Development of novel drugs from marine surface associated microorganisms

The potential of marine natural products and their synthetic derivatives as drugs targeting ion channels

Ion channels are a type of protein channel that play a vital role in numerous physiological functions by facilitating the passage of ions through cell membranes, thereby enabling ion and electrical signal transmission. As a crucial target for drug action, ion channels have been implicated in various diseases. Many natural products from marine organisms, such as fungi, algae, sponges, and sea cucumber, etc. have been found to have activities related to ion channels for decades. These interesting natural product molecules undoubtedly bring good news for the treatment of neurological and cardiovascular diseases. In this review, 92 marine natural products and their synthetic derivatives with ion channel-related activities that were identified during the period 2000-2024 were systematically reviewed. The synthesis and mechanisms of action of selected compounds were also discussed, aiming to offer insights for the development of drugs targeting ion channels.

Current approaches to genetic modification of marine bacteria and considerations for improved transformation efficiency

Marine bacteria play vital roles in symbiosis, biogeochemical cycles and produce novel bioactive compounds and enzymes of interest for the pharmaceutical, biofuel and biotechnology industries. At present, investigations into marine bacterial functions and their products are primarily based on phenotypic observations, -omic type approaches and heterologous gene expression. To advance our understanding of marine bacteria and harness their full potential for industry application, it is critical that we have the appropriate tools and resources to genetically manipulate them in situ. However, current genetic tools that are largely designed for model organisms such as E. coli, produce low transformation efficiencies or have no transfer ability in marine bacteria. To improve genetic manipulation applications for marine bacteria, we need to improve transformation methods such as conjugation and electroporation in addition to identifying more marine broad host range plasmids. In this review, we aim to outline the reported methods of transformation for marine bacteria and discuss the considerations for each approach in the context of improving efficiency. In addition, we further discuss marine plasmids and future research areas including CRISPR tools and their potential applications for marine bacteria.

A culture-independent approach, supervised machine learning, and the characterization of the microbial community composition of coastal areas across the Bay of Bengal and the Arabian Sea

BACKGROUND

Coastal areas are subject to various anthropogenic and natural influences. In this study, we investigated and compared the characteristics of two coastal regions, Andhra Pradesh (AP) and Goa (GA), focusing on pollution, anthropogenic activities, and recreational impacts. We explored three main factors influencing the differences between these coastlines: The Bay of Bengal's shallower depth and lower salinity; upwelling phenomena due to the thermocline in the Arabian Sea; and high tides that can cause strong currents that transport pollutants and debris.

RESULTS

The microbial diversity in GA was significantly higher than that in AP, which might be attributed to differences in temperature, soil type, and vegetation cover. 16S rRNA amplicon sequencing and bioinformatics analysis indicated the presence of diverse microbial phyla, including candidate phyla radiation (CPR). Statistical analysis, random forest regression, and supervised machine learning models classification confirm the diversity of the microbiome accurately. Furthermore, we have identified 450 cultures of heterotrophic, biotechnologically important bacteria. Some strains were identified as novel taxa based on 16S rRNA gene sequencing, showing promising potential for further study.

CONCLUSION

Thus, our study provides valuable insights into the microbial diversity and pollution levels of coastal areas in AP and GA. These findings contribute to a better understanding of the impact of anthropogenic activities and climate variations on biology of coastal ecosystems and biodiversity.

A review: Marine aquaculture impacts marine microbial communities

Marine aquaculture is key for protein production but disrupts marine ecosystems by releasing excess feed and pharmaceuticals, thus affecting marine microbes. Though vital, its environmental impact often remains overlooked. This article delves into mariculture's effects on marine microbes, including bacteria, fungi, viruses, and antibiotic-resistance genes in seawater and sediments. It highlights how different mariculture practices-open, pond, and cage culture-affect these microbial communities. Mariculture's release of nutrients, antibiotics, and heavy metals alters the microbial composition, diversity, and functions. Integrated multi-trophic aquaculture, a promising sustainable approach, is still developing and needs refinement. A deep understanding of mariculture's impact on microbial ecosystems is crucial to minimize pollution and foster sustainable practices, paving the way for the industry's sustainable advancement.

Exploring the hidden treasures of Nitella hyalina: a comprehensive study on its biological compounds, nutritional profile, and unveiling its antimicrobial, antioxidative, and hypoglycemic properties

Macroalgae has the potential to be a precious resource in food, pharmaceutical, and nutraceutical industries. Therefore, the present study was carried out to identify and quantify the phyco-chemicals and to assess the nutritional profile, antimicrobial, antioxidant, and anti-diabetic properties of Nitella hyalina extracts. Nutritional composition revealed0.05 ± 2.40% ash content, followed by crude protein (24.66 ± 0.95%), crude fat (17.66 ± 1.42%), crude fiber (2.17 ± 0.91%), moisture content (15.46 ± 0.48%) and calculated energy value (173.50 ± 2.90 Kcal/100 g). 23 compounds were identified through GC-MS analysis in ethyl acetate extract, with primary compounds being Palmitic acid, methyl ester, (Z)-9-Hexadecenoic acid, methyl ester, and Methyl tetra decanoate. Whereas 15 compounds were identified in n-butanol extract, with the major compounds being Tetra decanoic acid, 9-hexadecanoic acid, Methyl pentopyranoside, and undecane. FT-IR spectroscopy confirmed the presence of alcoholic phenol, saturated aliphatic compounds, lipids, carboxylic acid, carbonyl, aromatic components, amine, alkyl halides, alkene, and halogen compounds. Moreover, n-butanol contains 1.663 ± 0.768 mg GAE/g, of total phenolic contents (TPC,) and 2.050 ± 0.143 QE/g of total flavonoid contents (TFC), followed by ethyl acetate extract, i.e. 1.043 ± 0.961 mg GAE/g and 1.730 ± 0.311 mg QE/g respectively. Anti-radical scavenging effect in a range of 34.55-46.35% and 35.39-41.79% was measured for n-butanol and ethyl acetate extracts, respectively. Antimicrobial results declared that n-butanol extract had the highest growth inhibitory effect, followed by ethyl acetate extract. Pseudomonas aeruginosa was reported to be the most susceptible strain, followed by Staphylococcus aureus and Escherichia coli, while Candida albicans showed the least inhibition at all concentrations. In-vivo hypoglycemic study revealed that both extracts exhibited dose-dependent activity. Significant hypoglycemic activity was observed at a dose of 300 mg/kg- 1 after 6 h i.e. 241.50 ± 2.88, followed by doses of 200 and 100 mg/kg- 1 (245.17 ± 3.43 and 250.67 ± 7.45, respectively) for n-butanol extract. In conclusion, the macroalgae demonstrated potency concerning antioxidant, antimicrobial, and hypoglycemic properties.

