Cytotoxic and Antibacterial Compounds from the Coral-Derived Fungus Aspergillus tritici SP2-8-1

Marine Fungi: A Prosperous Source of Novel Bioactive Natural Products

As the number of viruses, bacteria, and tumors that are resistant to drugs continues to rise, there is a growing need for novel lead compounds to treat them. Marine fungi, due to their unique secondary metabolic pathways and vast biodiversity, have become a crucial source for lead compounds in drug development. This review utilizes bibliometric methods to analyze the research status of natural products from marine fungi in the past decade, revealing the hotspots and trends in this field from Web of Science database. Furthermore, this review summarizes the biological activities and effects on molecular mechanisms of novel natural compounds isolated from marine fungi in the past five years. These novel compounds belong to six different structural classes, such as alkaloids, terpenoids, anthraquinones, polyketones, etc. They also exhibited highly potent biological properties, including antiviral, antitumor, antibacterial, antiinflammatory, and other properties. This review demonstrates the hotspots and trends of marine fungi research in recent years, as well as the variety of chemical structure and biological activities of their natural products, and it may provide guidance for those interested in discovering new drugs from marine fungi and specific targeting mechanisms.

Anti-Vibrio potential of natural products from marine microorganisms

The emergence of drug-resistant Vibrio poses a serious threat to aquaculture and human health, thus there is an urgent need for the discovery of new related antibiotics. Given that marine microorganisms (MMs) are evidenced as important sources of antibacterial natural products (NPs), great attention has been gained to the exploration of potential anti-Vibrio agents from MMs. This review summarizes the occurrence, structural diversity, and biological activities of 214 anti-Vibrio NPs isolated from MMs (from 1999 to July 2022), including 108 new compounds. They were predominantly originated from marine fungi (63%) and bacteria (30%) with great structural diversity, including polyketides, nitrogenous compounds, terpenoids, and steroids, among which polyketides account for nearly half (51%) of them. This review will shed light on the development of MMs derived NPs as potential anti-Vibrio lead compounds with promising applications in agriculture and human health.

A glyoxylate-containing benzene derivative and butenolides from a marine algicolous fungus Aspergillus sp. SCSIO 41304

A new glyoxylate-containing benzene derivative, methyl 2-(4-hydroxy-3-(3'-methyl-2'-butenyl)phenyl)-2-oxoacetate (1), together with ten known compounds (2-11), were isolated from the marine algicolous fungus, Aspergillus sp. SCSIO 41304. Their planar structures and absolute configurations were elucidated by detailed NMR, MS spectroscopic analysis and comparing with literature data. Compound 1 was isolated as a new fungal secondary metabolite, possessing a methyl glyoxylate moiety R-CO-CO-OCH₃, which is rare in natural sources. All the isolated compounds (1-11) were tested for their antibacterial and enzyme inhibitory activities against acetylcholinesterase (AChE) and pancreatic lipase (PL). Among these compounds, aspulvinone H (4) showed moderate inhibition against AChE and PL with IC₅₀ values of 25.95 and 47.06 μM, respectively. Further molecular docking simulation exhibited that compound 4 could well bind to the catalytic pockets of the AChE and PL.

Insights into metabolic and pharmacological profiling of Aspergillus ficuum through bioinformatics and experimental techniques

BACKGROUND

Recently, numerous novel bioactive fungal metabolites have been identified that possess broad therapeutic activities including anti-inflammatory, antibiotic, antioxidant, and antitumor. The fungal mycochemicals as well as extracts have increased the interest of the scientific community in drug discovery research through a combination approach such as, molecular metabolic, pharmacological and computational techniques. Therefore, the natural fungus Aspergillus ficuum (A. ficuum) (FCBP-DNA-1266) was selected for metabolic and pharmacological profiling in this study.

