Angiotensin-I converting enzyme inhibitory activity of coffee melanoidins

Melanoidins formed at the last stage of the Maillard reaction have been pointed out to possess certain functional properties. Potential antihypertensive activity of food melanoidins (coffee, beer, and sweet-wine) has been evaluated according to in-vitro ACE-inhibitory activity. Precision of the assay (3.2% of coefficient of variation, n = 10) for melanoidins is similar to those reported of well-known antihypertensive peptides. Assay was applied on food melanoidins obtained from coffee (three roasting degrees), beer, and sweet-wine. All samples showed in-vitro ACE-inhibitory activity. The activity in coffee melanoidins was significantly higher at more severe heating conditions. These experiments demonstrate that food melanoidins could inhibit ACE activity. In-vitro ACE-inhibitory activity of coffee melanoidins is likely located within the melanoidin structure. But ACE-inhibitory activity is also partly due to the low-molecular-weight compound nonchemically bound to the melanoidin structure, then melanoidins can act as carrier-protecting agents. These compounds could be naturally phenolic compounds present in the green beans or intermediary Maillard reaction products with antihypertensive activity.