A new anthraquinone derivative from the marine fish-derived fungus Alternaria sp. X112

A new anthraquinone, altermodinacid A (1), and five known derivatives, pachybasic acid (2), emodic acid (3), emodin (4), phomarin (5), and 1,7-dihydroxy-3-methylanthracene-9,10-dione (6), were discovered from a halotolerant fungus Alternaria sp. X112 isolated from a marine fish Gadus macrocephalus. Their structures were determined by analysing MS and NMR data. The cytotoxic effect, antiagricultural pathogens activity, antibacterial activity and quorum sensing inhibitory potential of new compound 1 were evaluated.

Seaweed-associated heterotrophic Bacillus altitudinis MTCC13046: a promising marine bacterium for use against human hepatocellular adenocarcinoma

Since the report of the antibiotic with anticancer properties, scientists have been focusing to isolate and characterize novel anti-microbial natural products possessing anticancer activities. The current study describes the production of seaweed-associated heterotrophic Bacillus altitudinis MTCC13046 with potential anticancer properties. The bacterium was screened for its capacity to diminish the cell proliferation of the human hepatocellular adenocarcinoma (HepG2) cell line, without upsetting the normal cells. The bacterial extract showed anticancer properties in a dose-reactive form against HepG2 (IC₅₀, half maximal inhibitory concentration ~ 29.5 µg/ml) on tetrazolium bromide analysis with less significant cytotoxicity on common fibroblast (HDF) cells (IC₅₀ ~ 77 µg/ml). The potential antioxidant ability of the organic extract of B. altitudinis MTCC13046 (IC₉₀ 133 µg/ml) could corroborate its capacity to attenuate the pathophysiology leading to carcinogenesis. The results of the apoptosis assay showed that the crude extracts of B. altitudinis maintained 68% viability in normal cells compared to 11% in the cancer cells (IC₅₀ 76.9 µg/ml). According to the findings, B. altitudinis MTCC13046 could be used to develop prospective anticancer agents.

Pharmacological potential of seaweed-associated heterotrophic bacterium Bacillus atrophaeus

Extremities in marine environmental conditions led the marine macroalga-associated bacteria to adapt and biosynthesize potential bioactive agents. The myriad of marine macroalgae and the bacterial flora they are associated with constitute a potential source of bioactive components with significant biotechnological and pharmacological applications. Heterotrophic bacteria associated with the intertidal macroalgae were isolated and assessed for their pharmacological properties. Subsequently, Firmicutes dominated more than half of the 152 cultivable isolates from macroalgae-associated bacteria collected from the Gulf of Mannar (9°17'0'' N, 79°7'0'' E), on Peninsular India's southern coast. A total of 43 of those demonstrated steady antibacterial activities against a wide range of nosocomial pathogens. Among the bacteria isolated from marine macroalgae, Bacillus atrophaeus SHB2097 (MW821482) exhibited significant antimicrobial activities against clinically important pathogens. Organic extract of B. atrophaeus SHB2097 showed potential antimicrobial activities against test pathogens (minimum inhibitory concentration 6.25 µg/mL). Organic extract of B. atrophaeus SHB2097 revealed promising inhibition potential against cyclooxygenase-2 (IC₉₀ 53.26 µg/mL) and 5-lipoxygenase (IC₉₀ 9.74 µg/mL). The carbolytic enzyme α-glucosidase inhibition potential of the organic extract of the studied heterotrophic bacterium was significantly greater than (IC₉₀ 118 µg/mL) than that displayed by acarbose (IC₉₀ 645 µg/mL, p < 0.05). The significance of nuclear magnetic resonance-centered analyses of distinguishing signals in the organic extract and correlating those with bioactive potential was accentuated. The utilities of nuclear magnetic resonance-based fingerprinting emphasized the assessment of the distinctive signals in the solvent extracts and their correlation with the pharmacological properties. Thus, the heterotrophic B. atrophaeus SHB2097 could be used to develop potential therapeutic and biomedical agents.

Evaluation of the Marine Bacterial Population in the Great Bitter Lake, Egypt, as a Source of Antimicrobial Secondary Metabolites

The ecological uniqueness of the Great Bitter Lake ecosystem makes its bacterial population interesting for investigation. Here, we present the first trial to evaluate the biosynthetic capacity of the bacterial population at the lake as a source of novel antimicrobials. We collected different samples from various locations throughout the lake including the oxic sediment, anoxic sediment, shore water, and off-shore water. We modified a molecular approach to compare and choose the samples with the highest bacterial biosynthetic capacity by quantifying the polyketide synthase gene clusters in their total community DNA. Furthermore, we screened the bacterial isolates recovered from these samples and their metabolic extracts for antimicrobial activity. We tried to tentatively investigate the identity of the active metabolites by PCR screening and LC–MS. The bacterial population in the oxic sediment had the highest biosynthetic capacity compared to other sample types. Four active Bacillus isolates were identified. The isolated Bacillus species were expected to produce numerous probable bioactive metabolites encoded by biosynthetic gene clusters related to the polyketide synthases (either individual or hybrid with non-ribosomal peptide synthetase), such as Bacillomycin D, Iturin A, Bacilosarcin B, Bacillcoumacin G and Macrolactin (N and G). These results suggest that the under-explored bacterial community of the Great Bitter Lake has a prospective biosynthetic capacity and can be a promising source for novel antibiotics.

Pharmacological potential of seaweed-associated heterotrophic Firmicutes

Seaweed-associated bacterial symbionts are sources of potential pharmacological properties. The present study resulted in the culture-dependent isolation of bioactive heterotrophs belonging to the bacterial phylum Firmicutes, which were dominated more than 30% of the 127 cultivable isolates, among which 23 of them showed potential antimicrobial activities against a wide range of pathogens. The symbionts isolated from the seaweed Sargassum wightii showed significant bioactivity. Those were characterised as Bacillus safensis MTCC13040, B. valismortis MTCC13041, B. velezensis MTCC13044, B. methylotrophicus MTCC13042, Oceanobacillus profundus MTCC13045, B. tequilensis MTCC13043, and B. altitudinis MTCC13046. The organic extracts of the studied isolates showed potential antimicrobial properties against methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococci (minimum inhibitory concentration 6.25-12.5 μg ml^-1 ). The organic extract of B. altitudinis MTCC13046 displayed significantly greater radical quenching ability (IC₉₀ 133 μg ml^-1 , p < 0.05) other than attenuating hydroxymethyl glutaryl coenzyme A reductase (IC₉₀ 10.21 μg ml^-1 , p < 0.05) and angiotensin converting enzyme-1 (IC₉₀ 498 μg ml^-1 , p < 0.05) relative to other studied heterotrophs. The organic extract of B. tequilensis MTCC13043 displayed significantly greater attenuation potential against pro-inflammatory 5-lipooxygenase (IC₉₀ 5.94 μg ml^-1 , p < 0.05) and dipeptidyl peptidase-4 (IC₉₀ 271 μg ml^-1 , p < 0.05). The seaweed-associated B. altitudinis MTCC13046 and B. tequilensis MTCC13043 could be used to develop promising pharmacological leads.

