Heating of food and haemoglobin adducts from carcinogens: possible precursor role of glycidol

Studies of adducts from reactive compounds to haemoglobin (Hb) by gas chrom atography-tandem mass spectrometry according to the N-alkyl Edman method re veals the occurrence of N-(2,3-dihydroxypropyl)valine (diHOPrVal) at Levels of 1-2 pmol/g Hb, in persons without known exposure. The hypothesis that t his background originates from glycidol or related compounds during heating of food was tested in experiments with rats. Animals fed fried animal feed for 30 or 72 days showed an increase of the diHOPrVal level by about 50% c ompared with controls. Several arguments, such as the formation of reactive oxiranes by heat-induced dehydration of glycol configurations in glycerol and sugars, support the idea that glycidol (or e.g. glycidyl esters) are pr ecursors of the adduct. In Hb samples, reduced for stabilisation of aldehyd e adducts, relatively high levels of adducts determined as diHOPrVal were f ound, although without significant relation to frying of the feed. There is thus no indication that reduction in vivo of, for example, the Schiff base from glyceraldehyde, is a pathway for formation of the diHOPrVal, The back ground level of diHOPrVal in humans Hb is low, and the cancer risk associat ed with exposure to the specific alkylator-probably glycidol-formed in cook ing, is therefore presumably low. The result implies, however, that low-mol ecular mass mutagenic oxiranes formed during the heating of food should be studied further. (C) 2000 Elsevier Science Ltd. All rights reserved.