Inhibition of human leukocyte function, alanyl aminopeptidase (APN, CD13) and dipeptidylpeptidase IV (DP IV, CD26) enzymatic activities by aqueous extracts of Cistus incanus L. ssp incanus

Short-boiled aqueous extract from leaves of Cistus incanus L. ssp. incanus (CIT) dose-dependently inhibit the enzymatic activities of both alanyl aminopeptidase (APN, CD13, EC 3.4.11.2) and dipeptidylpeptidase IV (DP IV, CD26, EC 3.4.14.5). This inhibition is not reversible and very likely results from a covalent binding of reactive compounds to the enzymes. Furthermore, we show that aqueous CIT extracts decrease the DNA-synthesis of human T cells and mononuclear cells and inhibit the proliferation rate of the human T cell line KARPAS-299 in a dose-dependent manner. Data are presented suggesting that the antiproliferative effects of CIT extracts are due to their strong cytotoxic activity. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.