Immunosuppressive Cytochalasins from the Mangrove Endophytic Fungus Phomopsis asparagi DHS-48

Abstract

Three new cytochalasins, phomoparagins A-C (1–3), along with five known analogs (4–8), were isolated from Phomopsis asparagi DHS-48, a mangrove-derived endophytic fungus. Their structures, including their absolute configurations, were elucidated using a combination of detailed HRESIMS, NMR, and ECD techniques. Notably, 1 possessed an unprecedented 5/6/5/8/5-fused pentacyclic skeleton. These compounds were tested for their inhibitory activity against concanavalin A (ConA)/lipopolysaccharide (LPS)-induced spleen lymphocyte proliferation and calcineurin (CN) enzyme. Several metabolites (2 and 4–6) exhibited fascinating inhibitory activities with a relatively low toxicity. Furthermore, 2 was demonstrated to inhibit ConA-stimulated activation of NFAT1 dephosphorylation and block NFAT1 translocation in vitro, subsequently inhibiting the transcription of interleukin-2 (IL-2). Our results provide evidence that 2 may, at least partially, suppress the activation of spleen lymphocytes via the CN/NFAT signaling pathway, highlighting that it could serve as an effective immunosuppressant that is noncytotoxic and natural.

Metabolomics-Guided Discovery of New Dimeric Xanthones from Co-Cultures of Mangrove Endophytic Fungi Phomopsis asparagi DHS-48 and Phomopsis sp. DHS-11

“…All the isolated metabolites were evaluated for their cytotoxic and immunosuppressive activities according to the previously described methods [ 46 , 47 , 48 ]. Compounds 1 – 9 showed broad cytotoxic activity ( Table 2 ).…”

“…In continuing the search for structurally novel and biologically active natural products from mangrove endophytic fungi [ 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 ], a strain of Phomopsis asparagi DHS-48 isolated from the fresh root of Rhizophora mangle was found to be particularly productive with regard to the accumulation of a series of immunosuppressive chromones and cytochalasins [ 46 , 47 , 48 ]. With the goal of tapping the metabolic potential of this titled fungal strain, we initiated the co-culture fermentation process of well-characterized DHS-48 with other fungal strains.…”

Epigenetic Manipulation Induced Production of Immunosuppressive Chromones and Cytochalasins from the Mangrove Endophytic Fungus Phomopsis asparagi DHS-48

“…Previous feeding experiments with sodium 13 C-labeled acetate by Lösgen et al [ 56 ] in 2007 revealed that a heptaketide precursor is involved in the biosynthesis of 3 and 4 , which are analogues to phomochromenones D-G isolated in our previous study [ 46 ], implying some cryptic post-synthesis modification genes were stimulated by the currently adopted epigenetic manipulation for the production of those metabolites previously unobserved or merely increased sufficiently under epigenetic control to be detected. Cytochalasins 5–11 might rationally share a common biosynthetic precursor as we previously described via polyketide synthase (PKS)/nonribosomal peptide synthetase (NRPS) hybrid machinery [ 38 ]. The stimulated metabolite 5 was is likely to be also derived from 6 by epoxidation, meanwhile 9 feasibly converted through catalytic dehydration.…”

“…The coelomycetous genus Phomopsis belongs to the family Diaporthaceae and consists of approximately 900 fungal species from a wide range of hosts [ 29 ]. The different species belonging to the genus Phomopsis are especially known for producing a wide variety of compounds with pharmacological properties, notably cytotoxic [ 30 , 31 , 32 ], antimicrobial [ 33 , 34 , 35 ], β -site amyloid precursor protein cleaving enzyme 1 (BACE1) inhibitory [ 36 ], anti-Tobacco mosaic virus (TMV) [ 37 ] and immunosuppressive activities [ 38 ]. As part of our research on discovering structurally novel and biologically active natural products from mangrove-derived endophytic fungal strains [ 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 ], a strain of Phomopsis asparagi DHS-48 isolated from the fresh root of Rhizophora mangle attracted our attention for the characterization of a series of immunosuppressive chromones [ 46 ] and cytochalasins [ 38 ].…”

“…The colony growth, dry biomass, 1 H NMR, and HPLC chromatogram were detected under the cultivation with small molecule epigenetic modifiers, the DNMT inhibitor 5-aza, the HDAC inhibitor sodium butyrate, and a combination of these inhibitors at various concentrations. A follow-up fermentation of an optional modifier (50 µM sodium butyrate) led to the isolation of two new compounds, phaseolorin J ( 1 ) and phomoparagin D ( 5 ), along with nine known phaseolorin D ( 2 ) [ 49 ], chaetochromone B ( 3 ) [ 50 ], pleosporalin D ( 4 ) [ 51 ], cytochalasins J, J1, J2, J3, H ( 6 – 10 ) [ 31 ] and phomopchalasin D ( 11 ) [ 38 ]. Herein, we report the epigenetic manipulation of this fungus, and the isolation, structural determination, and bioactivity evaluation of the induced products ( Figure 1 ).…”