title: Intestinal absorption of aspartame decomposition products in adult rats.
abstract: The dipeptide sweetener aspartame (N-L-alpha-aspartyl-L-phenylalanine, 1-methyl ester; alpha-APM) is relatively stable in dry powder form. However, when exposed to elevated temperature, extremes of pH and/or moisture, alpha-APM is converted into a variety of products. In aqueous solution alpha-APM decomposes to yield methanol, two isomeric forms of L-aspartyl-L-phenylalanine (Asp-Phe) [alpha-Asp-Phe and beta-Asp-Phe], and APM's diketopiperazine cyclo-Asp-Phe. Depending on beverage storage conditions, individuals drinking alpha-APM-sweetened beverages may consume small quantities of these three compounds. Relatively little has been published about the metabolism of beta-Asp-Phe and cyclo-Asp-Phe. We compared the absorption and metabolism of alpha-Asp-Phe, beta-Asp-Phe, and cyclo-Asp-Phe with that of L-phenylalanine (Phe) in adult rats. Steady-state perfusion studies of rat jejunum indicated rapid carrier-assisted uptake of Phe and alpha-Asp-Phe, but only slow passive diffusion of beta-Asp-Phe and cyclo-Asp-Phe from the lumen. Homogenates of rat intestinal mucosa, liver, and cecal contents, as well as homogenates of pure cultures of Escherichia coli B, catalyzed the hydrolysis of alpha-Asp-Phe, but not cyclo-Asp-Phe. Homogenates of E coli and rat cecal contents, but not homogenates of rat liver or intestinal mucosa catalyzed the hydrolysis of beta-Asp-Phe.
authors.affiliation: Department of Pediatrics, University of Iowa, Iowa City 52242.
authors.forename: W E
authors.initials: WE
authors.lastname: Lipton
authors.forename: Y N
authors.initials: YN
authors.lastname: Li
authors.forename: M K
authors.initials: MK
authors.lastname: Younoszai
authors.forename: L D
authors.initials: LD
authors.lastname: Stegink
mesh_terms: D000042:Absorption; D000818:Animals; D001218:Aspartame / Q000378:metabolism*; D002384:Catalysis; D004151:Dipeptides / Q000493:pharmacokinetics*; D004926:Escherichia coli / Q000502:physiology; D006868:Hydrolysis; D007413:Intestinal Mucosa / Q000166:cytology / Q000378:metabolism* / Q000502:physiology; D008099:Liver / Q000502:physiology; D008297:Male; D008954:Models, Biological; D009994:Osmolar Concentration; D010649:Phenylalanine / Q000493:pharmacokinetics*; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D004151:Dipeptides; C045207:aspartyl-phenylalanine; D010649:Phenylalanine; D001218:Aspartame