Highly oxygenated chromones from mangrove-derived endophytic fungus Rhytidhysteron rufulum

Endophytic Fungi: Cellular factories of novel medicinal chemistries

Inflammation and associated disorders have been a major contributing factor to mortality worldwide. The augmented mortality rate and emerging resistance against the approved therapeutics necessitate the discovery of novel chemistries destined for multiple clinical settings. Cellular factories including endophytic fungi have been tapped for chemical diversity with therapeutic potential. The emerging evidence has suggested the potential of bioactive compounds isolated from the endophytic fungi as putative agents to combat inflammation-associated disorders. The review summarizesand assists the readers in comprehending the structural and functional aspects of the medicinal chemistries identified from endophytic fungi as anticancer, antiobesity, antigout, and immunomodulatory agents.

Using nanotechnology to progress the utilization of marine natural products in combating multidrug resistance in cancer: A prospective strategy

Achieving targeted, customized, and combination therapies with clarity of the involved molecular pathways is crucial in the treatment as well as overcoming multidrug resistance (MDR) in cancer. Nanotechnology has emerged as an innovative and promising approach to address the problem of drug resistance. Developing nano-formulation-based therapies using therapeutic agents poses a synergistic effect to overcome MDR in cancer. In this review, we aimed to highlight the important pathways involved in the progression of MDR in cancer mediated through nanotechnology-based approaches that have been employed to circumvent them in recent years. Here, we also discussed the potential use of marine metabolites to treat MDR in cancer, utilizing active drug-targeting nanomedicine-based techniques to enhance selective drug accumulation in cancer cells. The discussion also provides future insights for developing complex targeted, multistage responsive nanomedical drug delivery systems for effective cancer treatments. We propose more combinational studies and their validation for the possible marine-based nanoformulations for future development.

Chemical Constituents and Biological Activities of Bruguiera Genus and Its Endophytes: A Review

The genus Bruguiera, a member of the Rhizophoraceae family, is predominantly found in coastal areas as a mangrove plant, boasting a rich and diverse community of endophytes. This review systematically compiled approximately 496 compounds derived from both the Bruguiera genus and its associated endophytes, including 152 terpenoids, 17 steroids, 16 sulfides, 44 alkaloids and peptides, 66 quinones, 68 polyketides, 19 flavonoids, 38 phenylpropanoids, 54 aromatic compounds, and 22 other compounds. Among these, 201 compounds exhibited a spectrum of activities, including cytotoxicity, antimicrobial, antioxidant, anti-inflammatory, antiviral, antidiabetic, insecticidal and mosquito repellent, and enzyme inhibitory properties, etc. These findings provided promising lead compounds for drug discovery. Certain similar or identical compounds were found to be simultaneously present in both Bruguiera plants and their endophytes, and the phenomenon of their interaction relationship was discussed.

Cytotoxic Compounds from Marine Fungi: Sources, Structures, and Bioactivity

Marine fungi, such as species from the Penicillium and Aspergillus genera, are prolific producers of a diversity of natural products with cytotoxic properties. These fungi have been successfully isolated and identified from various marine sources, including sponges, coral, algae, mangroves, sediment, and seawater. The cytotoxic compounds derived from marine fungi can be categorized into five distinct classes: polyketides, peptides, terpenoids and sterols, hybrids, and other miscellaneous compounds. Notably, the pre-eminent group among these compounds comprises polyketides, accounting for 307 out of 642 identified compounds. Particularly, within this collection, 23 out of the 642 compounds exhibit remarkable cytotoxic potency, with IC50 values measured at the nanomolar (nM) or nanogram per milliliter (ng/mL) levels. This review elucidates the originating fungal strains, the sources of isolation, chemical structures, and the noteworthy antitumor activity of the 642 novel natural products isolated from marine fungi. The scope of this review encompasses the period from 1991 to 2023.

