Identification and Antifungal Activity of Metabolites from the Mangrove Fungus Phoma sp. L28

Actinomycins produced by endophyte Streptomyces sp. GLL-9 from navel orange plant exhibit high antimicrobial effect against Xanthomonas citri susp. citri and Penicillium italicum

BACKGROUND

Citrus canker and citrus blue mold are two severe diseases in citrus plants, which are mainly caused by Xanthomonas citri susp. citri (Xcc) and Penicillium italicum, respectively. The currently widely used pesticides for these two diseases are harmful to human health and the environment. Therefore, searching for novel antimicrobial agents, especially from natural resources, is getting increasing interest.

RESULTS

In this study, the crude extract of Streptomyces sp. GLL-9, an endophyte from a navel orange tree, was found to exhibit excellent antimicrobial effects against Xcc and P. italicum. Bioassay-guided isolation led to the discovery of three actinomycins (Acts), actinomycin X2 (Act-X2 ), actinomycin D (ActD), and actinomycin XOβ (Act-XOβ ). The MIC (minimum inhibitory concentration) values of Act-X2 , ActD, and Act-XOβ were 31.25, 62.50, and 62.50 μg mL-1 against Xcc, respectively, while 62.50 (Act-X2 ) and 125.00 μg mL-1 (ActD) against P. italicum, being better or comparable to the positive controls. The highest yield of Acts was obtained by solid-state fermentation with rice containing 1% L-tryptophan as a culture medium, being 6.03, 3.07, and 1.02 mg g-1 , for Act-X2 , ActD, and Act-XOβ , respectively. The ethyl acetate extract of Streptomyces sp. GLL-9 cultivated under the optimal fermentation conditions (EAE-1) can efficiently control these two citrus diseases by excessively producing reactive oxygen species (ROS) in both pathogens, damaging the cell membranes of P. italicum, and inhibiting the growth of Xcc. In addition, Act-X2 , ActD, and EAE-1 displayed broad-spectrum antifungal activity.

CONCLUSION

EAE-1 and Acts produced by Streptomyces sp. GLL-9 have high potential as novel antimicrobial agents against plant pathogens. © 2023 Society of Chemical Industry.

Natural products from marine fungi as a source against agricultural pathogenic fungi

There are many kinds of agricultural pathogenic fungi, which may belong to pathogenic fungi in different species, such as Fusarium, Alternaria, Colletotrichum, Phytophthora, and other agricultural pathogens. Pathogenic fungi from different sources are widely distributed in agriculture, which threaten the lives of crops around the world and caused great damage to agricultural production and economic benefits. Due to the particularity of the marine environment, marine-derived fungi could produce natural compounds with unique structures, rich diversities, and significant bioactivities. Since marine natural products with different structural characteristics could inhibit different kinds of agricultural pathogenic fungi, secondary metabolites with antifungal activity could be used as lead compounds against agricultural pathogenic fungi. In order to summarize the structural characteristics of marine natural products against agricultural pathogenic fungi, this review systematically overview the activities against agricultural pathogenic fungi of 198 secondary metabolites from different marine fungal sources. A total of 92 references published from 1998 to 2022 were cited. KEY POINTS: • Pathogenic fungi, which could cause damage to agriculture, were classified. • Structurally diverse antifungal compounds from marine-derived fungi were summarized. • The sources and distributions of these bioactive metabolites were analyzed.

Chemical diversity, medicinal potentialities, biosynthesis, and pharmacokinetics of anthraquinones and their congeners derived from marine fungi: a comprehensive update

Marine fungi receive excessive attention as prolific producers of structurally unique secondary metabolites, offering promising potential as substitutes or conjugates for current therapeutics, whereas existing research has only scratched the surface in terms of secondary metabolite diversity and potential industrial applications as only a small share of bioactive natural products have been identified from marine-derived fungi thus far. Anthraquinones derived from filamentous fungi are a distinct large group of polyketides containing compounds which feature a common 9,10-dioxoanthracene core, while their derivatives are generated through enzymatic reactions such as methylation, oxidation, or dimerization to produce a large variety of anthraquinone derivatives. A considerable number of reported anthraquinones and their derivatives have shown significant biological activities as well as highly economical, commercial, and biomedical potentialities such as anticancer, antimicrobial, antioxidant, and anti-inflammatory activities. Accordingly, and in this context, this review comprehensively covers the state-of-art over 20 years of about 208 structurally diverse anthraquinones and their derivatives isolated from different species of marine-derived fungal genera along with their reported bioactivity wherever applicable. Also, in this manuscript, we will present in brief recent insights centred on their experimentally proved biosynthetic routes. Moreover, all reported compounds were extensively investigated for their in-silico drug-likeness and pharmacokinetics properties which intriguingly highlighted a list of 20 anthraquinone-containing compounds that could be considered as potential drug lead scaffolds.

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.

