Anti-phytopathogenic activity of sporothriolide, a metabolite from endophyte Nodulisporium sp. A21 in Ginkgo biloba

Why Do We Need Alternative Methods for Fungal Disease Management in Plants?

Fungal pathogens pose a major threat to food production worldwide. Traditionally, chemical fungicides have been the primary means of controlling these pathogens, but many of these fungicides have recently come under increased scrutiny due to their negative effects on the health of humans, animals, and the environment. Furthermore, the use of chemical fungicides can result in the development of resistance in populations of phytopathogenic fungi. Therefore, new environmentally friendly alternatives that provide adequate levels of disease control are needed to replace chemical fungicides-if not completely, then at least partially. A number of alternatives to conventional chemical fungicides have been developed, including plant defence elicitors (PDEs); biological control agents (fungi, bacteria, and mycoviruses), either alone or as consortia; biochemical fungicides; natural products; RNA interference (RNAi) methods; and resistance breeding. This article reviews the conventional and alternative methods available to manage fungal pathogens, discusses their strengths and weaknesses, and identifies potential areas for future research.

Bioactive compounds and biomedical applications of endophytic fungi: a recent review

Human life has been significantly impacted by the creation and spread of novel species of antibiotic-resistant bacteria and virus strains that are difficult to manage. Scientists and researchers have recently been motivated to seek out alternatives and other sources of safe and ecologically friendly active chemicals that have a powerful and effective effect against a wide variety of pathogenic bacteria as a result of all these hazards and problems. In this review, endophytic fungi and their bioactive compounds and biomedical applications were discussed. Endophytes, a new category of microbial source that can produce a variety of biological components, have major values for study and broad prospects for development. Recently, endophytic fungi have received much attention as a source for new bioactive compounds. In addition, the variety of natural active compounds generated by endophytes is due to the close biological relationship between endophytes and their host plants. The bioactive compounds separated from endophytes are usually classified as steroids, xanthones, terpenoids, isocoumarins, phenols, tetralones, benzopyranones and enniatines. Moreover, this review discusses enhancement methods of secondary metabolites production by fungal endophytes which include optimization methods, co-culture method, chemical epigenetic modification and molecular-based approaches. Furthermore, this review deals with different medical applications of bioactive compounds such as antimicrobial, antiviral, antioxidant and anticancer activities in the last 3 years.

Antifungal alkaloids from the branch-leaves of Clausena lansium Lour. Skeels (Rutaceae)

BACKGROUND

The rational utilization of botanical secondary metabolites is one of the strategies to reduce the application of chemical fungicides. The extensive biological activities of Clausena lansium indicate that it has the potential to develop botanical fungicides.

RESULTS

A systematic investigation on the antifungal alkaloids from C. lansium branch-leaves following bioassay-guided isolation was implemented. Sixteen alkaloids, including two new and nine known carbazole alkaloids, one known quinoline alkaloid and four known amides, were isolated. Compounds 4, 7, 12 and 14 showed strong antifungal activity on Phytophthora capsiciwith EC₅₀ values ranging from 50.67 to 70.82 μg mL^-1 . Compounds 1, 3, 8, 10, 11, 12 and 16 displayed different degrees of antifungal activity against Botryosphaeria dothidea with EC₅₀ values ranging from 54.18 to 129.83 μg mL^-1 . It was reported for the first time that these alkaloids had antifungal effects on P. capsici or B. dothidea, and their structure-activity relationships were further discussed systematically. Additionally, among all alkaloids, dictamine (12) had the strongest antifungal activities against P. capsici (EC₅₀  = 50.67 μg mL^-1 ) and B. dothidea (EC₅₀  = 54.18 μg mL^-1 ), and its physiological effects on P. capsici and B. dothidea also were further evaluated.

CONCLUSION

Capsicum lansium is a potential source of antifungal alkaloids, and C. lansium alkaloids had the potential as lead compounds of botanical fungicides in the development of new fungicides with novel action mechanism. © 2023 Society of Chemical Industry.

