic effects. The emergence of new virus strains and viral resistance leads to continuing efforts to develop more effective antiviral drugs. Interestingly, antimicrobial peptides (AMPs) that possess antiviral properties and are alternatively regarded as antiviral peptides (AVPs) demonstrate vast potential as alternative peptide-based drug candidates available for viral infection treatments. Hence, AVPs obtained from various marine organisms have been evaluated. This brief review features recent updates of marine-derived AVPs from 2011 to 2021. Moreover, the biosynthesis of this class of compounds and their possible mechanisms of action are also discussed. Selected peptides from various marine organisms possessing antiviral activities against important human viruses—such as human immunodeficiency viruses, herpes simplex viruses, influenza viruses, hepatitis C virus, and coronaviruses—are highlighted herein.

Effects of Marine Antagonistic Fungi against Plant Pathogens and Rice Growth Promotion Activity

Ten marine-derived fungi crude extracts, namely Emericella stellatus KUFA0208, Eupenicillium parvum KUFA0237, Neosartorya siamensis KUFA0514, N. spinosa KUFA 0528, Talaromyces flavus KUFA 0119, T. macrosporus KUFA 0135, T. trachyspermus KUFA0304, Trichoderma asperellum KUFA 0559, T. asperellum KUFA 0559 and T. harzianum KUFA 0631 were determined for their fungicidal activity against five rice pathogens in vitro. The results showed that the extracts of E. stellatus KUFA0208 and N. siamensis KUFA0514 exhibited the best antifungal activity, causing complete cessation of the mycelial growth of Alternaria padwickii, Bipalaris oryzae, Fusarium semitectum, Pyricularia oryzae and Rhizoctonia solani at 10 g/L. The N. siamensis KUFA0514 extract was fractioned and antifungal compounds were found in the fractions derived from petroleum-ether and chloroform (7: 3) evidenced by inhibition zones against the mycelial growth of A. padwickii around the disc containing each fraction. Moreover, in rice growth promotion tests, diluted cultural broth of T. asperellum KUFA 0559 and T. harzianum KUFA 0631 were found to strongly promote rice shoot and root elongation; however, higher concentrations of all marine fungal broths resulted in significantly reduced rice seedling growth rather than promotion. Meanwhile, Trichoderma showed great indole-3-acetic acid (IAA) production leading to the optimum IAA values of 45.38 and 52.30 µg/ml at 11 and 13 days after inoculation, respectively. The results of this study indicated that marine fungi are promising agents having antagonistic mechanisms involving antibiosis production and plant growth promotion and may be developed as novel biocontrol agents for rice disease management.

A critical review on the health benefits of fish consumption and its bioactive constituents

As one of food sources, fish provides sufficient nutrition to human. Diverse nutrients in fish make fish an important nutrient source available easily across the globe. Fish is proven to possess several health benefits, such as anti-oxidation, anti-inflammation, wound healing, neuroprotection, cardioprotection, and hepatoprotection properties. Fish proteins, such as immunoglobins, act as defense agents against viral and bacterial infections and prevent protein-calorie malnutrition. Besides, fish oil constituents, such as polyunsaturated fatty acids (PUFAs), regulate various signaling pathways, such as nuclear factor kappa B pathway, Toll-like receptor pathway, transforming growth factor-β (TGF-β) pathway, and peroxisome proliferators activated receptor (PPAR) pathways. In this review, the literature about health benefits of fish consumption are accumulated from PubMed, Google Scholar, Scopus, and the mechanistic action of health benefits are summarized. Fish consumption at least twice per week as part of a healthy diet is beneficial for a healthy heart. More advances in this field could pose fish as a major nutrients source of foods.

New dihydronaphthothiophene derivatives by the biological transformation of seriniquinone using marine-derived actinomycete Streptomyces albogriseolus OM27-12

Seriniquinone was originally isolated as a melanoma-selective anti-cancer agent from a culture broth of marine bacteria. Pharmacological studies on its selectivity and unique target are ongoing. A new dihydronaphthothiophene (1) was synthesized by the biological transformation of seriniquinone using marine-derived actinomycete Streptomyces albogriseolus OM27-12, and its derivatives (2-4) were chemically synthesized. Compounds 1-4 exhibited selective cytotoxic activity against melanoma and improved solubility.

