Polyketides from the endophytic fungus Phomopsis sp. sh917 by using the one strain/many compounds strategy

New Phthalides and Isochromanone Derivatives from the Deep-Sea-Derived Fungus Penicillium bialowiezense A3

Two new phthalide derivatives, namely bialowalides A (1) and B (8), and one new isochromanone analogue biourgalide C (11), together with 8 known phthalides (2-7, 9, and 10) as well as two known isochromanones (12 and 13) were discovered from the EtOAc extract of the deep-sea-derived fungus Penicillium bialowiezense A3. The structures were resolved on the basis of extensive spectroscopic analyses (NMR and HRESIMS data), in association with the modified Mosher's method and ECD data for the determination of the absolute configurations. All isolated secondary metabolites (1-13) were tested their antiviral activities against the SARS-CoV-2 trVLP pseudovirus at a concentration of 25 μM. As a result, compounds 1, 5, 11, and 12 exhibited the inhibitory effects against the luminescence at 46.2 %, 39.6 %, 45.5 %, and 48.8 %, respectively.

Novel compound, pleuropyronine, and other polyketides isolated from the edible mushroom Pleurotus ostreatus suppress bacterial biofilm formation

An increase in the number of drug-resistant microbes is a major threat to human health. Bacterial drug resistance is mostly mediated by biofilm formation. In this study, the culture filtrate from the edible mushroom, Pleurotus ostreatus, was fractionated to isolate compounds that inhibit the biofilm formation of six pathogenic bacteria. Notably, we isolated compounds 1-6 using bioassay-guided chromatographic separations. Spectroscopic and X-ray diffraction analyses identified 1 as a novel fused bicyclic pyrone-furan, named pleuropyronine, whereas 2-6 were known polyketides. Pleuropyronine inhibited biofilm formation in four Gram-negative bacteria, with IC50 values ranging from 5.4 to 8.7 µg/mL, whereas 2-6 exhibited IC50 values between 1.0 and 5.3 µg/mL against five bacteria. Additionally, pleuropyronine bioactivity was confirmed by the inhibition of exopolysaccharide and biofilm formation induced by C6-homoserine lactone. Thus, this may serve as a pioneering study on the pharmacological potential of isolated compounds, offering valuable insights for future research.

Three new isocoumarin analogues from an endolichenic fungus Aspergillus flavus CPCC 400810

Five isocoumarin derivatives including three new compounds, aspermarolides A-C (1-3), and two known analogues, 8-methoxyldiaporthin (4) and diaporthin (5) were obtained from the culture extract of Aspergillus flavus CPCC 400810. The structures of these compounds were elucidated by spectroscopic methods. The double bond geometry of 1 and 2 were assigned by the coupling constants. The absolute configuration of 3 was determined by electronic circular dichroism experiment. All compounds showed no cytotoxic activities against the two human cancer cells HepG2 and Hela.

Exploring the antioxidant potential of endophytic fungi: a review on methods for extraction and quantification of total antioxidant capacity (TAC)

Endophytic fungi have emerged as a significant source of natural products with remarkable bioactivities. Recent research has identified numerous antioxidant molecules among the secondary metabolites of endophytic fungi. These organisms, whether unicellular or micro-multicellular, offer the potential for genetic manipulation to enhance the production of these valuable antioxidant compounds, which hold promise for promoting health, vitality, and various biotechnological applications. In this study, we provide a critical review of methods for extracting, purifying, characterizing, and estimating the total antioxidant capacity (TAC) of endophytic fungi metabolites. While many endophytes produce metabolites similar to those found in plants with established symbiotic associations, we also highlight the existence of novel metabolites with potential scientific interest. Additionally, we discuss how advancements in nanotechnology have opened new avenues for exploring nanoformulations of endophytic metabolites in future studies, offering opportunities for diverse biological and industrial applications.

Fungal Naphthalenones; Promising Metabolites for Drug Discovery: Structures, Biosynthesis, Sources, and Pharmacological Potential

Fungi are well-known for their abundant supply of metabolites with unrivaled structure and promising bioactivities. Naphthalenones are among these fungal metabolites, that are biosynthesized through the 1,8-dihydroxy-naphthalene polyketide pathway. They revealed a wide spectrum of bioactivities, including phytotoxic, neuro-protective, cytotoxic, antiviral, nematocidal, antimycobacterial, antimalarial, antimicrobial, and anti-inflammatory. The current review emphasizes the reported naphthalenone derivatives produced by various fungal species, including their sources, structures, biosynthesis, and bioactivities in the period from 1972 to 2021. Overall, more than 167 references with 159 metabolites are listed.

