Uncommon N‐Methoxyindolediketopiperazines from Acrostalagmus luteoalbus, a Marine Algal Isolate of Endophytic Fungus

Abstract

Main observation and conclusion Four new N‐methoxyindolediketopiperazines (acrozines D—G, 1—4) and six known congeners (5—10) were purified from the organic extract of Acrostalagmus luteoalbus TK‐43, which was a marine algal‐derived fungus obtained from Codium fragile. Their structures were determined by interpretation of NMR and mass spectroscopic data. The structures of compounds 1, 2, and 4 including their absolute configurations were confirmed by single‐crystal X‐ray diffraction, while the absolute configuration of compound 3 was elucidated by comparative analysis of ECD and TDDFT‐ECD calculations. Compounds 1—4, with a unique methoxy substitution at N‐2, were rarely discovered among indolediketopiperazine alkaloids. All these compounds were evaluated for antimicrobial activities against human‐ and aquatic‐pathogenic bacteria and plant‐related pathogenic fungi, with compounds 5 and 7 exhibiting potent activity against Edwardsiella icataluri (MIC = 3 and 5 μmol/L, respectively), while compound 9 displayed a broad spectrum of antibacterial activities. The four new compounds were further tested for anti‐acetylcholinesterase (AChE) properties, and compound 3 exhibited inhibitory activity with IC50 value of 8.4 μmol/L.

Bioactivity-Guided Screening of Antimicrobial Secondary Metabolites from Antarctic Cultivable Fungus Acrostalagmus luteoalbus CH-6 Combined with Molecular Networking

“…In order to identify the compounds’ structures in the first family with the maximum nodes, the literature [ 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ] about secondary metabolites of A. luteoalbus were studied and it was found that thiodiketopiperazine derivatives were the main products of this species, and then annotated 20 analogs in the first family in the molecular network according to the previous studies about thiodiketopiperazine derivatives ( Figure 1 and Figure 2 ) [ 16 , 20 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 ].…”

“…HSXSD-12 and Acrostalagmus luteoalbus CH-6, exhibited significant antifungal activities and the crude extracts of A. luteoalbus CH-6 showed the strongest antifungal and antibacterial activities. A series of active compounds, focusing on alkaloids and terpenoids, had been isolated from the genus of Acrostalagmus by previous researchers [ 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ], which further proved the potential capacity of the fungus A. luteoalbus CH-6 to produce novel antibiotics. Molecular networking has become an outstanding method to visualize and identify the secondary metabolites of the fungi crude extracts in non-targeted MS 2 data [ 23 , 24 , 25 ].…”

Verrucosidin Derivatives from the Deep Sea Cold-Seep-Derived Fungus Penicillium polonicum CS-252

“…The instruments, organic solvents, and reagents used in this work were the same as those used in our previous reports [ 13 , 14 , 15 ].…”

“…The antimicrobial activities of the isolated compounds against the human and aquatic pathogenic bacteria, Aeromonas hydrophilia QDIO-1, Edwardsiella ictarda QDIO-9, E. tarda QDIO-2, Escherichia coli EMBLC-1, Klebsiella pneumoniae EMBLC-3, S. aureus (MASA) EMBLC-4, Micrococcus luteus QDIO-3, Pseudomonas aeruginosa QDIO-4, Vibrio alginolyticus QDIO-5, V. anguillarum QDIO-6, V. harveyi QDIO-7, V. parahemolyticus QDIO-8, and V. vulnificus QDIO-10, and the plant pathogenic fungi Alternaria solani QDAU-1, Colletotrichum gloeosporioides QDAU-2, Fusarium graminearum QDAU-4, F. oxysporum QDAU-8, Gaeumannomyces graminis QDAU-21, Rhizoctonia cerealis QDAU-20, and Valsa mali QDAU-16 were determined with a serial dilution technique using 96-well microtiter plates as in our previous report [ 14 ]. The human and aquatic pathogenic bacteria and plant pathogenic fungi were supplied by the Institute of Oceanology, Chinese Academy of Sciences.…”

“…In our ongoing research for the discovery of bioactive secondary metabolites from marine-derived fungi [ 13 , 14 , 15 ], the fungal strain P. polonicum CS-252, which was obtained from sediments collected at the deep-sea cold seep area in the South China Sea, attracted our attention due to its unique HPLC profiles which showed peaks with different UV absorptions from those in our HPLC database. A chemical investigation of the culture extract of P. polonicum CS-252 led to the characterizations of six new verrucosidin derivatives, designated as poloncosidins A–F ( 1 – 6 , Figure 1 ), together with a known analogue, deoxyverrucosidin ( 7 ).…”