Bioprospecting of endophytic fungi from medicinal plant Anisomeles indica L. for their diverse role in agricultural and industrial sectors

Endophytes are microorganisms that inhabit various plant parts and cause no damage to the host plants. During the last few years, a number of novel endophytic fungi have been isolated and identified from medicinal plants and were found to be utilized as bio-stimulants and bio fertilizers. In lieu of this, the present study aims to isolate and identify endophytic fungi associated with the leaves of Anisomeles indica L. an important medicinal plant of the Terai-Duars region of West Bengal. A total of ten endophytic fungi were isolated from the leaves of A. indica and five were identified using ITS1/ITS4 sequencing based on their ability for plant growth promotion, secondary metabolite production, and extracellular enzyme production. Endophytic fungal isolates were identified as Colletotrichum yulongense Ai1, Colletotrichum cobbittiense Ai2, Colletotrichum alienum Ai2.1, Colletotrichum cobbittiense Ai3, and Fusarium equiseti. Five isolates tested positive for their plant growth promotion potential, while isolates Ai4. Ai1, Ai2, and Ai2.1 showed significant production of secondary metabolites viz. alkaloids, phenolics, flavonoids, saponins, etc. Isolate Ai2 showed maximum total phenolic concentration (25.98 mg g-1), while isolate Ai4 showed maximum total flavonoid concentration (20.10 mg g-1). Significant results were observed for the production of extracellular enzymes such as cellulases, amylases, laccases, lipases, etc. The isolates significantly influenced the seed germination percentage of tomato seedlings and augmented their growth and development under in vitro assay. The present work comprehensively tested these isolates and ascertained their huge application for the commercial utilization of these isolates both in the agricultural and industrial sectors.

Chromone a Privileged Scaffold in Drug Discovery: Developments on the Synthesis and Bioactivity

Chromones are the class of secondary metabolites broadly occurred in the plant kingdom in a noticeable quantity. This rigid bicyclic system has been categorized "as privileged scaffolds in compounds" in medicinal chemistry. The wide biological responses made them an important moiety in a drug discovery program. This review provides updates on the various methods of synthesis of chromones and biological applications in medicinal chemistry. Various synthetic strategies for the construction of chromones include readily available phenols, salicylic acid and its derivatives, ynones, chalcones, enaminones, chalcones and 2-hydroxyarylalkylketones as starting materials. Synthesis of chromones by using metal, metal free, nanomaterials and different catalysts are included. Details of diverse biological activities such as anti-cancer agents, antimicrobial agents, anti-viral property, anti-inflammatory agents, antioxidants, Monoamine Oxidase-B (MAO-B) Inhibitors, anti-Alzheimer's agents, anti-diabetic agent, antihistaminic potential, antiplatelet agents of chromone derivatives are diecussed.

Rhytidhylides A and B, Two New Phthalide Derivatives from the Endophytic Fungus Rhytidhysteron sp. BZM-9

Two new phthalide derivatives, rhytidhylides A (1) and B (2), together with ten known compounds (3–12) were isolated from cultures of Rhytidhysteron sp. BZM-9, an endophyte isolated from the leaves of Leptospermum brachyandrum. Their structures were identified by an extensive analysis of NMR, HRESIMS, ECD, and through comparison with data reported in the literature. In addition, the cytotoxic activities against two human hepatoma cell lines (HepG2 and SMMC7721) and antibacterial activities against MRSA and E. coli were evaluated.

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.

Endophytic fungi: A treasure trove of novel anticancer compounds

Cancer is a multifactorial disease with a convoluted genesis and progression. The emergence of multidrug resistance to presently be offered drug and relapse is by far, the most critical concern to tackle this deteriorating disease. Henceforth, there is undeniably an inflated necessity for safe, promising, and less harmful new anticancer drugs. Natural compounds from various sources like plants, animals, and microorganisms have occupied a center stage in drug discovery due to their tremendous chemical diversity and potential as therapeutic agents. Endophytic microbes are symbiotically associated with plants and have been proven to produce novel or analogues of host bioactive metabolites exhibiting a variety of biological activities including anticancer activity. This review emphasizes on structurally diverse unprecedented anticancer natural compounds that have been reported exclusively from endophytic fungi from 2016 to 2020. It covers chemical nature of metabolites, its fungal source associated with terrestrial, as well as marine plants and anticancer activity based on their cytotoxicity profile against various cancer cell lines. Many of these fungal metabolites with promising anticancer activity can be used as lead molecules for in silico experiments and deserve special attention from scientists for further in vitro and clinical research.