Xylaria feejeensis, SRNE2BP a Fungal Endophyte with Biocontrol Properties to Control Early Blight and Fusarium Wilt Disease in Tomato and Plant Growth Promotion Activity

Over the past decade endophytic fungi have been known as a source of secondary metabolites with the ability to act as a biocontrol agents. Xylaria feejeensis, SRNE2BP a fungal endophyte isolated from a mangrove tree exhibited antagonistic activity against two fungal pathogens of tomato. Crude extract of X. feejeensis SRNE2BP significantly inhibited Fusarium oxysporum MFLUCC 19-0157 growth as shown approximately 60-75% in in vitro and in situ assays. Both assays showed that the endophyte also inhibited mycelium formation of Alternaria solani MFLUCC 19-0093 by 56% and 87%, respectively. The half maximal inhibitory concentration of X. feejeensis SRNE2BP crude extract against A. solani and F. oxysporum was approximately 7 mg/l. Crude extract and mycelium of X. feejeensis SRNE2BP showed potential in controlling early blight and fusarium wilt disease in tomato, respectively. Seedlings from seeds coated with crude extract of X. feejeensis SRNE2BP had lower disease severity (31.71%) of early blight disease compared to un-treated seeds (57.13%). Soil treated with 10% endophytic mycelium not only reduced fusarium wilt in tomato plant (55.55% severity compared with 91.66% in un-treated soil) but also promoted seed emergence and growth of tomato. Structure analysis revealed that 12 secondary metabolites, especially mellein derivatives, are major components of the crude extract of X. feejeensis SRNE2BP. These compounds could be responsible for antifungal activities; however, further study is required. Our findings strongly suggest that colonization with this fungal endophyte can be beneficial to the host plant especially with regards to plant growth promotion and broad antagonistic activity.

Acetylcholinesterase and butyrylcholinesterase inhibition by nectriapyrone and tryptophol isolated from endophytic fungus Phomopsis sp

Cholinesterase (ChE) inhibitors are currently the main drugs used to treat the cognitive symptoms of Alzheimer's disease (AD). Dual cholinesterase inhibitors, that is, compounds capable of inhibiting both acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE), are considered a new potential approach for the long-term treatment of patients with AD. We evaluated the ethyl acetate extract of Phomopsis sp., grown in liquid medium malt extract and potato dextrose (PDB), an endophyte isolated from the Brazilian medicinal plant Hancornia speciosa. The anticholinesterase (AChE) and butyrylcholinesterase (BuChE) activities were evaluated. The extracts exhibited dual action against AChE and BuChE. The compounds isolated from these extracts, nectriapyrone (1) and tryptophol (2), showed inhibitory action on BuChE (IC50 = 29.05 and 34.15 μM respectively), being selective towards BuChE. The discovery of selective BuChE inhibitors is extremely important for the development of drugs that can be used in the treatment of patients diagnosed with AD.

Chlorinated metabolites with antibacterial activities from a deep-sea-derived Spiromastix fungus

Chromatographic separation of the solid cultures of a deep-sea-derived Spiromastix fungus (MCCC 3A00308) resulted in the isolation of eight compounds. Their structures were identified on the basis of the spectroscopic data. Compounds 1–8 are classified as depsidone-type (1–4), isocoumarin-type (5 and 6), and benzothiazole-type (7 and 8), of which 1–7 are new compounds and 1–3 along with 5 and 6 are chlorinated. Compound 3 is characterized by trichlorination and shows potent activities against Gram-positive pathogenic bacteria including Staphylococcus aureus ATCC 25923, Bacillus thuringiensis ATCC 10792, and Bacillus subtilis CMCC 63501, with minimum inhibitory concentration (MIC) values ranging from 0.5 to 1.0 μg mL⁻¹. This study extends the chemical diversity of chlorinated natural products from marine-derived fungi and provides a promising lead for the development of antibacterial agents.