Marine sediment derived bacteria Enterobacter asburiae ES1 and Enterobacter sp. Kamsi produce laccase with high dephenolisation potentials

Purified laccases from bacterial species isolated from marine sediment were applied to degrade Bisphenol A (BPA). The Bacterial species were isolated from marine water sediments sampled from Cove Rock and Bonza Bay beach of the Eastern Cape Province, South Africa was tested for laccase activity on varied phenolic plates. The two most promising strains, Enterobacter asburiae ES1 and Enterobacter sp. Kamsi was subjected to extracellular laccase production and were identified using molecular methods. Both extracted bacterial laccases showed an affinity for ABTS and PFC substrates and were purified to homogeneity by ammonium sulfate precipitation, anion exchange, and size exclusion chromatography. A specific laccase activity of 231.67 and 218.15 U/mg of protein and a molecular weight of 50 and 55 kDa was obtained from the purified ES1 and Kamsi laccases. Laccase activity was optimum at pH8 and 5 and at 80 °C and 60 °C for ES1 and Kamsi laccases, and they manifested 71.7% and 65.8% BPA decolorizing effects. The optimized treatment condition applied showed maximum BPA removal effects of 85% and 86% at pH7 and 6, while 78% and 79% was degraded at 70 °C and 80 °C while at 250 µL enzyme volume, BPA was actively degraded to 85%, and 75% removal effect showed by ES1 and Kamsi laccases. The molecular identification of the pure colonies using 16S rRNA showed the isolate belonged to the class of gammaproteobacterial. Their nucleotide sequence has been deposited in NCBI with the accession number MN686602 and MN686603. Conclusively, marine habitat serves as a reservoir for active bacterial laccase producers suitable for bioprocess application.

Venom peptides - A comprehensive translational perspective in pain management

Venom peptides have been evolving complex therapeutic interventions that potently and selectively modulate a range of targets such as ion channels, receptors, and signaling pathways of physiological processes making it potential therapeutic. Several venom peptides were deduced in vivo for clinical development targeting pain management, diabetes, cardiovascular diseases, antimicrobial activity. Several contributions have been detailed for a clear perspective for a better understanding of venomous animals, their venom, and their pharmacological effects. Here we unravel and summarize the recent advances in wide venom peptides across varieties of species for their therapeutics prospects.

Biologically Active Antimicrobial Compounds from Marine Microorganisms (2005-2019)

INTRODUCTION

The increase in contagious diseases like nosocomial infections, urinary tract infections, and meningitis has led to the emergence of antimicrobial resistance urgently needs new antimicrobial medication with new modes of action. Some of the antibiotics present in the market have been obtained from terrestrial plants, or extracted semisynthetically from materials which can be fermented.

METHODS

Marine microorganisms account for approximately 80% of sea biomass. They are essential for the survival and well-being of aquatic habitats due to their indispensable contribution to biogeochemical cycles and biological processes. In marine ecosystems, microorganisms live as microbial communities in seawater, where symbiotic relationships are formed, and their ecological functions are fulfilled.

RESULTS

Marine microorganisms remain the largest, most diverse and most exciting source of structurally and functionally complex antimicrobial agents. They are extremely involved in their structure and functions. Enormous biological wealth lies in marine habitats. These microorganisms are potential sources of novel antimicrobial compounds to combat the most infectious diseases like nosocomial infections, and urinary tract infections.

CONCLUSION

This study deals with biologically active antimicrobial compounds taken from marine microorganism source, which was reported between the years 2005 and 2019. This review highlights their chemical groups, their bioactivities and sources. Marine microorganism exploitation techniques have also been reported by the authors.

Hemolymph proteins: An overview across marine arthropods and molluscs

In this compilation we collect information about the main protein components in hemolymph and stress the continued interest in their study. The reasons for such an attention span several areas of biological, veterinarian and medical applications: from the notions for better dealing with the species - belonging to phylum Arthropoda, subphylum Crustacea, and to phylum Mollusca - of economic interest, to the development of 'marine drugs' from the peptides that, in invertebrates, act as antimicrobial, antifungal, antiprotozoal, and/or antiviral agents. Overall, the topic most often on focus is that of innate immunity operated by classes of pattern-recognition proteins. SIGNIFICANCE: The immune response in invertebrates relies on innate rather than on adaptive/acquired effectors. At a difference from the soluble and membrane-bound immunoglobulins and receptors in vertebrates, the antimicrobial, antifungal, antiprotozoal and/or antiviral agents in invertebrates interact with non-self material by targeting some common (rather than some highly specific) structural motifs. Developing this paradigm into (semi) synthetic pharmaceuticals, possibly optimized through the modeling opportunities offered by computational biochemistry, is one of the lessons today's science may learn from the study of marine invertebrates, and specifically of the proteins and peptides in their hemolymph.

