Mutagenicity of various Japanese foodstuffs treated with nitrite. II. Directly-acting mutagens produced from N-containing compounds in foodstuffs.

Various Japanese foodstuffs show mutagenicity after nitrite treatment at pH 4.2. Among 13 groups of foodstuffs, classified by the 'market basket' method, the group containing fish showed the highest mutagenicity in the absence of metabolic activation. Taking the daily intake of these foodstuffs into consideration, the combination of groups V (soya bean paste), VI (juice), VIII (pickles and seaweed), IX (alcoholic beverages, coffee), X (fish) and XI (meat) represents 90% of the total mutagenic activity that may be supplied by food each day. The mutagenic activities of foodstuffs in groups VII (vegetables), VII and IX were increased remarkably by nitrite treatment; the mutagenicity of alcoholic beverages was particularly affected by nitrite. The separation of wine, sake and beer into acidic, basic and neutral fractions scattered the premutagenic activities, with a large decrease in total activity. The chemical properties of the basic fraction of beer, which gave the highest mutagenicity after nitrite treatment, were examined, and two tetrahydro-beta-carboline derivatives were identified.