Determination of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in hemoglobin using on-line coupling of restricted access material to liquid chromatography–mass spectrometry

A new method for the analysis of 2-amino-l-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in hemoglobin has been developed. The method is based on a protein hydrolysis with hydrochloric acid to release the bound PhIP followed by purification and preconcentration steps. The sample clean-up consisted of an ultratiltration of the hydrolyzed protein and preconcentration of PhIP by freeze-drying. An ultimate cleaning step of the sample using restricted access material (RAM) coupled to liquid chromatography performs extraction and enrichment of the analyte from the sample matrix. Three different RAM columns were tested, LiChrospher((R))ADS C-4, C-8 and C-18. Two mass spectrometers (ion trap and triple quadrupole) operating in different modes were also evaluated for the determination of PhIP released from hemoglobin adducts. Quality parameters were established and good precision (relative standard deviation (R.S.D.) 95%) and low detection limits were reached, up to 0.03 fmol PhIP/mg hemoglobin, when using the triple quadrupole. (c) 2005 Elsevier B.V. All rights reserved

Effect of red wine marinades on the formation of heterocyclic amines in fried chicken breast

Genotoxic heterocyclic amines (HAs) are formed via the Maillard reaction and free radical reaction mechanisms when meat or fish is cooked at usual cooking conditions. In this paper, the effect of the addition of red wine was tested to study if it interferes in HA formation. Fried chicken breast was the food item chosen, and three different red wines, characterized in terms of grape varieties, free amino acids, antioxidant properties, and metallic composition, were used to marinate meat prior to the heating process. Unmarinated samples and samples marinated with an ethanol-water mixture provided reference HA levels. The frying experiments were performed under well-controlled temperature and time conditions. The samples were analyzed for HA content using solid-phase extraction and LCMS/MS. DMIP, PhIP, MeIQx, 4,8-DiMeIQx, IFP, TMIP, harman, and norharman were identified in fried chicken breast. Red wine marinades were found to reduce the formation of some of the HAs formed. PhIP, with a reduction of up to 88%, was the most minimized amine, although the formation of harman was enhanced

Liquid chromatography-tandem mass spectrometry analysis of 2-amino-1-methyl-6-(4-hydroxyphenyl)imidazo[4,5-b]pyridine in cooked meats.

Several cooked meats such as beef (fried, coated-fried), pork (fried, coated-fried), and chicken (fried, griddled, coated-fried, roasted) were analyzed for the heterocyclic amine 2-amino-1-methyl-6-(4-hydroxyphenyl)imidazo[4,5-b]pyridine (4′-OH-PhIP) not commonly determined in food and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP). The highest content of 4′-OH-PhIP was found in fried and griddled chicken breast, the concentration being 43.7 and 13.4 ng/g, respectively, whereas the corresponding PhIP concentrations were 19.2 and 5.8 ng/g. The estimated concentration of both pyridines in fried pork loin, in fried pork sausages, and in coated-fried chicken was below 2.5 ng/g. In the rest of the samples, 4′-OH-PhIP was not detected. The analyses were performed by solid-phase extraction and LC-MS/MS. The fragmentation of 4′-OH-PhIP in an ion trap mass analyzer was studied in order to provide information for the identification of 4′-OH-PhIP. Additionally, the effect of red wine marinades on the formation of 4′-OH-PhIP in fried chicken was examined, finding a notable reduction (69%) in the amine’s occurrence

Identification of seafood as an important dietary source of heterocyclic amines by chemometry and chromatography–mass spectrometry

Heterocyclic amines (HCAs), which are formed during the cooking of protein-rich foods, are potent mutagens and a risk factor for human cancers. Levels of HCAs have been extensively investigated in meat products but not in fish products. Here, we report levels of HCAs in fried salmon, tuna, hake, sardine, angler fish, cod, sole, swordfish, squid, and cuttlefish. The HCA levels of some of these foods have not been previously analyzed. We employed multivariate factor-analysis tools, including principal components analysis (PCA) and partial least-squares (PLS) regression, to study the effects of cooking weight loss and levels of creatine, glucose, and free amino acids on HCA levels. The highest concentrations of mutagenic HCAs, 159.3 ng·g–1 total, where 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) accounted for 121 ng·g–1, were found in fried swordfish (cooking loss of 51.8%). These levels are higher than those generally found in fried chicken, which is typically cited as the most contaminated food item. Thus, swordfish is among the richest known sources of HCAs. The other cooked seafood items contained from 0.4 to 35.4 ng·g–1 HCAs, comparable to concentrations typically reported for meat. Chemometric analysis showed that the fish species is the most influential parameter on the formation of HCAs such as DMIP, PhIP, and norharman. Concentrations of histidine, lysine, creatine, and glucose, as well as weight loss, also influence the yield of HCAs. These results suggest that seafood is an important dietary source of HCAs. The formation of HCAs in fish is influenced by multiple factors, some of which remain unknown