Gerontoxanthone B from Maclura cochinchinensis var. gerontogea exhibits anti-inflammatory potential as an aryl hydrocarbon receptor agonist.

The aryl hydrocarbon receptor (AhR) is a ligand-dependent transcriptional factor belonging to the basic helix-loop-helix-Per-Ahr/Arnt-Sim family. In this study, we evaluated the AhR agonistic activities of 12 xanthones isolated from the roots of M. cochinchinensis var. gerontogea using HepG2 cells transfected with pX4TK-Luc reporter plasmids. Gerontoxanthone B (GXB) showed the most potent activity at a concentration of 10μM, and the activity was inhibited by AhR antagonists such as GNF-351. GXB also increased cytochrome P450 1A1 mRNA and protein levels in HepG2 cells. Similar to the AhR agonist 2,3,7,8-tetrachlorodibenzo-p-dioxin, however, GXB suppressed the IL-1β-induced mRNA level of SAA1, an acute-phase response gene that is up-regulated AhR-dependently but XRE-independently. Thus, GXB shows XRE-dependent transcriptional activity and XRE-independent activity involving AhR.