An epigenetic modifier enhances the generation of anti-phytopathogenic compounds from the endophytic fungus Chaetomium globosporum of Euphorbia humifusa

Endophytic fungi are striking resources rich in bioactive structures with agrochemical significance. In order to maximize the opportunity of search for bioactive compounds, chemical epigenetic manipulation was introduced to enhance the structural diversity of the fungal products, and an UPLC-ESIMS and bioassay-guided separation was used to detect novel bioactive metabolites. Consequently, four previously undescribed compounds including two cyclopentenones (globosporins A and B) and two monoterpenoid indole alkaloids (globosporines C and D), as well as three known compounds, were isolated from the endophytic fungus Chaetomium globosporum of Euphorbia humifusa by exposure to a DNA methyltransferase inhibitor 5-azacytidine. Their structures including the absolute configurations were elucidated by the analysis of NMR spectroscopic data, HRESIMS, and TD-DFT-ECD calculations. The indole alkaloids (globosporines C and D) showed antimicrobial activities against three phytopathogenic microbes (Xanthomonas oryzae pv. oryzae, X. oryzae pv. oryzicola, and Pseudomonas syringae pv. lachrymans) with MICs in the range of 14-72 μg/mL. Mostly, globosporine D was proved to be potently anti-phytopathogenic against X. oryzae pv. oryzae in vitro and in vivo, which suggested that it has the potential to be developed as a candidate for the prevention of rice bacterial leaf blight. This work provides an efficient and environmentally friendly approach for expanding fungal products with agricultural importance.

Endophytic Fungi: Key Insights, Emerging Prospects, and Challenges in Natural Product Drug Discovery

Plant-associated endophytes define an important symbiotic association in nature and are established bio-reservoirs of plant-derived natural products. Endophytes colonize the internal tissues of a plant without causing any disease symptoms or apparent changes. Recently, there has been a growing interest in endophytes because of their beneficial effects on the production of novel metabolites of pharmacological significance. Studies have highlighted the socio-economic implications of endophytic fungi in agriculture, medicine, and the environment, with considerable success. Endophytic fungi-mediated biosynthesis of well-known metabolites includes taxol from Taxomyces andreanae, azadirachtin A and B from Eupenicillium parvum, vincristine from Fusarium oxysporum, and quinine from Phomopsis sp. The discovery of the billion-dollar anticancer drug taxol was a landmark in endophyte biology/research and established new paradigms for the metabolic potential of plant-associated endophytes. In addition, endophytic fungi have emerged as potential prolific producers of antimicrobials, antiseptics, and antibiotics of plant origin. Although extensively studied as a “production platform” of novel pharmacological metabolites, the molecular mechanisms of plant–endophyte dynamics remain less understood/explored for their efficient utilization in drug discovery. The emerging trends in endophytic fungi-mediated biosynthesis of novel bioactive metabolites, success stories of key pharmacological metabolites, strategies to overcome the existing challenges in endophyte biology, and future direction in endophytic fungi-based drug discovery forms the underlying theme of this article.

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.

Endophytic Bacterial Communities of Ginkgo biloba Leaves During Leaf Developmental Period

Plant-specialized secondary metabolites have ecological functions in mediating interactions between plants and their entophytes. In this study, high-throughput gene sequencing was used to analyze the composition and abundance of bacteria from Ginkgo leaves at five different sampling times. The results indicated that the bacterial community structure varied during leaf developmental stage. Bacterial diversity was observed to be the highest at T2 stage and the lowest at T1 stage. Proteobacteria, Firmicutes, Actinobacteria, Chloroflexi, Cyanobacteria, and Bacteroidetes were found as the dominant phyla. The major genera also showed consistency across sampling times, but there was a significant variation in their abundance, such as Bacillus, Lysinibacillus, and Staphylococcus. Significant correlations were observed between endophytic bacteria and flavonoids. Especially, Staphylococcus showed a significant positive correlation with quercetin, and changes in the abundance of Staphylococcus also showed a strong correlation with flavonoid content. In order to determine the effect of flavonoids on endophytic bacteria of Ginkgo leaves, an extracorporeal culture of related strains (a strain of Staphylococcus and a strain of Deinococcus) was performed, and it was found that the effect of flavonoids on them remained consistent. The predicted result of Tax4Fun2 revealed that flavonoids might lead to a lower abundance of endophytic microorganisms, which further proved the correlation between bacterial communities and flavonoids. This study provided the first insight into the bacterial community composition during the development of Ginkgo leaves and the correlation between the endophytic bacteria and flavonoids.