Promising antimicrobials from Phoma spp.: progress and prospects

The increasing multidrug-resistance in pathogenic microbes and the emergence of new microbial pathogens like coronaviruses have necessitated the discovery of new antimicrobials to treat these pathogens. The use of antibiotics began after the discovery of penicillin by Alexander Fleming from Penicillium chrysogenum. This has attracted the scientific community to delve deep into the antimicrobial capabilities of various fungi in general and Phoma spp. in particular. Phoma spp. such as Phoma arachidicola, P. sorghina, P. exigua var. exigua, P. herbarum, P. multirostrata, P. betae, P. fimeti, P. tropica, among others are known to produce different bioactive metabolites including polyketides, macrosporin, terpenes and terpenoids, thiodiketopiperazines, cytochalasin derivatives, phenolic compounds, and alkaloids. These bioactive metabolites have already demonstrated their antimicrobial potential (antibacterial, antifungal, and antiviral) against various pathogens. In the present review, we have discussed the antimicrobial potential of secondary metabolites produced by different Phoma species. We have also deliberated the biogenic synthesis of eco-friendly antimicrobial silver nanoparticles from Phoma and their role as potential antimicrobial agents.

Growing multidrug-resistance and emerging pathogens need new antimicrobial drugs

Different species of Phoma produce antimicrobial metabolites

Phoma spp. are potential synthesizers of silver nanoparticles demonstrating antimicrobial activity.

Metabolites Produced by Fungi against Fungal Phytopathogens: Review, Implementation and Perspectives

Many fungi, especially endophytes, have been found to produce multiple benefits in their plant hosts, with many of these benefits associated with the protection of plants against fungal diseases. This fact could be used in the development of new bio-products that could gradually reduce the need for chemical fungicides, which have been associated with multiple health and environmental problems. However, the utilization of the living organism may present several issues, such as an inconsistency in the results obtained and more complicated management and application, as fungal species are highly influenced by environmental conditions, the type of relationship with the plant host and interaction with other microorganisms. These issues could be addressed by using the bioactive compounds produced by the fungus, in cases where they were responsible for positive effects, instead of the living organism. Multiple bioactive compounds produced by fungal species, especially endophytes, with antifungal properties have been previously reported in the literature. However, despite the large amount of these metabolites and their potential, extensive in-field application on a large scale has not yet been implemented. In the present review, the main aspects explaining this limited implementation are analyzed, and the present and future perspectives for its development are discussed.

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.

Antifungal Secondary Metabolites Produced by the Fungal Endophytes: Chemical Diversity and Potential Use in the Development of Biopesticides

Plant diseases caused by phytopathogenic fungi can lead to huge losses in the agricultural fields and therefore remain a continuous threat to the global food security. Chemical-based fungicides contributed significantly in securing crop production. However, indiscriminate application of fungicides has led to increased chemical resistance and potential risks to human health and environment. Thus, there is an urgent need for searching for new bioactive natural products and developing them into new biopesticides. Fungal endophytes, microorganisms that reside in the fresh tissues of living plants, are regarded as untapped sources of novel natural products for exploitation in agriculture and/or medicine. Chemical examination of endophytic fungi has yielded enormous antifungal natural products with potential use in the development of biopesticides. This review summarizes a total of 132 antifungal metabolites isolated from fungal endophytes in the past two decades. The emphasis is on the unique chemical diversity of these metabolic products, together with their relevant antifungal properties. Moreover, some "star molecules," such as griseofulvin and trichothecene, as well as their synthetic derivatives that possess high potential as candidates of new natural fungicides, are also presented herein.

Bioactive Compounds from Mangrove Endophytic Fungus and Their Uses for Microorganism Control

Mangroves are ecosystems with unique characteristics due to the high salinity and amount of organic matter that house a rich biodiversity. Fungi have aroused much interest as they are an important natural source for the discovery of new bioactive compounds, with potential biotechnological and pharmacological interest. This review aims to highlight endophytic fungi isolated from mangrove plant species and the isolated bioactive compounds and their bioactivity against protozoa, bacteria and pathogenic viruses. Knowledge about this type of ecosystem is of great relevance for its preservation and as a source of new molecules for the control of pathogens that may be of importance for human, animal and environmental health.

Pharmacological Potential of Fungal Endophytes Associated with Medicinal Plants: A Review

Endophytic microbes are microorganisms that colonize the intracellular spaces within the plant tissues without exerting any adverse or pathological effects. Currently, the world population is facing devastating chronic diseases that affect humans. The resistance of pathogens to commercial antibiotics is increasing, thus limiting the therapeutic potential and effectiveness of antibiotics. Consequently, the need to search for novel, affordable and nontoxic natural bioactive compounds from endophytic fungi in developing new drugs with multifunction mechanisms to meet human needs is essential. Fungal endophytes produce invaluable bioactive metabolic compounds beneficial to humans with antimicrobial, anticancer, antidiabetic, anti-inflammatory, antitumor properties, etc. Some of these bioactive compounds include pestacin, taxol, camptothecin, ergoflavin, podophyllotoxin, benzopyran, isopestacin, phloroglucinol, tetrahydroxy-1-methylxanthone, salidroside, borneol, dibenzofurane, methyl peniphenone, lipopeptide, peniphenone etc. Despite the aforementioned importance of endophytic fungal metabolites, less information is available on their exploration and pharmacological importance. Therefore, in this review, we shall elucidate the fungal bioactive metabolites from medicinal plants and their pharmacological potential.