Current Knowledge on the Bioavailability of Thymol as a Feed Additive in Humans and Animals with a Focus on Rabbit Metabolic Processes

Simple Summary

This review provides general information on the possible health benefits in animals and humans of herbal additives, particularly thymol, whose phenolic group is responsible for the neutralisation of free radicals, and information concerning its detection through body action, bioavailability and mechanisms in rabbits. Plants containing thymol have been used in traditional medicine for the treatment of various diseases, such as cardiovascular diseases, cancer and diabetes. Although a great number of in vitro studies of cardiovascular and cancer diseases are available, in vivo studies that confirm these findings have not been sufficiently reported. To determine the beneficial dose, further clinical studies are necessary, with preclinical comprehensive research on animal models.

Abstract

The aim of this review is to describe the therapeutic effect of thymol on various human diseases, followed by its bioavailability in humans and animals. Based on our knowledge from the current literature, after thymol addition, thymol metabolites—mostly thymol sulphate and glucuronide—are detected in the plasma and urine of humans and in the plasma, intestinal content, faeces and tissues in rats, pigs, chickens, horses and rabbits after enzymatic cleavage. In rabbits, thymol absorption from the gastrointestinal tract, its distribution within the organism, its accumulation in tissues and its excretion from the organism have been described in detail. It is necessary and important for these studies to suggest the appropriate dose needed to achieve the required health benefits not only for animals but also for humans. Information from this review concerning the mode of action of thymol in animal organisms could also be applied to human medicine and may help in the utilisation of herbal medicine in humans and in veterinary healthcare. This review summarises the important aspects of thymol’s effects on health and its bioavailability in organisms, particularly in rabbits. In future, herbal-based drugs must be extensively investigated in terms of their mode of action, efficiency of administration and clinical effect.

Turbinaria ornata and its associated epiphytic Bacillus sp. A promising molecule supplier to discover new natural product approaches

Marine ecosystems are highly dependent on macroalgea in providing food and shelter for aquatic organisms, interacting with many bacteria and mostly producing secondary metabolites of potent therapeutic antibacterial property. Screening of marine microbial secondary metabolites of valuable biotechnological and therapeutical applications are now extensively studied. In this study, Bacillus spp. identified by DNA sequencing and found associated with Turbinaria ornata, was screened and characterized for its cell free supernatant (CFS) possible antimicrobial and antibiofilm applications. Among the 7 microbial isolates tested, CFS greatly affected Bacillus subitilis (12 mm) and inhibited equally the yeast isolates Candida albicans, Candida tropicalis and Candida glabrata (10 mm) and had no or negligible effect on S.aureus, E.coli, P. aeruginosa. As for the CFS antibiofilm activity, no difference was revealed from the positive control. Algal crude extracts (methanol, acetone and aqueous), on the other hand, were similarly tested for their antimicrobial activity against the seven microbial isolates, where highest activity was observed with the aqueous crude extract against Staphylococcus aureus(10 mm) and Pseudomonas aeruginosa (9 mm) compared to the negligible effects of methanol and acetone crude extracts. Chemical analysis was performed to reveal the major constituents of both crude algal extracts and Bacillus spp. CFS. FTIR spectrum of the bacterial CFS indicated the presence of bacteriocin as the major lipopeptide responsible for its biological activity. Whereas, methanol and water crude algal extract GC-MS spectra revealed different chemical groups of various combined therapeutical activity mainly Naphthalene, amino ethane-sulfonic acid, pyrlene, Biotin and mercury chloromethyl correspondingly. Thus, the present study, demonstrated the moderate activity of both crude algal extract and the bacterial CFS, however, further investigations are needed for a better biological activity.

Bioactive Molecules from Ciliates: Structure, Activity, and Applicative Potential

Ciliates are a rich source of molecules synthesized to socialize, compete ecologically, and interact with prey and predators. Their isolation from laboratory cultures is often straightforward, permitting the study of their mechanisms of action and their assessment for applied research. This review focuses on three classes of these bioactive molecules: (i) water‐borne, cysteine‐rich proteins that are used as signaling pheromones in self/nonself recognition phenomena; (ii) cell membrane‐associated lipophilic terpenoids that are used in interspecies competitions for habitat colonization; (iii) cortical granule‐associated molecules of various chemical nature that primarily serve offence/defense functions.

First report of steroid derivatives isolated from starfish Acanthaster planci with anti-bacterial, anti-cancer and anti-diabetic activities

Chemical studies on Acanthaster planci have afforded two steroids, 5α-cholesta-24-en-3β,20β-diol-23-one (1) and 5α-cholesta-9(11)-en-3β, 20β-diol (2). Structures compounds 1 and 2 were determined with the help of spectroscopic studies. Compound 1 showed strong antibacterial activity (21.0 ± 0.06 mm) against P. aeruginosa. Compounds 1 and 2 were also active against human breast carcinoma cells (MCF-7) with LC₅₀ values of 49 ± 1.6 and 57.5 ± 1.5 μg/ml, respectively. This bioactivity was comparable to the currently used anticancer agent, cisplatin (LC₅₀ 46 ± 1.1 µg/ml). Compounds 1 and 2 exhibited anti-α-glucosidase activity with IC₅₀ values of 58 ± 0.8 and 55 ± 0.5 µg/ml, respectively, whereas IC₅₀ of Acarbose as a positive control was found to be 36 ± 0.4 µg/ml in our bioassay.

Towards Advances in Medicinal Plant Antimicrobial Activity: A Review Study on Challenges and Future Perspectives

The increasing incidence of drug- resistant pathogens raises an urgent need to identify and isolate new bioactive compounds from medicinal plants using standardized modern analytical procedures. Medicinal plant-derived compounds could provide novel straightforward approaches against pathogenic bacteria. This review explores the antimicrobial activity of plant-derived components, their possible mechanisms of action, as well as their chemical potential. The focus is put on the current challenges and future perspectives surrounding medicinal plants antimicrobial activity. There are some inherent challenges regarding medicinal plant extracts and their antimicrobial efficacy. Appropriate and optimized extraction methodology plant species dependent leads to upgraded and selective extracted compounds. Antimicrobial susceptibility tests for the determination of the antimicrobial activity of plant extracts may show variations in obtained results. Moreover, there are several difficulties and problems that need to be overcome for the development of new antimicrobials from plant extracts, while efforts have been made to enhance the antimicrobial activity of chemical compounds. Research on the mechanisms of action, interplay with other substances, and the pharmacokinetic and/or pharmacodynamic profile of the medicinal plant extracts should be given high priority to characterize them as potential antimicrobial agents.