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.

Eremophilane Sesquiterpenes and Benzene Derivatives from the Endophyte Microdiplodia sp. WGHS5

Three new eremophilane sesquiterpenes phomadecalins G-I (1-3) and two new benzene derivatives microdiplzenes A and B (12 and 13), together with nine known eremophilane sesquiterpenes (4-11 and 14) were isolated from an endophytic fungus, Microdiplodia sp. WGHS5. Their structures were elucidated by the interpretation of HR-ESI-MS and NMR data; meanwhile, the absolute configurations of new compounds were determined on the base of ECD calculations. All compounds were evaluated for the antimicrobial activities and antiproliferative effect on human gastric cancer cell lines (BGC-823).

Enantiomeric Dibenzo-α-Pyrone Derivatives from Alternaria alternata ZHJG5 and Their Potential as Agrochemicals

Three pairs of enantiomeric dibenzo-α-pyrone derivatives (1-3) including two pairs of new racemates (±)-alternaone A (1) and (±)-alternaone B (2) and one new enantiomer (-)-alternatiol (3), together with five known compounds (4-8) were isolated from the fungus Alternaria alternata ZHJG5. Their structures were confirmed by spectroscopic data and single-crystal X-ray diffraction analysis. All enantiomers were separated via chiral high-performance liquid chromatography, with their configurations determined by electronic circular dichroism calculation. Biogenetically, a key epoxy-rearrangement step was proposed for the formation of skeletons in 1-3; (+) 1, (-)-1, and 5 presented moderate antibacterial inhibition on phytopathogenic bacteria Xanthomonas oryzae pv. oryzae and Xanthomonas oryzae pv. oryzicola. In the antifungal test, compounds 7 and 8 showed a moderate protective effect against Botrytis cinerea in vivo.

Antifungal meroterpenes and dioxolanone derivatives from plant-associated endophytic fungus Phyllosticta sp. WGHL2

Four new meroterpenes named as guignardones U-X (1-4), along with eleven known meroterpenes (5-15) and three known dioxolanone derivatives (16-18), were obtained from the endophytic fungus Phyllosticta sp. WGHL2. The structural elucidation was conducted by HRESIMS, NMR, single crystal X-ray diffraction, along with ECD calculations and comparison. In antifungal tests, compound 16 possessed broad-spectrum antifungal activities against Rhizoctonia solani, Fusarium graminearum and Botrytis cinerea with inhibition ratio of 48.43%, 40.98%, and 49.53% at 50 μg/mL, respectively. Moreover, compound 16 showed moderate protective effect against B. cinerea in vivo at 200 μg/mL and exhibited effective inhibition on the spore germination of B. cinerea.

The sporothriolides. A new biosynthetic family of fungal secondary metabolites

The biosynthetic gene cluster of the antifungal metabolite sporothriolide 1 was identified from three producing ascomycetes: Hypomontagnella monticulosa MUCL 54604, H. spongiphila CLL 205 and H. submonticulosa DAOMC 242471. A transformation protocol was established, and genes encoding a fatty acid synthase subunit and a citrate synthase were simultaneously knocked out which led to loss of sporothriolide and sporochartine production. In vitro reactions showed that the sporochartines are derived from non-enzymatic Diels-Alder cycloaddition of 1 and trienylfuranol A 7 during the fermentation and extraction process. Heterologous expression of the spo genes in Aspergillus oryzae then led to the production of intermediates and shunts and delineation of a new fungal biosynthetic pathway originating in fatty acid biosynthesis. Finally, a hydrolase was revealed by in vitro studies likely contributing towards self-resistance of the producer organism.

