Complexation of Calcium by Melanoidin and Its Role in Determining Bioavailability

Abstract

Model melanoidins, pigments formed by nonenzymic browning reactions of amino acids with reducing sugars and glyoxal, behaved like anionic polymers that form moderately stable complexes with Ca*+ and, if incorporated into diets, could possibly influence calcium bioavailability. Hydrogen ions were released during complexation. The influence of pH on degree of binding by soluble and insoluble forms of mode1 melanoidins was determined. Pigments in coffee brew and toasted bread (milk-free) had no measurable calcium-binding ability, which suggested that there might be important structural differences between pigments formed in food systems and those formed from the interaction of simple amino acids with sugars. INTRODUCTIONNONENZYMIC BROWNING REACTIONS are of considerable importance to food chemistry and have been the subject of much research for many years (Nursten, 1980-81;Hodge, 1953). In foods the reaction of reducing sugars with proteins and other compounds containing free amino groups produces not only brown polymeric pigments (melanoidins) but also compounds that contribute to aroma and flavor. These products may be either desirable or undesirable, depending upon the food system in question. Browning reactions that incorporate proteins into the molecular structure of pigments can cause undesirable decreases in the nutritional availability of those proteins. This decrease is probably the result of a lowering of the ability of digestive enzymes to hydrolyze the protein, as the protein becomes chemically modified during the course of browning (Folk, 1956; Tu and Eskin, 1973).Although no published reports were found on the possible influence of browning on mineral bioavailability, observations by several investigators strongly indicate that melanoidins might behave as chelating agents for polyvalent metal cations and, therefore, influence the bioavailability of these metals. Hrdlicka (1976) reported that when salts of either Fe3+ or Cu2+ were heated with a glucose-glycine mixture or a fructose-glycine mixture, water-insoluble browning products that contained bound metal cations were formed. Copper was more strongly bound than iron. Adhikari and Tappel (1973) have provided flurometric evidence that Europium (Eu3+) is chelated by a water-soluble glucose-glytine melanoidin, and suggested that the chromophoric group responsible for the fluorescence is

Effects of oxidized lipids (4,5 (E)-epoxy-2(E)-heptenal and 4,5 (E)-epoxy-2 (E) -decenal) and lysine reaction products on zinc and calcium utilization: assays in Caco-2 cells

“…La capacidad de los compuestos pardos producidos en la RM para formar complejos con el calcio ha sido descrita hace años (Rendleman, 1987). En función de su poder quelante, algunos PRM podrían afectar la absorción cálcica por un doble mecanismo: los compuestos de elevado peso molecular, insolubles, disminuirían su absorción; mientras que las premelanoidinas y melanoidinas solubles, al quelar al elemento y mantenerlo en solución, incluso la favorecerían.…”

“…Así, por ejemplo, los pigmentos pardos del café o los del pan tostado sin leche, presentan muy baja capacidad para fijar al Ca (Rendleman, 1987). En la misma línea, O'Brien y Morrissey (1997) indican que mientras se conocen mejor los ligandos que fijan al Zn o al Cu, no se ha establecido la identidad de los PRM capaces de acomplejar al Ca; además, aunque la afinidad de los PRM para unir a distintos minerales no está bien definida, sugieren un orden en el que el Ca ocuparía el último lugar.…”

“…Además de los efectos negativos en el valor biológico de la proteína de la dieta, en los últimos años se viene prestando especial atención al efecto de los productos de la RM (PRM) sobre el metabolismo mineral, ya que parece que estos compuestos pueden comportarse como polímeros aniónicos que forman complejos moderadamente estables con algunos minerales (Rendleman, 1987), capaces de afectar su biodisponibilidad. En este sentido, la bibliografía actual es escasa y contradictoria, y los resultados dependen en gran medida de los productos utilizados y de las condiciones experimentales.…”

Comparative effects of glucose-lysineversus glucose-methionine Maillard reaction products consumption:in vitro andin vivo calcium availability

“…Rendleman [5] showed the bindings of calcium to soluble and insoluble melanoidins from glucose-glycine, fructoseglycine, and glucose-glutamic acid. According to O'Brien and Morrissey [6], using potentiometric titration, calcium and magnesium have a lower affinity for browning products than that observed for copper or iron.…”

Antioxidative Activity of a Zinc-Chelating Substance in Coffee

“…1) It is well-known that brewed coffee has very strong antioxidative activity, 7,8) and that such browning substances as melanoidins and polyphenolic compounds greatly contribute to this strong antioxidative activity and to the metal-chelating activity of coffee beverages. 1,[9][10][11][12][13] This activity is not restricted to use as an antioxidant in food systems, but is also related to the function of protecting cells from oxidative damage in a biological system. It would be interesting on the basis of the relationship between health and coffee intake to find a positive effect of brewed coffee on the biological system.…”