RESULTS

The metabolic profile of A. ficuum was explored for the first time and revealed the presence of bioactive compounds such as choline sulfate, noruron, hydroxyvittatine, aurasperone D, cetrimonium, kurilensoside, heneicosane, nonadecane and eicosane. Similarly, a pharmacological screen of A. ficuum was performed for the first time in in vivo and in vitro models. Interestingly, both the ethyl acetate and n-hexane fractions of A. ficuum were found to be more active against Bacillus subtilis among five tested bacteria with their zone of inhibition (ZOI) values of 21.00 mm ±1.00 and 23.00 mm ±1.00, at a concentration of 150 μgmL^-1 respectively. Similarly, a significant decrease (P<0.001) and (P<0.01) in paw edema was observed in A. ficuum-treated animals at doses of 50 and 150 mgkg^-1, respectively, reflecting its potent anti-inflammatory effect. Furthermore, the docking results supported the antibacterial and anti-inflammatory effects of A. ficuum. In addition, the crude extract demonstrated no acute toxicity and the highest percent radical scavenging was recorded for both n-hexane and ethyl acetate extracts.

CONCLUSION

The metabolic profile of A. ficuum indicated the presence of biological relevant compounds. A. ficuum extract exhibited potent antibacterial and anti-inflammatory effects supported by docking results. Furthermore, A. ficuum extract demonstrated the highest percentage of radical scavenging activity along with no acute toxicity.

Anthraquinones and Their Analogues from Marine-Derived Fungi: Chemistry and Biological Activities

Anthraquinones are an interesting chemical class of polyketides since they not only exhibit a myriad of biological activities but also contribute to managing ecological roles. In this review article, we provide a current knowledge on the anthraquinoids reported from marine-derived fungi, isolated from various resources in both shallow waters such as mangrove plants and sediments of the mangrove habitat, coral reef, algae, sponges, and deep sea. This review also tentatively categorizes anthraquinone metabolites from the simplest to the most complicated scaffolds such as conjugated xanthone-anthraquinone derivatives and bianthraquinones, which have been isolated from marine-derived fungi, especially from the genera Apergillus, Penicillium, Eurotium, Altenaria, Fusarium, Stemphylium, Trichoderma, Acremonium, and other fungal strains. The present review, covering a range from 2000 to 2021, was elaborated through a comprehensive literature search using the following databases: ACS publications, Elsevier, Taylor and Francis, Wiley Online Library, MDPI, Springer, and Thieme. Thereupon, we have summarized and categorized 296 anthraquinones and their derivatives, some of which showed a variety of biological properties such as enzyme inhibition, antibacterial, antifungal, antiviral, antitubercular (against Mycobacterium tuberculosis), cytotoxic, anti-inflammatory, antifouling, and antioxidant activities. In addition, proposed biogenetic pathways of some anthraquinone derivatives are also discussed.

Marine fungal metabolites as a source of drug leads against aquatic pathogens

Aquatic pathogens, including Vibrio, Edwardsiella, Pseudomonas, and Aeromonas, which could result in bacterial diseases to aquaculture, have seriously threatened the world aquaculture production. Marine-derived fungi, which could produce novel secondary metabolites with significant antibacterial activity, may be an important source for finding effective agents against aquatic pathogens. In this review, a systematically overview of the harm of several aquatic pathogens, and 134 antibacterial secondary metabolites against aquatic pathogens from 13 genera of marine-derived fungi, were summarized and concluded. The aim of this review is to find out the relationships between activity and structural type, between bioactive compounds and their hosts, and so on. Altogether, 95 references published during 1997-2021 were cited. KEY POINTS: •Aquatic pathogens, which could result in bacterial diseases to aquaculture, were described. •Marine fungal metabolites with activities against aquatic pathogens were summarized. •The distributions of these bioactive marine fungal metabolites were analyzed.

