Chemical examination of an EtOAc extract of cultured Aspergillus versicolor fungus
from deep-sea sediments resulted in the isolation of four xanthones, eight anthraquinones
and five alkaloids, including a new xanthone, oxisterigmatocystin D ( 1 ) and a new
alkaloid, aspergillusine A ( 13 ). High resolution electron impact mass spectrometry
(HR-EI-MS), FT-IR spectroscopy, and NMR techniques were used to elucidate the structures
of these compounds, and the absolute configuration of compound 1 was established
by its NMR features and coupling constant. Furthermore, the biosynthesis pathway of
these xanthones and anthraquinones were deduced, and their antioxidant activity and
cytotoxicity in human cancer cell lines (HTC-8, Bel-7420, BGC-823, A549, and A2780)
were evaluated. The trolox equivalent antioxidant capacity (TEAC) assay indicated
most of the xanthones and anthraquinones possessing moderate antioxidant activities.
The Nrf2-dependent luciferase reporter gene assay revealed that compounds 6, 7, 9,
and 12 potentially activated the expression of Nrf2-regulated gene. In addition,
compounds 5 and 11 showed weak cytotoxicity on A 549 with the IC 50 values of
25.97 and 25.60 μmol·L –1 , respectively.