Itaconic acid derivatives: structure, function, biosynthesis, and perspectives

Itaconic acid possessing a vinylidene group, which is mainly produced by fungi, is used as a biobased platform chemical and shows distinctive bioactivities. On the other hand, some fungi and lichens produce itaconic acid derivatives possessing itaconic acid skeleton, and the number of the derivatives is currently more than seventy. Based on the molecular structures, they can be categorized into two groups, alkylitaconic acids and α-methylene-γ-butyrolactones. Interestingly, some itaconic acid derivatives show versatile functions such as antimicrobial, anti-inflammatory, antitumor, and plant growth-regulating activities. The vinylidene group of itaconic acid derivatives likely participates in these functions. It is suggested that α-methylene-γ-butyrolactones are biosynthesized from alkylitaconic acids which are first biosynthesized from acyl-CoA and oxaloacetic acid. Some modifying enzymes such as hydroxylase and dehydratase are likely involved in the further modification after biosynthesis of their precursors. This contributes to the diversity of itaconic acid derivatives. In this review, we summarize their structures, functions, and biosynthetic pathways together with a discussion of a strategy for the industrial use. KEY POINTS: • Itaconic acid derivatives can be categorized into alkylitaconic acids and α-methylene-γ-butyrolactones. • The vinylidene group of itaconic acid derivatives likely participates in their versatile function. • It is suggested that α-methylene-γ-butyrolactones are biosynthesized from alkylitaconic acids which are first synthesized from acyl-CoA and oxaloacetic acid.

Nematicidal metabolites from endophytic fungus Chaetomium globosum YSC5

Management of nematodes is a very hectic job due to a highly diverse group of organisms. To find lead compounds for new nematicide development, five metabolites (1-5) were isolated from the culture broth of Chaetomium globosum YSC5 and tested for nematicidal activities against the second stage juveniles (J2s) of Meloidogyne javanica. The results revealed that chaetoglobosin A (1), chaetoglobosin B (2) and flavipin (3) exhibited strong adverse effects (91.6, 83.8 and 87.4%, respectively) on J2 mortality at 200 μg/mL with LC50 values of 88.4, 107.7 and 99.2 μg/mL after 72 h, respectively, while 3-methoxyepicoccone (4) and 4,5,6-trihydroxy-7-methylphthalide (5) showed moderate effects (78.0 and 75.5%, respectively) with LC50 values of 124.0 and 131.6 μg/mL, respectively. Furthermore, in pot assay compounds 1 and 2 appeared to be promising metabolites at 200 μg/mL that significantly reduced nematode reproduction and showed a positive influence on plant growth. Our findings could be helpful for development of new potential bio-based pesticides for integrated management of plant-parasitic nematode.

Microbial Screening Based on the Mizoroki-Heck Reaction Permits Exploration of Hydroxyhexylitaconic-Acid-Producing Fungi in Soils

Recently, we developed a unique microbial screening method based on the Mizoroki–Heck reaction for itaconic acid (IA)-producing fungi. This method revealed that 37 out of 240 fungal strains isolated from soils produce vinyl compounds, including IA. In this study, we further characterized these compounds in order to verify that the screening method permits the isolation of fungi that produce other vinyl compounds, excluding IA. HPLC analysis showed that 11 out of 37 isolated strains produced IA, similar to Aspergillus terreus S12-1. Surprisingly, the other 8 isolated strains produced two vinyl compounds with HPLC retention times different from that of IA. From these strains, the vinyl compounds of Aspergillus niger S17-5 were characterized. Mass spectrometric and NMR analyses showed that they were identical to 8-hydroxyhexylitaconic acid (8-HHIA) and 9-HHIA. This finding showed that 8-HHIA- and 9-HHIA-producing fungi, as well as IA-producing fungi, are ubiquitously found in soils. Neither 8-HHIA nor 9-HHIA showed antibacterial or anti-inflammatory activities. Interestingly, 8-HHIA and 9-HHIA showed cytotoxicity against the human cervical cancer cell line (HeLa) and human diploid cell line (MRC-5), and MRC-5 only, respectively, compared to IA at the same concentration. This study indicates that the screening method could easily discover fungi producing 8-HHIA and 9-HHIA in soils.