Chromatographic separation of the solid cultures of a deep-sea-derived Spiromastix fungus (MCCC 3A00308) resulted in the isolation of five chlorinated compounds with antibacterial activities.

Bioactive Secondary Metabolites of the Genus Diaporthe and Anamorph Phomopsis from Terrestrial and Marine Habitats and Endophytes: 2010-2019

The genus Diaporthe and its anamorph Phomopsis are distributed worldwide in many ecosystems. They are regarded as potential sources for producing diverse bioactive metabolites. Most species are attributed to plant pathogens, non-pathogenic endophytes, or saprobes in terrestrial host plants. They colonize in the early parasitic tissue of plants, provide a variety of nutrients in the cycle of parasitism and saprophytism, and participate in the basic metabolic process of plants. In the past ten years, many studies have been focused on the discovery of new species and biological secondary metabolites from this genus. In this review, we summarize a total of 335 bioactive secondary metabolites isolated from 26 known species and various unidentified species of Diaporthe and Phomopsis during 2010-2019. Overall, there are 106 bioactive compounds derived from Diaporthe and 246 from Phomopsis, while 17 compounds are found in both of them. They are classified into polyketides, terpenoids, steroids, macrolides, ten-membered lactones, alkaloids, flavonoids, and fatty acids. Polyketides constitute the main chemical population, accounting for 64%. Meanwhile, their bioactivities mainly involve cytotoxic, antifungal, antibacterial, antiviral, antioxidant, anti-inflammatory, anti-algae, phytotoxic, and enzyme inhibitory activities. Diaporthe and Phomopsis exhibit their potent talents in the discovery of small molecules for drug candidates.

Biological Activities of Some New Secondary Metabolites Isolated from Endophytic Fungi: A Review Study

Secondary metabolites isolated from plant endophytic fungi have been getting more and more attention. Some secondary metabolites exhibit high biological activities, hence, they have potential to be used for promising lead compounds in drug discovery. In this review, a total of 134 journal articles (from 2017 to 2019) were reviewed and the chemical structures of 449 new metabolites, including polyketides, terpenoids, steroids and so on, were summarized. Besides, various biological activities and structure-activity relationship of some compounds were aslo described.

Natural Polyketides Isolated from the Endophytic Fungus Phomopsis sp. CAM212 with a Semisynthetic Derivative Downregulating the ERK/IκBα Signaling Pathways

Three previously undescribed natural products, phomopsinin A - C (1:  - 3: ), together with three known compounds, namely, cis-hydroxymellein (4: ), phomoxanthone A (5: ) and cytochalasin L-696,474 (6: ), were isolated from the solid culture of Phomopsis sp. CAM212, an endophytic fungus obtained from Garcinia xanthochymus. Their structures were determined on the basis of spectroscopic data, including IR, NMR, and MS. The absolute configurations of 1: and 2: were assigned by comparing their experimental and calculated ECD spectra. Acetylation of compound 1: yielded 1A: , a new natural product derivative that was tested together with other isolated compounds on lipopolysaccharide-stimulated RAW 264.7 cells. Cytochalasin L-696,474 (6: ) was found to significantly inhibit nitric oxide production, but was highly cytotoxic to the treated cells, whereas compound 1: slightly inhibited nitric oxide production, which was not significantly different compared to lipopolysaccharide-treated cells. Remarkably, the acetylated derivative of 1: , compound 1A: , significantly inhibited nitric oxide production with an IC₅₀ value of 14.8 µM and no cytotoxic effect on treated cells, thereby showing the importance of the acetyl group in the anti-inflammatory activity of 1A: . The study of the mechanism of action revealed that 1A: decreases the expression of inducible nitric oxide synthase, cyclooxygenase 2, and proinflammatory cytokine IL-6 without an effect on IL-1β expression. Moreover, it was found that 1A: exerts its anti-inflammatory activity in lipopolysaccharide-stimulated RAW 264.7 macrophage cells by downregulating the activation of ERK1/2 and by preventing the translocation of nuclear factor κB. Thus, derivatives of phomopsinin A (1: ), such as compound 1A: , could provide new anti-inflammatory leads.

