title: Metal chelates of 2-hydroxy-4-methylthiobutanoic acid in animal feeding. Part 2: Further characterizations, in vitro and in vivo investigations.
abstract: 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.
authors.affiliation: Dipartimento di Chimica G.I.A.F., Universitá di Parma, Parco Area delle Scienze 17/A, 43100 Parma, Italy. predieri@unipr.it
authors.forename: Giovanni
authors.initials: G
authors.lastname: Predieri
authors.forename: Lisa
authors.initials: L
authors.lastname: Elviri
authors.forename: Matteo
authors.initials: M
authors.lastname: Tegoni
authors.forename: Ingrid
authors.initials: I
authors.lastname: Zagnoni
authors.forename: Enrico
authors.initials: E
authors.lastname: Cinti
authors.forename: Giacomo
authors.initials: G
authors.lastname: Biagi
authors.forename: Simonetta
authors.initials: S
authors.lastname: Ferruzza
authors.forename: Giuliano
authors.initials: G
authors.lastname: Leonardi
mesh_terms: 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
chemical_list: D002614:Chelating Agents; D019266:Iron, Dietary; D008670:Metals; D014131:Trace Elements; C008391:alpha-hydroxy-gamma-methylmercaptobutyric acid; D008715:Methionine; D015032:Zinc