Inhibition of STAT3 Signaling Pathway by Terphenyllin Suppresses Growth and Metastasis of Gastric Cancer

Gastric cancer is a common type of malignant tumor with a relatively poor prognosis and presents a serious threat to global health. Signal Transducer and Activator of Transcription-3 (STAT3) has been strongly implicated in many cancers, and its constitutive activation promotes growth, angiogenesis, inflammation, and immune evasion. Therefore, considerable efforts have been put into developing effective and safe STAT3 inhibitors. In this study, we performed a virtual screening by molecular docking and found that terphenyllin, a marine-derived natural product, directly interacted with STAT3. We further found that terphenyllin inhibited the phosphorylation and activation of STAT3 and decreased the protein levels of STAT3-dependent target genes, including c-Myc and Cyclin D1. Subsequently, we demonstrated that terphenyllin exerted its potent anticancer efficacy against gastric cancer in vitro and in vivo. Terphenyllin concentration-dependently inhibited growth, proliferation, and colony formation and induced cell cycle arrest and apoptosis of gastric cancer cells in vitro. Moreover, terphenyllin treatment suppressed the tumor growth and metastasis in a gastric cancer orthotopic mouse model without notable toxicity in vivo. Taken together, our results indicated that terphenyllin exerts its anticancer activity by inhibiting the STAT3 signaling pathway and may serve as a potent STAT3 inhibitor for gastric cancer treatment.

Production and characterization of a broad-spectrum antimicrobial 5-butyl-2-pyridine carboxylic acid from Aspergillus fumigatus nHF-01

The present study aims at the production optimization, purification, and characterization of a potent broad-spectrum antimicrobial compound (AMC) produced by Aspergillus fumigatus nHF-01 (GenBank Ac. No. MN190286). The culture conditions were optimized for a higher amount of AMC. The AMC was solvent extracted and characterized by UV–Vis, FT–IR, ESI–MS, and ¹H-NMR spectroscopy. The MIC, MBC and mode of action were determined against a set of Gram-positive and Gram-negative human pathogenic bacteria. Its antibiofilm, synergistic and cytotoxic effects were also tested. The putative target site of action was evaluated through in silico molecular docking study. The stain A. fumigatus nHF-01 produced the maximum AMC (5-butyl-2-pyridine carboxylic acid) in 2% MEB (w/v) and 4% YE (w/v) at pH 6.0 and 20 °C temperature with 100 rpm agitation for ten days. It caused complete lethality of the Gram-positive and Gram-negative human pathogenic bacteria at a 129 µg/mL dose by rupture and entire dissolution of cell integrity. It showed moderate antibiofilm activity and had a synergistic activity with streptomycin and additive effects with ciprofloxacin and vancomycin. It targets a respiratory enzyme, Quinol-Fumarate Reductase (1l0v), with the highest binding affinities. It had cytotoxicity against human lung carcinoma A549 cell line and was stable up to 100 °C. Thus, the study revealed that the strain A. fumigatus nHF-01 produces a potent broad-spectrum AMC 5-butyl-2-pyridine carboxylic acid that could be used against human food and topical pathogenic bacteria. This is the first report of such a compound produced from the A. fumigatus.

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

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

Biocontrol Potential of Aspergillus Species Producing Antimicrobial Metabolites

Microbial metabolites have been recognized as an important source for the discovery of new antifungal agents because of their diverse chemical structures with novel modes of action. In the course of our screening for new antifungal agents from microbes, we found that culture filtrates of two fungal species Aspergillus candidus SFC20200425-M11 and Aspergillus montenegroi SFC20200425-M27 have the potentials to reduce the development of fungal plant diseases such as tomato late blight and wheat leaf rust. From these two Aspergillus spp., we isolated a total of seven active compounds, including two new compounds (4 and 6), and identified their chemical structures based on the NMR spectral analyses: sphaeropsidin A (1), (R)-formosusin A (2), (R)-variotin (3), candidusin (4), asperlin (5), montenegrol (6), and protulactone A (7). Based on the results of the in vitro bioassays of 11 plant pathogenic fungi and bacteria, sphaeropsidin A (1), (R)-formosusin A (2), (R)-variotin (3), and asperlin (5) exhibited a wide range of antimicrobial activity. Furthermore, when plants were treated with sphaeropsidin A (1) and (R)-formosusin A (2) at a concentration of 500 μg/ml, sphaeropsidin A (1) exhibited an efficacy disease control value of 96 and 90% compared to non-treated control against tomato late blight and wheat leaf rust, and (R)-formosusin A (2) strongly reduced the development of tomato gray mold by 82%. Asperlin (5) at a concentration of 500 μg/ml effectively controlled the development of tomato late blight and wheat leaf rust with a disease control value of 95%. Given that culture filtrates and active compounds derived from two Aspergillus spp. exhibited disease control efficacies, our results suggest that the Aspergillus-produced antifungal compounds could be useful for the development of new natural fungicides.

