Two new bioactive steroids from a mangrove-derived fungus Aspergillus sp

Coastal natural products: a review applied to antimycobacterial activity

Despite the many advances in drug research, natural products are still being explored as a promising source for discovering new bioactive compounds to treat global diseases such as tuberculosis. However, there is a lack of studies and information about coastal natural products, which thrive in the transitional environment between two different ecosystems and produce unique secondary metabolites. Mangroves, estuaries, and mudflats make up areas for coastal species and have shown promising results in antituberculosis research, some of them are present in hotspot areas. This review focuses on research conducted in coastal environments and explores the reasons why these natural products tend to outperform non-coastal ones against the causative agent of tuberculosis, Mycobacterium tuberculosis.

Structure and Biological Activity of Ergostane-Type Steroids from Fungi

Mushrooms are known not only for their taste but also for beneficial effects on health attributed to plethora of constituents. All mushrooms belong to the kingdom of fungi, which also includes yeasts and molds. Each year, hundreds of new metabolites of the main fungal sterol, ergosterol, are isolated from fungal sources. As a rule, further testing is carried out for their biological effects, and many of the isolated compounds exhibit one or another activity. This study aims to review recent literature (mainly over the past 10 years, selected older works are discussed for consistency purposes) on the structures and bioactivities of fungal metabolites of ergosterol. The review is not exhaustive in its coverage of structures found in fungi. Rather, it focuses solely on discussing compounds that have shown some biological activity with potential pharmacological utility.

Azaphilone derivatives with anti-inflammatory activity from the mangrove endophytic fungus Penicillium sclerotiorum ZJHJJ-18

Nine undescribed azaphilone derivatives, sclerazaphilones A-H (1-9), and three known analogues (10-12), were obtained and identified from the fermented rice cultures of a mangrove endophytic fungus Penicillium sclerotiorum ZJHJJ-18. 1D and 2D NMR, HRESIMS and spectral data indicated the chemical structures of 1-9, and their absolute configurations were assigned by experimental and computational analyses of electronic circular dichroism (ECD) spectra, and application of the chemical transformations. Compounds 1-4 were the first reported N-containing azaphilone derivatives with 5/6 dicyclic core. The bioassay results showed that compounds 3-5 exhibited effective inhibitory effects on the nitric oxide (NO) production in lipopolysaccharide (LPS)-induced RAW264.7 macrophage cells with IC₅₀ values in the range of 6.30-9.45 μM. Moreover, a molecular docking study was conducted to investigate the probable binding interaction of 3-5 with inducible nitric oxide synthase (iNOS).

Ecotoxicological assessment of toxic elements contamination in mangrove ecosystem along the Red Sea coast, Egypt

Identifying biochemical aspects of the potentially toxic elements (PTEs) is of particular concern in mangrove ecosystems, Avicennia marina (Forssk.) Vierh., due to their importance as natural buffers in coastal areas. Nonetheless, the microbial community dynamics and potential scavenging responses of mangrove ecosystems to the phytotoxicity of PTEs remain questionable. This study assesses the ecological risk benchmarks of some PTEs, including aluminum (Al), boron (B), barium (Ba), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), mercury (Hg), manganese (Mn), nickel (Ni), lead (Pb), and zinc (Zn), and their microbial responses in the bottom sediments of mangrove ecosystems along Egypt's Red Sea coast. In particular, we assessed the role of microbial metabolites in biochemical cycling of nutrients and scavenging against phytotoxicity hazards. We quantified a spectrum of ecological risk assessment indices, which suggested elevated levels of PTEs in sediment, particularly Cr, Hg, and Pb. Canonical correspondence analysis and generalized linear mixed effects models indicate that the spatial biodiversity of microbial taxa is impacted significantly by the physicochemical characteristics of sediments and concentrations of PTEs. Results demonstrate that the microbial communities and their metabolites exert a significant influence on organic matter (OM) decomposition and the biochemical cycling of phytoavailable nutrients including nitrogen (N), phosphorus (P), and potassium (K). Spatially, nitrogenase activities were higher (411.5 μmoL h^-1 mL^-1) in the southern sites of the Red Sea coast relative to the northern locations (93.8 μmoL h^-1 mL^-1). In contrast, higher concentrations of phytohormones, including indole-3-acetic acid (IAA) (61.5 mg mL^-1) and gibberellins (534.2 mg mL^-1), were more evident in northern sites. Siderophores correlated positively with Fe concentration in sediments and averaged 307.4 mg mL^-1. Overall, these findings provide insights into the biochemical signals of PTEs contamination in hostile environments, contributing to a better understanding of the future prospects of PTEs bioremediation in contaminated coastal environments.

