Effects of some Tyrosine-derived Maillard Reaction Products (MRPs) on Key-enzymes Linked with Type-2 Diabetes and Hypertension

Abstract

Maillard reaction products are generated during heat processing of foods but with little information on their health impact. Hence, this study sought to investigate the effect of tyrosine-derived Maillard reaction products (MRPs) on key enzymes linked to type-2 diabetes (α-amylase and α-glucosidase) and hypertension (Angiotensin-I converting enzyme, ACE) in vitro. MRPs were produced from the reaction between equimolar (5mM) solutions of tyrosine and four different saccharides each, namely; glucose, sucrose, fructose and maltose at 135 oC for 90 min to give products designated glucose-tyrosine MRPs, sucrose-tyrosine MRPs, fructose-tyrosine MRPs and maltose-tyrosine MRPs respectively. The MRPs inhibited α-amylase and α-glucosidase (0 – 24 μg/mL) and ACE (0 – 7.5 μg/mL) activities in a dose-dependent manner. Furthermore, the MRPs significantly (P<0.05) inhibited pro-oxidants (sodium nitroprusside and FeSO4) -induced lipid peroxidation in isolated tissue (pancreas, liver and heart) homogenates, and also demonstrated strong antioxidant properties as evident by their radical (DPPH and ˙OH) scavenging abilities. The melanoidin content of the MRPs determined by Gas Chromatography (GC) analysis ranged from 33.98 (glucose-tyrosine MPRs) to 47.18 mg/100 g (fructose-tyrosine MRPs). However, the melanoidin content agreed with the α-amylase and ACE inhibition. Nevertheless, the bioactivities of the MRPs is suggested to be a synergistic effect between the melanoidins and other compounds in the MRPs. Hence, tyrosine-derived MRPs could be relevant in the management of postprandial hyperglycaemia (major risk factor of type-2 diabetes) and its complications due to their modulatory effect on α-amylase, α-glucosidase and ACE activities, as well as their antioxidant properties.