Homoseongomycin, a compound isolated from marine actinomycete bacteria K3-1, is a potent inhibitor of encephalitic alphaviruses

Marine microorganisms have been a resource for novel therapeutic drugs for decades. In addition to anticancer drugs, the drug acyclovir, derived from a marine sponge, is FDA-approved for the treatment of human herpes simplex virus-1 infections. Most alphaviruses that are infectious to terrestrial animals and humans, such as Venezuelan and eastern equine encephalitis viruses (VEEV and EEEV), lack efficient antiviral drugs and it is imperative to develop these remedies. To push the discovery and development of anti-alphavirus compounds forward, this study aimed to isolate and screen for potential antiviral compounds from cultured marine microbes originating from the marine environment. Compounds from marine microbes were of interest as they are prolific producers of bioactive compounds across the spectrum of human diseases and infections. Homoseongomycin, an actinobacteria isolated from a marine sponge displayed impressive activity against VEEV from a total of 76 marine bioactive products. The 50% effective concentration (EC₅₀) for homoseongomycin was 8.6 μM for suppressing VEEV TC-83 luciferase reporter virus replication. Homoseongomycin was non-toxic up to 50 μM and partially rescued cells from VEEV induced cell death. Homoseongomycin exhibited highly efficient antiviral activity with a reduction of VEEV infectious titers by 8 log₁₀ at 50 μM. It also inhibited EEEV replication with an EC₅₀ of 1.2 μM. Mechanism of action studies suggest that homoseongomycin affects both early and late stages of the viral life cycle. Cells treated with 25 μM of homoseongomycin had a ~90% reduction in viral entry. In comparison, later stages showed a more robust reduction in infectious titers (6 log₁₀) and VEEV extracellular viral RNA levels (4 log₁₀), but a lesser impact on intracellular viral RNA levels (1.5 log₁₀). In sum, this work demonstrates that homoseongomycin is a potential anti-VEEV and anti-EEEV compound due to its low cytotoxicity and potent antiviral activity.

A new antibacterial 3,5-dimethylorsellinic acid-based meroterpene from the marine fungus Aspergillus sp. CSYZ-1

Chemical investigation of the extracts of Aspergillus sp. CSYZ-1 resulted in the identification of compound 1, aspergillactone, a new 3,5-dimethylorsellinic acid-based meroterpenoid, together with four known metabolites (2-5). The structure and relative configuration of 1 were unambiguously determined by nuclear magnetic resonance (NMR), mass spectrometry. The absolute configuration of 1 was defined by quantum chemical TDDFT calculated and the experimental ECD spectra. The possible biosynthetic pathway of compound 1 was also proposed. The new compound exhibited potent antimicrobial activity against Helicobacter pylori and Staphylococcus aureus with MIC values of around 1-4 and 2-16 μg/mL, respectively.

Antiproliferative and antioxidant properties of nematocysts crude venom from jellyfish Acromitus flagellatus against human cancer cell lines

This study aimed to investigate the antiproliferative and antioxidant properties of crude venom from the nematocyst of Jellyfish Acromitus flagellates on human lung cancer (A549) and liver cancer (HepG2) cell lines. The prepared crude venom was subjected to analyses of the biochemical constituents, protein profiles, antioxidant and anticancer activities by standard methods. The extracted venom was pale-yellow in color and viscous/sticky. The biochemical composition such as, protein (1.547 mg/ml), lipid (0.039 mg/ml) and carbohydrate (0.028 mg/ml) was estimated. Protein profiles were determined by SDS PAGE, the result revealed that the molecular weight range from 205 - 3.5 kDa. The free radical scavenging activity was analyzed by the reducing potential (56.36%), DPPH (72.47%), hydroxyl (68.50%), superoxide anion (65.75%), and nitric oxide (33.04%). The cell viability was observed by using different concentrations (20 to 100 µg/ml) of crude venom on A549 and HepG2 cancer cell lines and the IC50 values were recorded in (60 μg/ml and 40 μg/ml) respectively, while it had none cytotoxic effects on Vero cell line up to the concentration of 90 μg/ml. These results suggest that crude venom from nematocyst of A. flagellatus possesses anti-cancer activity and able to develop novel drugs on marine-derived compounds.

Identification and characterization of Pseudomonas aeruginosa derived bacteriocin for industrial applications

Drug resistance has become a major threat due to the frequent use of commercial antibiotics and there is an urgent need to combat this problem. Having this in mind, the present research was aimed at developing a novel P. aeruginosa puBac bacteriocin molecule. The bacteriocin was purified by ammonium sulfate precipitation followed by Sepharose FF and Sephadex G15 column purification and the purified bacteriocin has been reported to have the molar mass of 43 kDa. The findings of the optimization showed that 3500 AU/mL of bacteriocin was obtained at 37 °C, 3410 AU/mL of bacteriocin at 6.5 pH and 3780 AU/mL of bacteriocin at 48 h of incubation time. In addition, 3863 AU/mL of bacteriocin activity was obtained with Tween-80 followed by 3789 AU/mL with a concentration of 2% NaCl and 4200 AU/mL for Fe²⁺. PuBac bacteriocin has been shown to have a significant effect on test pathogens. For example, E. coli was found to have 3.6 μM of MIC, followed by Staphylococcus sp. with 6.15 μM of MIC and Bacillus sp. with a 7.5 μM of MIC. The remarkable properties of bacteriocin suggest that it could be used in various pharmaceutical and food industries.

