Metal chelates of 2-hydroxy-4-methylthiobutanoic acid in animal feeding. Part 2: Further characterizations, in vitro and in vivo investigations.
The alpha-hydroxyacid 2-hydroxy-4-methylthiobutanoic acid (the so-called methionine hydroxy-analogue, MHA), largely used in animal nutrition as a source of methionine, forms stable metal chelates with divalent metals of formula [{CH(3)SCH(2) CH(2)CH(OH)COO}(2)M].nH(2)O. Protonation and iron(III) and copper(II) complex formation constants have been determined by potentiometry at 25 degrees C. Distribution diagrams show that no free Fe(3+) cations are present in solution at pH>2.5. ESI-MS (Electron-Spray Ionization Mass Spectrometry) investigations carried out both on iron and zinc complexes in solution have evidenced various species with different MHA/metal ratios. In vivo trials were carried out with rats. After receiving a zinc-deficient diet for 3 weeks, animals were fed the same diet added with zinc sulfate or zinc/MHA chelate; the zinc content of faeces was higher (+45%; P<0.05) in sulfate fed rats, whereas zinc retention was higher (+61%; P<0.05) in the Zn/MHA diet. Experiments in vitro with human intestinal Caco-2 cells indicated that the MHA/Fe chelate was taken up by the cells without any apparent toxic effect. The iron uptake was higher than that of iron nitrilotriacetate (Fe(3+)NTA), an effective chelate for delivering iron to milk diets. In conclusion, these data indicate that the use of MHA chelates could be a valuable tool to increase bioavailability of trace minerals and reduce the environmental impact of animal manure.
Predieri
Giovanni
G
Dipartimento di Chimica G.I.A.F., Universitá di Parma, Parco Area delle Scienze 17/A, 43100 Parma, Italy. predieri@unipr.it
Elviri
Lisa
L
Tegoni
Matteo
M
Zagnoni
Ingrid
I
Cinti
Enrico
E
Biagi
Giacomo
G
Ferruzza
Simonetta
S
Leonardi
Giuliano
G
D000821:Animal Feed / Q000032:analysis*; D000818:Animals; D001682:Biological Availability; D018938:Caco-2 Cells; D002614:Chelating Agents / Q000008:administration & dosage / Q000737:chemistry* / Q000493:pharmacokinetics; D006801:Humans; D066298:In Vitro Techniques; D019266:Iron, Dietary / Q000008:administration & dosage / Q000493:pharmacokinetics; D008670:Metals / Q000008:administration & dosage / Q000737:chemistry* / Q000493:pharmacokinetics; D008715:Methionine / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000493:pharmacokinetics; D051381:Rats; D021241:Spectrometry, Mass, Electrospray Ionization; D014131:Trace Elements / Q000008:administration & dosage / Q000737:chemistry / Q000493:pharmacokinetics; D015032:Zinc / Q000008:administration & dosage / Q000737:chemistry / Q000493:pharmacokinetics
D002614:Chelating Agents; D019266:Iron, Dietary; D008670:Metals; D014131:Trace Elements; C008391:alpha-hydroxy-gamma-methylmercaptobutyric acid; D008715:Methionine; D015032:Zinc