Shionone is an effective inhibitor of human neutrophil elastase which may be used as a treatment for inflammatory lung diseases including H1N1 and SARS virus infections. Shiononeis a tetracyclic triterpenoid is the major triterpenoid component of Aster tataricus possessing a unique all six-membered tetracyclic skeleton and 3-oxo-4-monomethyl structure. is perhydrochrysene which is substituted by methyl groups at positions 1, 4bβ, 6aα, 8β, 10aβ and 12a positions, by a 4-methylpent-3-enyl group at the 8α position, and with an oxo group at position 2.