Pestalopyrones A-D, four tricyclic pyrone derivatives from the endophytic fungus Pestalotiopsis neglecta S3

Sativene Sesquiterpenoids from the Plant Endophytic Fungus Bipolaris victoriae S27 and Their Potential as Plant-Growth Regulators

Thirteen new sativene sesquiterpenoids (1 and 3-14), one new natural product (2), and 16 known compounds (15-30) were isolated from the endophytic fungus Bipolaris victoriae S27. Their structures were elucidated by extensive spectroscopic analysis, NMR and ECD calculations, and X-ray crystal diffractions. Compound 1 represented the first example of sativene sesquiterpenoids with a 6/5/3/5-caged tetracyclic ring system. All obtained compounds were evaluated for their plant-growth regulatory activity. The results showed that 1, 3, 4, 6, 8, 11, 12, 17, 19, 26, and 27 could suppress the growth of Arabidopsis thaliana, while 2, 5, 13, 15, 18, and 25 showed promoting effects. Among them, compound 3 showed the most potent plant-growth inhibitory activity, which is obviously superior to that of the marked herbicide glyphosate.

Novel phenolic metabolites isolated from plant endophytic fungus Fusarium guttiforme

Two new phenolic compounds Fusagunolics A (1) and B (2) were isolated from the plant endophytic fungus Fusarium guttiforme, in addition to the previously known metabolites (3-6). The structures of these compounds was elucidated using a combination of spectroscopic analyses, including UV, HRESIMS, 1 D, and 2 D NMR, as well as electronic circular dichroism (ECD) and the optical rotatory dispersion (ORD). Further, the anti-inflammatory activity of all the compounds was evaluated to assess their capability to inhibit nitric oxide (NO) production by RAW 264.7 macrophages. The bioactive screening revealed that compounds 2 and 6 exhibited moderate inhibitory effects against NO production with the IC50 values 28.6 and 37.6 μM, respectively.

Recent advances on Pestalotiopsis genus: chemistry, biological activities, structure-activity relationship, and biosynthesis

Strains of the fungal genus Pestalotiopsis are reported as large promising sources of structurally varied biologically active metabolites. Many bioactive secondary metabolites with diverse structural features have been derived from Pestalotiopsis. Moreover, some of these compounds can potentially be developed into lead compounds. Herein, we have systematically reviewed the chemical constituents and bioactivities of the fungal genus Pestalotiopsis, covering a period ranging from January 2016 to December 2022. As many as 307 compounds, including terpenoids, coumarins, lactones, polyketides, and alkaloids, were isolated during this period. Furthermore, for the benefit of readers, the biosynthesis and potential medicinal value of these new compounds are also discussed in this review. Finally, the perspectives and directions for future research and the potential applications of the new compounds are summarized in various tables.

The Natural Alkaloid (-)-N-Hydroxyapiosporamide Suppresses Colorectal Tumor Progression as an NF-κB Pathway Inhibitor by Targeting the TAK1-TRAF6 Complex

Colorectal cancer (CRC) is an exceptionally deadly disease, whereas effective therapeutic drugs for CRC have declined over the past few decades. Natural products have become a reliable source of anticancer drugs. Previously we isolated an alkaloid named (-)-N-hydroxyapiosporamide (NHAP), which exerts potent antitumor effects, but its effect and mechanism in CRC remain unclear. This study aimed to reveal the antitumor target of NHAP and identify NHAP as a promising lead compound for CRC. Various biochemical methods and animal models were used to investigate the antitumor effect and molecular mechanism for NHAP. These results showed that NHAP exhibited potent cytotoxicity, induced both apoptosis and autophagic cell death of CRC cells, and inhibited the NF-κB signaling pathway by blocking the interaction of the TAK1-TRAF6 complex. NHAP also markedly inhibited CRC tumor growth in vivo without obvious toxicities and possessed good pharmacokinetic characteristics. These findings identify, for the first time, that NHAP is an NF-κB inhibitor with potent antitumor activity in vitro and in vivo. This study clarifies the antitumor target of NHAP against CRC, which will contribute to the future development of NHAP as a novel therapeutic lead compound for CRC.

Neuropyrones A-E, five undescribed α-pyrone derivatives with tyrosinase inhibitory activity from the endophytic fungus Neurospora dictyophora WZ-497

Five undescribed α-pyrone derivatives, named neuropyrones A-E, were isolated from the endophytic fungus Neurospora dictyophora WZ-497 derived from the stems of Aster tataricus L. f. The structures of these α-pyrones with absolute configurations were determined by comprehensive spectroscopic analysis and computational calculations. All isolated compounds were tested for various bioactivities, including tyrosinase inhibitory activity. The results showed that neuropyrones A-C displayed potent inhibitory effects on tyrosinase with IC₅₀ values of 0.38 ± 0.07, 0.49 ± 0.06, and 0.12 ± 0.01 mM, respectively, which were comparable to that of the positive control, kojic acid (IC₅₀ = 0.14 ± 0.021 mM). A molecular docking study revealed the interaction between 3 and the His263, His85, Val283, Asn260, Phe264, and Val248 residues of tyrosinase.

Pestalotiopsis Diversity: Species, Dispositions, Secondary Metabolites, and Bioactivities

Pestalotiopsis species have gained attention thanks to their structurally complex and biologically active secondary metabolites. In past decades, several new secondary metabolites were isolated and identified. Their bioactivities were tested, including anticancer, antifungal, antibacterial, and nematicidal activity. Since the previous review published in 2014, new secondary metabolites were isolated and identified from Pestalotiopsis species and unidentified strains. This review gathered published articles from 2014 to 2021 and focused on 239 new secondary metabolites and their bioactivities. To date, 384 Pestalotiopsis species have been discovered in diverse ecological habitats, with the majority of them unstudied. Some may contain secondary metabolites with unique bioactivities that might benefit pharmacology.

