Abstract
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.
Highlights
Marine-derived fungi have been evidenced as a prolific source for the discovery of pharmacologically-active natural products [1,2]
The fungal strain used in the present work was isolated from the inner tissue of the fresh collected marine red alga Laurencia okamurai
Compound 4 is an atypical xanthone with a methyl group at C‐2, which is different from from
Summary
Marine-derived fungi have been evidenced as a prolific source for the discovery of pharmacologically-active natural products [1,2]. As part of our ongoing research toward the discovery of secondary metabolites from marine-derived fungi [3,4,5,6,7,8], an endophytic fungal strain, Talaromyces islandicus EN-501, was selected for chemical investigation. Several new natural products were isolated from plant-derived endophytic species of the genus Talaromyces [9,10,11]. Radicals, as well as antibacterial activity strains, were evaluated. Radicals, as well as antibacterial activityagainst against six six pathogenic pathogenic strains, were evaluated. ThisThis paperpaper describes the isolation, characterization, and bioactivity of compounds. Describes the isolation, characterization, and bioactivity of compounds 1–4
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