Penispidins A-C, Aromatic Sesquiterpenoids from Penicillium virgatum and Their Inhibitory Effects on Hepatic Lipid Accumulation

Penispidins A-C (1-3), new aromatic sesquiterpenoids with two classes of rare carbon skeletons, were isolated from the endophytic fungus Penicillium virgatum HL-110. 1 represents the first example of a dunniane-type aromatic sesquiterpenoid, possessing a novel 4/6/6 tricyclic system, while (±)-2 and 3 have a 7,12-cyclized bisabolene skeleton, featuring a 3,4-benzo-fused 2-oxabicyclo[3.3.1]nonane central framework. Their structures were elucidated on the basis of spectroscopic methods, single-crystal X-ray diffraction, and ECD calculations. 1 inhibited hepatic lipid accumulation in HepG2 cells.

Exploring the therapeutic potential of marine-derived bioactive compounds against COVID-19

The ocean is the most biodiverse habitat of various organisms. The organisms surviving in the harsh conditions of the ocean consist of several spectacular properties and produce bioactive compounds of pharmacological importance. These compounds are effective even in small quantities with various immunomodulatory qualities such as antioxidant and anti-inflammatory properties. Though the vaccines for COVID-19 are developed, and drug development is also in progress, but till now no effective drug is available for this deadly virus. Researchers are mining the huge data of bioactive compounds to develop the specific drug for COVID-19. The use of the repurposed drugs is challenging against the rapidly mutating virus with variable symptoms and mode of transmission. This review is an attempt to compile all the spattered data of marine-derived bioactive compounds with antiviral properties and to explore their therapeutic potential against COVID-19.

Neuronal Modulators from the Coral-Associated Fungi Aspergillus candidus

Three new p-terphenyl derivatives, named 4″-O-methyl-prenylterphenyllin B (1) and phenylcandilide A and B (17 and 18), and three new indole-diterpene alkaloids, asperindoles E-G (22-24), were isolated together with eighteen known analogues from the fungi Aspergillus candidus associated with the South China Sea gorgonian Junceela fragillis. The structures and absolute configurations of the new compounds were elucidated on the basis of spectroscopic analysis, and DFT/NMR and TDDFT/ECD calculations. In a primary cultured cortical neuronal network, the compounds 6, 9, 14, 17, 18 and 24 modulated spontaneous Ca²⁺ oscillations and 4-aminopyridine hyperexcited neuronal activity. A preliminary structure-activity relationship was discussed.

Marine Anthraquinones: Pharmacological and Toxicological Issues

The marine ecosystem, populated by a myriad of animals, plants, and microorganisms, is an inexhaustible reservoir of pharmacologically active molecules. Among the multiple secondary metabolites produced by marine sources, there are anthraquinones and their derivatives. Besides being mainly known to be produced by terrestrial species, even marine organisms and the uncountable kingdom of marine microorganisms biosynthesize anthraquinones. Anthraquinones possess many different biological activities, including a remarkable antitumor activity. However, due to their peculiar chemical structures, anthraquinones are often associated with toxicological issues, even relevant, such as genotoxicity and mutagenicity. The aim of this review is to critically describe the anticancer potential of anthraquinones derived from marine sources and their genotoxic and mutagenic potential. Marine-derived anthraquinones show a promising anticancer potential, although clinical studies are missing. Additionally, an in-depth investigation of their toxicological profile is needed before advocating anthraquinones as a therapeutic armamentarium in the oncological area.