Natural products from mangrove sediments-derived microbes: Structural diversity, bioactivities, biosynthesis, and total synthesis

The mangrove forests are a complex ecosystem, and the microbial communities in mangrove sediments play a critical role in the biogeochemical cycles of mangrove ecosystems. Mangrove sediments-derived microbes (MSM), as a rich reservoir of natural product diversity, could be utilized in the exploration of new antibiotics or drugs. To understand the structural diversity and bioactivities of the metabolites of MSM, this review for the first time provides a comprehensive overview of 519 natural products isolated from MSM with their bioactivities, up to 2021. Most of the structural types of these compounds are alkaloids, lactones, xanthones, quinones, terpenoids, and steroids. Among them, 210 compounds are obtained from bacteria, most of which are from Streptomyces, while 309 compounds are from fungus, especially genus Aspergillus and Penicillium. The pharmacological mechanisms of some representative lead compounds are well studied, revealing that they have important medicinal potentials, such as piericidins with anti-renal cell cancer effects, azalomycins with anti-MRSA activities, and ophiobolins as antineoplastic agents. The biosynthetic pathways of representative natural products from MSM have also been summarized, especially ikarugamycin, piericidins, divergolides, and azalomycins. In addition, the total synthetic strategies of representative secondary metabolites from MSM are also reviewed, such as piericidin A and borrelidin. This review provides an important reference for the research status of natural products isolated from MSM and the lead compounds worthy of further development, and reveals that MSM have important medicinal values and are worthy of further development.

A Review on Microbial Products and Their Perspective Application as Antimicrobial Agents

Microorganisms including actinomycetes, archaea, bacteria, fungi, yeast, and microalgae are an auspicious source of vital bioactive compounds. In this review, the existing research regarding antimicrobial molecules from microorganisms is summarized. The potential antimicrobial compounds from actinomycetes, particularly Streptomyces spp.; archaea; fungi including endophytic, filamentous, and marine-derived fungi, mushroom; and microalgae are briefly described. Furthermore, this review briefly summarizes bacteriocins, halocins, sulfolobicin, etc., that target multiple-drug resistant pathogens and considers next-generation antibiotics. This review highlights the possibility of using microorganisms as an antimicrobial resource for biotechnological, nutraceutical, and pharmaceutical applications. However, more investigations are required to isolate, separate, purify, and characterize these bioactive compounds and transfer these primary drugs into clinically approved antibiotics.

Research Progress in Anti-Inflammatory Bioactive Substances Derived from Marine Microorganisms, Sponges, Algae, and Corals

Inflammation is the body’s defense reaction in response to stimulations and is the basis of various physiological and pathological processes. However, chronic inflammation is undesirable and closely related to the occurrence and development of diseases. The ocean gives birth to unique and diverse bioactive substances, which have gained special attention and been a focus for anti-inflammatory drug development. So far, numerous promising bioactive substances have been obtained from various marine organisms such as marine bacteria and fungi, sponges, algae, and coral. This review covers 71 bioactive substances described during 2015–2020, including the structures (65 of which), species sources, evaluation models and anti-inflammatory activities of these substances. This review aims to provide some reference for the research progress of marine-organism-derived anti-inflammatory metabolites and give more research impetus for their conversion to novel anti-inflammatory drugs.

Secondary metabolites from mangrove-associated fungi: source, chemistry and bioactivities

Covering 1989 to 2020The mangrove forests are a complex ecosystem occurring at tropical and subtropical intertidal estuarine zones and nourish a diverse group of microorganisms including fungi, actinomycetes, bacteria, cyanobacteria, algae, and protozoa. Among the mangrove microbial community, mangrove associated fungi, as the second-largest ecological group of the marine fungi, not only play an essential role in creating and maintaining this biosphere but also represent a rich source of structurally unique and diverse bioactive secondary metabolites, attracting significant attention of organic chemists and pharmacologists. This review summarizes the discovery relating to the source and characteristics of metabolic products isolated from mangrove-associated fungi over the past thirty years (1989-2020). Its emphasis included 1387 new metabolites from 451 papers, focusing on bioactivity and the unique chemical diversity of these natural products.

