Studies of adducts from reactive compounds to haemoglobin (Hb) by gas chromatography-tandem mass spectrometry according to the N-alkyl Edman method reveals 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 this 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% compared 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 precursors of the adduct. In Hb samples, reduced for stabilisation of
aldehyde adducts, relatively high levels of adducts determined as
diHOPrVal were found, 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 background level of
diHOPrVal in humans Hb is low, and the
cancer risk associated with exposure to the specific
alkylator-probably
glycidol-formed in cooking, is therefore presumably low. The result implies, however, that low-molecular mass mutagenic
oxiranes formed during the heating of food should be studied further.