Antioxidant Hydroanthraquinones from the Marine Algal-Derived Endophytic Fungus <i>Talaromyces islandicus</i> EN-501

Five new polyhydroxylated hydroanthraquinone
derivatives, namely,
8-hydroxyconiothyrinone B (1), 8,11-dihydroxyconiothyrinone
B (2), 4R,8-dihydroxyconiothyrinone
B (3), 4S,8-dihydroxyconiothyrinone
B (4), and 4S,8-dihydroxy-10-O-methyldendryol E (5), were isolated and identified
from the culture extract of Talaromyces islandicus EN-501, an endophytic fungus obtained from the inner tissue of the
marine red alga Laurencia okamurai. The structures
of these compounds were established on the basis of detailed interpretation
of their NMR and mass spectroscopic data, and the structures and absolute
configurations of compounds 1 and 2 were
confirmed by X-ray crystallographic analysis, while the absolute configurations
of compounds 3–5 were determined
by TDDFT calculations of the ECD spectra. The antimicrobial, antioxidant,
and cytotoxic activities of compounds 1–5 were evaluated.