Potential of Endophytic Diaporthe sp. as a New Source of Bioactive Compounds

Antimicrobial properties of unusual eremophilanes from the endophytic Diaporthe sp. BCC69512

Six undescribed infrequent eremophilane derivatives including diaportheremopholins A - F and its previously undescribed side chain (E)-2-methyloct-2-enoic acid, together with three known compounds (testacein, xestodecalactones B and C), were isolated from the endophytic fungus Diaporthe sp. BCC69512. The chemical structures were determined based on NMR spectroscopic information in conjunction with the evidence from NOESY spectrum, Mosher's application, and chemical reactions for corroborating the absolute configurations. The isolated compounds were evaluated for biological properties such as antimalarial, anti-TB, anti-phytopathogenic fungal, antibacterial activities and for cytotoxicity against malignant (MCF-7 and NCI-H187) and non-malignant (Vero) cells. Diaportheremopholins B (2) and E (5) possessed broad antimicrobial activity against Mycobacterium tuberculosis, Bacillus cereus, Alternaria brassicicola and Colletotrichum acutatum with MICs in a range of 25.0-50.0 μg/mL. Testacein (7) exhibited strong anti-A. brassicicola and anti-C. acutatum activities with equal MIC values of 3.13 μg/mL. Moreover, diaportheremopholin F (6) and compound 8 displayed antitubercular activity with equal MIC values of 50.0 μg/mL. All tested compounds were non-cytotoxic against MCF-7, NCI-H187, and Vero cells, except those compounds 2 and 5-7 exhibited weak cytotoxicity against both malignant and non-malignant cells with IC50 values in a range of 15.5-115.5 μM.

Phomopamide A, a cyclic pentadepsipeptide with α-glucosidase inhibition activity from the endophytic fungus Diaporthe sp

An undescribed cytotoxic cyclopeptide named phomopamide A (1) was isolated from Diaporthe sp., which is an endophytic fungus from Artemisia argyi. Phomopamide A (1) featured an pentadepsipeptide skeleton and composed of two Phe, one Val, one Leu, and one 2-hydroxyoctanoic acid units. The structure of this new compound was fully characterised on the basis of extensive spectroscopic analysis. Moreover, phomopamide A was evaluated for in vitro cyctotoxic and α-glucosidase inhibitory activity. As a result, phomopaminde A exhibited no cytotoxic activity against four tumour cell lines, while it showed a potent α-glucosidase inhibition effect with IC50 value of 62.35 µM.

Diaporaustalides A-L, Austalide Meroterpenoids from a Plant Endophytic Diaporthe sp

Twelve new austalide meroterpenoids (1-12) were isolated from the endophytic fungus Diaporthe sp. XC1211. Their structures were elucidated by extensive spectroscopic analysis. The absolute configurations of compounds 1, 3, 4, and 6 were established by single-crystal X-ray diffraction, whereas those for the others were established by experimental electronic circular dichroism (ECD) data analysis. Compounds 1-12 represent a rare class of austalides with a 24α-CH3. Compounds 2 and 5 demonstrated potent proliferation inhibitory effects against LPS-induced B cells with IC50 values of 6.7 (SI = 3.6) and 3.8 (SI > 13) μM, respectively. Compounds 2 and 5 decreased the secretion of IL-6 in LPS-induced B cells in a dose-dependent manner.

Prunolactones A-G, proangiogenic isocoumarin derivatives with an unusual 6/6/6/6/6 spiropentacyclic skeleton from the endophytic fungus Phomopsis prunorum

Seven novel isocoumarins, prunolactones A-G (1-7), featuring an unusual 6/6/6/6/6 spiropentacyclic skeleton, together with two biosynthetic precursors phomopsilactone (8) and methyl 3-epi-shikimate (9), were isolated from the endophytic fungus Phomopsis prunorum guided by UPLC-QTOF-MS and 1H NMR spectroscopic analytical techniques. Their structures including absolute configurations of 1-7 were elucidated based on extensive spectroscopic data, X-ray diffraction analysis, and ECD calculations. Biogenetically, compounds 1-7 are proposed to be derived from polyketide and shikimate pathways via key intermolecular Diels - Alder reactions. Compounds 2, 3, and 7 showed significant in vivo proangiogenic activity in transgenic zebrafish.