Marine Pharmacology in 2016-2017: Marine Compounds with Antibacterial, Antidiabetic, Antifungal, Anti-Inflammatory, Antiprotozoal, Antituberculosis and Antiviral Activities; Affecting the Immune and Nervous Systems, and Other Miscellaneous Mechanisms of Action

The review of the 2016-2017 marine pharmacology literature was prepared in a manner similar as the 10 prior reviews of this series. Preclinical marine pharmacology research during 2016-2017 assessed 313 marine compounds with novel pharmacology reported by a growing number of investigators from 54 countries. The peer-reviewed literature reported antibacterial, antifungal, antiprotozoal, antituberculosis, and antiviral activities for 123 marine natural products, 111 marine compounds with antidiabetic and anti-inflammatory activities as well as affecting the immune and nervous system, while in contrast 79 marine compounds displayed miscellaneous mechanisms of action which upon further investigation may contribute to several pharmacological classes. Therefore, in 2016-2017, the preclinical marine natural product pharmacology pipeline generated both novel pharmacology as well as potentially new lead compounds for the growing clinical marine pharmaceutical pipeline, and thus sustained with its contributions the global research for novel and effective therapeutic strategies for multiple disease categories.

Structure elucidation of a novel cyclic tripeptide from the marine-derived fungus Aspergillus ochraceopetaliformis DSW-2

A novel cyclic tripeptide, sclerotiotide M (1), was isolated from the culture of a marine derived fungus Aspergillus ochraceopetaliformis DSW-2, together with four known compounds (2-5). The planar structure of 1 was established by 1 D and 2 D NMR data, supported by mass spectrometry, and the relative configuration was established by calculated NMR chemical shifts coupled with a statistical method (DP4+). All the compounds (1-5) displayed weak cytotoxic activities against cancer cell lines HPAC and BXPC3, with IC₅₀ values over 20 μM.

Bioactivity Potential of Marine Natural Products from Scleractinia-Associated Microbes and In Silico Anti-SARS-COV-2 Evaluation

Marine organisms and their associated microbes are rich in diverse chemical leads. With the development of marine biotechnology, a considerable number of research activities are focused on marine bacteria and fungi-derived bioactive compounds. Marine bacteria and fungi are ranked on the top of the hierarchy of all organisms, as they are responsible for producing a wide range of bioactive secondary metabolites with possible pharmaceutical applications. Thus, they have the potential to provide future drugs against challenging diseases, such as cancer, a range of viral diseases, malaria, and inflammation. This review aims at describing the literature on secondary metabolites that have been obtained from Scleractinian-associated organisms including bacteria, fungi, and zooxanthellae, with full coverage of the period from 1982 to 2020, as well as illustrating their biological activities and structure activity relationship (SAR). Moreover, all these compounds were filtered based on ADME analysis to determine their physicochemical properties, and 15 compounds were selected. The selected compounds were virtually investigated for potential inhibition for SARS-CoV-2 targets using molecular docking studies. Promising potential results against SARS-CoV-2 RNA dependent RNA polymerase (RdRp) and methyltransferase (nsp16) are presented.

Fungal Bioactive Anthraquinones and Analogues

This review, covering the literature from 1966 to the present (2020), describes naturally occurring fungal bioactive anthraquinones and analogues biosynthesized by the acetate route and concerning several different functionalized carbon skeletons. Hydrocarbons, lipids, sterols, esters, fatty acids, derivatives of amino acids, and aromatic compounds are metabolites belonging to other different classes of natural compounds and are generated by the same biosynthetic route. All of them are produced by plant, microorganisms, and marine organisms. The biological activities of anthraquinones and analogues comprise phytotoxic, antibacterial, antiviral, anticancer, antitumor, algicide, antifungal, enzyme inhibiting, immunostimulant, antiplatelet aggregation, cytotoxic, and antiplasmodium activities. The review also covers some practical industrial applications of anthraquinones.

