Reference Number: 128
Nutrition: Amino Acids
Emerging evidence from laboratory researches has highlighted the bioactivity of food melanoidins and melanoproteins. Whilst such studies have been carried out with different in vitro systems, information about melanoidins absorption and bioavailability are scarce. However, they are generally considered as poorly absorbable and bioavailable compounds. Therefore, we present a review in which the gastrointestinal tract is hypothesized to be the main site of action of food melanoidins and melanoproteins biological activity. We described recent data supporting this hypothesis both in vitro model systems and in vivo. Importantly, we focused this review only on the effect of melanoidins and melanoproteins extracted from food. Most of the studies had been carried out using water soluble carbohydrate based melanoidins isolated from different food sources (beer, barley coffee, coffee). In bakery products, melanoidins are protein based structure (melanoproteins) which are largely insoluble in water. Dietary melanoidins and melanoproteins have been demonstrated to exert in vitro antioxidant and metal chelating ability in the gastrointestinal tract reducing the formation of lipid hydroperox- ides and advanced lipid oxidation end products during the digestion of meat. The reduction in the formation of these pro-atherogenic compounds has been shown to be followed by a decrease in their absorption in human volunteers. Food melanoidins have also shown in vitro anti-caries and prebiotic activities. We conclude by underlining the possible role of food melanoidins in the prevention of gastrointestinal tract cancers. We hope this review will stimulate further research on food melanoidins and their biological activities in the gastro-intestinal tract.
SIGNIFICANCE OF THIS STUDY
Melanoidins are the final products of the Maillard reaction and are defined as brown coloured, nitrogen containing, high molecular weight compounds. Maillard reaction is a chemical browning reaction that occurs between carbohydrates and amino acids, peptides or proteins during roasting, baking, cooking or ageing of foods and beverages. Considering the high intake of melanoidins as part of our daily diets, their biological activity and potential impact on human health are topics of great interest. Previous studies have looked into the biological activities that have been attributed to melanoidins, namely their antioxidant, antimicrobial, prebiotic, anti-cancer, antihypertensive activities. The current study looks at the specific interactions of melanoidins on the GI tract. The current study states that in foods a single type of melanoidin does not exist but different melanoidin populations co-exist within a single sample and the results have demonstrated that different melanoidin populations behave differently and have different biological properties and physiological activities. For example, in the stomach they act as antioxidants and metal chelators, inhibiting the oxidation of meat derived fats and decreasing the synthesis of of compounds that may increase the risk of atherosclerosis. The ability of melanoidins to inhibit lipid oxidation may contribute to their health benefits, since dietary oxidized lipid are involved in the development of atherosclerosis and other diseases. Although most of the studies have been carried out in vitro and suffer some limitations concerning mainly the lack of knowledge about their interactions in humans, the current results still provide us with valuable insights.