Demethylation kinetics of aspartame and L-phenylalanine methyl ester in aqueous solution

The kinetics of demethylation of aspartame and L-phenylalanine methyl ester were studied in aqueous solution at 25 degrees C over the pH range 0.27-11.5. The pseudo-first-order rate constant for aspartame was resolved into individual contributions from methyl ester hydrolysis and diketopiperazine fo...

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Bibliographic Details
Published in:Pharmaceutical research 1993-08, Vol.10 (8), p.1174-1180
Main Authors: SKWIERCZYNSKI, R. D, CONNORS, K. A
Format: Article
Language:English
Subjects:
Aspartame - chemistry
Biological and medical sciences
Chromatography, High Pressure Liquid
Dealkylation
General pharmacology
Hydrogen-Ion Concentration
Hydrolysis
Kinetics
Medical sciences
Pharmacognosy. Homeopathy. Health food
Pharmacology. Drug treatments
Phenylalanine - analogs & derivatives
Phenylalanine - chemistry
Potentiometry
Solutions
Water
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Summary:The kinetics of demethylation of aspartame and L-phenylalanine methyl ester were studied in aqueous solution at 25 degrees C over the pH range 0.27-11.5. The pseudo-first-order rate constant for aspartame was resolved into individual contributions from methyl ester hydrolysis and diketopiperazine formation. pH-rate profiles were quantitatively described by chemically reasonable kinetic schemes. Aspartame is maximally stable at pH 4 (t90 = 53 days at 25 degrees C); phenylalanine methyl ester, at pH 3. The potentiometrically measured pKa values were pKa1 3.19 and pKa2 7.87 for aspartame and pKa 7.11 for phenylalanine methyl ester.
ISSN:0724-8741
1573-904X
DOI:10.1023/A:1018920402644