Terphenyllin Suppresses Orthotopic Pancreatic Tumor Growth and Prevents Metastasis in Mice

Pancreatic cancer (PC) is an aggressive and fatal disease with high incidences of metastasis and recurrence. However, there are no effective treatment options for the majority of PC patients, especially for those with locally advanced tumors and metastatic diseases. Therefore, it is urgently needed to develop safe and effective anti-PC therapeutic agents. We have recently identified a novel marine-derived natural product terphenyllin with potent anti-PC activity. The present study was designed to investigate the efficacy and mechanisms of action of terphenyllin in several human PC cell lines and an orthotopic PC mouse model. The results showed that terphenyllin significantly inhibited the viability of all PC cell lines with minimal effects on a normal human pancreatic cell line (HPNE). We next demonstrated the effects of terphenyllin on colony formation, apoptosis, migration, and invasion in both Panc1 and HPAC cell lines in a concentration-dependent manner. Terphenyllin also suppressed the tumor growth and metastasis in the Panc1 orthotopic mouse model. We further showed the profound effects of terphenyllin on the expression of apoptosis-associated proteins, including Bax, Bad, Puma, BimL, Bcl-2, phos-Bcl-2 (Ser70), Bcl-xL, caspase 7, and PARP, which contributed to its anti-PC activity. In summary, terphenyllin suppressed the PC cell growth and metastasis in vitro and in vivo and may be developed as an anti-PC therapeutic agent in the future.

Biological activities and variation of symbiotic fungi isolated from Coral reefs collected from Red Sea in Egypt

Ten specimens of coral reefs were collected from the Red Sea in the Ein El-Sukhna region. Fungal isolation was done using two media, Dextrose Yeast Extract Agar (DYA) and Rose Bengal Agar (RBA). The morphological traits identified 18 fungal isolates belonging to the phyla Ascomycota, Mucoromycota and Deuteromycota. Five genera in three orders have been isolated: Eutrotiales (Aspergillus, Penicillium and Byssochlamys), Mucorales (Rhizopus) and Moniliales (Curvularia). The heat mapping clustering of the isolated fungi declared that Aspergillus and Penicillium were the most frequently isolate fungi in coral reefs. It was found that A. fumigatus colonised eight coral samples with 80% colonisation rate. Moreover, about 50% of the isolated fungal species were specific to one coral reef only such as A.candidus and A.carneus isolated from Isophyllastrea rigida only, A.japonicus and A.ochraceopetaliformis from Glaxaea fascicularis, A.niger van Tieghem from Porites astreoides, A.sydowii, A.terreus and P.waksmanii from Cladocora arbuscula, P.janthinellum from Pterogorgia guadalupensis and Curvularia tuberculata, Byssochlamys spectabilis and Rhizopus oryzae from Acropora humilis. Biological activities (antimicrobial, antioxidant antiradical and cytotoxicity) of the most predominant fungal species were investigated. The antimicrobial activity of coral fungal filtrates were investigated against six pathogenic bacteria including Escherichia coli ATCC11775, Neisseria gonorrhoeae ATCC19424, Pseudomonas aeruginosa ATCC10145, Streptococcus faecalis ATCC19433, Staphylococcus aureus subsp. aureus ATCC25923, Bacillus subtilis subsp. spizizenii ATCC6633 and two pathogenic yeast including Candida albicans ATCC7102 and Candida parapsilosis ATCC22019. Most of these fungal filtrates exhibited moderate to high antibacterial activities against both gram positive and gram negative bacteria, however it showed relatively low bioactivity towards the pathogenic Candida species. Investigating the free radical scavenging activity using DPPH reagent showed low to moderate bioactivities. The highest cytotoxic activity against liver cancer cell line Hep-G2 with an IC₅₀ values of 18.8 µg/ml was exhibited by Aspergillus ochraceopetaliformis MN083316 and a metabolomics study was done on the ethyl acetate extract of this strain using LC-ESI-MS fingerprints leading to the isolation and purification of compound 1. Using 1D and 2D NMR techniques compound 1 was identified as ditryptophenaline. Compound 1 exhibited a strong antimicrobial, antioxidant activities as well as cytotoxic activities against MCF-7 and HEPG2 with IC₅₀ values of 5.8 and 7.6 mmole, respectively. The objective of this study, isolation of Coral-reef associated fungi and studying their biological activities to produce the most active secondary metabolite which might possess a novel biological activity.

