Chemical model investigation showed that both
epigallocatechin gallate (EGCG) and its peracetate, which has all the
hydroxyl groups acetylated, effectively reduced the formation of 2-amino-1-methyl-6-phenylimidazo[4,5-
b]pyridine (
PhIP), the most abundant mutagenic heterocyclic
amine found in foods. Mechanistic study was subsequently carried out to characterize the probable inhibitory mechanism involved. GC-MS analysis showed that EGCG in only one-
fourth molar quantity of
phenylalanine reduced formation of
phenylacetaldehyde, a key
PhIP intermediate by nearly 90%. Its peracetate also showed similar inhibitory activity. This further supported the existence of an
antioxidant-independent mechanism contributing to the inhibition of
PhIP formation by EGCG. Subsequent LC-MS analyses of samples from a wide range of model systems consisting of
PhIP precursors showed the generation of characteristic analytes with molecular weight corresponding to the sum of EGCG and
phenylalanine fragment(s) only in models where
phenylalanine and EGCG were simultaneously present. An
isotope-labeling study revealed that these analytes all contained fragment(s) of
phenylalanine origin. Direct reaction employing
phenylacetaldehyde and EGCG further confirmed the capability of EGCG to form adducts with
phenylacetaldehyde, thus reducing its availability for
PhIP formation. Finally, an investigation of the time course of the generation of postulated adduction products supported EGCG as an effective inhibitor of
PhIP formation in prolonged heating processes.