Recent Progress in Enzymatic Release of Peptides in Foods of Animal Origin and Assessment of Bioactivity

There is a wide variety of peptides released from food proteins that are able to exert a relevant benefit for human health, such as angiotensin-converting enzyme inhibition, antioxidant, anti-inflammatory, hypoglucemic, or antithrombotic activity, among others. This manuscript is reviewing the recent advances on enzymatic mechanisms for the hydrolysis of proteins from foods of animal origin, including the types of enzymes and mechanisms of action involved, the strategies followed for the isolation and identification of bioactive peptides through advanced proteomic tools, and the assessment of bioactivity and its beneficial effects. Specific applications in fermented and/or ripened foods where a significant number of bioactive peptides have been reported with relevant in vivo physiological effects on laboratory rats and humans as well as the hydrolysis of animal food proteins for the production of bioactive peptides are also reviewed.

Impact of lifestyle on cytochrome P450 monooxygenase repertoire is clearly evident in the bacterial phylum Firmicutes

Cytochrome P450 monooxygenases (CYPs/P450s), heme thiolate proteins, are well known for their role in organisms' primary and secondary metabolism. Research on eukaryotes such as animals, plants, oomycetes and fungi has shown that P450s profiles in these organisms are affected by their lifestyle. However, the impact of lifestyle on P450 profiling in bacteria is scarcely reported. This study is such an example where the impact of lifestyle seems to profoundly affect the P450 profiles in the bacterial species belonging to the phylum Firmicutes. Genome-wide analysis of P450s in 972 Firmicutes species belonging to 158 genera revealed that only 229 species belonging to 37 genera have P450s; 38% of Bacilli species, followed by 14% of Clostridia and 2.7% of other Firmicutes species, have P450s. The pathogenic or commensal lifestyle influences P450 content to such an extent that species belonging to the genera Streptococcus, Listeria, Staphylococcus, Lactobacillus, Lactococcus and Leuconostoc do not have P450s, with the exception of a handful of Staphylococcus species that have a single P450. Only 18% of P450s are found to be involved in secondary metabolism and 89 P450s that function in the synthesis of specific secondary metabolites are predicted. This study is the first report on comprehensive analysis of P450s in Firmicutes.

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.

Two antimicrobial genes from Aegilops tauschii Cosson identified by the Bacillus subtilis expression system

Antimicrobial genes play an important role as a primary defense mechanism in all multicellular organisms. We chose Bacillus subtilis as a target pathogen indicator and transferred the Aegilops tauschii Cosson cDNA library into B. subtilis cells. Expression of the candidate antimicrobial gene can inhibit B. subtilis cell growth. Using this strategy, we screened six genes that have an internal effect on the indicator bacteria. Then, the secreted proteins were extracted and tested; two genes, AtR100 and AtR472, were found to have strong external antimicrobial activities with broad-spectrum resistance against Xanthomonas oryzae pv. oryzicola, Clavibacter fangii, and Botrytis cinerea. Additionally, thermal stability tests indicated that the antimicrobial activities of both proteins were thermostable. Furthermore, these two proteins exhibited no significant hemolytic activities. To test the feasibility of application at the industrial level, liquid fermentation and spray drying of these two proteins were conducted. Powder dilutions were shown to have significant inhibitory effects on B. cinerea. Fluorescence microscopy and flow cytometry results showed that the purified protein impaired and targeted the cell membranes. This study revealed that these two antimicrobial peptides could potentially be used for replacing antibiotics, which would provide the chance to reduce the emergence of drug resistance.

In silico identification and functional validation of linear cationic α-helical antimicrobial peptides in the ascidian Ciona intestinalis

We developed a computing method to identify linear cationic α-helical antimicrobial peptides (LCAMPs) in the genome of Ciona intestinalis based on its structural and physicochemical features. Using this method, 22 candidates of Ciona LCAMPs, including well-known antimicrobial peptides, were identified from 21,975 non-redundant amino acid sequences in Ciona genome database, Ghost database. We also experimentally confirmed the antimicrobial activities of five LCAMP candidates, and three of them were found to be active in the presence of 500 mM NaCl, nearly equivalent to the salt concentration of seawater. Membrane topology prediction suggested that salt resistance of Ciona LCAMPs might be influenced by hydrophobic interactions between the peptide and membrane. Further, we applied our method to Xenopus tropicalis genome and found 11 LCAMP candidates. Thus, our method may serve as an effective and powerful tool for searching LCAMPs that are difficult to find using conventional homology-based methods.

