Four new indolediketopiperazine derivatives (1–4), along with nine known congeners (5–13), were isolated and identified from the culture extract of Eurotium cristatum EN-220, an endophytic fungus obtained from the marine alga Sargassum thunbergii. The structures of thesecompounds were elucidated on the basis of extensive spectroscopic analysis and the absolute configurations of compounds 1–4 were established by NOESY experiments and by chiral HPLC analyses of their acid hydrolysates. The absolute configuration of C-8 (a quaternary carbon substituted with a hydroxyl group) in 5 of preechinulin class was firstly determined by electronic circular dichroism (ECD) calculations. All these compounds were evaluatedfor brine shrimp (Artemia salina) lethality and nematicidal activity as well as antioxidativeand antimicrobial potency.

Two new antimicrobial bisabolane-type sesquiterpenoid derivatives, ent-aspergoterpenin C (compound 1) and 7-O-methylhydroxysydonic acid (2), and two new butyrolactone-type monoterpenoids, pestalotiolactones C (3) and D (4), along with a known monoterpenoid pestalotiolactone A (5) and four known bisabolane sesquiterpenoids (6−9), were isolated and identified from the deep-sea sediment-derived fungus Aspergillus versicolor SD-330. The structures of these compounds were elucidated on the basis of spectroscopic analysis, and the absolute configurations of the new compounds 1−4 were determined by the combination of NOESY and TDDFT-ECD calculations and X-ray crystallographic analysis. Additionally, we first determined and reported the absolute configuration of the known monoterpenoid pestalotiolactone A (5) through the X-ray crystallographic experiment. All of these isolated compounds were evaluated for antimicrobial activities against human and aquatic pathogenic bacteria. Compounds 1, 2, 6 and 9 exhibited selective inhibitory activities against zoonotic pathogenic bacteria such as Escherichia coli, Edwardsiella tarda, Vibrio anguillarum and V. harveyi, with MIC values ranging from 1.0 to 8.0 μg/mL.

Three new indolediterpenoids, namely, 22-hydroxylshearinine F (1), 6-hydroxylpaspalinine (2), and 7-O-acetylemindole SB (3), along with eight related known analogs (4–11), were isolated from the sea-anemone-derived fungus Penicillium sp. AS-79. The structures and relative configurations of these compounds were determined by a detailed interpretation of the spectroscopic data, and their absolute configurations were determined by ECD calculations (1 and 2) and single-crystal X-ray diffraction (3). Some of these compounds exhibited prominent activity against aquatic and human pathogenic microbes.

Four new thiodiketopiperazine alkaloids, namely, 5’-hydroxy-6’-ene-epicoccin G (1), 7-methoxy-7’-hydroxyepicoccin G (2), 8’-acetoxyepicoccin D (3), and 7’-demethoxyrostratin C (4), as well as a pair of new enantiomeric diketopiperazines, (±)-5-hydroxydiphenylalazine A (5), along with five known analogues (6–10), were isolated and identified from the culture extract of Epicoccum nigrum SD-388, a fungus obtained from deep-sea sediments (−4500 m). Their structures were established on the basis of detailed interpretation of the NMR spectroscopic and mass spectrometric data. X-ray crystallographic analysis confirmed the structures and established the absolute configurations of compounds 1–3, while the absolute configurations for compounds 4 and 5 were determined by ECD calculations. Compounds 4 and 10 showed potent activity against Huh7.5 liver tumor cells, which were comparable to that of the positive control, sorafenib, and the disulfide bridge at C-2/C-2’ is likely essential for the activity.

Five new polyketides, namely, 5R-hydroxyrecifeiolide (1), 5S-hydroxyrecifeiolide (2), ent-cladospolide F (3), cladospolide G (4), and cladospolide H (5), along with two known compounds (6 and 7), were isolated from the endophytic fungal strain Cladosporium cladosporioides MA-299 that was obtained from the leaves of the mangrove plant Bruguiera gymnorrhiza. The structures of these compounds were established by extensive analysis of 1D/2D NMR data, mass spectrometric data, ECDs and optical rotations, and modified Mosher’s method. The structures of 3 and 6 were confirmed by single-crystal X-ray diffraction analysis and this is the first time for reporting the crystal structures of these two compounds. All of the isolated compounds were examined for antimicrobial activities against human and aquatic bacteria and plant pathogenic fungi as well as enzymatic inhibitory activities against acetylcholinesterase. Compounds 1–4, 6, and 7 exhibited antimicrobial activity against some of the tested strains with MIC values ranging from 1.0 to 64 μg/mL, while 3 exhibited enzymatic inhibitory activity against acetylcholinesterase with the IC₅₀ value of 40.26 μM.