Linoleic acid from the endophytic fungus Diaporthe sp. HT-79 inhibits the growth of Xanthomonas citri subsp. citri by destructing the cell membrane and producing reactive oxygen species (ROS)

Citrus canker disease caused by Xanthomonas citri subsp. citri (Xac) severely influences the quality and quantity of citrus fruits. The current management of this disease mainly relies on the application of copper-associated chemicals, which poses a threat to human health and the environment. The present study isolated an endophytic fungus HT-79 from the healthy navel orange tree, whose crude fermentation product significantly inhibited the growth of Xac. The strain HT-79 was identified as a species of the Diaporthe genus. The petroleum ether extract (PEE) of the crude fermentation product of HT-79 exhibited remarkable activity against Xac with a MIC (minimum inhibitory concentration) value of 0.0625 mg/mL, significantly better than the positive control CuSO₄ (MIC = 0.125 mg/mL). Bioassay-guided isolation of PEE resulted in the discovery of one highly potent anti-Xac subfraction, namely fraction 5 (MIC = 0.0156 mg/mL). Gas chromatography-mass spectrometry (GC-MS) analysis revealed that fraction 5 mainly consisted of palmitic acid (18.17%), ethyl palmitate (15.66%), linoleic acid (6.80%), oleic acid (18.32%), ethyl linoleate (21.58%), ethyl oleate (15.87%), and ethyl stearate (3.60%). Among these seven compounds, linoleic acid (MIC = 0.0078 mg/mL) was found to be the most potent against Xac, followed by oleic acid (MIC = 0.0156 mg/mL), while all others were less pronounced than CuSO₄. Linoleic acid highly inhibited the growth of Xac via the destruction of the cell membrane and overproduction of reactive oxygen species (ROS). A preliminary in vivo experiment revealed that linoleic acid was effective in the control of citrus canker disease.

Cytochalasans from the endophytic fungus Diaporthe ueckerae associated with the fern Pteris vittata

Six previously undescribed cytochalasans, ueckerchalasins A-E and 4'-hydroxycytochalasin J₃, together with eight known congeners, were isolated from solid cultures of the endophytic fungus Diaporthe ueckerae SC-J0123 which was originally isolated from the leaves of Pteris vittata L. Their structures were elucidated by extensive spectroscopic analysis, single-crystal X-ray diffraction, and theoretical simulations of ECD spectra and ¹³C NMR shifts. Ueckerchalasins A-C have a carbon-carbon bridge between C-14 and C-20, forming a rare 5/6/6/7-fused heterocyclic core. Ueckerchalasins C and D displayed selective activity against human carcinoma HeLa and HepG2 cells. Ueckerchalasins C was also active against Staphylococcus aureus and methicillin-resistant S. aureus (MRSA).

Dendrobine biosynthesis in Dendrobium nobile in four different habitats is affected by the variations in the endophytic fungal community

Dendrobium nobile, an epiphytic plant, is a traditional medicinal herb with abundant endophytes. It is unclear whether the variation in the diversity and abundance of endophytes could stimulate the biosynthesis of medicinal compounds in the plant. In this study, we collected fresh stems of D. nobile from four habitats for investigating the fungal community structure, dendrobine content, and environment factors and their correlations. The results indicated no significant difference in endophytic fungal diversity among the habitats; however, different dominant or special endophytic genera were observed in the hosts from different habitats. The altitude was observed to be positively related to the dendrobine content, as the stems collected from the altitude of 692 m exhibited the highest level of dendrobine. Furthermore, the relative abundance of Toxicocladosporium was found to be positively correlated with the altitude and dendrobine content. The epiphytic matrix exhibited a significant negative correlation with the relative abundance of the endophytic fungus Gibberella but did not exhibit any significant correlation with the dendrobine content. The results indicated that the abundance of endophytes in D. nobile was affected by the altitude and epiphytic matrix and that high Toxicocladosporium abundance and high altitude were conducive to dendrobine production.

Two new ɑ-pyrone derivatives from the endophytic Diaporthe sp. ECN371

Diaportholides A (1) and B (2), two polyketides with ɑ-pyrone moieties, were isolated from the cultures of an endophytic Diaporthe sp. ECN371 isolated from Orixa japonica, together with four known polyketides, phomopsolide B (3), phomopsolidones A (4) and B (5), and 5-[(1R)-1-hydroxyethyl]-γ-oxo-2-furanbutanoic acid (6). The structures of 1 and 2 were determined by extensive analysis of NMR and MS spectroscopic data. Furthermore, the structure of 2 was confirmed by analyzing the single-crystal X-ray diffraction data. The luciferase reporter gene assay revealed that among all isolated compounds (1-6), 3, a known ɑ-pyrone derivative, exhibited agonistic activity against the peroxisome proliferator-activated receptor ɑ, which is an important regulator of lipid metabolism in humans.

Recent Developments in Metabolomics Studies of Endophytic Fungi

Endophytic fungi are microorganisms that colonize living plants' tissues without causing any harm. They are known as a natural source of bioactive metabolites with diverse pharmacological functions. Many structurally different chemical metabolites were isolated from endophytic fungi. Recently, the increasing trends in human health problems and diseases have escalated the search for bioactive metabolites from endophytic fungi. The conventional bioassay-guided study is known as laborious due to chemical complexity. Thus, metabolomics studies have attracted extensive research interest owing to their potential in dealing with a vast number of metabolites. Metabolomics coupled with advanced analytical tools provides a comprehensive insight into systems biology. Despite its wide scientific attention, endophytic fungi metabolomics are relatively unexploited. This review highlights the recent developments in metabolomics studies of endophytic fungi in obtaining the global metabolites picture.