Bioactive Polyketide and Diketopiperazine Derivatives from the Mangrove-Sediment-Derived Fungus Aspergillus sp. SCSIO41407

Ten polyketide derivatives (1–10), including a new natural product named (E)-2,4-dihydroxy-3-methyl-6-(2-oxopent-3-en-1-yl) benzaldehyde (1), and five known diketopiperazines (11–15), were isolated from the mangrove-sediment-derived fungus Aspergillus sp. SCSIO41407. The structures of 1–15 were determined via NMR and MS spectroscopic analysis. In a variety of bioactivity screening, 3 showed weak cytotoxicity against the A549 cell line, and 2 exhibited weak antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA). Compounds 3, 5, and 6 showed inhibition against acetylcholinesterase (AChE) with IC₅₀ values of 23.9, 39.9, and 18.6 μM. Compounds 11, 12, and 14 exhibited obvious inhibitory activities of lipopolysaccharide (LPS)-induced nuclear factor-κB (NF-κB) with IC₅₀ values of 19.2, 20.9, and 8.7 μM, and they also suppressed RANKL-induced osteoclast differentiation in bone marrow macrophages cells (BMMCs), with the concentration of 5 μM. In silico molecular docking with AChE and NF-κB p65 protein were also performed to understand the inhibitory activities, and 1, 11–14 showed obvious protein/ligand-binding effects to the NF-κB p65 protein.

Natural products against key Mycobacterium tuberculosis enzymatic targets: Emerging opportunities for drug discovery

For centuries, natural products (NPs) have served as powerful therapeutics against a variety of human ailments. Nowadays, they still represent invaluable resources for the treatment of many diseases, including bacterial infections. After nearly three decades since the World Health Organization's (WHO) declaration of tuberculosis (TB) as a global health emergency, Mycobacterium tuberculosis (Mtb) continues to claim millions of lives, remaining among the leading causes of death worldwide. In the last years, several efforts have been devoted to shortening and improving treatment outcomes, and to overcoming the increasing resistance phenomenon. Nature has always provided a virtually unlimited source of bioactive molecules, which have inspired the development of new drugs. NPs are characterized by an exceptional chemical and structural diversity, the result of millennia of evolutionary responses to various stimuli. Thanks to their favorable structural features and their enzymatic origin, they are naturally prone to bind proteins and exhibit bioactivities. Furthermore, their worldwide distribution and ease of accessibility has contributed to promote investigations on their activity. Overall, these characteristics make NPs excellent models for the design of novel therapeutics. This review offers a critical and comprehensive overview of the most promising NPs, isolated from plants, fungi, marine species, and bacteria, endowed with inhibitory properties against traditional and emerging mycobacterial enzymatic targets. A selection of 86 compounds is here discussed, with a special emphasis on their biological activity, structure-activity relationships, and mechanism of action. Our study corroborates the antimycobacterial potential of NPs, substantiating their relevance in future drug discovery and development efforts.

Biosynthetic versatility of marine-derived fungi on the delivery of novel antibacterial agents against priority pathogens

Despite the increasing number of novel marine natural products being reported from fungi in the last three decades, to date only the broad-spectrum cephalosporin C can be tracked back as marine fungal-derived drug. Cephalosporins were isolated in the early 1940s from a strain of Acremonium chrysogenum obtained in a sample collected in sewage water in the Sardinian coast, preliminary findings allowing the discovery of cephalosporin C. Since then, bioprospection of marine fungi has been enabling the identification of several metabolites with antibacterial effects, many of which proving to be active against multi-drug resistant strains, available data suggesting also that some might fuel the pharmaceutical firepower towards some of the bacterial pathogens classified as a priority by the World Health Organization. Considering the success of their terrestrial counterparts on the discovery and development of several antibiotics that are nowadays used in the clinical setting, marine fungi obviously come into mind as producers of new prototypes to counteract antibiotic-resistant bacteria that are no longer responding to available treatments. We mainly aim to provide a snapshot on those metabolites that are likely to proceed to advanced preclinical development, not only based on their antibacterial potency, but also considering their targets and modes of action, and activity against priority pathogens.

Recent updates on the bioactive compounds of the marine-derived genus Aspergillus

The genus Aspergillus is widely distributed in terrestrial and marine environments. In the marine environment, several Aspergillus species have proved their potential to produce a plethora of secondary metabolites including polyketides, sterols, fatty acids, peptides, alkaloids, terpenoids and miscellaneous compounds, displaying a variety of pharmacological activities such as antimicrobial, cytotoxicity, anti-inflammatory and antioxidant activity. From the beginning of 2015 until December 2020, about 361 secondary metabolites were identified from different marine Aspergillus species. In our review, we highlight secondary metabolites from various marine-derived Aspergillus species reported between January 2015 and December 2020 along with their biological potential and structural aspects whenever applicable.