2-Epi-anthracimycin, a new cytotoxic agent from the marine-derived actinomycete Streptomyces sp. OPMA00631

A new cytotoxic agent designated as 2-epi-anthracimycin (1) was isolated along with anthracimycin and anthracimycin B (2-demethylanthracimycin) from the culture broth of the marine-derived actinomycete Streptomyces sp. OPMA00631. The structure of 1 was elucidated based on spectroscopic analyses (1D and 2D NMR data and ROESY correlations). Compound 1 exhibited cytotoxicity against Jurkat cells with an IC₅₀ value of 50.5 μM in 20 h. The effect of 1 on the cell cycle distribution of Jurkat cells was investigated. Compound 1 (7.80 μM) increased G1 phase cells from 51.1 to 62.0% and conversely, decreased G2 and M phase cells from 30.7 to 19.3 % in 20 h. At a higher concentration, 1 (250 μM) markedly increased subG1 phase cells (1.9% at 0 h to 16.5% at 20 h), while the proportion of G1 phase cells was maintained (62.3%). These results suggest that 1 exhibits cytotoxicity against Jurkat cells by arresting the cell cycle at the G1 phase.

Anti-HSV-1 activity of Aspergillipeptide D, a cyclic pentapepetide isolated from fungus Aspergillus sp. SCSIO 41501

Background

Herpes simplex virus 1, an enveloped DNA virus belonging to the Herpesviridae family, spreads to neurons and causes pathological changes in the central nervous system. The purpose of this study was to investigate the potency and mechanism of antiviral activity of Aspergillipeptide D, a cyclic pentapeptide isolated from a culture broth of marine gorgonian-derived fungus Aspergillus sp. SCSIO 41501, At present, there are many studies on the anti-tumor, anti-clotting, anti-oxidant and immunoinflammatory effects of Aspergillipeptide D, but little research has been done on the anti-HSV-1 activity of Aspergillipeptide D.

Methods

The anti-HSV-1 activity of Aspergillipeptide D was evaluated by plaque reduction assay. The mechanism of action against HSV-1 was determined from the effective stage. Then we assayed the viral DNA replication, viral RNA synthesis and protein expression, respectively. We also identified the proteins that interact with gB by mass spectrometry, and assayed the effect of Aspergillipeptide D on the interaction between the virus gB protein and cell proteins.

Results

Plaque reduction experiments showed that Aspergillipeptide D did not affect HSV-1 early infection events, including viral inactivation, attachment and penetration. Interestingly, Aspergillipeptide D dramatically reduced both the gene and protein levels of viral late protein gB, and suppressed its location in the endoplasmic reticulum and Golgi apparatus. In contrast, overexpression of gB restored viral production. Finally, proteomic analysis revealed that the numbers of cellular proteins that interacted with gB protein was largely decreased by Aspergillipeptide D. These results suggested that Aspergillipeptide D inhibited gB function to affect HSV-1 intercellular spread.

Conclusions

Our results indicated that Aspergillipeptide D might be a potential candidate for HSV-1 therapy, especially for ACV-resistant strains.

The antimicrobial peptide MPX kills Actinobacillus pleuropneumoniae and reduces its pathogenicity in mice

Actinobacillus pleuropneumoniae is the causative agent of highly contagious and fatal respiratory infections, causing substantial economic losses to the global pig industry. Due to increased antibiotic resistance, there is an urgent need to find new antibiotic alternatives for treating A. pleuropneumoniae infections. MPX is obtained from wasp venom and has a killing effect on various bacteria. This study found that MPX had a good killing effect on A. pleuropneumoniae and that the minimum inhibitory concentration (MIC) was 16 μg/mL. The bacterial density of A. pleuropneumoniae decreased 1000 times after MPX (1 × MIC) treatment for 1 h, and the antibacterial activity was not affected by pH or temperature. Fluorescence microscopy showed that MPX (1 × MIC) destroyed the bacterial cell membrane after treatment for 0.5 h, increasing membrane permeability and releasing bacterial proteins and Ca²⁺, Na⁺ and other cations. In addition, MPX (1 × MIC) treatment significantly reduced the formation of bacterial biofilms. Quantitative RT-PCR results showed that MPX treatment significantly upregulated the expression of the PurC virulence gene and downregulated that of ApxI, ApxII, and Apa1. In addition, the Sap A gene was found to play an important role in the tolerance of A. pleuropneumoniae to antimicrobial peptides. Therapeutic evaluation in a murine model showed that MPX protects mice from a lethal dose of A. pleuropneumoniae and relieves lung inflammation. This study reports the use of MPX to treat A. pleuropneumonia infections, laying the foundation for the development of new drugs for bacterial infections.

Fatty acids-carotenoid complex: An effective anti-TB agent from the chlorella growth factor-extracted spent biomass of Chlorella vulgaris

ETHNOPHARMACOLOGICAL RELEVANCE

The multidrug-resistant (MDR) pathogen, Mycobacterium tuberculosis, still remains as one of the major threat to mankind, despite the availability of a live attenuated vaccine and effective antibiotics. Marine microalgae, at all times, act as a key resource for valuable therapeutic compounds with limited side effects.

