Alterbrassicicene A (1), a fusicoccane-derived diterpenoid with an unprecedented framework, together with two known biosynthetic intermediates (2 and 3), were characterized from Alternaria brassicicola. The absolute structure of 1 was assigned by extensive spectroscopic analyses and quantum chemical calculations. Compound 1 represents a newly transformed monocyclic carbon skeleton of a highly functionalized diterpenoid bearing unique dihydro-2(3H)-furanone and 2-cyclopenten-1-one motifs. Compound 1 was the first fusicoccane-derived diterpenoid functioning as a potent PPAR-γ agonist (EC 50 = 744.1 nM).
Three new dolabellane-type diterpenoids
(1–3) and three new atranones (4–6) were isolated
and identified from a marine-derived strain of the toxigenic fungus Stachybotrys chartarum. The planar and relative structures
of 1–6 were elucidated using extensive
spectroscopic methods, and their absolute configurations were fully
confirmed via single-crystal X-ray diffraction analysis. Structurally,
compounds 2 and 3 have a 1,14-seco dolabellane-type diterpenoid skeleton; compound 4 is
the first C23 atranone featuring a propan-2-one motif linked
to a dolabellane-type diterpenoid by a carbon–carbon bond;
compound 5 represents the first example of a C24 atranone with a 2-methyltetrahydrofuran-3-carboxylate motif fused
to a dolabellane-type diterpenoid at C-5–C-6. In an in vitro
antimicrobial activity assay, compound 2 was active against Acinetobacter baumannii and Enterococcus faecalis with MIC values of 16 and 32 μg/mL, respectively, while compound 4 exhibited significant inhibitory activities against Candida albicans, Enterococcus faecalis, and methicillin-resistant Staphylococcus aureus (MRSA) with MIC values of 8, 16, and 32 μg/mL, respectively.
Eight undescribed fusicoccane-type diterpenoids (1–8), wherein 1 had a rare 16-nor-dicyclopenta[a,d]cyclooctane skeleton, were isolated from Alternaria brassicicola.
A preliminary phytochemical investigation on the EtOAc extracts of the fungus Bipolaris sp. TJ403-B1 resulted in the identification of 12 ophiobolin-type phytotoxins (1−12), including nine new ones, termed bipolaricins A−I (1−9). The structures of 1−9 were elucidated via spectroscopic data (including HRESIMS and 1D and 2D NMR) and single-crystal X-ray diffraction (Cu Kα) analyses. All of the isolated compounds were tested in terms of HMG-CoA reductase inhibitory, anti-inflammatory, and cytotoxic activities. Compound 10 showed HMG-CoA reductase inhibitory activity (IC 50 = 8.4 ± 0.4 μM), and 2, 3, and 10−12 showed significant inhibitory potency against lipopolysaccharide (LPS)-induced nitric oxide production, with IC 50 values in the range of 5.1 ± 0.3 to 20 ± 1 μM. Further experiments showed that 10 could significantly inhibit the production of IL-1β, RANTES, MIP-1β, and TNF-α as well as enhance the release of IL-13 in macrophages through the inhibition of HO-1 induction as well as the NF-κB pathway. These findings provide a scientific rationale for an anti-inflammatory therapeutic and a template for a new HMG-CoA reductase inhibitor to produce a potential anti-hyperlipidemia agent.
Marine-derived fungi are a promising and untapped reservoir for discovering structurally interesting and pharmacologically active natural products. In our efforts to identify novel bioactive compounds from marine-derived fungi, four breviane spiroditerpenoids, including a new compound, brevione O (1), and three known compounds breviones I (2), J (3), and H (4), together with a known diketopiperazine alkaloid brevicompanine G (5), were isolated and identified from an ethyl acetate extract of the fermented rice substrate of the coral-derived fungus Penicillium sp. TJ403-1. The absolute structure of 1 was elucidated by HRESIMS, one- and two-dimensional NMR spectroscopic data, and a comparison of its electronic circular dichroism (ECD) spectrum with the literature. Moreover, we confirmed the absolute configuration of 5 by single-crystal X-ray crystallography. All the isolated compounds were evaluated for isocitrate dehydrogenase 1 (IDH1) inhibitory activity and cytotoxicity, and compound 2 showed significant inhibitory activities against HL-60, A-549, and HEP3B tumor cell lines with IC50 values of 4.92 ± 0.65, 8.60 ± 1.36, and 5.50 ± 0.67 µM, respectively.
Nine novel polyketide−terpenoid hybrids (1−9), characterized by a 1-alkylated-3,5-dihydroxyphenyl derivative coupled with a modified farnesyl pyrophosphate (FPP) unit, were isolated from a soil-derived fungus Bipolaris zeicola. Their structures were determined by comprehensive spectroscopic data, single-crystal X-ray diffraction analyses, and electronic circular dichroism calculations. Structurally, compounds 1, 2, 5, and 6 possess a rare thiazole moiety; compounds 3 and 4 are the first examples of meroterpenoids featuring an undescribed 6/6/6/6/5 pentacyclic system and bearing a tetrahydrofuran ring fused to a polyketide and a sesquiterpenoid subunit; compounds 7 and 8 possess a rare 2H-1,4-thiazin-3(4H)-one moiety; and compound 9 represents the first example of meroterpenoid having an unusual thiazol-2(3H)-one moiety. The bioactivity assays revealed that compounds 1, 2, 5, 6, and 9 exhibited a significant immunosuppressive effect against concanavalin A (ConA)-induced T lymphocyte proliferation with IC 50 values ranging from 5.6 to 8.8 μM, and compounds 1, 2, and 4 exhibited moderate cytotoxic activities with IC 50 values ranging from 18.4 to 29.4 μM.
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