Dual inhibition of metallopeptidases ACE and NEP by extracts, and iridoids from Ligustrum vulgare L.

Aim of the study: In order to confirm the traditional use of Ligustrum vulgare L. (common privet, Oleaceae) we investigated the inhibitory activity of different extracts from leaves (LIE), flowers (LflE) and fruits (LfrE) on metallopeptidases ACE and NER Materials and methods: Powdered plant materials were first extracted with water and then with ethyl acetate and n-butanol saturated with water. The metallopeptidases activity was determined using in vitro fluorimetric assays. Results: At a concentration of 100 mu g/ml the ethyl acetate extracts showed the highest activity. The bio-guided fractionation of the leaves extract led to the isolation of two iridoids which were identified by H-1, C-13 and HETCOR NMR spectroscopy as oleuropein and ligstroside aglycones. Both compounds are dual ACE/NEP inhibitors with IC50 of 20 and 25 mu M for ACE and IC50 of 35 and 75 mu M for NEP, respectively. Secoirydoids glycosides, tyrozol and hydroxytyrozol, as well as, flavonoids present in the ethyl acetate extracts showed little or no inhibitory activity. Conclusions: Our results partially support the diuretic and hypotensive activities of common privet. (C) 2008 Elsevier Ireland Ltd. All rights reserved.