Chemical Constituents from the Leaves of Ilex paraguariensis Inhibit Human Neutrophil Elastase

Human neutrophil elastase (HNE), a serine protease with broad target specificity, is the only enzyme responsible for the degradation of elastin which is an insoluble elastic fibrous protein in animal connective tissue. Biologically, elastase activity significantly increased with age, which results in a reduced skin elasticity and in the appearance of wrinkles or stretchmarks. In the course of our screening program for HNE inhibitors from natural source, the MeOH extract of Ilex paraguariensis leaves showed strong HNE inhibitory effect. Bioassay-guided fractionation led to the isolation of a new pyrrole alkaloid (1), along with seventeen known compounds (2-18) from the MeOH extract of Ilex paraguariensis leaves, and their chemical structures were elucidated on the basis of spectroscopic analysis. All isolated compounds were evaluated for HNE inhibitory activity, and the result demonstrated that dicaffeoylquinic acid derivatives (12, 13, 14, 15 and 16) and flavonoids (8 and 17) exhibited potent HNE inhibitory activity with IC50 values ranging from 1.4 to 7.3 mu M.