Inhibition of Human Neutrophil Elastase by Sesquiterpene Lactone Dimers from the Flowers of .

A new sesquiterpene lactone dimer , together with five known compounds , was isolated from the flowers of . The structures of these compounds were established by extensive spectroscopic studies and chemical evidence. The inhibitory activities of these isolated compounds against human neutrophil elastase (HNE) were also evaluated in vitro; compounds and exhibited significant inhibitory effects against HNE activity, with IC values of 8.2 and 10.4 μM, respectively, comparable to that of epigallocatechin gallate (EGCG; IC = 10.9 μM). In addition, compounds and exhibited moderate HNE inhibitory effects, with IC values of 21.9 and 42.5 μM, respectively. In contrast, compounds and exhibited no such activity (IC ＞ 100 μM). The mechanism by which and inhibited HNE was noncompetitive inhibition, with inhibition constant () values of 8.0 and 22.8 μM, respectively.