Kjell Olsson

Formation of heterocyclic amines using model systems.

Initially, modeling was used to identify the mutagenic heterocyclic amines and their precursors. Major precursors have been shown to be single amino acids or amino acids together with creatine or creatinine. There is also evidence that Maillard reactions are involved since heating sugar and amino acids together with creatine or creatinine has been shown to produce several of the mutagenic heterocyclic amines, especially the aminoimidazoazaarenes (AIA compounds), e.g., IQ, MeIQ, MeIQx, DiMeIQx and PhIP. Due to a low yield in the model systems, the mechanisms behind the formation of the mutagenic heterocyclic amines are still unclear and need further substantiation. The fact that some AIA compounds are also produced in the absence of sugar casts some doubts on an obligatory participation of the Maillard reaction; alternative routes might exist. Further work using isotopically labeled precursors needs to be done and so far such work has only been performed for PhiP. The formation of mutagenic heterocyclic amines is dependent on time, temperature, pH, concentration of the precursors, type of amino acid, and the presence of certain divalent ions. Water may have an impact both as a temperature regulator and as a solvent medium for the reactants.

Creatin(in)e and Maillard reaction products as precursors of mutagenic compounds: Effects of various amino acids

Abstract The participation of creatin(in)e and Maillard reaction products in developing mutagenic activity was studied in model systems. Glucose and an amino acid were boiled under reflux for 2 h at 130°C together with creatine or creatinine dissolved in water-diethylene glycol (1:6). Threonine produced the highest mutagenic activity, 1068 revertants per μmol amino acid, towards TA98 after S9 activation, followed by glycine (410 rev/μmol) and lysine (246 rev/μmol). Proline, glutamic acid and the sulfur-containing amino acids produced less than 40 rev/μmol. Protein-bound amino acids produced no detectable mutagenic activity. When added to the reaction mixtures, the pure Maillard reaction products increased the mutagenic activity significantly. All precursors used occur in free form in meat. Work is now in progress to identify the mutagenic compounds produced in the model systems and to establish whether they also occur in fried meat.

Formation of a new mutagenic DiMeIQx compound in a model system by heating creatinine, alanine and fructose

A mixture of creatinine, D-fructose and DL-alanine was heated in diethylene glycol containing 14% water for 2 h at ca. 128 degrees C. The mutagens formed were extracted with 1-butanol, and purified by cation-exchange column chromatography, C18 reversed-phase Sep-Pak treatment and reversed-phase HPLC. According to its UV absorption, mass and 1H NMR spectra, one isolated fraction was tentatively assigned the chemical name, 3,4,8-trimethyl-3H-imidazo[4,5-f]quinoxalin-2-amine (4,8-DiMeIQx). This finding is in agreement with the suggestion that sugars, amino acids and creatinine present in meat may be the precursors of the mutagenic imidazoquinolin- and imidazoquinoxalin-2-amines (IQ compounds).

The formation of 2-furaldehyde and formic acid from pentoses in slightly acidic deuterium oxide studied by 1H NMR spectroscopy

The title reaction at 96°C and pD 1.5, 3.0, or 4.5 was followed by 1H NMR spectroscopy. The rate of pentose degradation increased in the order: arabinose ≈ xylose < ribose < 2-pentuloses. At pD 1.5, the rate of 2-furaldehyde formation increased in the same order. Increasing pD strongly accelerated the degradation of the aldoses but slightly retarded that of the ketoses. Increasing pD also retarded the formation of 2-furaldehyde, particularly from the ketoses, and increased its deuterium content at H-α (from 8–25 to 50–83 atom %) and H-3 (from 79–100 to 100 atom %). This is explained by assuming that 2-furaldehyde had formed mainly via acyclic intermediates, with reversible formation of a 3-deoxypentosulose. The formation of formic acid was slow and did not proceed via 2-furaldehyde. As evident from experiments with 1- or 5-13C-substituted aldopentoses, the formic acid was derived exclusively from the terminal pentose carbons, C-1 being somewhat more important than C-5.

Isolation and identification of the food mutagens IQ and MeIQx from a heated model system of creatinine, glycine and fructose

Abstract A mixture of creatinine, d -fructose and glycine was heated in diethylene glycol containing 14% water for 2h at ca . 128°C. The reaction mixture was extracted with 1-butanol and the extract subjected to cation exchange column chromatography, C 18 reversed-phase Sep-Pak treatment and reversed-phase HPLC. The first of the two HPLC fractions isolated was identified as the known beef mutagen, MeIQx. In the second HPLC fraction, MeIQx and the also known potent fish and beef mutagen, IQ, were co-eluted. HPLC, mass and 1 H NMR spectrometry were used for their identification. These results reinforce the hypothesis that creatinine, sugars and amino acids might be the precursors of these extremely potent mutagens.

1H-N.M.R., 13C-N.M.R., and mass spectra of glucosinolates and related compounds.

The mass spectra of per(trimethylsilyl) ethers of desulfated glucosinolates are dominated by ions derived from the glucose moiety. The ions at m/e 271 and 361 are much more abundant than in the spectra shown by the corresponding derivatives of hexoses and their simple glycosides. The individual glucosinolates are distinguished by a few ions originating from their respective aglycon groups. The 1H- and 13C-n.m.r. spectra of sinigrin and some closely related compounds have been analyzed.

One-Step Synthesis of 2-Amino-1-methylimidazo[4,5-b]quinoline

Abstract The novel title compound, a linear isomer of the food mutagen IQ, has been prepared in 67 % yield by Friedlander synthesis from creatinine and 2-aminobenzaldehyde.

Formation of 4,8-DiMeIQx from the model system fructose, alanine and creatinine Comparison with the isomeric 5,8-DiMeIQx

In a previous paper, the main mutagenic compound isolated from the model reaction system D-fructose, DL-alanine and creatinine was tentatively identified as 4,8-DiMeIQx. Its mutagenic activity and spectral characteristics have now been compared with those of the isomer 5,8-DiMeIQx. The comparison clearly demonstrates that the isolated compound was indeed 4,8-DiMeIQx. This finding is in agreement with the hypothesis that sugars, amino acids and creatinine present in meat may be the precursors of the mutagenic imidazoquinolin- and imidazoquinoxalin-2-amines (IQ compounds).

On the formation of reductic acid from pentoses or hexuronic acids

Abstract Careful hydrolysis of (±)- cis - or (±)- trans -tetrahydro-2,5-dimethoxy-2-furaldehyde dimethyl acetal proceeded via 5,5-dimethoxy-4-oxopentanal to give (±)- trans -4-hydroxy-5-methoxy-2-cyclopentenone and (±)- trans -4,5-dihydroxy-2-cyclopentenone. The latter product did not isomerize to 2,3-dihydroxy-2-cyclopentenone (reductic acid) on prolonged reaction.

On the formation of 2,3-dihydroxyacetophenone from pentoses or hexuronic acids

Abstract The structure of a previously isolated intermediate in the title reaction has been revised to 3-acetyl-2,3,4-trihydroxycyclohexanone by high-field 1 H NMR spectroscopy. The three hydroxyl groups are mutually cis -related.