Marine Microbial-Derived Antibiotics and Biosurfactants as Potential New Agents against Catheter-Associated Urinary Tract Infections

Catheter-associated urinary tract infections (CAUTIs) are among the leading nosocomial infections in the world and have led to the extensive study of various strategies to prevent infection. However, despite an abundance of anti-infection materials having been studied over the last forty-five years, only a few types have come into clinical use, providing an insignificant reduction in CAUTIs. In recent decades, marine resources have emerged as an unexplored area of opportunity offering huge potential in discovering novel bioactive materials to combat human diseases. Some of these materials, such as antimicrobial compounds and biosurfactants synthesized by marine microorganisms, exhibit potent antimicrobial, antiadhesive and antibiofilm activity against a broad spectrum of uropathogens (including multidrug-resistant pathogens) that could be potentially used in urinary catheters to eradicate CAUTIs. This paper summarizes information on the most relevant materials that have been obtained from marine-derived microorganisms over the last decade and discusses their potential as new agents against CAUTIs, providing a prospective proposal for researchers.

Combating Parasitic Nematode Infections, Newly Discovered Antinematode Compounds from Marine Epiphytic Bacteria

Parasitic nematode infections cause debilitating diseases and impede economic productivity. Antinematode chemotherapies are fundamental to modern medicine and are also important for industries including agriculture, aquaculture and animal health. However, the lack of suitable treatments for some diseases and the rise of nematode resistance to many available therapies necessitates the discovery and development of new drugs. Here, marine epiphytic bacteria represent a promising repository of newly discovered antinematode compounds. Epiphytic bacteria are ubiquitous on marine surfaces where they are under constant pressure of grazing by bacterivorous predators (e.g., protozoans and nematodes). Studies have shown that these bacteria have developed defense strategies to prevent grazers by producing toxic bioactive compounds. Although several active metabolites against nematodes have been identified from marine bacteria, drug discovery from marine microorganisms remains underexplored. In this review, we aim to provide further insight into the need and potential for marine epiphytic bacteria to become a new source of antinematode drugs. We discuss current and emerging strategies, including culture-independent high throughput screening and the utilization of Caenorhabditis elegans as a model target organism, which will be required to advance antinematode drug discovery and development from marine microbial sources.

Predicting disease occurrence with high accuracy based on soil macroecological patterns of Fusarium wilt

Soil-borne plant diseases are increasingly causing devastating losses in agricultural production. The development of a more refined model for disease prediction can aid in reducing crop losses through the use of preventative control measures or soil fallowing for a planting season. The emergence of high-throughput DNA sequencing technology has provided unprecedented insight into the microbial composition of diseased versus healthy soils. However, a single independent case study rarely yields a general conclusion predictive of the disease in a particular soil. Here, we attempt to account for the differences among various studies and plant varieties using a machine-learning approach based on 24 independent bacterial data sets comprising 758 samples and 22 independent fungal data sets comprising 279 samples of healthy or Fusarium wilt-diseased soils from eight different countries. We found that soil bacterial and fungal communities were both clearly separated between diseased and healthy soil samples that originated from six crops across nine countries or regions. Alpha diversity was consistently greater in the fungal community of healthy soils. While diseased soil microbiomes harbored higher abundances of Xanthomonadaceae, Bacillaceae, Gibberella, and Fusarium oxysporum, the healthy soil microbiome contained more Streptomyces Mirabilis, Bradyrhizobiaceae, Comamonadaceae, Mortierella, and nonpathogenic fungi of Fusarium. Furthermore, a random forest method identified 45 bacterial OTUs and 40 fungal OTUs that categorized the health status of the soil with an accuracy >80%. We conclude that these models can be applied to predict the potential for occurrence of F. oxysporum wilt by revealing key biological indicators and features common to the wilt-diseased soil microbiome.

Antioxidant Molecules from Marine Fungi: Methodologies and Perspectives

The marine environment represents a prosperous existing resource for bioprospecting, covering 70% of the planet earth, and hosting a huge biodiversity. Advances in the research are progressively uncovering the presence of unknown microorganisms, which have evolved unique metabolic and genetic pathways for the production of uncommon secondary metabolites. Fungi have a leading role in marine bioprospecting since they represent a prolific source of structurally diverse bioactive metabolites. Several bioactive compounds from marine fungi have already been characterized including antibiotics, anticancer, antioxidants and antivirals. Nowadays, the search for natural antioxidant molecules capable of replacing those synthetic currently used, is an aspect that is receiving significant attention. Antioxidants can inactivate reactive oxygen and nitrogen species, preventing the insurgence of several degenerative diseases including cancer, autoimmune disorders, cardiovascular and neurodegenerative diseases. Moreover, they also find applications in different fields, including food preservation, healthcare and cosmetics. This review focuses on the production of antioxidants from marine fungi. We begin by proposing a survey of the available tools suitable for the evaluation of antioxidants, followed by the description of various classes of marine fungi antioxidants together with their extraction strategies. In addition, a view of the future perspectives and trends of these natural products within the "blue economy" is also presented.

Seaweed-associated heterotrophic bacteria: new paradigm of prospective anti-infective and anticancer agents

Ever since the development of the first antibiotic compound with anticancer potential, researchers focused on isolation and characterization of prospective microbial natural products with potential anti-infective and anticancer activities. The present work describes the production of bioactive metabolites by heterotrophic bacteria associated with intertidal seaweeds with potential anti-infective and anticancer activities. The bacteria were isolated in a culture-dependent method and were identified as Shewanella algae MTCC 12715 (KX272635) and Bacillus amyloliquefaciens MTCC 12716 (KX272634) based on combined phenotypic and genotypic methods. Further, the bacteria were screened for their ability to inhibit drug-resistant infectious pathogens and prevent cell proliferation of human liver carcinoma (HepG2) and breast cancer (MCF7) cell lines, without affecting the normal cells. Significant anti-infective activity was observed with bacterial cells and their organic extracts against broad-spectrum multidrug-resistant pathogens, such as vancomycin-resistant Enterococcus faecalis, methicillin-resistant Staphylococcus aureus, Klebsiella pneumonia and Pseudomonas aeruginosa with minimum inhibitory concentration ≤ 3.0 µg mL^-1 as compared to the antibiotic agents' chloramphenicol and ampicillin, which were active at ≥ 6.25 mg mL^-1. The extracts also exhibited anticancer activity in a dose-responsive pattern against HepG2 (with IC₅₀, half maximal inhibitory concentration ~ 78-83 µg mL^-1) and MCF7 (IC₅₀ ~ 45-48 µg mL^-1) on tetrazolium bromide screening assay with lesser cytotoxic effects on normal fibroblast (L929) cell lines (IC₅₀ > 100 µg mL^-1). The results revealed that seaweed-associated heterotrophic bacteria could occupy a predominant role for a paradigm shift towards the development of prospective anti-infective and anticancer agents.

