Inhibitory effects of phenolics, teas and saliva on the formation of mutagenic nitrosation products of salted fish.

The objectives of this study were to simulate in vitro some of the conditions that may prevail in man during the ingestion of a meal and to quantitate the inhibitory effect of phenolics and phenolic-containing beverages on the formation of mutagenic nitrosation products. The test system consisted of nitrosating (pH 2, 1 h, 37 degrees C) an aqueous fraction of a salt-preserved Chinese fish (Pak Wik) with or without the inhibitors to be tested and estimating the frequency of his+ revertants per survivor of Salmonella typhimurium (strain TA1535). The phenolics and teas were added to the nitrosation mixture. Catechin, chlorogenic acid, gallic acid, pyrogallol and tannic acid suppressed the formation of mutagenic nitrosation products. The inhibitory efficiency was comparable to that of ascorbic acid. A Japanese, a Chinese and a Ceylonese tea also prevented the formation of mutagenic nitrosated fish products at doses which are usually consumed by man. Moreover, saliva exerted an inhibitory effect. The inhibitory effect was not additive when the phenolics or saliva were added concurrently to the nitrosation mixture. The possibility that phenolics are involved in the apparent chemopreventive effect of fruits and vegetables is discussed.