New Alkylpyridinium Anthraquinone, Isocoumarin, C-Glucosyl Resorcinol Derivative and Prenylated Pyranoxanthones from the Culture of a Marine Sponge-Associated Fungus, Aspergillus stellatus KUFA 2017

Abstract

An unreported isocoumarin, (3S,4R)-4-hydroxy-6-methoxymellein (2), an undescribed propylpyridinium anthraquinone (4), and an unreported C-glucosyl resorcinol derivative, acetyl carnemycin E (5c), were isolated, together with eight previously reported metabolites including p-hydroxybenzaldehyde (1), 1,3-dimethoxy-8-hydroxy-6-methylanthraquinone (3a), 1,3-dimethoxy-2,8-dihydroxy-6-methylanthraquinone (3b), emodin (3c), 5[(3E,5E)-nona-3,5-dien-1-yl]benzene (5a), carnemycin E (5b), tajixanthone hydrate (6a) and 15-acetyl tajixanthone hydrate (6b), from the ethyl acetate extract of the culture of a marine sponge-derived fungus, Aspergillus stellatus KUFA 2017. The structures of the undescribed compounds were elucidated by 1D and 2D NMR and high resolution mass spectral analyses. In the case of 2, the absolute configurations of the stereogenic carbons were determined by comparison of their calculated and experimental electronic circular dichroism (ECD) spectra. The absolute configurations of the stereogenic carbons in 6a and 6b were also determined, for the first time, by X-ray crystallographic analysis. Compounds 2, 3a, 3b, 4, 5a, 5b, 5c, 6a, and 6b were assayed for antibacterial activity against four reference strains, viz. two Gram-positive (Staphylococcus aureus ATCC 29213, Enterococcus faecalis ATCC 29212) and two Gram-negative (Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853), as well as three multidrug-resistant strains. However, only 5a exhibited significant antibacterial activity against both reference and multidrug-resistant strains. Compound 5a also showed antibiofilm activity against both reference strains of Gram-positive bacteria.

In Silico and In Vitro Identification of 1,8-Dihydroxy-4,5-dinitroanthraquinone as a New Antibacterial Agent against Staphylococcus aureus and Enterococcus faecalis

“…Comparing the activity of DHDNA with that of the previously reported chlorinated emodin [ 28 ], the latter has a higher activity against S. aureus (MIC = 4 µg/mL) but lower against E. faecalis (MIC = 256 µg/mL). In another study, Machado et al tested 1,3-dimethoxy-8-hydroxy-6-methylanthraquinone (MIC > 32 µg/mL), 1,3-dimethoxy-2,8-dihydroxy-6-methylanthraquinone (MIC > 64 µg/mL), and 3-propyl-pyridinium anthraquinone derivative (MIC > 32 µg/mL) against both bacteria, without detecting antibacterial effects [ 51 ].…”

Marine natural products

“…151 Aspergillus strains derived from deep-sea sediment yielded a variety of metabolites including phenols 355 , 356 (C-8 epimers), 357 , 358 , 152 aromatic polyketides 359 – 361 and isoquinoline alkaloids 362 , 363 , 153 364 – 377 , 154 acremolin alkaloid 378 , 155 and cyclopropane acids 379 – 382 . 156 Sponge-derived strains were the source of 2,5-diketopiperazines 383 – 385 , 157 isocoumarin 386 , propylpyridinium anthraquinone 387 , resorcinol derivative 388 , 158 and dipyrroloquinones 389 , 390 , 159 whilst notoamide alkaloids 391 – 396 , 160 prenylated notoamide-type alkaloids 397 – 406 , 161 butenolides 407 – 411 and p -hydroxybenzaldehyde derivative 412 (ref. 162) were obtained from gorgonian-derived strains.…”

The natural products discovered in marine sponge-associated microorganisms: structures, activities, and mining strategy

“…, 2 0 2 0 ) . (3 S ,4 R) -4 -h y d r o x y -6methoxymellein, anthraquinone, and acetyl carnemycin E (Figure 2B, 133-135) were identified from sponge-associated Aspergillus stellatus KUFA 2017 (Machado et al, 2022). Luo et al discovered 2 new isomeric-modified tripeptides, aspergillamides C-D (Figure 2B, 136-137) from the sponge-associated fungus Aspergillus terreus SCSIO 41008 (Luo et al, 2019).…”