AIM OF THE STUDY

The present explorative attempt is to isolate the biomolecules of pharmacological importance from the marine microalgae, Chlorella vulgaris, and to evaluate its effect on the ever dreadful disease, Tuberculosis. The study is also aimed to develop an economically feasible methodology for by-products extraction from microalgae.

MATERIALS AND METHODS

Fatty acids-carotenoid complexes (FACC), namely, FACC-1 (red oil) and FACC-2 (brown oil) were isolated, in addition to lipid and lutein from the Chlorella Growth Factor (CGF, a protein fraction enriched with vitamins, minerals and carbohydrates)-extracted spent biomass through column chromatography.

RESULTS

FACC-1 is a complex of fatty acids such as oleic and linoleic acids, and carotenoids such as canthaxanthin and neoxanthin. FACC-2 is a complex of oleic, linoleic and linolenic acids and carotenoids (cryptoxanthin and echinenone). Initial screening for evaluation of minimum bactericidal concentration (MBC) of FACC-1 and -2 was performed against Mycobacterium tuberculosis strains such as H37Rv, SHRE sensitive clinical isolate and SHRE resistant clinical isolate. MBC was noted at 10 μg/mL by FACC-1 and at 5 μg/mL by FACC-2, determined using colony forming and Lucipherase Reporter Mycobacteriophages (LRP) assay. Testing in the PAN sensitive isolates indicated that the MBC was noted at 5 μg/mL by FACC-1 and at 2.5 μg/mL by FACC-2. Complete inhibition (100%) was observed at 100 μg/mL by FACC-1 and at 50 μg/mL by FACC-2. Testing of FACC-1 and FACC-2 individually as well as in combination on two different types of MDR strains confirmed the efficacy of the algal oils, wherein in MDR-strain 1, FACC-1 revealed 50% inhibition at 10 μg/mL, while FACC-2 exhibited the same at 5 μg/mL. Conversely, in the case of MDR strain-2, MBC of FACC-1 was at 500 μg/mL and MBCof FACC-2 to be at 250 μg/mL. No significant synergistic effect was observed on combining both the oils.

CONCLUSION

The study signifies the development of a potent therapeutic agent comprising of a complex of anti-TB agent (fatty acids) and antioxidants (carotenoids) from the CGF-extracted spent biomass of C. vulgaris.

Review: Antibacterial components of the Bivalve's immune system and the potential of freshwater bivalves as a source of new antibacterial compounds

Antibacterial research is reaching new heights due to the increasing demand for the discovery of new substances capable of inhibiting bacteria, especially to respond to the appearance of more and more multi-resistant strains. Bivalves show enormous potential for the finding of new antibacterial compounds, although for that to be further explored, more research needs to be made regarding the immune system of these organisms. Beyond their primary cellular component responsible for bacterial recognition and destruction, the haemocytes, bivalves have various other antibacterial units dissolved in the haemolymph that intervene in the defense against bacterial infections, from the recognition factors that detect different bacteria to the effector molecules carrying destructive properties. Moreover, to better comprehend the immune system, it is important to understand the different survival strategies that bacteria possess in order to stay alive from the host's defenses. This work reviews the current literature regarding the components that intervene in a bacterial infection, as well as discussing the enormous potential that freshwater bivalves have in the discovery of new antibacterial compounds.

Exploring Antimicrobials from the Flora and Fauna of Marine: Opportunities and Limitations

About 95% of earth living space lies deep below the ocean's surface and it harbors extraordinary diversity of marine organisms. Marine biodiversity is an exceptional reservoir of natural products, bioactive compounds, nutraceuticals and other potential compounds of commercial value. Timeline for the development of the drug from a plant, synthetic and other alternative sources is too lengthy. Exploration of the marine environment for potential bioactive compounds has gained focus and huge opportunity lies ahead for the exploration of such vast resources in the ocean. Further, the evolution of superbugs with increasing resistance to the currently available drugs is alarming and it needs coordinated efforts to resolve them. World Health Organization recommends the need and necessity to develop effective bioactive compounds to combat problems associated with antimicrobial resistance. Based on these factors, it is imperative to shift the focus towards the marine environment for potential bioactive compounds that could be utilized to tackle antimicrobial resistance. Current research trends also indicate the huge strides in research involving marine environment for drug discovery. The objective of this review article is to provide an overview of marine resources, recently reported research from marine resources, challenges, future research prospects in the marine environment.