The genus Aspergillus is widely distributed in terrestrial and marine environments.

Marine natural products

This review covers the literature published between January and December in 2018 for marine natural products (MNPs), with 717 citations (706 for the period January to December 2018) 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 (1554 in 469 papers for 2018), 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. The proportion of MNPs assigned absolute configuration over the last decade is also surveyed.

Bioactive isocoumarins isolated from a mangrove-derived fungus Penicillium sp. MGP11

Two new isocoumarins penicimarins L-M (1-2), along with seven known analogues (3-9) were isolated from the mangrove-derived fungus Penicillium sp. MGP11. Compounds 1-2 were established by spectroscopic methods and comparison of their circular dichroism (CD) spectra with the literature. All isolated compounds were evaluated for antioxidant and α-glucosidase inhibitory activities. Compound 8 had better antioxidant activity (IC₅₀ = 4.6 μM) than positive control trolox (IC₅₀ = 12.9 μM). Compounds 5, 8 and 9 exhibited α-glucosidase inhibitory activity with the IC₅₀ values of 776.5, 683.7 and 868.7 μM, respectively.

Bioactive Metabolites from the Deep-Sea-Derived Fungus Diaporthe longicolla FS429

The chemical investigation of a methanol extract of the deep-sea-derived fungus Diaporthe longicolla FS429 led to the isolation of two novel diterpenoids longidiacids A and B (1 and 2), two new polyketides (3 and 4), two new cytochalasin analogues longichalasins A and B (6 and 8) and three known analogues 5, 7, 9. Their structures were elucidated through comprehensive spectroscopic analysis, while the absolute configurations were established by the comparison of the experimental and quantum chemical calculated ECD spectra. The structure of compound 7 was confirmed through X-ray diffraction for the first time. In the bioassays compound 8 exhibited antiproliferative effects against SF-268, with an IC₅₀ value of 16.44 μM. Moreover, compounds 1 and 8 were detected to inhibit 35.4% and 53.5% of enzyme activity of Mycobacterium tuberculosis protein tyrosine phosphatase B (MptpB) at a concentration of 50 μM.

Fungi in mangrove ecosystems and their potential applications

Mangrove fungi, their ecological role in mangrove ecosystems, their bioproducts, and potential applications are reviewed in this article. Mangrove ecosystems can play an important role in beach protection, accretion promotion, and sheltering coastlines and creeks as barriers against devastating tropical storms and waves, seawater, and air pollution. The ecosystems are characterized by high average and constant temperatures, high salinity, strong winds, and anaerobic muddy soil. The mangrove ecosystems also provide the unique habitats for the colonization of fungi which can produce different kinds of enzymes for industrial uses, recycling of plants and animals in the ecosystems, and the degradation of pollutants. Many mangrove ecosystem-associated fungi also can produce exopolysaccharides, Ca²⁺-gluconic acid, polymalate, liamocin, polyunsaturated fatty acids, biofuels, xylitol, enzymes, and bioactive substances, which have many potential applications in the bioenergy, food, agricultural, and pharmaceutical industries. Therefore, mangrove ecosystems are rich bioresources for bioindustries and ecology. It is necessary to identify more mangrove fungi and genetically edit them to produce a distinct array of novel chemical entities, enzymes, and bioactive substances.

Polypropionate Derivatives with Mycobacterium tuberculosis Protein Tyrosine Phosphatase B Inhibitory Activities from the Deep-Sea-Derived Fungus Aspergillus fischeri FS452

Fiscpropionates A-F (1-6), six new polypropionate derivatives featuring an unusual long hydrophobic chain, were isolated from the deep-sea-derived fungus Aspergillus fischeri FS452. Their structures were elucidated on the basis of spectroscopic analysis, and the absolute configurations were determined by J-HMBC analysis, electronic circular dichroism (ECD) calculations, and the modified Mosher's method. This is the first discovery of polypropionates from marine-derived fungi, and compounds 4 and 5 represent the first examples of polypropionate derivatives containing a 3-hydroxypiperidin-2-one as part of an imide linkage. In addition, compounds 1-4 exhibited significant inhibitory activities against Mycobacterium tuberculosis protein tyrosine phosphatase B (MptpB) with the IC₅₀ values of 5.1, 12, 4.0, and 11 μM, respectively. Enzyme kinetic experiments suggested that they all acted through a noncompetitive mechanism. A preliminary structure-activity relationship is discussed.