Evaluation of human neutrophil elastase inhibitory effect of iridoid glycosides from Hedyotis diffusa

Five iridoid glycosides ( 1– 5) were isolated from Hedyotis diffusa and their human neutrophil elastase inhibitory effects were evaluated. Five iridoid glycosides were isolated from the MeOH extract of Hedyotis diffusa, and their structures were elucidated as E-6- O- p-methoxycinnamoyl scandoside methyl ester ( 1), Z-6- O- p-methoxycinnamoyl scandoside methyl ester ( 2), E-6- O- p-feruloyl scandoside methyl ester ( 3), E-6- O- p-coumaroyl scandoside methyl ester ( 4), and Z-6- O- p-coumaroyl scandoside methyl ester ( 5) by interpretation of their spectroscopic data. All the isolated compounds were evaluated for human neutrophil elastase inhibitory effect, and compound 1 showed potent activity with an IC 50 value of 18.0 μM. The molecular docking simulation suggested a structural model for the inhibition of human neutrophil elastase by compound 1.