Pharmacological Research 53 (2006) 1–5
The effect of aspartame metabolites on human erythrocyte
membrane acetylcholinesterase activity
Stylianos Tsakirisa,∗, Aglaia Giannoulia-Karantanab,
Irene Simintzia, Kleopatra H. Schulpisb
aDepartment of Experimental Physiology, Medical School, University of Athens, P.O. Box 65257, GR-154 01 Athens, Greece
bInstitute of Child Health, Research Center, Aghia Sophia Children’s Hospital, GR-115 27 Athens, Greece
Accepted 19 July 2005
Studies have implicated aspartame (ASP) with neurological problems. The aim of this study was to evaluate acetylcholinesterase (AChE)
activity in human erythrocyte membranes after incubation with the sum of ASP metabolites, phenylalanine (Phe), methanol (met) and aspartic
acid (aspt), or with each one separately. Erythrocyte membranes were obtained from 12 healthy individuals and were incubated with ASP
ing with 34mg/kg, 150mg/kg or 200mg/kg of ASP consumption resulted in an enzyme activity reduction by −33%, −41%, and −57%,
respectively. Met concentrations 0.14mM, 0.60mM, and 0.80mM decreased the enzyme activity by −20%, −32% or −40%, respectively.
Aspt concentrations 2.80mM, 7.60mM or 10.0mM inhibited membrane AChE acitivity by −20%, −35%, and −47%, respectively. Phe con-
0.82mM or 0.07mM, respectively, did not alter the membrane AChE activity. It is concluded that low concentrations of ASP metabolites
had no effect on the membrane enzyme activity, whereas high or toxic concentrations partially or remarkably decreased the membrane AChE
activity, respectively. Additionally, neurological symptoms, including learning and memory processes, may be related to the high or toxic
concentrations of the sweetener metabolites.
© 2005 Elsevier Ltd. All rights reserved.
Keywords: Acetylcholinesterase; Aspartame; Phenylalanine; Methanol; Aspartic acid
Although aspartame (ASP) received Food and Drug
Administration (FDA) approval in 1981 and has been judged
safe by medical groups such as the AMA Counsil on Sci-
entific Affairs , there has been persistent concern that the
use of ASP, an O-methyl ester of the dipeptide l-a-aspartyl-
or other abnormalities [1,2]. Clinical studies have demon-
strated that administration of ASP can alter some aspects of
blood chemistry, in particular plasma phenylalanine (Phe)
∗Corresponding author. Tel.: +30 210 7462662; fax: +30 210 7462571.
E-mail address: email@example.com (S. Tsakiris).
have implicated ASP in the occurrence of such problems as
seizures , memory loss , headache  and hypersen-
sitivity reactions [7,9]. In addition, most of clinical studies
investigating ASP have used as subjects healthy adults 
and individuals likely to use large amount of ASP, like dia-
betics or in weight reduction [10,11]. Furthermore, other
short-term studies have been conducted and none of these
have suggested any relationship between ASP consumption
and memory loss [3,11]. In contrast, various neurochemical
effects due to ASP ingestion have been reported . Certain
brain amino acid levels, including aspt or Phe, have been
shown to be increased after the consumption of the sweet-
ener . Taken collectively, these studies suggest that ASP
may become more prominent with long-term consumption
1043-6618/$ – see front matter © 2005 Elsevier Ltd. All rights reserved.