The present invention provides a method of improving or preventing various conditions through suppression of the expression of inflammatory cytokines based on the action mechanism of suppression of NF-.kappa.B activation. The present invention provides a composition for suppressing NF-.kappa.B activation, containing a serotonin derivative such as feruloyl serotonin (N-feruloyl serotonin) and p-coumaroyl serotonin (N-(p-coumaroyl)serotonin), a composition for suppressing the expression of VCAM-1 and/or MCP-1 via NF-.kappa.B, containing the serotonin derivative and an anti-inflammatory composition containing the serotonin derivative. The composition of the present invention can be used as a pharmaceutical agent or a food.