New rubrolides from the marine-derived fungus Aspergillus terreus OUCMDZ-1925.

Two new rubrolides, rubrolides R (1) and S (2), were isolated from the fermentation broth of the marine-derived fungus Aspergillus terreus OUCMDZ-1925. Their structures were elucidated on the basis of spectroscopic analysis and X-ray single crystal diffraction. Compound 1 showed comparable or superior antioxidation against 2,2'-azino-di(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radicals to those of trolox and ascorbic acid with an IC₅₀ value of 1.33 mM. Compound 2 showed comparable or superior anti-influenza A (H1N1) virus activity to that of ribavirin with an IC₅₀ value of 87.1 μM. Both compounds 1 and 2 showed weak cytotoxicity against the K562 cell line with IC₅₀ values of 12.8 and 10.9 μM, respectively.