Anti-phytopathogenic activity and the possible mechanisms of action of isoquinoline alkaloid sanguinarine

Isoquinoline alkaloids possess broad pharmacological activities. In this study, the antifungal activity of twelve isoquinoline alkaloids, including berberine (1), jatrorrhizine (2), coptisine (3), corydaline (4), tetrahydroberberine (5), chelidonine (6), dihydrosanguinarine (7), chelerythrine (8), sanguinarine (9), palmatine (10), tetrahydropalmatine (11) and columbamine (12) were evaluated against eight plant pathogenic fungi in vitro. All the tested compounds showed varying degrees of inhibition against the eight tested plant fungi. Among them, sanguinarine exhibited high antifungal activity (EC₅₀ ranging from 6.96-59.36 μg/mL). It displayed the best inhibitory activity against Magnaporthe oryzae (EC₅₀ = 6.96 μg/mL), compared with azoxystrobin (EC₅₀ = 12.04 μg/mL), and significantly suppressed spore germination of M. oryzae with the inhibition rate reaching 100% (50 μg/mL). The optical microscopy and scanning electron microscopy observations revealed that after treating M. oryzae mycelia with sanguinarine at 10 μg/mL, the mycelia appeared curved, collapsed and the cell membrane integrity was eventually damaged. Furthermore, the reactive oxygen species production, mitochondrial membrane potential and nuclear morphometry of mycelia had been changed, and the membrane function and cell proliferation of mycelia were destroyed. These results will enrich our insights into action mechanisms of antifungal activity of sanguinarine against M. oryzae.

Generation of Indoles with Agrochemical Significance through Biotransformation by Chaetomium globosum

Six new (1-6) and two known (7 and 8) indole alkaloids were produced by the marine fish-derived fungus Chaetomium globosum 1C51 through biotransformation. The structures of these alkaloids were elucidated by a combination of MS, NMR, and X-ray crystallography analyses. Chaetoindolone A (1) was shown to inhibit the growth of the rice-pathogenic bacteria Xanthomonas oryzae pv. oryzae (xoo) both in vitro and in vivo. Chaetogline A (7) was found to be fungicidal against Sclerotinia sclerotiorum, a pathogen causing rape sclerotinia rot. Collectively, this work provides access to new indole alkaloids with potential agrochemical significance.

Diversity of biologically active secondary metabolites from endophytic and saprotrophic fungi of the ascomycete order Xylariales

Covering: up to December 2017 The diversity of secondary metabolites in the fungal order Xylariales is reviewed with special emphasis on correlations between chemical diversity and biodiversity as inferred from recent taxonomic and phylogenetic studies. The Xylariales are arguably among the predominant fungal endophytes, which are the producer organisms of pharmaceutical lead compounds including the antimycotic sordarins and the antiparasitic nodulisporic acids, as well as the marketed drug, emodepside. Many Xylariales are "macromycetes", which form conspicuous fruiting bodies (stromata), and the metabolite profiles that are predominant in the stromata are often complementary to those encountered in corresponding mycelial cultures of a given species. Secondary metabolite profiles have recently been proven highly informative as additional parameters to support classical morphology and molecular phylogenetic approaches in order to reconstruct evolutionary relationships among these fungi. Even the recent taxonomic rearrangement of the Xylariales has been relying on such approaches, since certain groups of metabolites seem to have significance at the species, genus or family level, respectively, while others are only produced in certain taxa and their production is highly dependent on the culture conditions. The vast metabolic diversity that may be encountered in a single species or strain is illustrated based on examples like Daldinia eschscholtzii, Hypoxylon rickii, and Pestalotiopsis fici. In the future, it appears feasible to increase our knowledge of secondary metabolite diversity by embarking on certain genera that have so far been neglected, as well as by studying the volatile secondary metabolites more intensively. Methods of bioinformatics, phylogenomics and transcriptomics, which have been developed to study other fungi, are readily available for use in such scenarios.

