Abstract
A new meroditerpene sartorenol (1), a new natural product takakiamide (2) and a new tryptoquivaline analog (3) were isolated, together with nine known compounds, including aszonapyrone A, chevalone B, aszonalenin, acetylaszonalenin, 3′-(4-oxoquinazolin-3-yl) spiro[1H-indole-3,5′-oxolane]-2,2′-dione, tryptoquivalines L, F and H, and the isocoumarin derivative, 6-hydroxymellein, from the ethyl acetate extract of the culture of the algicolous fungus Neosartorya takakii KUFC 7898. The structures of the new compounds were established based on 1D and 2D NMR spectral analysis, and, in the case of sartorenol (1) and tryptoquivaline U (3), X-ray analysis was used to confirm their structures and to determine the absolute configuration of their stereogenic carbons. Compounds 1, 2 and 3 were evaluated for their antimicrobial activity against Gram-positive and Gram-negative bacteria, and multidrug-resistant isolates from the environment; however, none exhibited antibacterial activity (MIC ˃ 256 mg/mL). The three new compounds did not show any quorum sensing inhibition in the screening protocol based on the pigment production by Chromobacterium violaceum (ATCC 31532).
Highlights
In recent years, marine-derived fungi have been demonstrated to be a rich and promising source of novel anticancer, antibacterial, antiplasmodial, anti-inflammatory, and antiviral agents [1]
Since we have previously found that the meroditerpenes aszonapyrone A and sartorypyrone A, isolated from the culture of N. fischeri KUFC 6344, exhibited potent antibacterial activity as well as synergism with antibiotics against the Gram-positive multidrug-resistant strains [7], we evaluated sartorenol (1), takakiamide (2) and tryptoquivaline U (3) for their antibacterial activity against four reference strains (Staphylococcus aureus, Bacillus subtillis, Escherichia coli and Pseudomonas aeruginosa), as well as the environmental multidrug-resistant isolates, according to the previously described method [7]
N. takakii has been previously isolated from a soil sample; this is the first report of the secondary metabolites from a marine-derived strain of this species
Summary
Marine-derived fungi have been demonstrated to be a rich and promising source of novel anticancer, antibacterial, antiplasmodial, anti-inflammatory, and antiviral agents [1]. Marine-derived fungi, which successfully fostered their armamentarium against bacterial competitors for millions of years, can be considered as a potential source of antibiotics. In our ongoing pursuit of new natural products with antibacterial activity produced by marine-derived fungi of the genera Neosartorya and Aspergillus, we have investigated the secondary metabolites of a. Thai collection of Neosartorya takakii KUFC 7898, isolated from the marine macroalga Amphiroa sp., collected from Samaesarn Island in the Gulf of Thailand. Compounds 1–3 were screened for their antibacterial activity against Gram-positive and Gram-negative bacteria, and multidrug-resistant isolates from the environment as well as for their quorum sensing inhibitory activity
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