Consumption of Terpenoids-Rich Padina pavonia Extract Attenuates Hyperglycemia, Insulin Resistance and Oxidative Stress, and Upregulates PPARγ in a Rat Model of Type 2 Diabetes

Seaweeds are rich in structurally diverse bioactive compounds with promising therapeutic effects. This study aimed to isolate and identify terpenes from the brown alga Padina pavonia and to investigate its antidiabetic activity, pointing to the possible involvement of peroxisome proliferator-activated receptor (PPAR)γ. Type 2 diabetes was induced by feeding rats a high fat diet (HFD) for 4 weeks followed by injection of 35 mg/kg streptozotocin (STZ). The diabetic rats received P. pavonia extract (PPE; 50, 100 and 200 mg/kg) for 4 weeks and samples were collected for analyses. HFD/STZ-induced rats showed hyperglycemia, dyslipidemia, impaired glucose tolerance, decreased insulin, and increased HbA1c and HOMA-IR. PPE ameliorated hyperglycemia and dyslipidemia, and improved glucose tolerance and insulin sensitivity in diabetic rats. Treatment with PPE increased hepatic hexokinase activity and glycogen, suppressed glucose-6-phosphatase, fructose-1,6-biphosphatase, and glycogen phosphorylase, and attenuated oxidative stress, inflammation, and liver injury and lipid infiltration in HFD/STZ-induced rats. In addition, PPE boosted antioxidants and upregulated PPARγ gene and protein expression in the liver of diabetic rats. Phytochemical investigation resulted in the isolation of six terpenes from PPE and in silico analysis revealed their binding affinity toward PPARγ. In conclusion, P. pavonia-derived terpenes attenuated hyperglycemia, dyslipidemia, oxidative stress, and inflammation, and improved insulin sensitivity and carbohydrate metabolism in type 2 diabetic rats. These beneficial effects are mediated via PPARγ activation. However, further studies to explore the exact mechanisms underlying the antidiabetic effect of PPE are recommended.

Marine Pharmacology in 2014-2015: Marine Compounds with Antibacterial, Antidiabetic, Antifungal, Anti-Inflammatory, Antiprotozoal, Antituberculosis, Antiviral, and Anthelmintic Activities; Affecting the Immune and Nervous Systems, and Other Miscellaneous Mechanisms of Action

The systematic review of the marine pharmacology literature from 2014 to 2015 was completed in a manner consistent with the 1998-2013 reviews of this series. Research in marine pharmacology during 2014-2015, which was reported by investigators in 43 countries, described novel findings on the preclinical pharmacology of 301 marine compounds. These observations included antibacterial, antifungal, antiprotozoal, antituberculosis, antiviral, and anthelmintic pharmacological activities for 133 marine natural products, 85 marine compounds with antidiabetic, and anti-inflammatory activities, as well as those that affected the immune and nervous system, and 83 marine compounds that displayed miscellaneous mechanisms of action, and may probably contribute to novel pharmacological classes upon further research. Thus, in 2014-2015, the preclinical marine natural product pharmacology pipeline provided novel pharmacology as well as new lead compounds for the clinical marine pharmaceutical pipeline, and thus continued to contribute to ongoing global research for alternative therapeutic approaches to many disease categories.

Calculation of the Global and Local Conceptual DFT Indices for the Prediction of the Chemical Reactivity Properties of Papuamides A-F Marine Drugs

A well-behaved model chemistry previously validated for the study of the chemical reactivity of peptides was considered for the calculation of the molecular properties and structures of the Papuamide family of marine peptides. A methodology based on Conceptual Density Functional Theory (CDFT) was chosen for the determination of the reactivity descriptors. The molecular active sites were associated with the active regions of the molecules related to the nucleophilic and electrophilic Parr functions. Finally, the drug-likenesses and the bioactivity scores for the Papuamide peptides were predicted through a homology methodology relating them with the calculated reactivity descriptors, while other properties such as the pKas were determined following a methodology developed by our group.

New Peptides from The Marine-Derived Fungi Aspergillus allahabadii and Aspergillus ochraceopetaliformis

Four new peptides were isolated from the culture broths of the marine-derived fungi Aspergillus allahabadii and A. ochraceopetaliformis. Based on the results of chemical and spectroscopic analyses, two compounds (1 and 2) from A. allahabadii were determined to be cyclopentapeptides, while those from A. ochraceopetaliformis were a structurally-related cyclodepsihexapeptide (3) and its linear analog (4). In addition to the presence of a D-amino acid residue, the almost reversed sequence of peptides in 3 and 4, relative to those of the 1 and 2, is notable. These new compounds exhibited moderate inhibition against the enzyme sortase A as well as a weak inhibition against isocitrate lyase (2).

