Praeruptorin D, a natural product isolated and purified from the roots of Peucedanum praeruptorum Dunn., can significantly inhibit the infiltration of activated polymorphonuclear leukocytes (PMNs) and decrease the levels of TNF-α and IL-6 in bronchoalveolar lavage fluid at the same dose, suppresses LPS induced Nuclear Factor-kappa B (NF-κB) pathway activation in the lung by decreasing the cytoplasmic loss of inhibitor κB-α (IκB-α) protein and inhibiting the translocation of p65 from cytoplasm to nucleus.