Antibiotics Development and the Potentials of Marine-Derived Compounds to Stem the Tide of Multidrug-Resistant Pathogenic Bacteria, Fungi, and Protozoa

As the search for new antibiotics continues, the resistance to known antimicrobial compounds continues to increase. Many researchers around the world, in response to antibiotics resistance, have continued to search for new antimicrobial compounds in different ecological niches such as the marine environment. Marine habitats are one of the known and promising sources for bioactive compounds with antimicrobial potentials against currently drug-resistant strains of pathogenic microorganisms. For more than a decade, numerous antimicrobial compounds have been discovered from marine environments, with many more antimicrobials still being discovered every year. So far, only very few compounds are in preclinical and clinical trials. Research in marine natural products has resulted in the isolation and identification of numerous diverse and novel chemical compounds with potency against even drug-resistant pathogens. Some of these compounds, which mainly came from marine bacteria and fungi, have been classified into alkaloids, lactones, phenols, quinones, tannins, terpenes, glycosides, halogenated, polyketides, xanthones, macrocycles, peptides, and fatty acids. All these are geared towards discovering and isolating unique compounds with therapeutic potential, especially against multidrug-resistant pathogenic microorganisms. In this review, we tried to summarize published articles from 2015 to 2019 on antimicrobial compounds isolated from marine sources, including some of their chemical structures and tests performed against drug-resistant pathogens.

A new p-terphenyl derivative from the insect-derived fungus Aspergillus candidus Bdf-2 and the synergistic effects of terphenyllin

A new p-terphenyl derivative 4″-deoxy-2′-methoxyterphenyllin (1), along with six known p-terphenyl derivatives (2–7), a known flavonoid derivative dechlorochlorflavonin (8) and a known fellutanine A (9), were isolated from the insect-derived strain of the fungus Aspergillus candidus Bdf-2, associated with Blaptica dubia. The structure of 1 was established by the analysis of the 1D and 2D NMR and HR-ESI-MS spectra. Compounds 1–9 were evaluated for antibacterial activities against Staphylococcus aureus ATCC29213, Escherichia coli ATCC25922 and Ralstonia solanacearum, and for antioxidant activities. Synergistic effects of compound 2 with the other compounds were also investigated. As a result, compound 6 displayed the best antibacterial activities in all single compound with MIC value of 32 µg/mL against S. aureus ATCC29213 and R. solanacearum, respectively. However, no antibacterial effect against E. coli ATCC25922 was detected from any single compound. The combination of 2 + 6 exhibited obvious synergistic effect against S. aureus ATCC29213 and the MIC value was 4 µg/mL. Compound 6 also showed the best antioxidant activity as a single compound with an IC₅₀ value of 17.62 µg/mL. Combinations of 5 + 6, 2 + 4 + 5 and 2 + 4 + 5 + 6 displayed synergistic effect and their antioxidant activities were better than that of any single compound.

Coral and Coral-Associated Microorganisms: A Prolific Source of Potential Bioactive Natural Products

Marine invertebrates and their associated microorganisms are rich sources of bioactive compounds. Among them, coral and its associated microorganisms are promising providers of marine bioactive compounds. The present review provides an overview of bioactive compounds that are produced by corals and coral-associated microorganisms, covering the literature from 2010 to March 2019. Accordingly, 245 natural products that possess a wide range of potent bioactivities, such as anti-inflammatory, cytotoxic, antimicrobial, antivirus, and antifouling activities, among others, are described in this review.