Anti-Inflammatory Polyketide Derivatives from the Sponge-Derived Fungus Pestalotiopsis sp. SWMU-WZ04-2

Five undescribed polyketide derivatives, pestaloketides A–E (1–5), along with eleven known analogues (6–16), were isolated from the sponge-derived fungus Pestalotiopsis sp. Their structures, including absolute configurations, were elucidated by analyses of NMR spectroscopic HRESIMS data and electronic circular dichroism (ECD) calculations. Compounds 5, 6, 9, and 14 exhibited weak cytotoxicities against four human cancer cell lines, with IC50 values ranging from 22.1 to 100 μM. Pestaloketide A (1) is an unusual polyketide, featuring a rare 5/10/5-fused ring system. Pestaloketides A (1) and B (2) exhibited moderately inhibited LPS-induced NO production activity, with IC50 values of 23.6 and 14.5 μM, respectively, without cytotoxicity observed. Preliminary bioactivity evaluations and molecular docking analysis indicated that pestaloketides A (1) and B (2) had the potential to be developed into anti-inflammatory activity drug leads.

Trichopsistides A and B: Two Highly Oxygenated Pentacyclic Polyketides with Promising Inhibitory Effects on the NF-κB Signaling Pathway from the Fungus Trichoderma koningiopsis WZ-196

Two highly oxygenated pentacyclic polyketides with two new carbon skeletons, trichopsistide A (1) and trichopsistide B (2), were isolated from the plant endophyte Trichoderma koningiopsis WZ-196 derived from the leaf of Rubia podantha Diels. The structures of these polyketides with full configurations were determined by comprehensive spectroscopic analysis, computer-assisted structure elucidation software, computational calculation, and X-ray crystal diffraction. Among them, 1 represented the first example of an unprecedented 5/6/6/6/5 pentacyclic ketal-containing polyketide pyridine alkaloid, and 2 possessed a novel 6/6/6/6/5 pentacyclic ketal-containing polyketide scaffold fused with an α-pyrone. The plausible biosynthetic route for 1 and 2 was also proposed. Moreover, biological activity assays showed that 1 and 2 possessed inhibitory effects on the NF-κB signaling pathway with IC₅₀ values of 14.77 and 8.58 μM, respectively. Furthermore, 1 and 2 could also inhibit the expression of IκBα and p65 phosphorylation, decrease the expression of MCP-1, E-selectin, and IL-8 at the mRNA level, and inhibit the TNF-α-induced nuclear translocation of p65.

Reassignment of the structures of pestalopyrones A-D

Pestalopyrones A-D are four unusual tricyclic pyrone derivatives with flexible chiral structures, isolated from the endophytic fungus Pestalotiopsis neglecta S3. The full elucidation of their structures was a challenging task, and remained unsolved in the original article. Herein, the relative configurations of pestalopyrones A and pestalopyrones B were unambiguously assigned by detailed analyses on spectroscopic data and GIAO ¹³C NMR calculation method with sorted training sets (STS). The planar structures of pestalopyrones C and pestalopyrones D were revised by reinterpretation of their reported spectroscopic data, and then their relative configurations were deduced by STS GIAO ¹³C NMR calculation and NOE analysis. The absolute configurations of all the mentioned compounds were determined by the comparison of their experimental and calculated ECD curves.

Rubichaetoglobin A, a new cytochalasan alkaloid isolated from the plant endophytic fungus Chaetomium tectifimeti S104

Rubichaetoglobin A (1), a new cytochalasan alkaloid, together with nine closely related known ones (2-10), were isolated from the ethyl acetate extracts of the endophytic fungus Chaetomium tectifimeti S104 harbored in the root of Rubia podantha Diels. Their structures were elucidated based on comprehensive spectroscopic analysis. All isolated compounds were tested for cytotoxic, antibacterial, and nitric oxide inhibitory activities. The results showed that 2, 4, and 5 possessed moderate cytotoxicity against MDA-MB-231 cells with the IC₅₀ values of 19.14, 11.43, and 10.27 μM, respectively.

Identification of meroterpenoids from Bipolaris victoriae S27 and their potential activity against tumor metastasis and inhibition of the NF-κB signaling pathway

Three undescribed meroterpenoids, named bipolacochlioquinones A-C, together with seven known compounds, were isolated from the plant endophytic fungus Bipolaris victoriae S27 derived from the fresh stems of Rubia podantha Diels. Their structures were mainly determined by extensive spectroscopic analysis. The relative configurations of bipolacochlioquinones A-C were assigned using the ROESY spectrum, comparison of their spectral data with that reported in the literatures, and NMR calculations. Moreover, their complete absolute configurations were further established by electronic circular dichroism calculations using density functional theory. Among them, bipolacochlioquinone A is found to represent the first example of previously undescribed 6/6/6/6/6 pentacyclic dioxane-containing cochlioquinones, and bipolacochlioquinone B possesses a rare 6/6/6/6/5 pentacyclic system bearing a tetrahydrofuran ring fused to a polyketide and a sesquiterpenoid subunit. All compounds were evaluated for their inhibitory effects on tumor growth, metastasis, and the NF-κB signaling pathway. Among them, bipolacochlioquinone C and cochlioquinone A show the most potent cytotoxicities and NF-κB inhibitory activities. The effects of bipolacochlioquinone C and cochlioquinone A on the expression of NF-κB-associated proteins were also evaluated using western blotting. These results indicate that bipolacochlioquinone C and cochlioquinone A can inhibit the growth and metastasis of HCT116 and MDA-MB-231 cells by suppressing the NF-κB signaling pathway.