Cyclodepsipeptide alveolaride C: total synthesis and structural assignment

First stereoselective total synthesis of naturally occurring bioactive cyclodepsipeptide alveolaride C has been achieved using a convergent approach. This synthetic study enabled us to establish unambiguously the stereochemistry of three unassigned chiral centres embedded in the nonpeptidic segment as well as revised the stereochemistry of the proposed β-phenylalanine counterpart of the molecule. The key strategic features of this synthesis include Sharpless asymmetric dihydroxylation for installing the vicinal diol moiety, Julia–Kocienski olefination for constructing the aliphatic side chain, the Shiina protocol for intermolecular esterification, amide coupling and macrolactamization for the ring formation.

First total synthesis of natural cyclodepsipeptide alveolaride C has been accomplished with an unambiguous solution to its structural riddle.

Anti-Neuroinflammatory Agent, Restricticin B, from the Marine-Derived Fungus Penicillium janthinellum and Its Inhibitory Activity on the NO Production in BV-2 Microglia Cells

A new compound containing a triene, a tetrahydropyran ring and glycine ester functionalities, restricticin B (1), together with four known compounds (2–5) were obtained from the EtOAc extract of the marine-derived fungus Penicillium janthinellum. The planar structure of 1 was determined by detailed analyses of MS, 1D and 2D NMR data. The relative and absolute configurations of 1 were established via the analyses of NOESY spectroscopy data, the comparison of optical rotation values with those of reported restricticin derivatives and electronic circular dichroism (ECD). All the compounds were screened for their anti-neuroinflammatory effects in lipopolysaccharide (LPS)-induced BV-2 microglia cells. Restricticin B (1) and N-acetyl restricticin (2) exhibited anti-neuroinflammatory effects by suppressing the production of pro-inflammatory mediators in activated microglial cells.

Hydrolytic Exoenzymes Produced by Bacteria Isolated and Identified From the Gastrointestinal Tract of Bombay Duck

Bacteria producing hydrolytic exoenzymes are of great importance considering their contribution to the host metabolism as well as for their various applications in industrial bioprocesses. In this work hydrolytic capacity of bacteria isolated from the gastrointestinal tract of Bombay duck (Harpadon nehereus) was analyzed and the enzyme-producing bacteria were genetically characterized. A total of twenty gut-associated bacteria, classified into seventeen different species, were isolated and screened for the production of protease, lipase, pectinase, cellulase and amylase enzymes. It was found that thirteen of the isolates could produce at least one of these hydrolytic enzymes among which protease was the most common enzyme detected in ten isolates; lipase in nine, pectinase in four, and cellulase and amylase in one isolate each. This enzymatic array strongly correlated to the previously reported eating behavior of Bombay duck. 16S rRNA gene sequence-based taxonomic classification of the enzyme-producing isolates revealed that the thirteen isolates were grouped into three different classes of bacteria consisting of eight different genera. Staphylococcus, representing ∼46% of the isolates, was the most dominant genus. Measurement of enzyme-production via agar diffusion technique revealed that one of the isolates which belonged to the genus Exiguobacterium, secreted the highest amount of lipolytic and pectinolytic enzymes, whereas a Staphylococcus species produced highest proteolytic activity. The Exiguobacterium sp. expressing a maximum of four hydrolases, appeared to be the most promising isolate of all.

Pharmacological properties of some mangrove sediment-associated bacillus isolates

Mangrove sediment-associated bacteria are of significantly important in the field of medicine and pharmaceuticals as new promising sources of biologically active pharmacophores due to the extreme conditions, such as high salt concentration and soil anoxia. The sediment bacteria associated with Acanthus ilicifolius and Avicennia officinalis collected from the Mangalavanam mangrove ecosystem of the Kerala State of India were evaluated using various in vitro models for the assessment of their pharmacological properties. The bacteria exhibiting significant antioxidant and antimicrobial activities were isolated, identified, and characterized by the integrated microbiological, biochemical, and 16S rRNA sequencing. Among the varied bacteria isolated from mangrove sediments, Bacillus amyloliquefaciens MBMS5 (GenBank accession number MK765025) exhibited significant antimicrobial activities against various pathogenic bacteria, such as Aeromonas caviae, Vibrio parahemolyticus, and methicillin-resistant Staphylococcus aureus. The extracellular extracts of B. amyloliquefaciens MBMS5 exhibited potential antioxidant activity against free radical species coupled with anti-inflammatory property as displayed by the attenuation activity against pro-inflammatory 5-lipoxygenase.

A review on fucoidan antitumor strategies: From a biological active agent to a structural component of fucoidan-based systems

Due to the severe side-effects and the toxicity to healthy tissues, cancer treatments based in chemotherapy have not fully achieved the desire outcomes so far. The use of natural compound may be of great value to develop better tolerated therapies. Fucoidan is a marine sulfated polysaccharide extracted from brown algae that, besides other biological activities, has been reported to present interesting anti-cancer potential. This review briefly introduces fucoidan chemical structure, physicochemical properties and the above-mentioned biological feature. Fucoidan usage as soluble agent presents promising results herein described for different types of cancer. Trying to enhance and optimize fucoidan usage in the cancer field, different systems, namely drug delivery, have been recently developed to target different types of cancers. This aspect will be presented in detail, highlighting the role of fucoidan on their reported or envisaged performance.

