Unexpected Noremestrin with a Sulfur-Bearing 15-Membered Macrocyclic Lactone from Emericella sp. 1454

Asperstrins A-H: Epipolythiodioxopiperazines from the endophytic fungus Aspergillus nidulans

Eight previously undescribed epipolythiodioxopiperazines (ETPs), asperstrins A-H (1-8), and three known analogues, dethiosecoemestrin (9), secoemestrin C (10), and secoemestrin D (11), were isolated from the endophytic fungus Aspergillus nidulans. Their structures and configurations were elucidated based on HRESIMS, one-dimensional and two-dimensional nuclear magnetic resonance spectroscopic data, electronic circular dichroism calculations, and X-ray crystallography. Asperstrins A-C (1-3) represent the first examples of O-methyl or O-ethyl derivatives of emestrin-type ETPs, respectively. Asperstrin C (3) showed moderate cytotoxic activities with IC50 values ranging from 3.00 to 4.60 μM; asperstrins F (6) and G (7) displayed potent butyrylcholinesterase inhibitory activities with IC50 values of 9.49 ± 0.51 and 2.03 ± 0.55 μM, respectively.

Peunipyrone A, an Unexpected Highly Oxygenated γ-Pyrone with a 6/6/6/6/6 Pentacyclic Ring System from a Sponge-Derived Fungus Aspergillus peuniceus

A highly oxygenated γ-pyrone with an unprecedented carbon skeleton, peunipyrone A (1), was isolated from the sponge-derived fungus Aspergillus peuniceus. Compound 1 features a unique fused 6/6/6/6/6 pentacyclic ring system. The chemical structure of compound 1 was elucidated by comprehensive spectroscopic techniques and single-crystal X-ray diffraction. The plausible biosynthetic pathway of compound 1 was proposed. Compound 1 promoted leukemic cell apoptosis by increasing p53 expression.

Nidustrin A, cysteine-retained emestrin with a unique 18-membered macrocyclic lactone from the endophytic fungus Aspergillus nidulans

Nidustrin A (1), the first cysteine-retained emestrin featuring a unique sulfur-containing 18-membered macrocyclic lactone, along with four biogenetically related compounds (2-5), and one known analogue secoemestrin C (6), were isolated from the large-scale culture of Aspergillus nidulans, an endophytic fungus derived from the Whitmania pigra. Compounds 2 and 3 represent the second examples of noremestrin besides the previously reported noremestrin A, and the single crystal X-ray diffraction analysis of compound 2 provided solid evidence for the intriguing skeleton of noremestrin. Their structures were determined by extensive spectroscopic data, electronic circular dichroism calculations, and single-crystal X-ray diffraction. Compounds 2-4 exhibited inhibitory activity against concanavalin A-induced T lymphocyte proliferation with IC50 values from 2.95 to 24.5 μM, respectively. Compound 4 could protect the liver from hepatocyte apoptosis in ConA-induced liver injury and showed moderate cytotoxic activities with IC50 values ranging from 3.26 to 15.70 μM.

New diketopiperazine dimers and 4-hydroxyphenylacetates from an endolichenic fungus Aspergillus sp

Two novel diketopiperazine dimers (1 and 2) and two new 4-hydroxyphenylacetates (5 and 6), along with two previously known diketopiperazine dimers were isolated from the culture of the endolichenic fungus Aspergillus sp. CPCC 400810. Their structures were determined through comprehensive spectroscopic analysis, including high-resolution electrospray ionization mass spectrometry (HRESIMS) and 1D and 2D nuclear magnetic resonance (NMR) data. The absolute configurations of the new compounds were confirmed using Marfey's method and chemical synthesis.

Aplospojaveedins A-C, unusual sulfur-containing alkaloids produced by the endophytic fungus Aplosporella javeedii using OSMAC strategy

Three sulfur-containing alkaloids aplospojaveedins A-C (1-3) with a hitherto undescribed carbon skeleton comprising octahy-dronaphthalene, α, β-unsaturated lactam and glycine-cysteine moieties were isolated from Aplosporella javeedii. Their structures were elucidated by 1D and 2D NMR spectroscopy, HR-MS, X-ray diffraction analysis, DFT-NMR and TDDFT-ECD calculations. A plausible biosynthetic pathway and putative targets are described. The blind docking suggested that 1-3 may have functional effects on several putative targets such as the GPCR cannabinoid receptor 2 or the integrin α5β1 complex.

Penidaleodiolides A and B, Cage-Like Polyketides with Neurotransmission-Regulating Activity from the Soil Fungus Penicillium daleae L3SO

Penicillium daleae L3SO is a fungus isolated from the rhizospheric soil of the chloroplast-deficient plant Monotropa uniflora. A chemical study on the rice fermentation of this fungus led to the isolation and identification of two cage-like polyketides, penidaleodiolide A (1) and its biosynthetic-related congener penidaleodiolide B (2). The structures of 1 and 2 were determined by a combination of extensive spectroscopic analysis, biosynthetic consideration, chemical derivatization, and computational methods. Compound 1 harbors an unusual tricyclo[4.3.04,9]nonane scaffold, unprecedented in polyketide natural products. The hypothetical biosynthetic pathways for 1 and 2 were postulated and were supported by CRISPR/Cas9 genome editing results. Penidaleodiolide A (1) showed a significant inhibitory effect on the action potentials of murine hippocampal basket neurons and decreased the frequency of spontaneous excitatory postsynaptic currents in a concentration-dependent manner (the inhibition ratios were 0.30 ± 0.02 for 1 μM, 0.37 ± 0.03 for 10 μM, and 0.50 ± 0.07 for 20 μM) while being devoid of cytotoxicity against the nerve cells.

New bioactive secondary metabolites from fungi: 2023

Fungi have been identified as a prolific source of structurally unique secondary metabolites, many of which display promising biological and pharmacological properties. This review provides an overview of the structures of new natural products derived from fungi and their biological activities along with the research strategies, which focuses on literature published in the representative journals in 2023. In this review, a total of 553 natural products including 219 polyketides, 145 terpenoids, 35 steroids, 106 alkaloids, and 48 peptides are presented. By summarising the latest findings, this review aims to provide a guide and inspire further innovation in the fields of the discovery of fungal natural products and pharmaceutical development.

Hot off the press

A personal selection of 32 recent papers is presented covering various aspects of current developments in bioorganic chemistry and novel natural products such as dcalycinumine A from Daphniphyllum calycinum.