Anthraquinone derivatives from a coral associated fungus Stemphylium lycopersici

Two new anthraquinone derivatives, alterporriol Y (1) and macrosporin 2-O-α-D-glucopyranoside (2), together with five known analogues (3-7) were isolated from the fungus Stemphylium lycopersici associated with the gorgonian coral Dichotella gemmacea collected from the South China Sea. Their structures were determined on the basis of detailed spectroscopic analysis and comparison with reported data. The absolute configurations were determined by the ECD method. In an in vitro cytotoxic assay, compound 3 and 4 showed potent effects against HCT-116 and MCF-7 cell lines. Compound 4 also exhibited cytotoxicity toward Huh7 stem cell-like cells.

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.

Marine-derived Phoma-the gold mine of bioactive compounds

The genus Phoma contains several species ubiquitously present in soil, water, and environment. There are two major groups of Phoma, viz., terrestrial and marine. After 1981 researchers all over the world have focused on marine-derived Phoma for their bioactive compounds. The marine Phoma are very rich sources for novel bioactive secondary metabolites, which could potentially be used as drugs. Recently, a large number of structurally unique metabolites with potential biological and pharmacological activities have been isolated from the marine Phoma species particularly Phoma herbarum, P. sorghina, and P. tropica. These metabolites mainly include diterpenes, enolides, lactones, quinine, phthalate, and anthraquinone. Most of these compounds possess antimicrobial, anticancer, radical scavenging, and cytotoxic properties. The present review has been focused on the general background of Phoma, current approaches used for its identification and their limitations, difference between terrestrial and marine Phoma species. In addition, this review summarizes the novel bioactive compounds derived from marine Phoma and their biological activities.

Novel Salt-Tolerant Xylanase from a Mangrove-Isolated Fungus Phoma sp. MF13 and Its Application in Chinese Steamed Bread

A novel glycosyl hydrolase family 11 xylanase gene, xynMF13A, was cloned from Phoma sp. MF13, a xylanase-producing fungus isolated from mangrove sediment. xynMF13A was heterologously expressed in Pichia pastoris, and the recombinant XynMF13A (rXynMF13A) was purified by Ni-affinity chromatography. The temperature and pH optima of purified rXynMF13A were 45 °C and pH 5.0, respectively. rXynMF13A showed a high level of salt tolerance, with maximal enzyme activity being seen at 0.5 M NaCl and as much as 53% of maximal activity at 4 M NaCl. The major rXynMF13A hydrolysis products from corncob xylan were xylobiose, xylotriose, xylotetraose, and xylopentaose, but no xylose was found. These hydrolysis products suggest an important potential for XynMF13A in the production of xylooligosaccharides (XOs). Furthermore, rXynMF13A had beneficial effects on Chinese steamed bread production, by increasing specific volume and elasticity while decreasing hardness and chewiness. These results demonstrate XynMF13A to be a novel xylanase with potentially significant applications in baking, XOs production, and seafood processing.

Penochalasin K, a new unusual chaetoglobosin from the mangrove endophytic fungus Penicillium chrysogenum V11 and its effective semi-synthesis

A new chaetoglobosin, penochalasin K (1) bearing an unusual six-cyclic 6/5/6/5/6/13 fused ring system, along with the known analogues, chaetoglobosin C (2), penochalasin I (3), and chaetoglobosin A (4) were isolated from the solid culture of the mangrove endophytic fungus Penicillium chrysogenum V11. Their structures were elucidated by 1D, 2D NMR spectroscopic analysis and high resolution mass spectroscopic data. The absolute configuration of compound 1 was determined by comparing the theoretical and experimental electronic circular dichroism curves. Compound 1 displayed significant inhibitory activities against Colletotrichum gloeosporioides and Rhizoctonia solani (MICs=6.13, 12.26μM, respectively), which was better than those of carbendazim, and exhibited potent cytotoxicity against MDA-MB-435, SGC-7901 and A549 cells (IC₅₀<10μM). An effective biomimetic transformation of chaetoglobosin C (2)/chaetoglobosin A (4) into penochalasin K (1)/penochalasin I (3) was developed, which provided a simple method for the semi-synthesis of chaetoglobosins with a six-cyclic 6/5/6/5/6/13 fused system formed by the connectivity of C-5 and C-2' from their corresponding epoxide analogues.