New Polyketides from the Marine-Derived Fungus Letendraea sp. 5XNZ4-2

Marine-derived fungi have been reported to have great potential to produce structurally unique metabolites. Our investigation on secondary metabolites from marine-derived fungi resulted in the isolation of seven new polyketides (phomopsiketones D–G (1–4) and letendronols A–C (5–7)) as well as one known xylarinol (8) in the cultural broth of Letendraea sp. Their structures and absolute configurations were elucidated using a set of spectroscopic and chemical methods, including HRESIMS, NMR, single-crystal X-ray diffraction, ECD calculation, and a modified version of Mosher’s method. Compound 2 showed weak inhibition against nitric oxide production in lipopolysaccaride-activated macrophages with an IC₅₀ value of 86 μM.

(+)- and (-)-Alternarilactone A: Enantiomers with a Diepoxy-Cage-like Scaffold from an Endophytic Alternaria sp

The enantiomers (+)- and (-)-alternarilactone A (1), the first examples of dibenzo-α-pyrones bearing a diepoxy-cage-like moiety, were isolated from the endophytic fungus Alternaria sp. hh930. The deficiency in ¹H-¹H COSY and HMBC correlations caused by the highly oxidized caged system of 1 and the deceptive and ambiguous signals such as "W" couplings in NMR data increased the risk of structure misassignment of 1. By performing a quantum chemical calculation of the NMR chemical shifts together with a DP4+ probability analysis and single-crystal X-ray crystallographic experiment, their structures were unambiguously determined, and their absolute configurations were determined by ECD calculations.

Exploring Structural Diversity of Microbe Secondary Metabolites Using OSMAC Strategy: A Literature Review

Microbial secondary metabolites (MSMs) have played and continue to play a highly significant role in the drug discovery and development process. Genetically, MSM chemical structures are biologically synthesized by microbial gene clusters. Recently, however, the speed of new bioactive MSM discovery has been slowing down due to consistent employment of conventional cultivation and isolation procedure. In order to alleviate this challenge, a number of new approaches have been developed. The strategy of one strain many compounds (OSMAC) has been shown as a simple and powerful tool that can activate many silent biogenetic gene clusters in microorganisms to make more natural products. This review highlights important and successful examples using OSMAC approaches, which covers changing medium composition and cultivation status, co-cultivation with other strain(s), adding enzyme inhibitor(s) and MSM biosynthetic precursor(s). Available evidences had shown that variation of cultivation condition is the most effective way to produce more MSMs and facilitate the discovery of new therapeutic agents.

Secondary Metabolites from the Endophytic Fungus Xylaria sp. hg1009

A detailed chemical investigation of the secondary metabolites produced by the endophytic fungus Xylaria sp. isolated from the stems of Isodon sculponeatus afforded six new compounds, xylariahgins A-F (1-6), two new natural products (7 and 8), along with two known compounds (9 and 10) (Fig. 1). The structures of all compounds were unambiguously established by analyzing their spectroscopic data or referring to pertinent literature. Compounds 1-8 were tested for their cytotoxic activity against five human tumor cell lines.

Bioprospecting of Diaporthe terebinthifolii LGMF907 for antimicrobial compounds

Antibiotic-resistant bacteria have been observed with increasing frequency over the past decades, driving the search for new drugs and stimulating the interest in natural products sources. Endophytic fungi from medicinal plants represent a great source of novel bioactive compounds useful to pharmaceutical and agronomical purposes. Diaporthe terebinthifolii is an endophytic species isolated from Schinus terebinthifolius, a plant used in popular medicine for several health problems. The strain D. terebinthifolii LGMF907 was previously reported by our group to produce secondary metabolites with biological activity against phytopathogens. Based on these data, strain LGMF907 was chosen for bioprospecting against microorganisms of clinical importance and for characterization of major secondary metabolites. In this study, different culture conditions were evaluated and the biological activity of this strain was expanded. The crude extracts demonstrated high antibacterial activity against Escherichia coli, Micrococcus luteus, Saccharomyces cerevisiae, methicillin-sensitive Staphylococcus aureus, and methicillin-resistant S. aureus. The compounds diaporthin and orthosporin were characterized and also showed activity against the clinical microorganisms evaluated. This study discloses the first isolation of diaporthin and orthosporin from D. terebinthifolii, and revealed the potential of this endophytic fungus to produce secondary metabolites with antimicrobial activity.