The O-methylation of chrysin markedly improves its intestinal anti-inflammatory properties: Structure-activity relationships of flavones.

The aim of this study was to investigate whether methoxylated flavones versus their unmethylated analogs can modulate the intestinal inflammatory response. Flavone effects were assessed on soluble pro-inflammatory mediator (IL-8, IL-6, macrophage chemoattractant protein-1 (MCP-1), and cyclooxygenase-2 (COX-2)-derived PGE2) production and on nuclear factor (NF)-κB activation in 3d-confluent and 21d-differentiated Caco-2 cells stimulated with interleukin (IL)-1β. Chrysin (CHRY) showed anti-inflammatory properties by decreasing COX-2-derived PGE2 and reducing NF-κB activation. Compared to CHRY, the dimethoxylated form (CHRY-DM) significantly reduced the secretion of all pro-inflammatory mediators, except IL-8, at both cellular stages (P<0.05); these effects being dose-dependent in 3d-cells. The reduction of NF-κB activation was significantly more pronounced with CHRY-DM. By evaluating other flavones, it was established that several structural dispositions of flavones seemed to be determinant in order to attenuate the intestinal inflammatory response, such as methoxylation of the 5- and 7-hydroxyl groups on the A-ring, non-methoxylation of the 3'-hydroxyl groups on the B-ring, and methoxylation of the 3-hydroxyl group on the C-ring. Of all flavones examined, CHRY-DM exhibited the strongest anti-inflammatory activity. These data indicate that, in the Caco-2 cell model, methoxylation of CHRY greatly improves its anti-inflammatory properties, probably through a more pronounced inhibition of the NF-κB signaling pathway. Nevertheless, methoxylation of other flavones was not systematically beneficial.