Visconata: A rare flavonol having long chain fatty acid from Dodonaea viscosa which inhibits Human neutrophil elastase (HNE)

A series of flavonoids were isolated from Dodonaea Viscosa and tested for inhibition of human neutrophil elastase (HNE), enzyme involved in inflammatory disorders. Isolated compounds were identified as a novel flavonol (1) along with eight known flavonoids (2-9). Novel flavonol, visconata (1) has a very rare skeleton having odd numbered long chain (C19) fatty acid, which was completely identified by mass fragmentation and 2D NMR analysis. All compounds (1-9) inhibited HNE in dose dependent manner with IC(50)s ranging between 2.4 and 150 mu M. Visconata (1) emerged to be the most potent compound with 2.4 mu M of IC50. In kinetic studies, compound (1) was observed to be reversible, noncompetitive inhibitor having K, = 1.8 mu M, whereas other flavonoids (2-9) displayed mixed type inhibition. (C) 2017 Elsevier Ltd. All rights reserved.