In Vitro Antiviral Activity Against Zika Virus From a Natural Product of the Brazilian Brown Seaweed Dictyota menstrualis

Natural products isolated from seaweeds have shown great antiviral potential against numerous viruses such as human type 1 herpes, human immunodeficiency virus, and dengue. Diterpenes produced by the brown seaweeds Dictyota and Canistrocarpus, in particular, have shown antiviral or virucidal activity. Recently, the Zika virus (ZIKV) has become a major public health concern due to its widespread dissemination throughout the Americas. Since no vaccines are available, and no drugs have effectively treated recent cases of infection, our group evaluated products from Dictyota menstrualis for their antiviral potential, alone and in combination with Ribavirin. We first evaluated the compounds’ cytotoxicity at high concentrations, and then evaluated the inhibition of ZIKV replication by crude extracts and acetylated crude extracts and their fractions at 20 μg/mL. The F-6 and FAc-2 fractions, rich in cyclic diterpenes with aldehyde groupings, inhibited ZIKV replication by >74%, with inhibition behaving in a dose-dependent manner and the 50% effective concentration (EC50) values of 2.80 (F-6) and 0.81 (FAc-2) μg/mL. Regarding the mechanism of action, FAc-2 had strong virucidal potential, and F-6 inhibited viral adsorption. Associating FAc-2 with Ribavirin at suboptimal dosages produced a strong synergistic effect that completely inhibited viral replication. Our results indicate that these natural products have excellent inhibitory potential against ZIKV replication and may be promising for developing affective therapies.

Antimicrobial and Immunomodulatory Properties and Applications of Marine-Derived Proteins and Peptides

Marine organisms provide an abundant source of potential medicines. Many of the marine-derived biomaterials have been shown to act as different mechanisms in immune responses, and in each case they can significantly control the immune system to produce effective reactions. Marine-derived proteins, peptides, and protein hydrolysates exhibit various physiologic functions, such as antimicrobial, anticancer, antioxidant, antihypertensive, and anti-inflammatory activities. Recently, the immunomodulatory properties of several antimicrobial peptides have been demonstrated. Some of these peptides directly kill bacteria and exhibit a variety of immunomodulatory activities that improve the host innate immune response and effectively eliminate infection. The properties of immunomodulatory proteins and peptides correlate with their amino acid composition, sequence, and length. Proteins and peptides with immunomodulatory properties have been tested in vitro and in vivo, and some of them have undergone different clinical and preclinical trials. This review provides a comprehensive overview of marine immunomodulatory proteins, peptides, and protein hydrolysates as well as their production, mechanisms of action, and applications in human therapy.

The Biotechnological Potential of Secondary Metabolites from Marine Bacteria

Marine habitats are a rich source of molecules of biological interest. In particular, marine bacteria attract attention with their ability to synthesize structurally diverse classes of bioactive secondary metabolites with high biotechnological potential. The last decades were marked by numerous discoveries of biomolecules of bacterial symbionts, which have long been considered metabolites of marine animals. Many compounds isolated from marine bacteria are unique in their structure and biological activity. Their study has made a significant contribution to the discovery and production of new natural antimicrobial agents. Identifying the mechanisms and potential of this type of metabolite production in marine bacteria has become one of the noteworthy trends in modern biotechnology. This path has become not only one of the most promising approaches to the development of new antibiotics, but also a potential target for controlling the viability of pathogenic bacteria.

Marine sponges of the genus Stelletta as promising drug sources: chemical and biological aspects

Marine sponges of the genus Stelletta are well known as rich sources of diverse and complex biologically relevant natural products, including alkaloids, terpenoids, peptides, lipids, and steroids. Some of these metabolites, with novel structures and promising biological activities, have attracted a lot of attention from chemists seeking to perform their total synthesis in parallel to intensive biological studies towards new drug leads. In this review, we summarized the distribution of the chemically investigated Stelletta sponges, the isolation, synthesis and biological activities of their secondary metabolites, covering the literature from 1982 to early 2018.

A Computer-Driven Approach to Discover Natural Product Leads for Methicillin-Resistant Staphylococcus aureus Infection Therapy

The risk of methicillin-resistant Staphylococcus aureus (MRSA) infection is increasing in both the developed and developing countries. New approaches to overcome this problem are in need. A ligand-based strategy to discover new inhibiting agents against MRSA infection was built through exploration of machine learning techniques. This strategy is based in two quantitative structure–activity relationship (QSAR) studies, one using molecular descriptors (approach A) and the other using descriptors (approach B). In the approach A, regression models were developed using a total of 6645 molecules that were extracted from the ChEMBL, PubChem and ZINC databases, and recent literature. The performance of the regression models was successfully evaluated by internal and external validation, the best model achieved R² of 0.68 and RMSE of 0.59 for the test set. In general natural product (NP) drug discovery is a time-consuming process and several strategies for dereplication have been developed to overcome this inherent limitation. In the approach B, we developed a new NP drug discovery methodology that consists in frontloading samples with 1D NMR descriptors to predict compounds with antibacterial activity prior to bioactivity screening for NPs discovery. The NMR QSAR classification models were built using 1D NMR data (¹H and ¹³C) as descriptors, from crude extracts, fractions and pure compounds obtained from actinobacteria isolated from marine sediments collected off the Madeira Archipelago. The overall predictability accuracies of the best model exceeded 77% for both training and test sets.