Two new sponge species (Demospongiae: Chalinidae and Suberitidae) isolated from hyperarid mangroves of Qatar with notes on their potential antibacterial bioactivity

This study presents the taxonomic description of two new sponge species that are intimately associated with the hyperarid mangrove ecosystem of Qatar. The study includes a preliminary evaluation of the sponges' potential bioactivity against pathogens. Chalinula qatari sp. nov. is a fragile thinly encrusting sponge with a vivid maroon colour in life, often with oscular chimneys and commonly recorded on pneumatophores in the intertidal and shallow subtidal zone. Suberites luna sp. nov. is a massive globular-lobate sponge with a greenish-black colour externally and a yellowish orange colour internally, recorded on pneumatophores in the shallow subtidal zone, with large specimens near the seagrass ecosystem that surrounds the mangrove. For both species, a drug extraction protocol and an antibacterial experiment was performed. The extract of Suberites luna sp. nov. was found to be bioactive against recognized pathogens such as Staphylococcus epidermidis, Staphylococcus aureus and Enterococcus faecalis, but no bioactive activity was recorded for Chalinula qatari sp. nov. This study highlights the importance of increasing bioprospecting effort in hyperarid conditions and the importance of combining bioprospecting with taxonomic studies for the identification of novel marine drugs.

Total synthesis of nafuredin B

Total synthesis of marine secondary metabolite nafuredin B has been achieved for the first time using a convergent strategy. Sharpless epoxidation followed by acid catalyzed epoxide opening were adopted to install the tetrasubstituted hydroxy center, whereas the iterative Julia-Kocienski olefination, Wittig olefination and HWE olefination afforded the olefin bonds. Ring closing metathesis in the presence of a free tetrasubstituted hydroxy group provided the unsaturated δ-lactone moiety. This synthetic study provided unambiguous structural confirmation of the isolated nafuredin B.

From Seabed to Bedside: A Review on Promising Marine Anticancer Compounds

The marine environment represents an outstanding source of antitumoral compounds and, at the same time, remains highly unexplored. Organisms living in the sea synthesize a wide variety of chemicals used as defense mechanisms. Interestingly, a large number of these compounds exert excellent antitumoral properties and have been developed as promising anticancer drugs that have later been approved or are currently under validation in clinical trials. However, due to the high need for these compounds, new methodologies ensuring its sustainable supply are required. Also, optimization of marine bioactives is an important step for their success in the clinical setting. Such optimization involves chemical modifications to improve their half-life in circulation, potency and tumor selectivity. In this review, we outline the most promising marine bioactives that have been investigated in cancer models and/or tested in patients as anticancer agents. Moreover, we describe the current state of development of anticancer marine compounds and discuss their therapeutic limitations as well as different strategies used to overcome these limitations. The search for new marine antitumoral agents together with novel identification and chemical engineering approaches open the door for novel, more specific and efficient therapeutic agents for cancer treatment.

Epigenetic Agents Trigger the Production of Bioactive Nucleoside Derivatives and Bisabolane Sesquiterpenes From the Marine-Derived Fungus Aspergillus versicolor

Epigenetic agents, histone deacetylase inhibitor (SAHA) and DNA methyltransferase inhibitor (5-Aza), were added to Czapek-Dox medium to trigger the chemical diversity of marine-derived fungus Aspergillus versicolor XS-20090066. By HPLC and 1H NMR analysis, the diversity of fungal secondary metabolites was significantly increased compared with the control. With the aid of MS/MS-based molecular networking, two new nucleoside derivatives, kipukasins K (1) and L (2) were obtained. Meanwhile, the yields of four known nucleoside derivatives were significantly enhanced. In addition, one new bisabolane sesquiterpene, aspergillusene E (7), along with ten known derivatives were also isolated. The structures were elucidated by comprehensive spectroscopic methods of NMR and HRESIMS analysis. Compounds 1 and 7 displayed antibacterial activities against Staphylococcus epidermidis and Staphylococcus aureus with the MIC values of 8-16 μg/mL. Our study revealed that the fungus A. versicolor XS-20090066 has been effectively induced by chemical epigenetic manipulation with a combination of SAHA and 5-Aza to produce new metabolites.

The Shewanella genus: ubiquitous organisms sustaining and preserving aquatic ecosystems

The Gram-negative Shewanella bacterial genus currently includes about 70 species of mostly aquatic γ­-proteobacteria, which were isolated around the globe in a multitude of environments such as surface freshwater and the deepest marine trenches. Their survival in such a wide range of ecological niches is due to their impressive physiological and respiratory versatility. Some strains are among the organisms with the highest number of respiratory systems, depending on a complex and rich metabolic network. Implicated in the recycling of organic and inorganic matter, they are important components of organism-rich oxic/anoxic interfaces, but they also belong to the microflora of a broad group of eukaryotes from metazoans to green algae. Examples of long-term biological interactions like mutualism or pathogeny have been described, although molecular determinants of such symbioses are still poorly understood. Some of these bacteria are key organisms for various biotechnological applications, especially the bioremediation of hydrocarbons and metallic pollutants. The natural ability of these prokaryotes to thrive and detoxify deleterious compounds explains their use in wastewater treatment, their use in energy generation by microbial fuel cells and their importance for resilience of aquatic ecosystems.

Emerging molecular biology tools and strategies for engineering natural product biosynthesis

Natural products and their related derivatives play a significant role in drug discovery and have been the inspiration for the design of numerous synthetic bioactive compounds. With recent advances in molecular biology, numerous engineering tools and strategies were established to accelerate natural product synthesis in both academic and industrial settings. However, many obstacles in natural product biosynthesis still exist. For example, the native pathways are not appropriate for research or production; the key enzymes do not have enough activity; the native hosts are not suitable for high-level production. Emerging molecular biology tools and strategies have been developed to not only improve natural product titers but also generate novel bioactive compounds. In this review, we will discuss these emerging molecular biology tools and strategies at three main levels: enzyme level, pathway level, and genome level, and highlight their applications in natural product discovery and development.

A Comprehensive Review on Medicinal Plants as Antimicrobial Therapeutics: Potential Avenues of Biocompatible Drug Discovery

The war on multidrug resistance (MDR) has resulted in the greatest loss to the world's economy. Antibiotics, the bedrock, and wonder drug of the 20th century have played a central role in treating infectious diseases. However, the inappropriate, irregular, and irrational uses of antibiotics have resulted in the emergence of antimicrobial resistance. This has resulted in an increased interest in medicinal plants since 30-50% of current pharmaceuticals and nutraceuticals are plant-derived. The question we address in this review is whether plants, which produce a rich diversity of secondary metabolites, may provide novel antibiotics to tackle MDR microbes and novel chemosensitizers to reclaim currently used antibiotics that have been rendered ineffective by the MDR microbes. Plants synthesize secondary metabolites and phytochemicals and have great potential to act as therapeutics. The main focus of this mini-review is to highlight the potential benefits of plant derived multiple compounds and the importance of phytochemicals for the development of biocompatible therapeutics. In addition, this review focuses on the diverse effects and efficacy of herbal compounds in controlling the development of MDR in microbes and hopes to inspire research into unexplored plants with a view to identify novel antibiotics for global health benefits.

