Gray, Jennifer C., Habtemariam, Abraha, Winnig, Marcel, Meyerhof, Wolfgang and Sadler, P. J.. (2008) Sweetening ruthenium and osmium : organometallic arene complexes containing aspartame. Journal of Biological Inorganic Chemistry, Vol.13 (No.7). pp. 1111-1120. ISSN 0949-8257

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Abstract

The novel organometallic sandwich complexes [(eta(6)-p-cymene)Ru(eta(6)-aspartame)](OTf)(2) (1) (OTf = trifluoromethanesulfonate) and [(eta(6)-p-cymene)Os(eta(6)-aspartame)](OTf)(2) (2) incorporating the artificial sweetener aspartame have been synthesised and characterised. A number of properties of aspartame were found to be altered on binding to either metal. The pK (a) values of both the carboxyl and the amino groups of aspartame are lowered by between 0.35 and 0.57 pH units, causing partial deprotonation of the amino group at pH 7.4 (physiological pH). The rate of degradation of aspartame to 3,6-dioxo-5-phenylmethylpiperazine acetic acid (diketopiperazine) increased over threefold from 0.12 to 0.36 h(-1) for 1, and to 0.43 h(-1) for 2. Furthermore, the reduction potential of the ligand shifted from -1.133 to -0.619 V for 2. For the ruthenium complex 1 the process occurred in two steps, the first (at -0.38 V) within a biologically accessible range. This facilitates reactions with biological reductants such as ascorbate. Binding to and activation of the sweet taste receptor was not observed for these metal complexes up to concentrations of 1 mM. The factors which affect the ability of metal-bound aspartame to interact with the receptor site are discussed.

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Item Type:	Journal Article
Subjects:	Q Science > QD Chemistry
Divisions:	Faculty of Science > Chemistry
Library of Congress Subject Headings (LCSH):	Ruthenium, Osmium, Aspartame, Aromatic compounds, Organometallic compounds
Journal or Publication Title:	Journal of Biological Inorganic Chemistry
Publisher:	Springer
ISSN:	0949-8257
Date:	September 2008
Volume:	Vol.13
Number:	No.7
Number of Pages:	10
Page Range:	pp. 1111-1120
Identification Number:	10.1007/s00775-008-0396-1
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access
URI:	http://wrap.warwick.ac.uk/id/eprint/29373

Data sourced from Thomson Reuters' Web of Knowledge

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