Sappanone A, a homoisoflavanone isolated from the heartwood of Caesalpinia sappan (Leguminosae), induces HO-1 expression by activating Nrf2 through the p38 MAPK pathway, suppresses LPS-induced NF-κB activation by suppressing the phosphorylation of RelA/p65 at Ser536, exerting its anti-inflammatory effect.