The constituent, anti-inflammation, and human neutrophil elastase inhibitory activity of Gnaphalium affine

- The potent inflammation and HNE inhibition were observed on Gnaphalium affine.
- The isolated compounds inhibited NO, iNOS, and pro-inflammatory cytokines.
- A caffeoyl group in flavonol played a critical role as HNE inhibitor.
- The potent inhibitor 7 showed dose-dependent and noncompetitive behaviour.

Gnaphalium affine has long been used as a vegetable and as a traditional medicine to treat various diseases in East Asia. In this work, the human neutrophil elastase inhibitory activity and anti-inflammatory effects of the lead phytochemicals isolated from G. affine and their effects on respiratory disease agents were evaluated in vitro. Through activity-guided fractionation, eight compounds (1-8) with different scaffolds were isolated from the EtOAc fraction of G. affine extract (GAE). The GAE inhibited LPS-induced NO production with different potencies. The highest potency for the inhibition of NO, iNOS, and pro-inflammatory cytokine production was found in isolated compounds (1-8). A series of isolated compounds demonstrated modest to high inhibition of HNE with IC50 values of 2.3-46.1 µM. In particular, luteolin-4′-O-β-d-(6″-E-caffeoyl)-glucoside (7) showed noncompetitive inhibition kinetics against HNE. The results of this study support the traditional use of polyphenol-rich products in the prevention and treatment of respiratory disease.