New Alkylitaconic Acid Derivatives from Nodulisporium sp. A21 and Their Auxin Herbicidal Activities on Weed Seeds

Five alkylitaconic acid (AA) derivatives, including two novel compounds, epideoxysporothric acid (2) and sporochartine F (5), and three known compounds, deoxysporothric acid (1), deoxyisosporothric acid (3), and 1-undecen-2,3-dicarboxylic acid (4), were obtained from the fermentation culture of the endophytic fungus Nodulisporium sp. A21. The auxin herbicidal activities of compounds 1-4 against weed seeds were investigated under laboratory conditions. In general, the tested compounds displayed radicle growth promoting activity at low doses and inhibitory activity at higher doses. Compounds 1 and 2 could significantly inhibit the radicle growth of dicotyledon weeds, Eclipta prostrata and Veronica persica, at a concentration range from 50 to 200 μg mL^-1, while 3 notably stimulated radicle growth at the same concentration range. The results suggested that these AA derivatives have the potential to be used as the lead scaffold for novel auxin herbicide development. In addition, the biosynthetic pathways of 1-4 were deduced based on ¹³C labeling experiment.

Synthesis and characterization of novel chiral derivatizing agents containing β-keto-anthracene adducts (KAAs) by 1H-NMR: aromatic influence and chiral alcohol absolute configuration determination

New chiral derivatizing agents and the effect of aromatic rings were investigated for absolute configuration of chiral alcohols via¹H-NMR.

Nigrosporanenes C and D, two new cyclohexene derivatives from the enphytic fungus Nigrospora oryzae S4

Two new cyclohexene derivatives, nigrosporanenes C and D (1 and 2), together with three known compounds (3-5), were isolated from the culture of an endophyte Nigrospora oryzae S4. Their structures were characterized by a combination of detailed spectroscopic analysis and comparison of their NMR data with those reported in the literature. All compounds were tested for anti-phytopathogenic activity, however, none of them showed activity at a concentration of 20 μM.

Notopterygium incisum extract and associated secondary metabolites inhibit apple fruit fungal pathogens

In the search for antifungal lead compounds from natural resources, Notopterygium incisum, a medicine plant only distributed in China, showed antifungal potential against apple fruit pathogens. Based on the bioassay-guided isolation, chromatography fraction 6 of the ethyl acetate partition exhibited significant in vitro and in vivo antifungal activities against apple fruit pathogens. Furthermore, nine antifungal secondary metabolites, including five linear furocoumarins (1-5), two phenylethyl esters (6-7), one falcarindiol (8), and one sesquiterpenoid (9), were isolated and elucidated from fraction 6. Compound 5 is a new metabolite, and 9 isolated from the genus Notopterygium for the first time. The purified compounds (1-9) were firstly reported to exhibit antifungal activities against apple fruit pathogens of Colletotrichum gloeosporioides and Botryosphaeria dothidea with the MIC values ranging from 8 to 250 mg L^-1, especially 8 of 16 and 8 mg L^-1, respectively. Moreover, 8 could inhibit the spore germination and new sporulation of B. dothidea, as well as enhance the membrane permeabilization of B. dothidea spores. This was the first investigation for the antifungal components against apple fruit pathogens from Notopterygium incisum, which has great potential to be developed into bio-fungicides.

