Arctium minus (Hill) Bernh. (Asteraceae) aspartylendopeptidases with potential application in the formulation of nutraceutical products

Abstract

Food proteins encrypt bioactive peptides that can be released during gastrointestinal digestion or food processing by enzymatic proteolysis. Flowers of Carduae tribe, family Asteraceae, contain aspartic proteinases with milk clotting activity. Crude enzyme extracts with proteolytic activity were prepared from flowers of Arctium minus at pH 7.0, and were partially purified and characterized. Optimun bovine milk clotting activity was achieved with CaCl2 30 mM at 35 ºC. Inhibition of milk clotting activity was only promoted by pepstatin A, a highly selective inhibitor for aspartic peptidases. Analysis of crude extract by isoelectric focusing and zymogram showed an unique active band (pI 5.0). Molecular exclusion chromatography (Sephadex G-25 Fine) was employed to eliminate pigments and phenolic compounds, in order to obtain the partially purified extract (EE). Whey bovine hydrolyzates were performed with EE and analyzed by SDS-PAGE. Hydrolyzed whey was ultrafiltrated, and low molecular fractions (peptide mass ≤ 3000 Da) showed angiotensin-converting enzyme (ACE) inhibitory activity. Therefore, these peptides with antihypertensive activity could be potentially used in food industry for formulation of nutraceutical products.