Coral and Coral-Associated Microorganisms: A Prolific Source of Potential Bioactive Natural Products

Marine invertebrates and their associated microorganisms are rich sources of bioactive compounds. Among them, coral and its associated microorganisms are promising providers of marine bioactive compounds. The present review provides an overview of bioactive compounds that are produced by corals and coral-associated microorganisms, covering the literature from 2010 to March 2019. Accordingly, 245 natural products that possess a wide range of potent bioactivities, such as anti-inflammatory, cytotoxic, antimicrobial, antivirus, and antifouling activities, among others, are described in this review.

Overview on antibacterial metabolites from terrestrial Aspergillus spp

Medicines developed from natural sources are a frequent target for the research and discovery of antimicrobial compounds. Discovering of penicillin in 1928 was a motive to explore of nature as a source of new antimicrobial agents. Fungi produce a diverse range of bioactive metabolites, making them rich source of different types of medicines. The purpose of this paper was to review studies on antibacterials from terrestrial Aspergillus published exclusively during 1942-2018, with emphasis on their antibacterial activities, structures, and mechanisms of action if present. According to the results from different studies in the world, large number of compounds and extracts showed different activities against different bacterial species, including Gram-positive and Gram-negative bacteria. The most prominent result was that of the compound CJ-17,665, isolated from A. ochraceus, showing good activity against multi-drug resistant Staphylococcus aureus, which is well-recognised to be one of the most important current public health problem. These findings may motivate scientists to undertake a project that may result in the development of novel antibacterial drugs from terrestrial-derived Aspergillus spp., although further toxicity assays (in vivo) must be performed before their application.

Marine natural products

Covering: January to December 2017This review covers the literature published in 2017 for marine natural products (MNPs), with 740 citations (723 for the period January to December 2017) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1490 in 477 papers for 2017), together with the relevant biological activities, source organisms and country of origin. Reviews, biosynthetic studies, first syntheses, and syntheses that led to the revision of structures or stereochemistries, have been included. Geographic distributions of MNPs at a phylogenetic level are reported.

Anti-Phytopathogenic and Cytotoxic Activities of Crude Extracts and Secondary Metabolites of Marine-Derived Fungi

Thirty-one isolates belonging to eight genera in seven orders were identified from 141 strains that were isolated from several marine plants. Alternaria sp. and Fusarium sp. were found to be the predominant fungi. Evaluation of the anti-phytopathogenic bacterial and fungal activities, as well as the cytotoxicity of these 31 extracts, revealed that most of them displayed different levels of bioactivities. Due to their interesting bioactivities, two fungal strains—Fusarium equiseti (P18) and Alternaria sp. (P8)—were selected for chemical investigation and compounds 1–4 were obtained. The structure of 1 was elucidated by 1D and 2D NMR analysis, as well as high-resolution electrospray ionization mass spectroscopy (HRESIMS), and the absolute configuration of its stereogenic carbon (C-11) was established by comparison of the experimental and calculated electronic circular-dichroism (ECD) spectra. Moreover, alterperylenol (4) exhibited antibacterial activity against Clavibacter michiganensis with a minimum inhibitory concentration (MIC) of 1.95 μg/mL, which was 2-fold stronger than that of streptomycin sulfate. Additionally, an antibacterial mechanism study revealed that 4 caused membrane hyperpolarization without evidence of destruction of cell membrane integrity. Furthermore, stemphyperylenol (3) displayed potent antifungal activity against Pestallozzia theae and Alternaria brassicicola with MIC values equal to those of carbendazim. The cytotoxicity of 1 and 2 against human lung carcinoma (A-549), human cervical carcinoma (HeLa), and human hepatoma (HepG2) cell lines were also evaluated.