Characterization of phenazine-1-carboxylic acid by Klebsiella sp. NP-C49 from the coral environment in Gulf of Kutch, India

Coral-associated microbes from Marine National Park (MNP), Gulf of Kutch (GoK), Gujarat, India, were screened for siderophore production. Maximum siderophore-producing isolate NP-C49 and its compound were identified and characterized. The isolate was identified as Klebsiella sp. through 16S rRNA genes sequencing (GenBank accession nos. KY412519 and MTCC 25160). Antibiotic susceptibility profile against 20 commercial antibiotics showed its more sensitivity compared to human pathogenic strain, i.e., Klebsiella pneumonia. The compound was identified as phenazine-1-carboxylic acid (PCA) using the multinuclear ID (¹H and ¹³C) and 2D (¹H-¹H COSY and ¹H-¹³C HETCOR) NMR along with high-resolution mass spectrometry. No significant difference in the bacterial growth in the presence of PCA, FeCl₃ and Fe(OH)₃ indicated involvement of factors other than PCA in bacterial growth. The study first reports the identification and characterization of PCA from Klebsiella sp. both from terrestrial and marine sources.

A horizon scan of priorities for coastal marine microbiome research

Research into the microbiomes of natural environments is changing the way ecologists and evolutionary biologists view the importance of microorganisms in ecosystem function. This is particularly relevant in ocean environments, where microorganisms constitute the majority of biomass and control most of the major biogeochemical cycles, including those that regulate Earth's climate. Coastal marine environments provide goods and services that are imperative to human survival and well-being (for example, fisheries and water purification), and emerging evidence indicates that these ecosystem services often depend on complex relationships between communities of microorganisms (the 'microbiome') and the environment or their hosts - termed the 'holobiont'. Understanding of coastal ecosystem function must therefore be framed under the holobiont concept, whereby macroorganisms and their associated microbiomes are considered as a synergistic ecological unit. Here, we evaluate the current state of knowledge on coastal marine microbiome research and identify key questions within this growing research area. Although the list of questions is broad and ambitious, progress in the field is increasing exponentially, and the emergence of large, international collaborative networks and well-executed manipulative experiments are rapidly advancing the field of coastal marine microbiome research.

High-throughput sequencing revealed differences of microbial community structure and diversity between healthy and diseased Caulerpa lentillifera

Background

Caulerpa lentillifera is one of the most important economic green macroalgae in the world. Increasing demand for consumption has led to the commercial cultivation of C. lentillifera in Japan and Vietnam in recent decades. Concomitant with the increase of C. lentillifera cultivation is a rise in disease. We hypothesise that epiphytes or other microorganisms outbreak at the C. lentillifera farm may be an important factor contributing to disease in C. lentillifera. The main aims are obtaining differences in the microbial community structure and diversity between healthy and diseased C. lentillifera and key epiphytes and other microorganisms affecting the differences through the results of high-throughput sequencing and bioinformatics analysis in the present study.

Results

A total of 14,050, 2479, and 941 operational taxonomic units (OTUs) were obtained from all samples using 16S rDNA, 18S rDNA, and internal transcribed spacer (ITS) high-throughput sequencing, respectively. 16S rDNA sequencing and 18S rDNA sequencing showed that microbial community diversity was higher in diseased C. lentillifera than in healthy C. lentillifera. Both PCoA results and UPGMA results indicated that the healthy and diseased algae samples have characteristically different microbial communities. The predominant prokaryotic phyla were Proteobacteria, Planctomycetes, Bacteroidetes, Cyanobacteria, Acidobacteria, Acidobacteria and Parcubacteria in all sequences. Chlorophyta was the most abundant eukaryotic phylum followed by Bacillariophyta based on 18S rDNA sequencing. Ascomycota was the dominant fungal phylum detected in healthy C. lentillifera based on ITS sequencing, whereas fungi was rare in diseased C. lentillifera, suggesting that Ascomycota was probably fungal endosymbiont in healthy C. lentillifera. There was a significantly higher abundance of Bacteroidetes, Cyanobacteria, Bacillariophyta, Ulvales and Tetraselmis in diseased C. lentillifera than in healthy C. lentillifera. Disease outbreaks significantly change carbohydrate metabolism, environmental information processing and genetic information processing of prokaryotic communities in C. lentillifera through predicted functional analyses using the Tax4Fun tool.

Conclusions

Bacteroidetes, Cyanobacteria, Bacillariophyta, Ulvales and Tetraselmis outbreak at the C. lentillifera farm sites was an important factor contributing to disease in C. lentillifera.

Bromination of alkyl quinolones by Microbulbifer sp. HZ11, a marine Gammaproteobacterium, modulates their antibacterial activity

Alkyl quinolones (AQs) are multifunctional bacterial secondary metabolites generally known for their antibacterial and algicidal properties. Certain representatives are also employed as signalling molecules of Burkholderia strains and Pseudomonas aeruginosa. The marine Gammaproteobacterium Microbulbifer sp. HZ11 harbours an AQ biosynthetic gene cluster with unusual topology but does not produce any AQ-type metabolites under laboratory conditions. In this study, we demonstrate the potential of strain HZ11 for AQ production by analysing intermediates and key enzymes of the pathway. Moreover, we demonstrate that exogenously added AQs such as 2-heptyl-1(H)-quinolin-4-one (referred to as HHQ) or 2-heptyl-1-hydroxyquinolin-4-one (referred to as HQNO) are brominated by a vanadium-dependent haloperoxidase (V-HPO_HZ11 ), which preferably is active towards AQs with C5-C9 alkyl side chains. Bromination was specific for the third position and led to 3-bromo-2-heptyl-1(H)-quinolin-4-one (BrHHQ) and 3-bromo-2-heptyl-1-hydroxyquinolin-4-one (BrHQNO), both of which were less toxic for strain HZ11 than the respective parental compounds. In contrast, BrHQNO showed increased antibiotic activity against Staphylococcus aureus and marine isolates. Therefore, bromination of AQs by V-HPO_HZ11 can have divergent consequences, eliciting a detoxifying effect for strain HZ11 while simultaneously enhancing antibiotic activity against other bacteria.

