Inhibition of human neutrophil elastase by labdane diterpenes from the fruiting bodies of Ramaria formosa.

ABSTRACT

Two new labdane diterpenes (1 and 2) were isolated from the fruiting bodies of Ramaria formosa. The structures of these compounds were established by extensive spectroscopic studies and chemical evidence. The inhibitory activity of compounds 1 and 2 against human neutrophil elastase (HNE) was evaluated in vitro. Compounds 1 and 2 inhibited HNE activity moderately. The IC50 values for compounds 1 and 2 were 36.4 ± 1.2 and 40.8 ± 1.5 µM, respectively; the IC50 value for the positive control, EGCG, was 12.5 ± 0.8 µM. In addition, the mechanism by which 2 inhibited HNE was a mixed-type noncompetitive inhibition, with a Ki of 41.5 ± 1.8 µM.