Rhytidhyesters A - D, 4 New Chlorinated Cyclopentene Derivatives from the Endophytic Fungus Rhytidhysteron sp. BZM-9

Four new chlorinated cyclopentene derivatives, rhytidhyesters A - D (1:  - 4: ), were isolated from Rhytidhysteron sp. BZM-9, an endophytic fungus from Leptospermum brachyandrum. The planar structures of compounds 1:  - 4: were mainly elucidated by 1D, 2D NMR, and HRESIMS data. Their absolute configurations were established by X-ray crystallographic analysis, quantum chemical ¹³C NMR, and electronic circular dichroism calculations. Compounds 1: and 2: are a pair of epimers. Moreover, all the isolated compounds were evaluated for cytotoxic activities against 3 human colon cancer cell lines (SW620, HT29, SW480) and antimicrobial activity against Staphylococcus aureus. All compounds exhibited weak to moderate antiproliferative activities with IC₅₀ values ranging from 15.4 to 37.7 µM but were inactive against S. aureus.

Fungal endophytes from leaves of Avicennia marina growing in semi-arid environment as a promising source for bioactive compounds

Endophytic fungi are broadly dispersed residing inside plant tissues and have been demonstrated as a treasure for bioactive natural products. Unexplored harsh and heavy metal contaminant habitat of Avicennia marina may have diverse and potential fungal association. Therefore, this work aimed to isolate the culturable fungal endophytes associated with leaves of A. marina and to evaluate their medical potentialities. Seventeen isolates of endophyte fungi were isolated from healthy leaves and their antimicrobial activities were evaluated. Results showed that isolates had activity against micro-organisms in addition to their antioxidant activity produced a variety of phenolic compounds, besides exhibited a lowest cytotoxicity against ATCC-CCL-81 cell line. Consequently, selected endophytic fungal isolates were identified genetically as Chaetomium sp., Chaetomium madrasense, Chaetomium sp., Chaetomium globosum, Aspergillus hiratsukae, Aspergillus ochraceus, Alternaria tenuissima and Curvularia lunata with gene bank accession numbers MT089951, MT089952, MT089953, MT089954, MT089955, MT089956, MT089957 and MT089958 respectively. The most potent fungus extract was analysed using Gas chromatography-mass spectrometry which verified the presence of numerous bioactive compounds. These findings confirmed that new endophytic fungal strains derived from A. marina thrive in harsh ecosystem produce bioactive metabolites which can be recommended as a novel source for drug discovery.

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.

Mainland and island populations of Mussaenda kwangtungensis differ in their phyllosphere fungal community composition and network structure

We compared community composition and co-occurrence patterns of phyllosphere fungi between island and mainland populations within a single plant species (Mussaenda kwangtungensis) using high-throughput sequencing technology. We then used 11 microsatellite loci for host genotyping. The island populations differed significantly from their mainland counterparts in phyllosphere fungal community structure. Topological features of co-occurrence network showed geographic patterns wherein fungal assemblages were less complex, but more modular in island regions than mainland ones. Moreover, fungal interactions and community composition were strongly influenced by the genetic differentiation of host plants. This study may advance our understanding of assembly principles and ecological interactions of phyllosphere fungal communities, as well as improve our ability to optimize fungal utilization for the benefit of people.

Mangrove-Associated Fungi: A Novel Source of Potential Anticancer Compounds

Cancer is the second leading cause of death worldwide, and the number of cases is increasing alarmingly every year. Current research focuses on the development of novel chemotherapeutic drugs derived from natural as well as synthetic sources. The abundance and diversity in natural resources offer tremendous potential for the discovery of novel molecules with unique mechanisms for cancer therapy. Mangrove-derived fungi are rich source of novel metabolites, comprising novel structure classes with diverse biological activities. Across the globe, coastal areas are primarily dominated by mangrove forests, which offer an intensely complex environment and species that mostly remain unexplored. In recent years, many structurally diverse compounds with unique skeletons have been identified from mangrove fungi and evaluated for their antiproliferative properties. These compounds may serve as lead molecules for the development of new anticancer drugs. Mangrove endophytes can be modulated using epigenetic means or culture optimization methods to improve the yield or to produce various similar analogs. The present review provides an insight into the bioactive metabolites from mangrove endophytes reported during the period from 2012 to 2018 (up to April, 2018) along with their cytotoxic properties, focusing on their chemical structures and mode of action, as indicated in the literature.

