Chemical constituents of culture broth of the marine-derived fungus Towyspora aestuari and their antioxidant activity

Seven compounds including a new pyrone, towyspyrone A (1), and six known naphthalenes, 8-methoxy-1-naphthol (2), 5-methoxy-1-naphthol (3), 3,4,5-trihydroxy-1-tetralone (4), 3,4-dihydro-3,4,6,8-tetrahydroxy-1(2 H)-naphthalenone (5), scytalone (6), and 4,6,8-trihydroxy-3,4-dihydronaphthalene-1(2 H)-one (7), were isolated from culture broth of the marine-derived fungus Towyspora aestuari. Their structures were determined by extensive NMR and mass analyses. Free radical scavenging activity of the isolated compounds was assessed using 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals. Compounds 2 and 3 showed potent free radical scavenging activity with IC₅₀ values of 12.6 µM and 10.8 µM, respectively, against the ABTS radical and of 224.0 µM and 191.1 µM against the DPPH radical.