The ability of Alchornea cordifolia (Schum. and Thonn.) Mll. Arg. (Euphorbiaceae) leaves to inhibit human neutrophil elastase (HNE) and superoxide anion (O 2 •-) activities was evaluated on aqueous and ethyl acetate extracts as they allow for a targeted extraction of polyphenols. The direct effect of A. cordifolia extracts on HNE and O 2 •- was assessed in an acellular system. Results showed that extracts scavenge HNE and O 2 •- in a dose-dependent manner. Better activity was exhibited by the ethyl acetate extract with lower IC 50 (2.2 and 4.1mg/L for HNE and O 2 •-, respectively) than for the aqueous extract. Cellular systems including isolated human polymorphonuclear neutrophils (PMN) were investigated to assess the effect of extracts on PMN metabolism. PMN were stimulated with 4β-phorbol-12- myristate-13-acetate (PMA), calcium ionophore (CaI), or N-formyl-methionyl- leucine-phenylalanine (fMLP), each stimulant having its own stimulation pathway. From the IC 50 obtained, it can be concluded that A. cordifolia reduces HNE and O 2 •- liberation. Furthermore it was demonstrated that A. cordifolia extracts have no cytotoxic activity on PMN by measuring release of the cytosolic enzyme lactate dehydrogenase. As the ethyl acetate extract offers a higher rate of total phenols than the aqueous extract as well as better scavenging activity, it can be supposed that polyphenols, which are well known for their potent antioxidant and antielastase activity, are implicated in the activity of the plant. Phenolic substances such as quercetin, myricetin-3-glucopyranoside, myricetin-3-rhamnopyranoside, and proanthocyanidin A2 were identified in the ethyl acetate extract. In conclusion, the study provides proof of ethnomedical claims and partly explains the mechanisms of the anti-inflammatory action of A. cordifolia leaves. © 2010 Informa UK Ltd.