Endophytic Fungi: A Source of Potential Antifungal Compounds

The emerging and reemerging forms of fungal infections encountered in the course of allogeneic bone marrow transplantations, cancer therapy, and organ transplants have necessitated the discovery of antifungal compounds with enhanced efficacy and better compatibility. A very limited number of antifungal compounds are in practice against the various forms of topical and systemic fungal infections. The trends of new antifungals being introduced into the market have remained insignificant while resistance towards the introduced drug has apparently increased, specifically in patients undergoing long-term treatment. Considering the immense potential of natural microbial products for the isolation and screening of novel antibiotics for different pharmaceutical applications as an alternative source has remained largely unexplored. Endophytes are one such microbial community that resides inside all plants without showing any symptoms with the promise of producing diverse bioactive molecules and novel metabolites which have application in medicine, agriculture, and industrial set ups. This review substantially covers the antifungal compounds, including volatile organic compounds, isolated from fungal endophytes of medicinal plants during 2013⁻2018. Some of the methods for the activation of silent biosynthetic genes are also covered. As such, the compounds described here possess diverse configurations which can be a step towards the development of new antifungal agents directly or precursor molecules after the required modification.

Sporothriolide-Related Compounds from the Fungus Hypoxylon monticulosum CLL-205 Isolated from a Sphaerocladina Sponge from the Tahiti Coast

Two sporothriolide-related compounds were obtained from an extract of the fungus Hypoxylon monticulosum CLL-205, isolated from a Sphaerocladina sponge collected from the Tahiti coast. Compound 2 is a deoxy analogue of sporothric acid (4). Compound 3 is a newly reported unusual scaffold combining sporothriolide (1) and trienylfuranol A (5) moieties, through a Diels-Alderase-type reaction. Various experimental and analytical arguments supported the biocatalytic origin of compound 3. The structures of the isolated compounds were elucidated using 1D and 2D NMR, HRMS, and IR data. The structure and the absolute configuration of 3 were unambiguously confirmed by a single-crystal X-ray diffraction analysis.

Terphenyl derivatives and drimane - Phathalide/isoindolinones from Hypoxylon fendleri BCC32408

The genus Hypoxylon, a member of the family Xylariaceae, has been known to produce significant secondary metabolites in terms of chemical diversity. Moreover, the compounds isolated can also be used as chemotaxonomic characters for differentiation among the two sections, which are sect. Annulata and sect. Hypoxylon. In our continuing chemical screening programme for novel compounds, the crude extracts of H. fendleri BCC32408 gave significant chemical profiles in HPLC analyses. Thus, the chemical investigation of these crude extracts was then carried out. The investigation led to the isolation of ten previously undescribed compounds including three terphenylquinones (fendleryls A - C), one terphenyl (fendleryl D), and six novel drimane - phthalide-type lactone/isoindolinones derivatives (fendlerinines A - F) along with seven known compounds (2-O-methylatromentin, rickenyl E, atromentin, rickenyls C - D, (+)-ramulosin, and O-hydroxyphenyl acetic acid). The chemical structures were determined on the basis of spectroscopic analyses, including 1D, 2D NMR and high-resolution mass spectrometry, as well as chemical transformations. In addition, these isolated compounds were assessed for antimicrobial activity including antimalarial (against Plasmodium falciparum, K-1 strain), antifungal (against Candida albicans), antibacterial (against Bacillus cereus) activities. Cytotoxicity against both cancerous (KB, MCF-7, NCI-H187) and non-cancerous (Vero) cells of these compounds were also evaluated.

Synthesis and Biological Evaluation of Benzimidazole Phenylhydrazone Derivatives as Antifungal Agents against Phytopathogenic Fungi

A series of benzimidazole phenylhydrazone derivatives (6a–6ai) were synthesized and characterized by ¹H-NMR, ESI-MS, and elemental analysis. The structure of 6b was further confirmed by single crystal X-ray diffraction as (E)-configuration. All the compounds were screened for antifungal activity against Rhizoctonia solani and Magnaporthe oryzae employing a mycelium growth rate method. Compound 6f exhibited significant inhibitory activity against R. solani and M. oryzae with the EC₅₀ values of 1.20 and 1.85 μg/mL, respectively. In vivo testing demonstrated that 6f could effectively control the development of rice sheath blight (RSB) and rice blast (RB) caused by the above two phytopathogens. This work indicated that the compound 6f with a benzimidazole phenylhydrazone scaffold could be considered as a leading structure for the development of novel fungicides.