Mutagen formation in a model beef boiling system III. purification and identification of three heterocyclic amine mutagens‐carcinogens

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Abstract
An extensively boiled supernatant2 (S2) fraction from beef round steak contains two major Salmonella frameshift mutagens, designated as HPLC peaks A and B. These same mutagens arise, but in different proportions, when S2 is boiled with creatine phosphate (CP), and they are produced in much greater quantities from a boiled mixture of S2 + L‐tryptophan (Trp) + CP + FeSO4 (S2 ∗). A third mutagen, peak C, is also generated in the S2 ∗ mixture. Mutagen peaks A, B, and C were purified to homogeneity and shown by their absorption spectra, mass fragmentation patterns, and other data to be 2‐amino‐3‐methylimidazo[4,5‐f]quinoline (IQ), 3‐amino‐l‐methyl‐5H‐pyrido[4,3‐b]‐indole (Trp‐P‐2), and 3‐amino‐l,4‐dimethyl‐5H‐pyrido[4,3‐b]indole (Trp‐P‐1), respectively. This is the first demonstration that IQ, Trp‐P‐2, and Trp‐P‐1 can form under aqueous conditions at 100°C from reactions between low molecular wt precursors that are present in meat juice. Further simplification of and studies with the S2 fraction of beef muscle should provide relevant information about the mechanisms of frameshift mutagen formation during the cooking of meats and fish.