Two new diphenylketones (1 and 2), a new xanthone (3), and a known xanthone analogue (4) were isolated and identified from Talaromyces islandicus EN-501, an endophytic fungus obtained from the fresh collected marine red alga Laurencia okamurai. Their structures were elucidated on the basis of NMR spectroscopic and X-ray crystallographic analysis. The joint isolation of benzophenones and xanthones from the same fungal strain supports the biogenesis of xanthones via a benzophenone intermediate. It is worth mentioning that xanthones 3 and 4 have a methyl group at C-6 and C-2, respectively, which is uncommon compared with typical xanthones usually having a methyl group at C-8. Compounds 1–4 exhibited potent antioxidative activities against DPPH (1,1-diphenyl-2-picrylhydrazyl) and ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonate) radicals with IC₅₀ values ranging from 0.58 to 6.92 μg/mL, which are stronger than that of the positive controls BHT (butylated hydroxytoluene) and ascorbic acid. Compounds 1, 3, and 4 also showed inhibitory activities against several pathogenic bacteria.

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.

The co-cultivation of two or more different microbial strains in one culture vessel was supposed to be a viable experimental approach for enhancing the diversity of the compounds produced. Two new meroterpenoid derivatives, chermebilaenes A (1) and B (2), together with three known sesquiterpenoids, sesquicaranoic acid B (3), cyclonerodiol (4) and bisabol-l-on-13-säuremethylester (5), were characterized from a co-culture of the marine-derived fungal isolates of Penicillium bilaiae MA-267 and Penicillium chermesinum EN-480. Neither fungus produced these compounds when cultured alone under the same conditions. Compound 1 represents an unprecedented acorane-type sesquiterpene hybridized with an octadecadienoic acid skeleton. The structures were elucidated on the basis of spectroscopic analysis, and the absolute configurations were assumed on the basis of acidic hydrolysis combined with modified Mosher’s method and electronic circular dichroism (ECD) calculations. Compound 1 showed potent inhibitory activities against Ceratobasidium cornigerum and Edwardsiella tarda.