Identification of Asparagopsis armata-associated bacteria and characterization of their bioactive potential

Macroalgae‐associated bacteria have already proved to be an interesting source of compounds with therapeutic potential. Accordingly, the main aim of this study was to characterize Asparagopsis armata‐associated bacteria community and evaluate their capacity to produce substances with antitumor and antimicrobial potential. Bacteria were selected according to their phenotype and isolated by the streak plate technique. The identification was carried out by the RNA ribosomal 16s gene amplification through PCR techniques. The antimicrobial activities were evaluated against seven microorganisms (Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, Salmonella enteritidis, Staphylococcus aureus, Saccharomyces cerevisiae, Candida albicans) by following their growth through spectrophotometric readings. Antitumor activities were evaluated in vitro on human cell lines derived from hepatocellular (HepG‐2) and breast carcinoma (MCF‐7) using the MTT method. The present work identified a total of 21 bacteria belonging to the genus Vibrio, Staphylococcus, Shewanella, Alteromonadaceae, Bacillus, Cobetia, and Photobacterium, with Vibrio being the most abundant (42.86%). The extract of Shewanella sp. ASP 26 bacterial strain induced the highest antimicrobial activity, namely against Bacillus subtilis and Staphylococcus aureus with an IC₅₀ of 151.1 and 346.8 μg/mL, respectively. These bacteria (Shewanella sp.) were also the ones with highest antitumor potential, demonstrating antiproliferative activity on HepG‐2 cells. Asparagopsis armata‐associated bacteria revealed to be a potential source of compounds with antitumor and antibacterial activity.

Chemical Profiling and Biological Screening of Some River Nile Derived-Microorganisms

AIMS

Chemical and biological studies of the River Nile derived-microorganisms are limited. Hence, this work was carried out to screen the River Nile habitat. Identification of the isolated organisms, chemical profiling of their ethyl acetate extracts as well as screening of their antimicrobial, antileishmanial, antitrypanosomal, and antimalarial activities were investigated.

METHODS

Identification of the microbial isolates were carried out using bacterial 16S rRNA and fungal 18S rRNA gene sequencing. Chemical profiling of the EtOAc extracts using LC-HRESIMS spectroscopy was carried out. The in vitro antimicrobial screening using the modified version of the CLSI method, antileishmanial and antitrypanosomal activities were screened using Leishmania donovani promastigote assay, L. donovani axenic amastigote assay, Trypanosoma brucei trypamastigotes assay and THP1 toxicity assay. The in vitro antimalarial activities against D6 (chloroquine sensitive) and W2 (chloroquine-resistant) strains of Plasmodium falciparum were evaluated.

RESULTS

Seven isolated microorganisms were identified as Streptomyces indiaensis, Bacillus safensis, B. anthracis, Bacillus sp., and Aspergillus awamori. Chemical investigation of different extracts showed several bioactive compounds, identified as; nigragillin, 5-caboxybenzofuran and dyramide B from A. awamori and actinopolysporin B from S. indiaensis. On the other hand many nitrogenous compounds with high molecular weights showed no hits that may correspond to new long chain and/or cyclic peptides. The EtOAc extract of B. safensis fermentation broth showed the highest activity against P. falciparum D6 and P. falciparum W2 (IC50 = 25.94 and 27.28 μg/mL, respectively), while two isolates S. indiaensis and Bacillus sp. RN-011 extracts showed the highest antitrypanosomal activity (IC50 = 0.8 and 0.96 μg/mL).

CONCLUSION

The River Nile could be a new source for production of promising bioactive leading compound where antimicrobial and antiparasitic activities may be correlated.

Jellyfish-Associated Microbiome in the Marine Environment: Exploring Its Biotechnological Potential

Despite accumulating evidence of the importance of the jellyfish-associated microbiome to jellyfish, its potential relevance to blue biotechnology has only recently been recognized. In this review, we emphasize the biotechnological potential of host⁻microorganism systems and focus on gelatinous zooplankton as a host for the microbiome with biotechnological potential. The basic characteristics of jellyfish-associated microbial communities, the mechanisms underlying the jellyfish-microbe relationship, and the role/function of the jellyfish-associated microbiome and its biotechnological potential are reviewed. It appears that the jellyfish-associated microbiome is discrete from the microbial community in the ambient seawater, exhibiting a certain degree of specialization with some preferences for specific jellyfish taxa and for specific jellyfish populations, life stages, and body parts. In addition, different sampling approaches and methodologies to study the phylogenetic diversity of the jellyfish-associated microbiome are described and discussed. Finally, some general conclusions are drawn from the existing literature and future research directions are highlighted on the jellyfish-associated microbiome.

Structures, Activities and Drug-Likeness of Anti-Infective Xanthone Derivatives Isolated from the Marine Environment: A Review

Marine organisms represent almost half of total biodiversity and are a very important source of new bioactive substances. Within the varied biological activities found in marine products, their antimicrobial activity is one of the most relevant. Infectious diseases are responsible for high levels of morbidity and mortality and many antimicrobials lose their effectiveness with time due to the development of resistance. These facts justify the high importance of finding new, effective and safe anti-infective agents. Among the variety of biological activities of marine xanthone derivatives, one that must be highlighted is their anti-infective properties. In this work, a literature review of marine xanthones with anti-infective activity, namely antibacterial, antifungal, antiparasitic and antiviral, is presented. Their structures, biological activity, sources and the methods used for bioactivity evaluation are described. The xanthone derivatives are grouped in three sets: xanthones, hydroxanthones and glycosylated derivatives. Moreover, molecular descriptors, biophysico-chemical properties, and pharmacokinetic parameters were calculated, and the chemical space occupied by marine xanthone derivatives is recognized. The chemical space was compared with marketed drugs and framed accordingly to the drug-likeness concept in order to profile the pharmacokinetic of anti-infective marine xanthone derivatives.

Traditional Chinese Medicine as a Potential Source for HSV-1 Therapy by Acting on Virus or the Susceptibility of Host

Herpes simplex virus type 1 (HSV-1) is the most common virus, with an estimated infection rate of 60–95% among the adult population. Once infected, HSV-1 can remain latent in the host for a lifetime and be reactivated in patients with a compromised immune system. Reactivation of latent HSV-1 can also be achieved by other stimuli. Though acyclovir (ACV) is a classic drug for HSV-1 infection, ACV-resistant strains have been found in immune-compromised patients and drug toxicity has also been commonly reported. Therefore, there is an urge to search for new anti-HSV-1 agents. Natural products with potential anti-HSV-1 activity have the advantages of minimal side effects, reduced toxicity, and they exert their effect by various mechanisms. This paper will not only provide a reference for the safe dose of these agents if they are to be used in humans, referring to the interrelated data obtained from in vitro experiments, but also introduce the main pharmacodynamic mechanisms of traditional Chinese medicine (TCM) against HSV-1. Taken together, TCM functions as a potential source for HSV-1 therapy by direct (blocking viral attachment/absorption/penetration/replication) or indirect (reducing the susceptibility to HSV-1 or regulating autophagy) antiviral activities. The potential of these active components in the development of anti-HSV-1 drugs will also be described.