Novel natural compounds from endophytic fungi with anticancer activity

Plant endophytes are microorganisms that live in healthy plant tissues in part or all of their life history without causing obvious symptoms of infection in the host plants. Endophytes, a new type of microbial resource that can produce a variety of biological constituents, have great values for research and broad prospects for development. This article reviewed the research and development progress of endophytic fungi with cytotoxic activity between 2014 and 2017, including endophytic fungi sources, microbial taxonomy, compound classification and cytotoxic activity. The results showed that the 109 strains of endophytic fungi belong to 3 phyla, 7 classes and 50 genera. The secondary metabolites mainly contained alkaloids, terpenes, steroids, polyketides, quinones, isocoumarins, esters etc. The results of this study provide references for the development of new antitumor drugs and endophytes resources.

Endophytic Fungi-Alternative Sources of Cytotoxic Compounds: A Review

Cancer is a major cause of death worldwide, with an increasing number of cases being reported annually. The elevated rate of mortality necessitates a global challenge to explore newer sources of anticancer drugs. Recent advancements in cancer treatment involve the discovery and development of new and improved chemotherapeutics derived from natural or synthetic sources. Natural sources offer the potential of finding new structural classes with unique bioactivities for cancer therapy. Endophytic fungi represent a rich source of bioactive metabolites that can be manipulated to produce desirable novel analogs for chemotherapy. This review offers a current and integrative account of clinically used anticancer drugs such as taxol, podophyllotoxin, camptothecin, and vinca alkaloids in terms of their mechanism of action, isolation from endophytic fungi and their characterization, yield obtained, and fungal strain improvement strategies. It also covers recent literature on endophytic fungal metabolites from terrestrial, mangrove, and marine sources as potential anticancer agents and emphasizes the findings for cytotoxic bioactive compounds tested against specific cancer cell lines.

Modeling and Optimum Extraction of Multiple Bioactive Exopolysaccharide from an Endophytic Fungus of Crocus sativus L

Background:

Crocus sativus L. (saffron) is a scarce plant that has been used as food flavoring agent, coloring agent, and traditional herbal medicine.

Methods:

The bioactivity of exopolysaccharide (EPS) extracted from an endophytic fungus of C. sativus was examined for the first time by antioxidative, antitumor, and antibacterial assays. The extraction conditions for EPS were optimized by combining the response surface methodology with Box-Behnken design.

Results:

EPS exhibited excellent scavenging activities against 1,1-diphenyl-2-picrylhydrazyl, hydroxyl and superoxide anion radicals, and moderate cytotoxicities against K562, A549, HL-60, and HeLa cells. The optimum extraction conditions for EPS were as follows: precipitation time of 16 h, precipitation temperature of 3.7°C, pH 7.2, and ratio of ethanol to fermented broth of 5:1 (L/L). Under the optimized conditions, the yield of EPS reached 162 ± 6 μg/L which was close to the predicted one (165 μg/L). Moreover, high-performance liquid chromatography of monosaccharide composition showed that EPS comprised mannose, glucose, galactose xylose, and arabinose in a molar ratio of 25.6:16.5:1.0:3.8:5.4.

Conclusion:

EPS may be an eligible substitute for C. sativus and a potential bioactive source applicable to pharmaceutical and food industries.

SUMMARY

Exopolysaccharide (EPS) from endophytic fungus of Crocus sativus was studied for the first time

EPS extraction was optimized by combining response surface methodology with Box-Behnken design

Monosaccharide composition and EPS structure were identified by high-performance liquid chromatography and Fourier-transform infrared spectroscopy.

Abbreviations used: EPS: Exopolysaccharide, RSM: Response surface methodology, BBD: Box-Behnken design, DPPH: 1,1-diphenyl-2-picrylhydrazyl, V_C: Ascorbic acid, MTT: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, LB: Luria Bertani, DMSO: dimethyl sulfoxide, PMP: 1-phenyl-3-methyl-5-pyrazolone, FT-IR: Fourier transform-infrared, HPLC: High-performance liquid chromatography, 3D: Three-dimensional, 2D: Two-Dimensional.

Marine natural products

Covering: 2016. Previous review: Nat. Prod. Rep., 2017, 34, 235-294This review covers the literature published in 2016 for marine natural products (MNPs), with 757 citations (643 for the period January to December 2016) 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 (1277 in 432 papers for 2016), 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.

Marine Fungi: A Source of Potential Anticancer Compounds

Metabolites from marine fungi have hogged the limelight in drug discovery because of their promise as therapeutic agents. A number of metabolites related to marine fungi have been discovered from various sources which are known to possess a range of activities as antibacterial, antiviral and anticancer agents. Although, over a thousand marine fungi based metabolites have already been reported, none of them have reached the market yet which could partly be related to non-comprehensive screening approaches and lack of sustained lead optimization. The origin of these marine fungal metabolites is varied as their habitats have been reported from various sources such as sponge, algae, mangrove derived fungi, and fungi from bottom sediments. The importance of these natural compounds is based on their cytotoxicity and related activities that emanate from the diversity in their chemical structures and functional groups present on them. This review covers the majority of anticancer compounds isolated from marine fungi during 2012-2016 against specific cancer cell lines.

Transition-metal-free insertion reactions of alkynes into the C–N σ-bonds of imides: synthesis of substituted enamides or chromones

Transition-metal-free insertion of ynones into the C–N σ-bonds of imides for the chemo-selective synthesis of chromones or enamides.

Endophytic fungi from mangrove inhibit lung cancer cell growth and angiogenesis in vitro

The secondary metabolites of mangrove-derived endophytic fungi contain multiple substances with novel structures and biological activities. In the present study, three types of mangrove plants, namely Kandelia candel, Rhizophora stylosa and Rhizophoraceae from Zhanjiang region including the leaves, roots and stems were collected, and endophytic fungi were isolated, purified and identified from these mangrove plants. MTT assay was used to observe the effects of the isolated endophytic fungi on the growth of A549 and NCI-H460 lung cancer cells. The effect of the endophytic fungi on lung cancer angiogenesis in vitro induced by the HPV-16 E7 oncoprotein was observed. Our results showed that 28 strains of endophytic fungi were isolated, purified and identified from the three types of mangrove plants. Ten strains of endophytic fungi significantly suppressed the growth of A549 and NCI-H460 cells. The average inhibitory rates in the A549 cells were 64.4, 59.5, 81.9, 43.9, 58.3, 56.2, 48.3, 42.4, 93.0 and 49.7%, respectively. The average inhibitory rates in the NCI-H460 cells were 41.2, 49.3, 82.7, 40.7, 53.9, 52.6, 56.8, 64.3, 91.0 and 45.6%, respectively. Particularly, three strains of endophytic fungi markedly inhibited HPV-16 E7 oncoprotein‑induced lung cancer angiogenesis in vitro. These findings contribute to the further screening of potential chemotherapeutic agents from mangrove-derived endophytic fungi.

Cytotoxic and antibacterial naphthoquinones from an endophytic fungus, Cladosporium sp

Objective

Endophytes have the potential to synthesize various bioactive secondary metabolites. The aim of the study was to find new cytotoxic and antibacterial metabolites from endophytic fungus, Cladosporium sp. isolated from the leaves of Rauwolfia serpentina (L.) Benth. ex Kurz. (Fam: Apocyanaceae).

Materials and methods

The endophytic fungus was grown on potato dextrose agar medium and extracted using ethyl acetate. Secondary metabolites were isolated by chromatographic separation and re-crystallization, and structures were confirmed by ¹H NMR, ¹³C NMR and mass spectroscopic data. The cytotoxicity was determined by WST-1 assay and brine shrimp lethality bioassay, while antibacterial activity was assessed by disc diffusion method.

Results

Two naphthoquinones, namely anhydrofusarubin (1) and methyl ether of fusarubin (2), were isolated from Cladosporium sp. The isolated compounds 1 and 2, by WST-1 assay against human leukemia cells (K-562) showed potential cytotoxicity with IC₅₀ values of 3.97 μg/mL and 3.58 μg/mL, respectively. Initial screening of crude ethyl acetate extract and column fractions F-8 and F-10 exhibited noticeable cytotoxicity to brine shimp nauplii with LC₅₀ values of 42.8, 1.2 and 2.1 μg/mL, respectively. Moreover, the isolated compound 2 (40 μg/disc) showed prominent activities against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Bacillus megaterium with an average zone of inhibition of 27 mm, 25 mm, 24 mm and 22 mm, respectively and the activities were compared with kanamycin (30 μg/disc).

Conclusion

Our findings indicate that anhydrofusarubin (1) and methyl ether of fusarubin (2) might be useful lead compounds to develop potential cytotoxic and antimicrobial drugs.